Home / Resources / Articles / Excess B Vitamins May Be Linked to Obesity

Excess B Vitamins May Be Linked to Obesity

Mar 20, 2014

New evidence suggests that increased intake of certain vitamins, including B vitamins, may play a role in the increased prevalence of obesity in recent years….

Researchers evaluated the causes of increased vitamin intake, the effects of excess vitamin intake on weight and fat gain, and the role of vitamin fortification in obesity disparities among different countries and even different groups within a country.


The prevalence of obesity has increased drastically since the 1970’s and 1980’s, particularly in developed countries. This is thought to be due to a change in the global food system that occurred during this time, specifically an increase in the vitamin content in foods of many developed countries as a result of changes in the laws and regulations in regards to food fortification. This has led to an increase in consumption of B vitamins in particular, which are known to promote fat synthesis. A trend towards a more meat-based diet has also occurred in developing countries, increasing the amount of vitamins ingested from animal sources, nicotinamide in particular. Cereals are one of the top sources of many vitamins since food fortification standards were updated in the 70’s, with less than a quarter pound of cereal providing the daily requirements for an average adult. Infant formulas also have a high amount of vitamin supplementation, with some formulas providing up to 20x the amount of vitamins found in human breast milk. Overall, the daily consumption of vitamin B1, B2, and niacin in the United States has doubled since the early 1900’s, providing today’s consumers with much higher amounts that the estimated average requirement.

Countries vary in their fortification policies, leading to variations in consumption among different countries. Obesity is seen to be more prevalent in those of low socioeconomic status in developed countries and in those of high socioeconomic status in developing countries. Also, in developing countries, those who live in more urban areas are more likely to have access to fortified foods, whereas in developed countries, more people of lower socioeconomic status consume fortified foods because of their cheaper cost. Because B vitamins are water-soluble, people who do a lot of physical work or live in hot climates where they sweat a lot are more likely to eliminate these vitamins through perspiration, and are therefore at less risk of accumulating high amounts. These concepts are supported by data showing that activity rates have been decreasing since the early 1900’s due to increased urbanization, mechanization, etc. and obesity rates did not begin to increase as substantially until the 1970’s when food fortification standards increased.

Vitamins are thought to have several mechanisms by which they induce weight gain. Because they act as coenzymes or as parts of enzymes in certain chemical reactions, excess vitamins can affect the degradation of neurotransmitters, cause increased fat synthesis, insulin resistance, and induce epigenetic changes. Frequent consumption of foods fortified with B vitamins is thought to be associated with type 2 diabetes as well, due to a possible increased burden on pancreatic β cells. This idea is supported by a sharp increase in prevalence of diabetes after both the initiation of food fortification and the update of fortification standards.

Studies have observed that further enriching foods and formulas with vitamins often causes less weight gain when compared to the current levels found in dietary products. This suggests that the amount of vitamins currently found in fortified food and formulas is the amount at which the weight-gain effect is saturated. Higher doses may actually cause weight loss due to toxic effects such as hepatotoxicity and oxidative tissue damage. Consumers should be cautious of foods fortified with vitamins as their consumption causes sustained high vitamin intake. Now that many fresh fruits and vegetables can be obtained year round, seasonal vitamin intake variations are not as common and may be reason for the standards of vitamin fortification to be reviewed and modified.

Practice Pearls:
  • Prevalence of obesity has been seen to increase in areas following initiation of food fortification and supplementation.
  • Obesity is more common in lower socioeconomic groups of developed countries and in higher socioeconomic groups of developing countries, both of which consume greater quantities of food fortified with vitamins.
  • Maximum weight gain with these vitamins is often observed at the levels present in fortified foods. Higher, more toxic levels may actually offset weight gain due to toxic effects such as hepatotoxicity and oxidative tissue damage.

Zhou SS, Zhou Yiming. "Excess vitamin intake: An unrecognized risk factor for obesity" World Journal of Diabetes. 2014; 5(1):1-13.