The (non-)sense of vitamin supplementation?
Almost one in two American adults is a regular user of vitamin and mineral supplements, either in the form of single- or multivitamin/mineral formulations (MVMS). It all adds up to a market of US$ 9 Billion annually, or one third of the total US supplements market. Does all the pill-popping help their users to achieve better health or longevity?
That's one question raised by Björn, one of the readers of my blog. Thanks, Björn, I wanted to write on this subject for some time. You just got me going on this a little earlier than I would have otherwise. And also thanks for the second question: Does the latest technology of delivering the drug (not to your house, but within your body to your organism's cells) via "nano-encapsulation" improve that health effect in any way? Let me try to answer these questions one by one.
When you talk about vitamins, you talk about essential micronutrients, for which the human organism has either no or only a very limited ability to produce (e.g. Vitamin D) on its own. If you want to group vitamins according to their solubility you'll find that they come in two flavors: water soluble and fat soluble. Of course, you could group them for any other biochemical characteristic, but grouping them according to their solubility makes immediate sense when you keep in mind that the fat soluble ones (A, D, E and K) can accumulate in your body's tissues, whereas the water soluble Vitamins typically can't. Whatever can accumulate, can also accumulate to the point where there is too much of it in a body's tissue. So, yes, too much of a good thing may turn into a not so good thing, as is the case for vitamins A and E for example. Or, too much of a good thing may just be flushed out of the body, as is the case with water-soluble vitamin C.
The supplement industry certainly does a good job convincing the public that supplementing one's diet with additional vitamin formulations is good for one's health. It's certainly good for the industry's bank accounts. In such cases it always pays to ask one simple question: Where is the evidence?
In a meta-analysis of randomized clinical trials (RCT, the gold standard of clinical research methodology), the authors investigated the effects of vitamins E and A on the risk of cardiovascular disease and death in altogether 220,000 patients . The effects? Zilch. The authors recommendation? The evidence does not support any recommendation for the use of Vitamins E and A. On the contrary, they found a slight increase in all-cause and cardiovascular disease mortality associated with vitamin A supplementation.
In another 2007 review on the subject, published in the American Journal of Clinical Nutrition, its author came to the same conclusion, stating that "Results to date are not compelling concerning a role for MVMs in preventing morbidity or mortality from cancer or CVD."  The two largest trials on Vitamin A and E supplementation in smokers, the Finnish Alpha-Tocopherol Beta-Carotene (ATBC Trial) and the US Carotene and Retinol Efficacy Trial (CARET) enrolled 29,000 and 18,000 smokers. In the Finnish trial, supplementation with Vitamin A increased the risk for lung cancers by 18% within a 5 to 8-year observation period . And the US trial was halted after 2 years for the same reason: a 28% increase in lung cancer risk, a 26% increase in risk for dying from cardiovascular disease . In 22,000 healthy men who had been observed for 12 years, supplementation with vitamin A showed neither benefit nor harm .
So where is the evidence for you to believe that buying Vitamin E and A supplements will make you healthier and live longer? Maybe I'm blinded by a perverse distrust of everything a sales man tells me, but I can't see it.
So, how about multi-vitamins? In the group of people with the highest take-up rate of multivitamins: post-menopausal women? Again, the authors of a study which pooled the data from the Women's Health Initiative trial and observational study cohorts, come to the same conclusion "the WHI CT and OS cohorts provide convincing evidence that multivitamin use has little or no influence on the risk of cancer or CVD in postmenopausal women." .
Not even for infections is there any evidence that MVMS have any protective effect on those most vulnerable, the elderly .
Of course, keeping all this in mind, the nagging question remains: would there be an effect if only the delivery of the drug in the human body was improved? After all, if vitamins are essential for survival, and if vitamin supplementation does not improve health, then there are several possible reasons for this observation. For instance, we might get enough vitamins from our food, and adding vitamins has simply no effect. Or, maybe we have vitamin deficiencies but the supplements are ineffective in delivering their vitamin loads.
Which brings us to Björn's second question: "Does nano-encapsulation improve the effect of MVMS?
And may I add my nagging question: Or is "nano-whatever" just a cool gimmick of the industry to push a market, which currently grows only moderately? In the next post (Monday 16. April) I'll try to answer this question. So, stay tuned.
1. Vivekananthan, D.P., et al., Use of antioxidant vitamins for the prevention of cardiovascular disease: meta-analysis of randomised trials. Lancet, 2003. 361(9374): p. 2017-23.
2. Prentice, R.L., Clinical trials and observational studies to assess the chronic disease benefits and risks of multivitamin-multimineral supplements. American Journal of Clinical Nutrition, 2007. 85(1): p. 308S-313S.
3. The Effect of Vitamin E and Beta Carotene on the Incidence of Lung Cancer and Other Cancers in Male Smokers. New England Journal of Medicine, 1994. 330(15): p. 1029-1035.
4. Omenn, G.S., et al., Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med, 1996. 334(18): p. 1150-5.
5. Hennekens, C.H., et al., Lack of Effect of Long-Term Supplementation with Beta Carotene on the Incidence of Malignant Neoplasms and Cardiovascular Disease. New England Journal of Medicine, 1996. 334(18): p. 1145-1149.
6. Neuhouser, M.L., et al., Multivitamin Use and Risk of Cancer and Cardiovascular Disease in the Women's Health Initiative Cohorts. Archives of Internal Medicine, 2009. 169(3): p. 294-304.
7. El-Kadiki, A. and A.J. Sutton, Role of multivitamins and mineral supplements in preventing infections in elderly people: systematic review and meta-analysis of randomised controlled trials. BMJ, 2005. 330(7496): p. 871.