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 [1].
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." [2]
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 [3]. 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 [4].
In 22,000 healthy men who had been observed for 12 years, supplementation with
vitamin A showed neither benefit nor harm [5].
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." [6].
Not even for infections is there any evidence that MVMS have
any protective effect on those most vulnerable, the elderly [7].
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.
Print
PDF