The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 8 No.
2 • April 2005
Slowing the Digestion of Carbohydrates for Better Blood Sugar Control and Possibly Longer Life
There are practical methods to slow the digestion of carbohydrates and the release of glucose. One way is to eat high-amylose carbohydrates, such as high-amylose starches, which are digested slowly. However, most carbohydrates, including those from whole grains, are composed largely of amylopectin carbohydrates, which are quickly broken down into glucose. Adequate amounts of vinegar eaten with food also slow down gastric emptying, thus slowing digestion. Another way to slow the digestion of carbohydrates is to eat foods that contain components that inhibit the enzyme alpha-glucosidase, which carries out the final step in the digestive process of carbohydrates. Drugs used for inhibiting this enzyme as a treatment for postprandial (after eating) hyperglycemia include acarbose, miglitol, and voglibose.
Two papers in a recent issue of The Journal of Agricultural and Food Chemistry identify some food-derived alpha-glucosidase inhibitors in in vitro tests. The first paper identifies a component of cumin seeds, cuminaldehyde, that potently inhibits alpha-glucosidase. The IC50 (quantity that reduces enzyme activity by 50%) is 0.00085 mg/ml for aldose reductase (enzyme that converts glucose to sorbitol—the polyol pathway—a source of serious hyperosmotic stress in diabetics) and 0.5 mg/ml for alpha-glucosidase.
A second paper reports testing a number of polyphenol-rich extracts of soft fruits for their ability to inhibit alpha-amylase (the first enzyme involved in carbohydrate metabolism, found in the mouth as well as in the gut) and alpha-glucosidase. The authors note that, in earlier studies by other scientists, “Polyphenolic extracts from a number of plants were found to be effective inhibitors of intestinal alpha-glucosidase activity with Ki values in the same range as synthetic inhibitors (acarbose and voglibose) already being used therapeutically to control non-insulin-dependent diabetes mellitus (NIDDM).” In their new study, the authors report that strawberry and raspberry extracts were more effective alpha-amylase inhibitors than blueberry and blackcurrant extracts. Alpha-glucosidase was more readily inhibited by blueberry and blackcurrant extracts. The extent of effectiveness in inhibiting alpha-glucosidase was related to the content of anthocyanins (anthocyanins are highly colored substances, usually blue or purple). The extracts most effective in inhibiting alpha-amylase contained larger amounts of tannins; other plant extracts with high tannin content, such as red grape, red wine, and green tea, were also effective inhibitors. In rats, intestinal alpha-glucosidase was also inhibited by the fruit extracts in the order of blueberry and blackcurrant, strawberry, raspberry, and red cabbage.
In the first paper, the authors note that “It has been reported that alpha-glucosidase inhibitors usually do not alter the total amount of carbohydrate absorbed and, therefore, do not cause any net nutritional caloric loss, although they slow carbohydrate digestion.” However, it has been clear for many years that in order to slow aging, it is important to reduce blood glucose and insulin levels, as well as insulin signaling (as occurs in calorically restricted rodents). For this purpose, these plants and their extracts may be of great value.
- Lee. Cuminaldehyde: aldose reductase and alpha-glucosidase inhibitor derived from Cuminum cyminum L. seeds. J Agric Food Chem 53:2446-50 (2005).
- McDougall et al. Different polyphenol components of soft fruits inhibit alpha-amylase and alpha-glucosidase. J Agric Food Chem 53:2760-6 (2005).