• More data on multivitamins

    I wrote last year about a study that showed that multivitamins appeared to lower your risk of cancer. Later, I wrote about how they didn’t appear to reduce your risk for cardiovascular disease, though. A research letter in the latest issue of JAMA Internal Medicine furthers this debate with some amazing 26-year follow-up data on an RCT conducted in China for 6 years in a undernourished population:

    Although substantial numbers of people worldwide take multivitamin supplements, including an estimated 40% or more of US adults, their effectiveness remains unclear. Recent reports from the Physicians’ Health Study (PHS) II, a randomized trial of daily multivitamins, found fewer total cancers in multivitamin recipients but no effect on overall or cause-specific mortality1- 2 in a Western population that was well nourished. However, few multivitamin trials have been conducted in undernourished populations where the potential for benefit is most likely.

    In 1985, we initiated the Linxian Dysplasia Nutrition Intervention Trial (NIT) to evaluate the effect of multivitamin supplements on cancer incidence and mortality in Linxian, China, a region with extremely high rates of esophageal and gastric cardia cancer and multiple vitamin and mineral deficiencies. Individuals with a previous cytological diagnosis of esophageal squamous dysplasia were randomized to receive multivitamin supplementation or placebo for 6 years.3 Results after the 6-year intervention period showed no statistically significant benefit on mortality.4 However, an additional 20 years of active follow-up after cessation of the intervention gave us the opportunity to examine the long-term effects of supplementation.

    This report updates the results of the Linxian Dysplasia NIT after 26 years of follow-up to provide informative data on the effect of multivitamin supplementation on mortality in an undernourished population. Our findings should be helpful for clinical practice and public health recommendations.

    This was a study of 3318 people between the ages of 40 and 69 years. Six years of MVI in this population showed no improvements in mortality. This 26-year follow-up data also showed no improvements.

    Let’s own one thing right up front. This is not a completely generalizable to a healthy population in the US, obviously. The people were undernorished, and had a previous diagnosis of esophageal squamous dysplasia. But in the interest of using all data, these people did not see a difference overall in mortality.

    I imagine this will move some people’s point estimate of the cost-effectiveness of MVIs. I think my prior conclusion still holds for me:

    Multivitamins are cheap. You can buy them by the barrel at Costco. There are few harms or side effects. And, unlike many of the things I often roll my eyes at, they appear to really reduce the risk of cancer. Plus, you get the nutritional benefits. I’ve been lazy about taking one for a while, but I think I may reconsider.

    @aaronecarroll

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    • Interesting that they didn’t see an effect in an undernourished population with previous dysplasia. Maybe the study is a bit underpowered since the effect of multivitamins seems to be small (if there is one). This study had 3318 participants, while the physician health study II had over 14000 participants.

    • I have read that substantial improvements in the economic position of the PRC over the last generation has led to good improvements in the diet in Linxian resulting in the placebo group getting the benefits of vitamin enrichement just like the experimental group.

    • I think it is a grave mistake to treat all vitamins made anywhere as the same. The large study on cardiovascular effects was using Centrum, a junk vitamin that does not even get absorbed. I don’t think a drug study would be accepted if the drug being checked was chosen only for being the cheapest or most readily available. why is it okay to do this for vitamins?

      • Well, don’t leave us in suspense: if Centrum is junk, what multivitamins *should* we be taking?

    • Oh, and let’s not hurry to deny the pleasure of Barney and Fred and the stone age sugar creatures which when we ate them made our parents feel that they had done the right thing and we too, the right thing for them. Harmless, surely, oh my.

      • I would think that chewable vitamins would be better than non-chewable ones, simply by virtue of more surface area leading to more absorption.

        But that begs the question about whether they’re useful in the first place.