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Potatoes Can Be Part of a Healthy Diet

Pennington Biomedical Research Center

BATON ROUGE, Louisiana — When we think of healthy vegetables, we don’t think of potatoes, but we should. Potatoes have developed a reputation for causing weight gain and an increased risk for type 2 diabetes, and often find themselves on a list of foods to avoid, especially for individuals with insulin resistance. However, a new study from Pennington Biomedical Research Center, published in the Journal of Medicinal Food, says that potatoes actually did not increase that risk, are filled with key nutrients, and packed with health benefits.

Candida Rebello, PhD, an assistant professor at Pennington Biomedical, served as co-investigator of the study which examined how a diet including potatoes affects key health measures. Rebello, who is also a registered dietitian, said, “We demonstrated that contrary to common belief, potatoes do not negatively impact blood glucose levels. In fact, the individuals who participated in our study lost weight.”

“People tend to eat the same weight of food regardless of calorie content in order to feel full,” Rebello explained. “By eating foods with a heavier weight that are low in calories, you can easily reduce the number of calories you consume. The key aspect of our study is that we did not reduce the portion size of meals but lowered their caloric content by including potatoes. Each participant’s meal was tailored to their personalized caloric needs, yet by replacing some meat content with potato, participants found themselves fuller, quicker, and often did not even finish their meal. In effect, you can lose weight with little effort.”

The study involved 36 participants between the ages of 18 and 60 who were overweight, had obesity, or insulin resistance. Insulin resistance refers to a health condition in which the body’s cells do not respond well to insulin and glucose does not enter into the cells to make energy. Insulin resistance is linked to obesity, high blood pressure, high cholesterol, and type 2 diabetes

Participants were fed precisely-controlled diets of widely available common foods including either beans, peas, and meat or fish, or white potatoes with meat or fish. Both diets were high in fruit and vegetable content and substituted an estimated 40% of typical meat consumption with either beans and peas or potatoes. Previous studies have shown that eating beans and peas improves blood glucose levels in individuals with newly diagnosed type 2 diabetes. To increase the dietary fiber component of the potatoes, they were boiled with the skin intact and then refrigerated between 12 and 24 hours. Potatoes were incorporated into the main lunch and dinner entrées, such as shepherd’s pie and creamy shrimp and potatoes, and served together with sides such as mashed potatoes, oven-roasted potato wedges, potato salad, and scalloped potatoes with lunch and dinner entrees.

“We prepared the potatoes in a way that would maximize their fiber content. When we compared a diet with potatoes to a diet with beans and peas, we found them to be equal in terms of health benefits,” Rebello said. “People typically do not stick with a diet they don’t like or isn’t varied enough. The meal plans provided a variety of dishes, and we showed that a healthy eating plan can have varied options for individuals striving to eat healthy. In addition, potatoes are a fairly inexpensive vegetable to incorporate into a diet.”

Pennington Biomedical Research Center’s Executive Director John Kirwan, PhD, and Principal Investigator on the study said, “Obesity is an incredibly complex disease that Pennington Biomedical is tackling on three different fronts: research that looks at how and why our bodies react the way they do, research that looks at individual responses to diet and physical activity, and policy-level discussions and community programs that bring our research into strategies our local and global communities can use to live healthier lives. These new data on the impact of potatoes on our metabolism is an exciting addition to the arsenal of evidence we have to do just that.”

This work was supported in part by an investigator-initiated grant from the Alliance for Potato Research and Education and in part by a grant from the National Institute on Aging and from the National Institute of General Medical Sciences of the National Institutes of Health, which funds the Louisiana Clinical and Translational Science Center. The funders (Alliance for Potato Research and Education and the National Institutes of Health) had no role in the design, analysis, or writing of the manuscript. The content is solely the responsibility of the authors and does not necessarily represent the official views of the sponsors.

About LSU’s Pennington Biomedical Research Center

The Pennington Biomedical Research Center is at the forefront of medical discovery as it relates to understanding the triggers of obesity, diabetes, cardiovascular disease, cancer and dementia. The Center architected the “Obecity, USA” awareness and advocacy campaign to help solve the obesity epidemic by 2040. The Center conducts basic, clinical, and population research, and is affiliated with Louisiana State University. The research enterprise at Pennington Biomedical includes over 480 employees within a network of 40 clinics and research laboratories, and 13 highly specialized core service facilities. Its scientists and physician/scientists are supported by research trainees, lab technicians, nurses, dietitians, and other support personnel. Pennington Biomedical is located in state-of-the-art research facilities on a 222-acre campus in Baton Rouge, Louisiana. For more information, see https://www.pbrc.edu.

Branding foods as ‘healthy’ or ‘unhealthy’ based on marginal data calls findings into question

Diabetologia. 2022; 65(10): 1751–1752.

Published online 2022 Aug 16. doi: 10.1007/s00125-022-05767-6

To the Editor: This letter is in response to the recently published manuscript entitled ‘Plasma metabolite profiles related to plant-based diets and the risk of type 2 diabetes’ by Hu and colleagues [1]. This manuscript assesses dietary factors that influence type 2 diabetes; given the astounding increase in diabetes prevalence in our society, the timeliness and gravity of this topic cannot be overstated. The authors conclude that plant-based diets are associated with a lower risk of developing diabetes, findings that complement a growing body of literature supporting this concept [1]. However, significant flaws in the study design and interpretation of selected results are cause for concern.

First, by distinguishing between ‘healthy’ and ‘unhealthy’ plant-based foods, the authors risk overstating the health effects of any given individual food item. The study identifies 264 metabolites, with 93 associated with the healthy plant index and 75 associated with the unhealthy plant index, yet only 50 and 32 metabolites, respectively, were unique to one group or the other [1]. This finding suggests a great deal of overlap in metabolites between the two groups. Noteworthy overlap exists between individual foods as well. For example, the metabolite profiles shown in Fig. 3 for nuts (in the ‘healthy plant foods’ group) and potatoes (in the ‘unhealthy plant foods’ group) are quite similar [1], which calls into question why one food is considered healthy while the other is considered unhealthy. Categorising potatoes as unhealthy is also questionable in light of US Department of Agriculture and Dietary Guidelines for Americans recommendations, which include three healthy food patterns characterised by regular consumption of starchy vegetables such as potatoes and refined grains [2]

Further, the reference cited to justify the grouping classification is a paper by Hu and colleagues from 2016 [3]. The authors of this study created a ‘healthy plant-based’ diet that excluded potatoes from the ‘healthy’ pattern, purportedly based on data from a publication by Martínez-González and colleagues [4]. Interestingly, Martínez-González and colleagues categorised potatoes as a ‘healthy plant-based’ food, and only limited evidence is provided in the current study by Hu and colleagues to rationalise the reassignment of potatoes to the ‘unhealthy plant foods’ category. More specifically, the rationale for this decision was based on a single 15-year-old observational study in female health providers that showed only modest associations between potato and French fry consumption and risk for type 2 diabetes. The decision by Hu and colleagues to re-classify potatoes as an unhealthy food based on such limited evidence is questionable.

Undoubtedly, lifestyle interventions are necessary to reduce the global burden of disease, especially regarding type 2 diabetes. Dietary modifications are a realistic and promising intervention strategy for not only improving human health, but also influencing the trajectory of our food system in favour of a plant-forward future. Nutrition researchers are responsible for producing objective data to guide dietary recommendations; unfortunately, the study in question falls short because of the characterisation of some individual foods as healthy or unhealthy based on seemingly subjective perspectives that are not supported by the totality of the available literature.

To this effect, carefully designed studies with objectively interpreted results are necessary to positively improve human health and shift agribusiness, nutrition policy and beyond in favour of a more sustainable, plant-forward food system.

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Authors’ relationships and activities

MK serves as a consultant for the Alliance for Potato Research and Education.

Contribution statement

The author was the sole contributor to this paper.

PODCAST EPISODE 202: DEFINING “QUALITY CARBOHYDRATES” – THE LATEST SCIENCE & RECOMMENDATIONS – DR. SIDDHARTHA ANGADI & DR. JULIE MILLER JONES

Jan 19, 2022

Carbohydrates: Consumer Confusion, Current Guidance & Future Recommendations

The physiological impacts of eating carbohydrate-containing foods are much more complex and individualized compared to dietary protein and fat; yet, there is still no globally accepted way to define ‘carbohydrate quality’. While some researchers often rely on the Glycemic Index as a leading marker for the quality of carbohydrate-containing foods, the research does not align with this approach. In fact, published studies continue to question the variability, reliability, and utility of the Glycemic Index, especially among the general population.   

During this episode, you will hear from cardiovascular physiologist Sid Angadi, PhD, FACSM, and food and nutrition scientist Julie Miller Jones, PhD, CNS, CFS, as they take a deep dive into the latest science and recommendations surrounding carbohydrate-containing foods. Tune in to learn about the limitations with using glycemic index as a marker of carbohydrate quality and get up-to-speed on the research that’s currently underway to develop a new definition for quality carbohydrate-containing foods.

Tune in to this episode to learn about:

  • Consumer confusion about carbohydrates and their role in a healthy diet
  • What the current nutrition guidance says about carbohydrates
  • The complexities of carbohydrate-containing foods
  • How the nutrition science community currently defines carbohydrate quality
  • Resistant starch, fiber and other nutrients in carbohydrate-containing foods
  • The evolving scientific literature on the Glycemic Index as a marker for carbohydrate quality 
  • Insights on how to best define quality carbohydrates moving forward
  • The strengths and limitations of epidemiological research versus randomized controlled trials and the appropriate way to relay findings from both types of research 
  • Takeaways for the public, health professionals and the research community regarding carbohydrate-containing foods 
  • Resources and research on carbohydrates

Link to Podcast

The Need for Nuance: Toward an Evidence-Based Definition and Classification of Carbohydrate Food Quality

The 2020 Dietary Guidelines for Americans (DGAs) recommends adults consume nearly two-thirds of calories from carbohydrate-containing foods; however, the advice falls short on how to choose quality sources. Unlike protein and fat quality, there are conflicting views among scientists on how to define carbohydrate quality. While some support the Glycemic Index (GI) as a surrogate marker for carbohydrate quality, new research calls into question its reliability, utility and value. A new method to defining carbohydrate quality – one that focuses on the unique nutrient contributions of carbohydrate-containing foods – is needed.

During this educational session, you will hear from experts in the fields of nutrition, exercise science, algorithm development and dietary patterns as they review the current evidence that illustrates the need for a globally accepted definition of ‘quality carbohydrates.’ The speakers will unveil an evidence-based algorithm for high-quality carbohydrate-containing foods that supports equitable healthy eating patterns and aligns with DGA recommendations.

Learning Objectives:

  • Summarize and evaluate existing approaches to define high-quality carbohydrate-containing foods
  • Recognize the need for nuance in defining high-quality carbohydrate-containing foods given the diversity within this food category
  • Interpret and utilize a more realistic approach to defining high-quality carbohydrate-containing foods

There is no fee to attend this event, but registration is required. To register, visit https://www.mcisemi.com/nutrition2022/ and select this event from the list of individual NUTRITION 2022 events available to register.

The Glycemic Index 40 Years Later: A Fresh Look at Its Reliability, Utility and Value

Over the past 30 years, the glycemic index (GI) has increasingly been used as shorthand for carbohydrate food quality, with some calling for its use in federal and global dietary guidance and policy. However, GI was not originally intended to be a broad-based tool, but rather a measure of predicted glycemic impact in people with type 2 diabetes. Studies have shown that the GI’s inter- and intra-individual variability limits its real-world utility, and reliance on GI has not been shown to improve overall diet quality or health outcomes compared to the U.S. Dietary Guidelines’ healthy dietary patterns. In this session, top researchers discuss more recent findings that demonstrate the GI’s limitations and offer new recommendations to more meaningfully assess the true quality of carbohydrate foods.

Learning Objectives:

  • Describe the purpose of the glycemic index and how it was developed
  • Summarize the body of scientific evidence connecting carbohydrate intake and GI values to health outcomes
  • Effectively communicate the limitations of the Glycemic Index as a maker for carb quality

“There is no fee to view the recording, but registration is required.  To register, visit https://www.mcisemi.com/nutrition2022/ and select this event from the list of individual NUTRITION 2022 events available to register.”

Direct Session Link

New study finds no association between potato consumption and elevated cardiometabolic disease risk

The latest findings show that overall diet and lifestyle mediate health outcomes associated with potato consumption, not potato preparation methods

Peer-Reviewed Publication

THE ALLIANCE FOR POTATO RESEARCH AND EDUCATION (APRE)

Although potatoes are a nutrient-rich vegetable, they are often singled out as a food to limit. In fact, despite the Dietary Guidelines for Americans’ recommendation to increase fruit and vegetable consumption, some health experts still recommend limiting or avoiding eating potatoes due to concerns that they may increase cardiometabolic risk. However, a newly published study in the Journal of Nutritional Science finds that advice may be unwarranted. Researchers at Boston University examined the influence of potatoes as part of overall diet and lifestyle patterns on cardiometabolic disease risk. They found no change in cardiometabolic risk factors associated with intake of either fried or non-fried potatoes in adults from the long-running Framingham Offspring cohort.

“In this study, we looked at the effects of higher intakes of potatoes on blood pressure, lipids, and glucose and we found that after accounting for other dietary and lifestyle factors, there was no increased risk of cardiometabolic disorders associated with potato consumption,” said lead study investigator Lynn L. Moore, DSc, MPH, associate professor of Medicine at the Boston University Chobanian & Avedisian School of Medicine. “In fact, we found that those in the highest potato intake category consumed 25% more total fruits and vegetables than those in the lower potato intake group. As a result, these participants who consumed more potatoes were more likely to meet the recommendations of the Dietary Guidelines.”

The findings from Moore’s research group observed no association between consuming 4 or more cup-equivalents of potatoes per week (both white and sweet, fried and non-fried) and type 2 diabetes (T2DM), impaired fasting glucose (IFG), hypertension, and dyslipidemia in a large population of healthy Caucasian adults. “We know that potatoes are rich in potassium, magnesium, and dietary fiber, all of which may be protective against the heart attacks and strokes that are a consequence of elevated levels of cardiometabolic risk,” explained Moore. “In fact, potatoes are one of the most important sources of potassium in the American diet.”

Meanwhile, the effects of fried potato consumption appeared to be modified by other diet and lifestyle factors. For example, those with higher intakes of fried potatoes and lower consumption of red meat had a 26% lower risk of elevated triglycerides. Additionally, more physically active adults who consumed higher levels of fried potatoes had a 25% lower risk of developing Type 2 diabetes. These findings underscore the importance of overall diet and lifestyle when it comes to cardiometabolic disease risk,” Moore added. “Public health messaging singling out potatoes, and even fried potatoes, is not supported by this evidence.”

These study results indicate that potatoes, both fried and non-fried sweet and white potato varieties, can be included as part of a healthy diet without impacting risk factors for cardiometabolic disease. Further, potatoes contribute to total fruit and vegetable intake, thus enabling consumers to more closely align with the Dietary Guidelines recommendations.

As Moore explained, “Previously published evidence on potato consumption has been conflicting. For example, some find higher potato intakes to be positively associated with elevated blood pressure while others find the opposite. In observational studies, it is important to try to separate out a food like potatoes from other dietary components. If the individuals consuming more potatoes, for example, also consume more refined grains or have other unhealthy lifestyle habits, then the adverse effect of potatoes may actually be a result of other things associated with diet and lifestyle.”

One strength of the current study is that diet was assessed with detailed dietary records, thus allowing the investigators to determine cooking methods. In addition, dietary records provide a more accurate assessment of the intake of most foods and nutrients than the food frequency questionnaires that have been used in many other studies.

The results of this study support the need for future randomized controlled trials to investigate the effects of potatoes as part of a healthy diet (including potatoes cooked in different ways) on cardiometabolic disease risk. In the interim, these data add to the evidence supporting a role for potatoes as part of a healthy lifestyle.

Study Design, Strengths, and Limitations 

Data from 2,523 offspring of the Framingham Heart Study, 30 years of age and older, were included in this prospective cohort study that began in 1971.

  • Approximately 16,000 collective days of dietary records were collected from roughly 70% of participants during exams 3 (1983-87) and 5 (1991-95).
  • The consumption of potatoes (both white and sweet potatoes) was derived from total vegetable servings. For these analyses, each participant’s usual potato intake was estimated as the mean from all days of diet records and grouped as follows: total potato intake (<1, 1-<2, 2-<4, and ≥4 cup-equivalents/week, and fried or non-fried (<1, 1-<2, and ≥2 cup-equivalents/week).
  • Health outcome data were provided from regular examination visits.
  • Researchers assessed the impact of both total potato consumption as well as fried versus non-fried potato consumption on hypertension, T2DM/IFG, and dyslipidemia risk.
  • Researchers further assessed whether other diet and lifestyle factors modified the effects of fried and non-fried potato intakes on cardiometabolic risk.

In addition to the large sample size, the use of a prospective study design allowed for the assessment of large amounts of data from subjects in a free-living environment. For example, potato consumption was averaged over 8 years before the beginning of a 16-year follow-up. Furthermore, dietary intake was analyzed from an average of 6 days of dietary records, thus providing a more stable intake assessment. Further studies will need to assess more diverse populations, as this current sample of Caucasian adults is not broadly generalizable. Future studies will also benefit from consideration of cooking methods and by studying the specific effects of potatoes when consumed as part of a healthy diet.

This research was supported by the Alliance for Potato Research and Education (APRE). APRE had no influence on the study design, conduct, execution, or data analysis after approving the initial proposal for funding.

The article “Potato Consumption is not Associated with Cardiometabolic Health Outcomes in Framingham Offspring Study Adults” is published in the Journal of Nutritional Science (doi: 10.1017/jns.2022.65).

Journal: Journal of Nutritional Science

DOI: 10.1017/jns.2022.65

Article title: Potato Consumption is not Associated with Cardiometabolic Health Outcomes in Framingham Offspring Study Adults

Article publication date: 09/02/2022


JOURNAL

Journal of Nutritional Science

DOI

10.1017/jns.2022.65 

ARTICLE TITLE

Potato consumption is not associated with cardiometabolic health outcomes in Framingham Offspring Study adults

Read the Full Study Summary

New study illustrates that potato protein ingestion strongly increases muscle protein synthesis rates at rest and during recovery from exercise

The latest findings challenge outdated assumptions about the anabolic effects of plant-derived proteins

Peer-Reviewed Publication

THE ALLIANCE FOR POTATO RESEARCH AND EDUCATION (APRE)

Exercise enthusiasts have long presumed animal protein to be superior to plant-derived options for muscle protein synthesis due to its essential amino acid profile. While many plant proteins are deficient in one or more essential amino acids necessary for optimal muscle growth and repair, a new randomized controlled study published in Medicine & Science in Sports & Exercise shows that plant-derived proteins can still induce strong anabolic responses. Researchers at Maastricht University, The Netherlands, found that consuming 30 grams of potato-derived protein concentrate following resistance exercise strongly increased muscle protein synthesis rates to levels that did not differ from the response following the ingestion of an equivalent amount of milk protein concentrate.

“The anabolic response to exercise depends on the exercise stimulus and the postprandial increases in circulating amino acids,” said lead study investigator Luc J.C. van Loon, PhD, a professor of physiology of exercise and nutrition at Maastricht University Medical Centre. “In general, plant-derived proteins are considered to have lesser anabolic properties, due to their lower digestibility and incomplete amino acid profile. Our results show that ingestion of 30 g potato-derived protein will support muscle growth and repair at rest and during recovery from exercise.”  

The findings from van Loon’s research group demonstrate that potato-derived protein concentrate powder can be used to increase muscle protein synthesis rates both at rest and during post-exercise recovery in healthy, young men, at rates that do not differ from the ingestion of an equivalent amount of milk protein.

“The potato’s amino acid profile has no apparent deficiencies and ingestion of 30 g protein was shown to strongly stimulate muscle protein synthesis during recovery from exercise,” explained van Loon.

These study results are part of a growing body of literature that demonstrate the benefits of potatoes in physical activity and exercise recovery.1-3 As van Loon explained, “Although further dose-response studies in broader populations are undoubtedly necessary, these data seem to support the use of potato-derived protein concentrate as an effective means to support muscle conditioning.”

Study Design, Strengths, and Limitations 

Twenty-four young, healthy males between the ages of 20-28 years volunteered to participate in this randomized, double blind, parallel group study.

  • Participants completed resistance exercise on a seated knee-extension machine (randomized to complete with either their dominant or non-dominant leg) following a warm-up on a supine leg press machine.
  • Participants rested for 10 minutes following their exercise session. Blood samples were drawn, and muscle biopsies were taken from each leg.
  • Immediately after the biopsies, 12 participants ingested 30 grams potato-derived protein while the other 12 ingested an equivalent amount of milk-derived protein. 
  • Blood samples were collected over a 5-hour period following ingestion to determine blood amino acid, glucose, and insulin concentrations.
  • Second and third muscle biopsies were taken to determine muscle protein synthesis rates at rest and during recovery from exercise.

The strategic use of a randomized double-blind study design with a unilateral exercise protocol allowed for assessment of postprandial muscle protein synthesis in both exercised and non-exercised muscle. Further studies will need to assess dose-response relationships between smaller and larger doses of protein on muscle protein synthesis. Future studies will also benefit from assessing the effects of plant-derived protein concentrates on muscle conditioning after repeated bouts of exercise in larger and more diverse populations.

Nonetheless, the current data show “there is ample room for high quality plant-derived proteins in sports nutrition, such as protein from nutrient-dense sources like potatoes,” stated van Loon.

This research was supported by the Alliance for Potato Research and Education (APRE). APRE had no influence on the study design, conduct, execution, or data analysis after approving the initial proposal for funding.

The article “Potato Protein Ingestion Increases Muscle Protein Synthesis Rates at Rest and during Recovery from Exercise in Humans” is published in Medicine & Science in Sports & Exercise (10.1249/MSS.0000000000002937).

References

  1. Oikawa SY, Bahniwal R, Holloway TM, Lim C, McLeod JC, McGlory C, Baker SK, Phillips SM. Potato Protein Isolate Stimulates Muscle Protein Synthesis at Rest and with Resistance Exercise in Young Women. Nutrients. 2020 Apr 27;12(5):1235. doi: 10.3390/nu12051235.
  2. Flynn S, Rosales A, Hailes W, Ruby B. Males and Females Exhibit Similar Muscle Glycogen Recovery with Varied Recovery Food Sources. Eur J Appl Physiol. 2020. doi: 10.1007/s00421-020-04352-2
  3. Salvador AF, McKenna CF, Alamilla RA, et al. Potato Ingestion is as Effective as Carbohydrate Gels to Support Prolonged Cycling Performance. J Appl Physiol. 2019;127(6):1651-1659. doi: 10.1152/japplphysiol.00567.2019

DOI

10.1249/MSS.0000000000002937 

METHOD OF RESEARCH

Randomized controlled/clinical trial

SUBJECT OF RESEARCH

People

Read the Full Study Summary

New nutrient profiling tools confirm starchy vegetables deliver comparable nutritional value as non-starchy vegetables and whole fruit

Peer-Reviewed Publication

THE ALLIANCE FOR POTATO RESEARCH AND EDUCATION (APRE)

A new study recently published in Frontiers in Nutrition has challenged the tendency in nutrition research to separate starchy vegetables from their non-starchy counterparts and categorize them with foods delivering lower nutritional value.

Whole grains, legumes, non-starchy vegetables, and fresh fruit are typically considered to be higher quality carbohydrate foods, yet starchy vegetables, including white potatoes, are typically categorized in nutrition studies with sweets, candy, and soda, when researchers assess subjects’ food intake and associations with health outcomes. This new study used five separate indices to assess carbohydrate quality to determine if this categorization of starchy vegetables is an accurate reflection of the foods’ nutritional value.

Four of those carbohydrate quality indices (CQIs), based on carbohydrate to fiber and sugar ratios, had been developed and validated in 2021 by researchers at Tufts University. The fifth index, the new carbohydrate food quality scoring system (CFQS-4) recently developed by scientists working with the Quality Carbohydrate Coalition, also incorporated potassium and sodium. All five indices had been previously published.

The new study screened more than 2,400 carbohydrate-containing foods for carbohydrate quality.  Recognizing that carbohydrates are present in a great variety of plant-based foods, the study expanded the range of food groups to include refined and whole grains, snacks and sweets, but also starchy and non-starchy vegetables, legumes and whole fruit. Starchy vegetables had not been tested before using the new carbohydrate quality metrics.

“Starchy vegetables are often not even viewed as vegetables and are routinely removed from high-quality food categories in nutrition research. That view is now challenged by the new nutrient profiling methods” said lead author Adam Drewnowski, PhD, researcher at the Center for Public Health Nutrition at the University of Washington. “Now that we have formal measures of carbohydrate quality that we can agree on, it is time to put starchy vegetables back where they belong.  There is no need to demonize ‘bad’ vegetables when the American diet could do with more produce of all kinds.”

“I certainly hope that the Dietary Guidelines Advisory Committee take note as they design a healthy diet at an affordable cost,” Dr. Drewnowski added

The four CQIs and the CFQS-4 had been published before but had not been applied to evaluating carbohydrate quality of legumes, vegetables and fruit.  The five indices were based on specific rations of carbohydrate, fiber, free sugar, potassium and sodium. Whereas potassium is under-consumed, sodium is consumed to excess. Both nutrients are recognized as ‘nutrients of public health concern’ in the Dietary Guidelines for Americans.

Based on the four CQI scores, nearly half of the 210 starchy vegetable foods analyzed in the study met the CQI definitions for high-quality carbohydrates, which were defined as those with evidence-based cut-off values for fiber and free sugar. Meanwhile, extremely few snacks and sweets (1-5%), candy and desserts (0-5%) and refined grain foods (10-12%) could be considered high-quality, according to the same CQI measures.

Based on the more comprehensive CFQS-4 model, which also accounts for foods’ potassium and sodium content, starchy vegetables scored most closely to non-starchy vegetables and fruit versus sweets and soda.

“I hope that this simple application of existing carbohydrate quality metrics to a wide spectrum of carb-containing foods will show that starchy vegetables belong with the high-quality carbohydrate foods” said Drewnowski. “Our application of other nutrient profiling has previously shown that potatoes and beans led the pack in terms of nutrients per penny. This latest demonstration clearly shows that all vegetables should remain together when it comes to both research and dietary guidance.”

Study Design, Strengths, and Limitations

More than 2,400 carbohydrate foods in the USDA Food and Nutrient Database for Dietary Studies were evaluated using four previously published CQIs, and one more recently created carbohydrate food quality scoring system (CFQS-4).

Specifically, the various CQI composites were:

  • 10:1 Carbohydrate-to-Fiber model: at least 1 gram of fiber for every 10 grams of carbohydrate
  • 10:1:1 Carbohydrate-to-Fiber-to-Free Sugars model: at least 1 gram of fiber and no more than 1 gram of free sugar for every 10 grams of carbohydrate 
  • 10:1:2 Carbohydrate-to-Fiber-to-Free Sugars model: at least 1 gram of fiber and no more than 2 grams of free sugar for every 10 grams of carbohydrate
  • 10:1|2:1 Carbohydrate-to-Fiber and Sugar-to-Fiber model: at least 1 gram of fiber for every 10 grams of carbohydrate and fewer than 2 grams of sugar per 1 gram of fiber
  • The CFQS-4 model builds upon previous 10:1 and 10:1:1 ratios for fiber and free sugars relative to carbohydrate, but also assesses sodium (an over-consumed nutrient of concern) and potassium content (a shortfall nutrient of concern) according to the Dietary Guidelines for Americans.

Foods with at least 40% energy from carbohydrates per 100g dry weight were included in all analyses. The frequency and percentage of foods that met the CQI criteria were calculated for each food group. Carbohydrate quality scores were measured against the average energy densities of food groups and subgroups.

This study included a large, comprehensive data set using multiple nutrient profiling models. Further research to build upon these models, however, should continue to incorporate other vitamins and minerals in food quality assessments. Nonetheless, this study aligns with a broader, evolving body of literature showcasing the multi-dimensionality of carbohydrate foods and their role in human health. As Dr. Drewnowski explained, “Current efforts to inform dietary guidelines and regulatory frameworks would benefit from modern, comprehensive tools to define and assess carbohydrate food quality.”

This research was supported by the Alliance for Potato Research and Education (APRE) and by the Quality Carbohydrate Coalition (QCC), which is funded by Potatoes USA. Neither APRE nor Potatoes USA had an influence on the study design, conduct, execution, or data analysis after approving the initial proposal for funding. Dr. Adam Drewnowski is a member of the QCC-Scientific Advisory Council.

The article “Multiple metrics of carbohydrate quality place starchy vegetables alongside non-starchy vegetables, legumes, and whole fruit” is published in Frontiers in Nutrition (doi: 10.3389/fnut.2022.867378).


JOURNAL

Frontiers in Nutrition

DOI

10.3389/fnut.2022.867378 

Read the Full Study Summary

The glycemic index may be counterproductive to helping Americans adopt healthier diets

Newly published perspective examines the shortcomings of the glycemic index as a measure of carbohydrate food quality

Peer-Reviewed Publication

THE ALLIANCE FOR POTATO RESEARCH AND EDUCATION (APRE)

Today, many people struggle to make healthy food and beverage choices in line with the Dietary Guidelines for Americans (DGA). In fact, the average American under-consumes nutrient-dense fruits, vegetables, whole grains, beans and dairy foods – and more than half of American adults have at least one diet-related chronic disease.1 To improve overall diet quality, Jill Nicholls, PhD, asserts in a recently published perspective in Frontiers in Nutritionpeople need tools that are relevant, reliable and applicable – and evidence suggests the glycemic index (GI) falls short on all of the above.

“The GI is increasingly used and interpreted as a measure of overall carbohydrate food quality, with some proponents advocating for its broader adoption as a public health tool. However, the GI model doesn’t address nutrient density or translate well to healthy dietary patterns, and its narrow focus on just one dimension of carbohydrate-containing foods may divert public attention away from approaches to improving health that are accessible, affordable, culturally appropriate and environmentally sustainable,” stated Nicholls, owner of Food Context, LLC. “At best, it’s an incomplete gauge of carbohydrate food quality. At worst, it may be counterproductive to achieving the dietary recommendations set forth in the DGA.”

Intended for People with Type 1 Diabetes – Not the General Public

Developed in the 1980s as a blood glucose management tool for people with type 1 diabetes, the GI is a comparative measure of glycemic impact. The GI measures the ability of the available carbohydrate in a food to increase blood glucose. It is determined by measuring blood glucose after consuming 50 grams of carbohydrate from a single test food and normalizing to a comparable portion of a control food, typically pure glucose or white bread.2

Carbohydrate-containing foods are quite varied and make important contributions to dietary patterns, yet the GI measures only glucose response. It does not account for overall nutrient content, and research has shown it may not be an accurate predictor of overall diet quality. And because low-GI foods are not necessarily high in essential nutrients, over-reliance on GI values may lead to food choices that are inconsistent with current dietary guidelines. Energy-dense choices such as ice cream and candy bars, for instance, can have low GI values, while nutrient-dense choices that support healthy dietary patterns can also be high-GI foods, including carrots, potatoes and grains.

An Unreliable and Highly Individualized Measure of Glycemic Response

“The reliability of the GI has been scrutinized since its introduction more than 40 years ago, including critiques about methodology and questions about the relationship between a food’s GI value and true post-meal glycemic response,” said Nicholls.

Because GI values are calculated based on foods consumed in isolation and analyzed under standard laboratory conditions, their real-world application may be limited. “Under the GI model, fat, protein and fiber are treated as entirely independent variables, but that assumption is at odds with current views about our understanding of how eating patterns influence health based on all food and beverage contributions,” Nicholls explained.

Much of the research has demonstrated significant variability in both inter- and intra-individual glycemic responses to the same food. Thus, it remains unclear whether the GI is a property of foods or a characteristic of each unique individual consuming those foods. Emerging studies have found that glycemic responses are more similar within individuals than between them, and an array of factors in addition to meal composition can influence individual carbohydrate metabolism, including, meal timing, physical activity and sleep habits. 4

A Questionable Predictor of Health Outcomes

Research also indicates that the GI may not be the best carbohydrate food quality metric to assess diets and chronic disease prevention. In a landmark series of systematic reviews and meta-analyses, Reynolds et al. found that the association between the GI and risk of non-communicable diseases was low to very low compared to fiber or whole grains.5 Meanwhile, the dietary patterns emphasized in the DGA contain more whole grains and fiber-containing foods than Americans usually eat, along with higher amounts of fruits, vegetables, and dairy foods. These patterns are associated with lower risk for NCDs. Eating nutrient-dense whole foods as part of balanced meals during the day is an easy way to improve glycemic responses and improve diet quality without monitoring the GI of foods.

“The Mediterranean Diet is one example of a dietary pattern that has been associated with reduced disease risk; yet, not every food in a Mediterranean eating pattern is low GI,” Nicholls added. In addition, clinical trials have shown compelling evidence that high GI foods eaten within the context of high-quality dietary patterns can yield improvements in cardiovascular disease risk factors, and weight loss regimens may be less reliant on glycemic responses than expected.6-7

“Evidence increasingly suggests that it’s the total diet that counts. Improving the overall quality of an individual’s dietary patterns can have beneficial effects on a variety of diet-related chronic disease, but the effect of any single food choice is mediated by the other foods and beverages eaten, physical activity and other lifestyle choices. While the GI may illuminate some narrow insights, it also keeps many of these relevant variables in the dark.”

The article, “Perspective: The Glycemic Index Falls Short as a Carbohydrate Food Quality Indicator to Improve Diet Quality,” is published in Frontiers in Nutrition (https://doi.org/10.3389/fnut.2022.896333). Funding was provided by the Alliance for Potato Research and Education.

References:

1U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. [Internet]. Available from: https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf

2Wolever, T.M., Jenkins, D.J., Jenkins, A.L., & Josse, R.G. (1991). The glycemic index: methodology and clinical implications. The American journal of clinical nutrition, 54 5, 846-54

3Zazpe, I., Sánchez-Taínta, A., Santiago, S., De la Fuente-Arrillaga, C., Bes-Rastrollo, M., Martínez, J., & Martínez-González, M. (2014). Association between dietary carbohydrate intake quality and micronutrient intake adequacy in a Mediterranean cohort: The SUN (Seguimiento Universidad de Navarra) Project. British Journal of Nutrition, 111(11), 2000-2009. doi:10.1017/S0007114513004364

4Berry SE, Valdes AM, Drew DA, Asnicar F, Mazidi M, Wolf J, et al, Human postprandial responses to food and potential for precision nutrition. Nat Med. (2020) 26:964–73. doi: 10.1038/s41591-020-0934-0

5Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet. (2019) 393:434–45. doi: 10.1016/S0140-6736(18)31809-9

6Sacks FM, Carey VJ, Anderson CAM, Miller ER III, Copeland T, Charleston J, et al. Effects of high vs. low glycemic index of dietary carbohydrate on cardiovascular disease risk factors and insulin sensitivity: the OmniCarb randomized clinical trial. J Am Med Assoc. (2014) 312:2531–41. doi: 10.1001/jama.2014.16658

7Gardner CD, Trepanowski JF, Del Gobbo LC, Hauser ME, Rigdon J, Ioannidis JPA, et al. Effect of low-fat vs. low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: the DIETFITS randomized clinical trial. J Am Med Assoc. (2018) 319:667–79. doi: 10.1001/jama.2018.0245


DOI

10.3389/fnut.2022.896333 

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Clarifying carb confusion: experts propose evidence-based scoring system to assess the overall healthfulness of carb-containing foods

New ‘Carbohydrate Food Quality Score’ considers a comprehensive and practical approach, aligning with the Dietary Guidelines for Americans

Peer-Reviewed Publication

THE ALLIANCE FOR POTATO RESEARCH AND EDUCATION (APRE)

April 11, 2022 – The dietary value of carbohydrate foods (CF) has come under increased scrutiny in recent years. While so-called good-carb/bad-carb designations are hotly contested, standardized methods for assessing CF health quality currently do not exist. In a paper recently published in Nutrientsthe Quality Carbohydrate Coalition-Scientific Advisory Council (QCC-SAC) proposes a novel, innovative approach to quantifying CF quality: the Carbohydrate Food Quality Score (CFQS). Representing a significant step forward in the evolution of CF analysis, the new CFQS incorporates a food’s fiber-to-carbohydrate and free sugar-to-carbohydrate ratios, as previous metrics have done, in addition to evaluating its sodium, potassium and (as applicable) whole grain content, making the index better reflect the nutritional contribution of the entire CF.

“While long-standing evidence clearly establishes that carbohydrate-containing foods are essential to building healthy dietary patterns, people need better tools to identify higher quality choices that can be balanced in a healthy dietary pattern,” said Joanne Slavin, PhD, RD, University of Minnesota. “While fiber and sugar content have been the focus in previously proposed systems, and they’re important pieces of the puzzle, there needs to be more nuance in our recommendations given the breadth of foods and food groups that fall into the carb category.” Slavin is a member of the QCC-SAC, which was formed by Potatoes USA and other commodity group stakeholders that comprise the Coalition.

To provide a more complete appraisal of CF quality – and to reflect the most up-to-date dietary guidance – the new carbohydrate quality scoring system is the first of its kind to include an assessment of sodium, potassium and whole grain content in addition to sugar and fiber. These three components were added because CFs are predominant dietary sources of these nutrients. Sodium, like sugar, is consumed at levels above those recommended in current dietary guidance, and potassium and whole grains, like dietary fiber, are consumed at levels well below those recommended. By including all these components, this approach not only aligns with the recommendations of the 2020-2025 Dietary Guidelines for Americans (DGA), but also the World Health Organization, and roughly half of the food-based dietary guidelines from around the world.

“Other systems to define carb quality exist, and many rely heavily on the glycemic index; however, research increasingly shows GI has far too much inter-individual variability to offer meaningful real-world utility,” noted QCC-SAC member Siddhartha Angadi, PhD, University of Virginia. “A truly effective measure of carbohydrate food quality is one that is both accurate and practical. By capturing a broader set of dietary parameters with relevance to public health, the CFQS aims to offer relevant, real-world recommendations to potentially improve nutrient intake and public health.”

The new system builds upon previously validated measures of CF quality, namely ratios of carbohydrate to fiber (i.e., at least one gram of fiber for every 10 grams of carbohydrate) and carbohydrate to free sugar (i.e., less than one gram of free sugar for every 10 grams of carbohydrate). The addition of potassium, sodium and whole grains to the algorithm was further validated by demonstrating a high correlation with two other scientifically substantiated nutrient profiling systems: the Nutrient Rich Food (NRF9.3) index, an algorithm for assessing a food’s nutrient density, and Nutri-Score, a European model used to assess foods’ nutritional value.

“The high degree of agreement between the CFQS models and these other established metrics further support the efficacy of our approach,” explained Adam Drewnowski, PhD, University of Washington, a QCC-SAC member and creator of the NRF9.3 index. “We can say with great confidence that the CFQS is assessing the quality of carbohydrate foods in an accurate and meaningful way.”

The Carbohydrate Food Quality Score: How It Works

So far, two models have been developed using the new scoring system. One model, known as the CFQS-4, assigns a score of zero to four points to all carbohydrate-containing foods, which in this study were defined as solid foods with ≥ 40% energy from carbohydrate (as measured by 100g dry weight). The more advanced model, known as the CFQS-5, assigns a score of zero to five points, in which grain foods can score an extra point if their whole-grain content is ≥25%, which was selected as the cutoff value based on previous studies and current U.S. front-of-pack regulations.

In the CFQS-4 model:

  • 1 point is awarded if fiber is ≥10g/100g carb portion
  • 1 point if free sugar is <10g/100g carb portion
  • 1 point if sodium is <600mg/100g dry weight
  • 1 point if K >300mg/100g dry weight

In the CFQS-5 model for grain-based foods, one additional point is awarded for whole grain content:

  • 1 additional point if whole grains ≥25g/100g dry weight

“This system is already much more comprehensive than previously published metrics, but it’s also designed to continue evolving with the science,” said Drewnowski. “As new data become available, the CFQS models can expand to reflect other measures of carbohydrate quality, such as the food’s prebiotic or polyphenol composition, degree of processing or aspects of fortification or enrichment.”

This report builds on an earlier QCC-SAC publication from July 2021, which reviewed the current state of CF quality metrics and established initial guiding principles for developing a new scoring metric for determining CF quality. The latest report advances this work by introducing a more broadly applicable Carbohydrate Food Quality Score and comparing it to other measures of nutrient density.

As a next step, the researchers are preparing a paper demonstrating how the new scoring system can be applied to a variety of eating patterns.

“We need tools that help people apply nutrition science to an array of cultural dietary traditions, socioeconomic contexts and personal needs and preferences,” added QCC-SAC member Judith Rodriguez, PhD, RD, University of North Florida. “That’s the ultimate aim of this work: to develop a metric that can be applied to build healthy dietary patterns for everyone.”

#### 

The Quality Carbohydrate Coalition (QCC) is a multi-stakeholder engagement of commodity groups across the food industry. Guided by the work of its Scientific Advisory Council (SAC), this group aims to support a collaborative, scientific dialogue around the unique and diverse roles that carbohydrate-containing foods play in healthful eating.  The council is made up of six world-renowned experts in carbohydrate research, nutrient profiling, cultural competency and epidemiology: Adam Drewnowski, PhD; Julie Miller Jones, PhD, LN, CNS; Judith Rodriguez, PhD, RD; Joanne Slavin, PhD, RD; Siddhartha Angadi, PhD; and Yanni Papanikolaou, MPH.  Potatoes USA provides the funding to support the research being conducted by the SAC.

The article, “A New Carbohydrate Food Quality Score to Reflect Dietary Guidelines: An Expert Panel Report,” is published in Nutrients (doi: 10.3390/nu14071485). All QCC-SAC members were authors, supported by Kevin Comerford, PhD. Funding was provided by Potatoes USA.


JOURNAL

Nutrients

DOI

10.3390/nu14071485 

ARTICLE TITLE

A New Carbohydrate Food Quality Scoring System to Reflect Dietary Guidelines: An Expert Panel Report

ARTICLE PUBLICATION DATE

28-Mar-2022

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