Nutritional Supplements That Lower Glucose Levels

When considering nutritional supplements to lower glucose levels, one need to keep a number of issues in mind:

   • There is limited information supporting the glucose-lowering effect of many supplements. Sometimes there are just a few anecdotal reports rather than carefully performed scientific studies. What scientific studies there are, on closer inspection, have major flaws. The reason there are no large clinical studies for supplements is that these studies are very expensive to do. In some cases, the evidence that a particular chemical may have a role in glucose control is based on experiments in animals with a severe deficiency of the chemical. But this type of deficiency may occur only infrequently in humans. For example, chromium deficiency in rats causes insulin resistance, but it is difficult to show that degree of deficiency in humans consuming a normal diet, and so the relevance to human diabetes is unclear.

• Since nutritional supplements are not regulated in the same manner as pharmaceutical medicines, supplements may vary in terms of potency.

• Just because a compound is not regulated and is natural does not make it safe—there could be serious side effects, and the supplement could also affect the metabolism of other drugs that are taken at the same time.

Here some of the more popular supplements.

CINNAMON

In a laboratory cell culture, extracts of cinnamon have been shown to enhance the action of insulin. In 2003, the journal Diabetes Care published a study that reported that cinnamon extract lowered fasting glucose, triglycerides, and LDL cholesterol in thirty patients with type 2 diabetes. This study got a lot of attention in the media, and many people with diabetes wonder if cinnamon would help their diabetes. However, a smaller study published in The Journal of Nutrition in 2006 with twelve subjects taking cinnamon extract did not show any benefit. In both studies the patients were also on other diabetes medicine. In the 2003 study they were all on sulfonylureas, whereas in the 2006 study they were on sulfonylureas with or without metformin or metformin or thiazolidinediones with or without metformin or a reduced-calorie diet. It is possible that this difference may explain the lack of response in the second study.

CHROMIUM

When rats are given a diet deficient in chromium, they have higher glucose levels. Similarly, humans who are on intravenous nutrition (total parenteral nutrition), if they are not given chromium supplements, have higher glucose levels and insulin resistance. It has not been shown that people with diabetes have chromium defi ­ciency, but when chromium picolinate has been given to people with diabetes, a number of studies have shown a benefit. For example, in a study published in the journal Diabetes Care in 2006, seventeen patients with type 2 diabetes on sulfonyl­ureas who were given 1,000 micrograms of chromium had an improvement in glu­cose control and insulin sensitivity. This dose is much higher than the recommended daily dose, which is 20 to 35 micrograms daily. It appears to be fairly safe at the high dose, although there have been two cases of kidney problems and one case of liver damage reported. A longer-duration study with a larger number of subjects is needed to find out if chromium supplements are beneficial for people with diabetes. An important question is whether the supplement adds much for patients who already may be on several drugs for their diabetes.

SELENIUM

The trace element selenium is important in the activity of a number proteins in the body—these are known as selenoproteins. Glutathione peroxidases and cellular antioxidants are selenoproteins, and so selenium’s antioxidant properties have been a focus of clinical studies. So far, however, there are no studies showing that sele­nium supplementation is beneficial in people with diabetes.

PANAX QUINQUEFOLIUS(AMERICAN GINSENG)

Several small studies reported an improvement in fasting glucose and HbA1c with 3 grams of American ginseng. The studies are of limited duration (eight weeks). Reported side effects of American ginseng include insomnia, high blood pressure, and anxiety.