Research Category: Glycemic Index

White Vegetables: Glycemia and Satiety

The objective of this review is to discuss the effect of white vegetable consumption on glycemia, satiety, and food intake. White vegetables is a term used to refer to vegetables that are white or near white in color and include potatoes, cauliflowers, turnips, onions, parsnips, white corn, kohlrabi, and mushrooms (technically fungi but generally considered a vegetable). They vary greatly in their contribution to the energy and nutrient content of the diet and glycemia and satiety. As with other foods, the glycemic effect of many white vegetables has been measured. The results illustrate that interpretation of the semiquantitative comparative ratings of white vegetables as derived by the glycemic index must be context dependent. As illustrated by using the potato as an example, the glycemic index of white vegetables can be misleading if not interpreted in the context of the overall contribution that the white vegetable makes to the carbohydrate and nutrient composition of the diet and their functionality in satiety and metabolic control within usual meals. It is concluded that application of the glycemic index in isolation to judge the role of white vegetables in the diet and, specifically in the case of potato as consumed in ad libitum meals, has led to premature and possibly counterproductive dietary guidance.

Potato Product Form Impacts In Vitro Starch Digestibility and Glucose Transport but Only Modestly Impacts 24h Blood Glucose Response in Humans

Potatoes are rich in phenolic compounds which have been reported to impact starch digestion and intestinal glucose transport in model systems through phenolic-starch interactions. While these effects are well documented for pigmented potatoes and in model systems, the relevance of phenolics to the glycemic properties of processed colorless potato-based foods under naturalistic conditions remains unclear. This study assessed impacts of processing on phenolic concentrations, resistant starch content and glycemic properties of Russet Burbank and Shepody potatoes. Product forms included French fries, shredded (hash browns) and diced (home fries) produced through commercial processing as well as parallel in-home techniques. Commercial products had significantly higher concentrations of resistant starch (p < 0.05, 1.48-6.57 vs. 1.23-2.22 g/100 fresh weight, FW) and resistant starch/total starch ratio (5.42-18.3 % vs. 3.58-7.62 %) compared to freshly prepared counterparts, while statistically lower total caffeoylquinic acid content (2.94-10.9 vs. 11.5-25.2 mg/100 FW). Glucose release and intestinal transport assessed using an in vitro digestion/Caco-2 cell monolayers model demonstrated a reduction in d7-glucose intestinal transport from commercially processed products relative to fresh prepared counterparts (p < 0.05, 31.3-61.2 % vs. 79.3-110 % at 60 min). Commercial Russet Burbank potato products including French fries, home fries and hash browns were then selected for clinical assessment of glycemic response and appetite rating by 23 participants (11 male and 12 female). The three products presented a subtle but discernable ascending trend (French fry ≥ home fry ≥ hash browns) for incremental area under the curve (IAUC, 95.2 ± 12 vs. 105 ± 10 vs. 107 ± 14 mM•min, p < 0.05) at 2 h post breakfast and for appetite rating (45.2 ± 6.3 vs. 52.4 ± 4.1 vs. 57.7 ± 7.2 for hunger) at 4 h post breakfast with no significant difference from the control (whole wheat pancake). These results suggest that potato phenolics have only a modest influence on acute glycemic responses.