Q. What should I take to help prevent the recurrent colds I get in the winter?
There are many strategies to help prevent recurrent colds and flu in the winter. Keeping your immune system strong is at the core of all of them. One botanical medicine you might want to think about is American ginseng (Panax quinquefolium)—one of the herbal immune modulators and stimulators that I suggest for patients with chronic respiratory infections.
A. Recent evidence suggests that taking a specific American ginseng extract called CVT-E002, an aqueous extract containing mainly oligosaccharides, can decrease the risk of a cold or flu and reduce the severity and duration of symptoms when infections do occur. CVT-E002 is patented and available over the counter as COLD-fX. There have been two new randomized, double-blind, placebo-controlled studies that both suggested a positive effect using 200 mg of the extract twice daily. One study reported an overall 89 percent relative risk reduction of acute respiratory infection in the CVT-E002 group,1 while in the second study researchers reported a modest difference of 12.8 percent in the number of colds reported in the ginseng vs. the placebo group.2
Q. My nutritionist told me I should be careful not to get too much calcium in my diet because it may increase my risk of prostate cancer. Why is this?
A. It's the old adage come to life: Too much of even a good thing may be bad. Some epidemiological studies have shown that high calcium or dairy product consumption is associated with an increased risk for prostate cancer. Specifically, higher milk intake consistently has been associated with increased risk, especially for advanced prostate cancer. Other studies implicate calcium itself.
A recent meta-analysis examined associations between calcium intakes, dairy products and the risk of prostate cancer. Results showed that men with the highest intake of calcium and dairy products were more likely to develop prostate cancer than men with the lowest intake, with a slightly higher risk for calcium. In both cases the increased risk was small.3 The reason for this may be that a high calcium intake lowers vitamin D levels. Because vitamin D has been shown as an important cell regulator and may be important in cell differentiation and cancer activity, lowering its levels could increase cancer risk.
How much is too much? One study found calcium intakes exceeding 1,500 mg per day are associated with a higher risk of advanced and fatal prostate cancer.4 Of course, calcium is important in many ways, from osteoporosis to colon cancer prevention, so too little puts a person at risk as well. Bottom line: I don't think it's advisable for men to consume more than 1,500 mg calcium per day from food and supplements combined, and they should make sure they are getting vitamin D, either in supplemental form or as sunlight, at about 750 to 1,000 IUs daily.
Q. I've heard there is an herb that when taken with food may lower a food's glycemic index. What is this?
A. You may be thinking of Salacia (Salacia oblonga). Salacia has a long tradition of use in Ayurvedic medicine. One possible action is as an alpha-glucosidase inhibitor (similar to some oral diabetes drugs), which impedes the body's absorption of carbohydrates from the gut. By so doing it decreases the rise in blood sugar.
In a recent study of healthy people without diabetes, researchers gave participants the herb in a shake containing a set amount of calories, carbohydrates, proteins and fat, and found that it had a minimizing effect on blood-sugar rise. There was a similar reduction in blood levels of insulin—another positive sign because elevated insulin is also a problem in diabetes. The researchers found that the drink with the largest Salacia oblonga dose (1,000 mg) cut the participants' post-shake blood-sugar rise by about 25 percent compared with sugar levels after an identical beverage without the herb.5,6 While Salacia oblonga's ability to slow post-meal sugar absorption in people with diabetes has not been tested, these studies are clearly suggesting a positive response. What's attractive about this herbal extract is that it seems to be easily incorporated into a food or beverage, which makes it quite convenient. In addition, animal and in vitro studies seem to show that the herb has a good safety profile.7,8
1. McElhaney JE, et al. A placebo-controlled trial of a proprietary extract of North American ginseng (CVT-E002) to prevent acute respiratory illness in institutionalized older adults. J Am Geriatr Soc, 2004;52(1):3-9.
2. Predy GN, et al. Efficacy of an extract of North American ginseng containing poly-furanosyl-pyranosyl-saccharides for preventing upper respiratory tract infections: a randomized controlled trial. CMAJ 2005, 173(9):1043-8.
3. Gao X, et al. Prospective studies of dairy product and calcium intakes and prostate cancer risk: a meta-analysis. J Natl Cancer Inst 2005;97(23):1768-77.
4. Giovannucci E, et al. A prospective study of calcium intake and incident and fatal prostate cancer. Cancer Epidemiol Biomarkers Prev, 2006;15(2): 203-10.
5. Collene AL, et al. Effects of a nutritional supplement containing Salacia oblonga extract and insulinogenic amino acids on postprandial glycemia, insulinemia, and breath hydrogen responses in healthy adults. Nutrition, 2005;21(7-8):848-54.
6. Heacock PM, et al. Effects of a medical food containing an herbal alpha-glucosidase inhibitor on postprandial glycemia and insulinemia in healthy adults. J Am Diet Assoc 2005;105(1):65-71.
7. Wolf BW and Weisbrode SE. Safety evaluation of an extract from Salacia oblonga. Food Chem Toxicol 2003;41(6):867-74.
8. Flammang AM, et al. Genotoxicity testing of a Salacia oblonga extract. Food Chem Toxicol 2006;44(11):1868-74.
Natural Foods Merchandiser volume XXVII/number 12/p. 40