Two teams of researchers from Canada and US have challenged the Recommended Dietary Allowance (RDA) for vitamin D as established by US’s National Academy of Sciences (NAS) and the Institute of Medicine (IOM) stating that the current recommendation is ten times lower than what we actually need.
Currently RDA for vitamin D established by the IOM is 600 international units per day until we reach 70 years of age, and 800 IU per day thereafter; however, a Canadian research team reviewed 10 studies the IOM used to arrive at their RDA and their calculations revealed that 600 IU of vitamin D per day puts only half of the amount that they had assumed in the blood.
This means that 97.5 per cent of individuals will have serum 25 values of vitamin D above 26.8 nmol/L rather than above 50 nmol/L as the IOM had thought. The study claims that for anyone to get a serum 25 value of vitamin D of at least 50 nmol/L, that person could need up to 8895 IU per day.
“The error has broad implications for public health regarding disease prevention and achieving the stated goal of ensuring that the whole population has enough vitamin D to maintain bone health,” says Dr. Cederic Garland, an adjunct professor at University of California, San Diego.
The findings of the Canadian team were echoed by Dr. Garland’s team; however, they have suggested a more conservative RDA for vitamin D at 7,000 IU/day.
In a letter, Dr. Garland and his colleagues urged the NAS-IOM and all other public health authorities responsible for transmitting accurate nutritional information to the public to designate 7,000 IU/day as the RDA from all sources. The researchers also note that their recommendation is well below the 10,000 IU currently considered safe by the IOM for teenagers and adults.
There are two versions of the vitamin, vitamin D2 (aka ergocalciferol) and vitamin D3 (aka cholecalciferol). The primary source of vitamin D3 are fatty fish including salmon, tuna, sardines, and cod liver oil. The body is also capable of syntheising vitamin D3 in the skin upon sun exposure. Some other established sources of vitamin D are cereals, cheese and milk.
Vitamin D plays an important role in maintaining health of skin, bones and heart and its deficiency results into various problems including skin pigmentation, and rickets.
Both the study and the letter were published in the journal Nutrients.
