The Easy-to-Swallow Story on Multivitamins
Last week, the European Journal of Clinical Nutrition published a paper reporting vitamin supplements significantly improve serum vitamin concentrations in patients after intestinal surgery. The capacity to absorb vitamins into the body from food or supplements is even greater in persons who have not undergone bypass surgery. Increasing vitamin intake, even from dietary supplements, can improve micronutrient status.
So why the persistence of articles demeaning vitamin supplements, apparently arising from a university press release on a study that never existed. The answer partially lies in scientific research methods. Until recently, it has been costly to assess vitamin status. Volunteers had to visit a clinical laboratory and have a sizable blood sample taken by venipuncture. Then, the blood sample needed to be sent to another laboratory for processing and analysis using sophisticated, labor-intensive tools. To reduce research costs, randomized controlled trials (RCTs) were designed using drug paradigms (placebo vs dietary supplement) to study health outcomes (heart disease, cancer incidence). The problem is nutrients are not drugs. There is not true placebo because everyone eats and has some level of nutritional adequacy. In the majority of studies, there was no attempt to assess vitamin status at baseline or during the RCT. What gets measured is compliance and healthy behaviors associated with willingness to participate in a nutritional RCT.
As Christopher Labos acknowledges, there are clear success stories of dietary supplementation. Folic acid supplementation helps prevent neural tube defects. Vitamin K supplementation helps prevent hemorrhagic disease in infants. Vitamin B12 helps resolve pernicious anemia. Iron supplementation is used to treat iron deficiency.
The US Preventive Services Task Force selected multivitamin/mineral RCTs. Unfortunately, most of these studies did not assess vitamin status. The 2 largest trials (almost 30,000 men) carried out for more than 10 years found a 7% reduced risk of cancer (SU.VI.MAX and Physicians’ Health Study II).
The Physicians’ Health Study II (PHS II) studied multivitamin supplement use and found reduced risk of total cancer in men with a baseline of cancer history who used multivitamins. PHS II followed a group of men who are leaner (BMI = 26) than most, very few current smokers (3.6%) and mostly former smokers (40.0%), and mostly using aspirin (77.4%). While cardiovascular risk was not affected by multivitamin supplementation, the reality is that the physicians who participated in PHS II are not representative of most US males, or even of most medical doctors. More recent analysis of PHS II finds greater multivitamin benefits in men consuming lower amounts of vitamin B12, total carotenoids, and vegetables.
The concern that dietary supplementation may increase total mortality in women is primarily associated with supplemental iron. Unfortunately, the vitamin status of these women is unknown.
According to the 2015 Dietary Guidelines Advisory Committee report, 8 nutrients (vitamins A, C, D, E, folate, calcium, magnesium, potassium and dietary fiber) are underconsumed by almost everybody. In addition, iron is a concern for adolescent and premenopausal females. Most people are not consuming enough of the omega-3 fatty acids eicospentaenoic acid (EPA) and docosahexaenoic acid (DHA) needed for brain and visual function. We also do not eat enough foods rich in lutein and zeaxanthin which are also needed to support our brain and vision.
Taking a multivitamin with approximately 100% of the DV for these nutrients is a nutritional insurance policy, one that most of us need.
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