The term vitamin is derived from the words vital and amine, because vitamins are required for life and were originally thought to be amines. And it’s not just vitamins D and E. The Physicians’ Health Study also looked into vitamin C and a one-a-day multivitamin and found the same results: no impacts on the risk of cancer mortality or the incidence of cardiovascular disease Of course there are exceptions — folic acid is generally a good idea for pregnant women — but the data increasingly suggests that most people simply do not benefit from supplements.
Recent studies suggest that the results of a vitamin D deficiency may be worsened by high supplemental intake of vitamin A. These studies reveal that when blood levels of vitamin D fall below 50 nanomoles per liter, higher supplemental intake of vitamin A can worsen problems related to this vitamin D deficiency, like bone health.
The Reference Nutrient Intake (RNI) measure used in the UK is calculated from studies of the physiological requirements of healthy people, but because these studies are subject to wide interpretation, the RNI value for a nutrient can vary from country to country.
And while children and younger adults are likely to get the B12 they need from food—it’s in meat and animal products including chicken, fish, dairy, and eggs —B12 is more poorly absorbed as the body ages, typically starting around 50 because that’s when stomach acid levels deplete (watch out for these 9 signs you’re not getting enough vitamin B12 ).
Once growth and development are completed, vitamins remain essential nutrients for the healthy maintenance of the cells, tissues, and organs that make up a multicellular organism; they also enable a multicellular life form to efficiently use chemical energy provided by food it eats, and to help process the proteins, carbohydrates, and fats required for cellular respiration 4.