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World J Diabetes. Feb 15, 2014; 5(1): 1-13
Published online Feb 15, 2014. doi: 10.4239/wjd.v5.i1.1
Excess vitamin intake: An unrecognized risk factor for obesity
Shi-Sheng Zhou, Yiming Zhou
Shi-Sheng Zhou, Institute of Basic Medical Sciences, Medical College, Dalian University, Dalian 116622, Liaoning Province, China
Yiming Zhou, Division of Cell Signaling, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan
Author contributions: Both authors contributed to this paper.
Correspondence to: Shi-Sheng Zhou, MD, PhD, Institute of Basic Medical Sciences, Medical College, Dalian University, University Street No. 10, Dalian 116622, Liaoning Province, China. zhouss@ymail.com
Telephone: +86-411-87402740 Fax: +86-411-87402053
Received: October 16, 2013
Revised: December 7, 2013
Accepted: December 17, 2013
Published online: February 15, 2014

Over the past few decades, food fortification and infant formula supplementation with high levels of vitamins have led to a sharp increase in vitamin intake among infants, children and adults. This is followed by a sharp increase in the prevalence of obesity and related diseases, with significant disparities among countries and different groups within a country. It has long been known that B vitamins at doses below their toxicity threshold strongly promote body fat gain. Studies have demonstrated that formulas, which have very high levels of vitamins, significantly promote infant weight gain, especially fat mass gain, a known risk factor for children developing obesity. Furthermore, ecological studies have shown that increased B vitamin consumption is strongly correlated with the prevalence of obesity and diabetes. We therefore hypothesize that excess vitamins may play a causal role in the increased prevalence of obesity. This review will discuss: (1) the causes of increased vitamin intake; (2) the non-monotonic effect of excess vitamin intake on weight and fat gain; and (3) the role of vitamin fortification in obesity disparities among countries and different groups within a country.

Keywords: Vitamin fortification, Refined grain, Infant formula, Obesity, Diabetes, Insulin resistance, Oxidative stress, Glycemic index, Formula feeding, Epigenetic

Core tip: B vitamins are a known fat gain promoting factor. Food fortification-induced high vitamin consumption is followed by a rapid increase in obesity prevalence. Why is the fat gain effect of B vitamins neglected in obesity studies? Why does obesity prevalence vary from country to country? Why are the poor in developed countries but the rich in developing countries at high risk of obesity? Why is obesity prevalence higher in blacks than whites in the United States? Why does formula feeding (which is associated with high energy expenditure) increase the risk for obesity? Why is physical inactivity associated with increased obesity risk? This paper reviews the role of excess vitamins in obesity and proposes a unified answer to these questions.