Controversies in Science: A Tempest in a Teapot?
The American Society for Nutrition held its Advances & Controversies in Clinical Nutrition conference. It began with an exciting discussion around the benefits of dietary supplementation. If you are interested in another summary, see ASN student blog by Sheela Sinharoy.
Dr Johanna Dwyer, Tufts University and NIH Office of Dietary Supplements, reviewed data NHANES dietary intake data. She emphasized that nationally representative data, NHANES, finds many Americans not consuming recommended micronutrient intakes from the foods we eat (see Keast et al, 2013 and Fulgoni et al, 2011).
Dr Joel Mason, Tufts University, an expert in folic acid metabolism, questioned whether excess micronutrient intake, eg folic acid, vitamin E, selenium, may be detrimental. He reviewed cancer data prior to and subsequent to mandatory food fortification with folic acid. While systematic reviews of increased intake through food and supplement intake can be found, the evidence is mixed. A 2013 meta-analysis found no effect of folic acid supplementation on cancer risk – total, colorectal, prostate, lung, breast or hematologic malignancy.
Based on meta-analyses of supplement use, Dr Eliseo Guallar, Johns Hopkins University, reiterated a position published in 2013 that supplement use provides little benefit. Dr Balz Frei, Linus Pauling Institute, countered Dr Guallar with arguments that the majority of Americans do not consume recommended nutrient intakes. Because so many are not ‘well nourished’, Dr Frei claimed supplements could be helpful, especially as the cost is so low. Moreover, it should not be forgotten that multivitamin supplementation has been shown to reduce cancer incidence by 8%.
Clearly, measurements of nutritional status are needed in the field of nutrition to properly assess the health impact of nutritional supplementation. Using randomized controlled trials to assess supplementation (placebo vs nutrient) without measuring nutritional status is equivalent to assessing the impact of physical activity by randomizing people to receive pedometers (vs none) and not bothering to measure physical activity (number of steps recorded daily).
Better nutrition in persons not consuming recommended amounts can affect health. Pharmacologic nutrient intakes may affect health; this is the basis of niacin prescriptions in hypercholesterolemic individuals and omega-3 prescriptions in hypertriglyceridemic individuals. However, the practice of testing supplements (yes vs no) in physicians with lower risk of mortality than their peers does not produce results which are relevant to the general population.
When food-based nutrient intake doesn’t meet recommended levels, a daily multivitamin and mineral supplement can augment food intake. Multivitamin and mineral supplements are safe. They are practical. What is the controversy?
Keast DR, Fulgoni VL, Nicklas TA, O’Neil CE. Food sources of energy and nutrients among children in the United States: National Health and Nutrition Examination Survey 2003-2006. 2013 Nutrients doi:10.3390/nu5010283
Fulgoni VL, Keast DR, Bailey RL, Dwyer J. Foods, fortificants, and supplements: where do Americans get their nutrients? 2011 J Nutr doi: 10.3945/jn.111.142257
Qin X, Cui Y, Shen L, Sun N, Zhang Y, Li J, Xu X, Wang B, Xu X, Huo Y, Wang X. Folic acid supplementation and cancer risk: a meta-analysis of randomized clinical trials. 2013 Int J Cancer doi: 10.1002/ijc.28038
Gaziano JM, Glynn RJ, Christen WG, Kurth T, Belanger C, MacFadyen J, Bubes V, Manson JE, Sesso HD, Buring JE. Vitamins E and C in the prevention of prostate and total cancer in men: the Physicians' Health Study II randomized controlled trial. JAMA. 2009 Jan 7;301(1):52-62. doi: 10.1001/jama.2008.862
Sesso HD, Gaziano JM, VanDenburgh M, Hennekens CH, Glynn RJ, Buring JE. Comparison of baseline characteristics and mortality experience of participants and nonparticipants in a randomized clinical trial: the Physicians’ Health Study. 2002 Control Clin Trial 23:686-702