Most experts believe the RDA or Recommended Daily Allowance for vitamin D of 200 IU (International Units) for those younger than 50 years old and 600 IU for 70+ years old per day are too low.
A study published in Genome Research (8/10) supports the idea that vitamin D interacts with the genes involved with cancer and certain autoimmune diseases.
Experts say 2000 IU may be the optimal dose to prevent diseases like multiple sclerosis, Crohn’s, lupus, colorectal cancer, rheumatoid arthritis, and chronic lymphocytic leukemia.
Vitamin D levels can be raised in the body by sunlight exposure and foods like fish and fortified milk, but as many as half of the U.S. population is deficient. The use of sunscreen has reduced sun exposure and most people do not get sufficient amounts from their diet.
Blood levels of the vitamin are measured as 25-hydroxyvitamin D. Levels below 20 nanograms per milliliter are generally considered deficient. Levels between 30 and 40 nanograms per milliliter may be the goal to reducing the risk of acquiring autoimmune diseases and certain cancers.
The impact of 2000 IU of vitamin D on 20,000 subjects for 5 years will be studied soon. We will soon have a better understanding of the optimal doses of vitamin D and the optimal blood levels associated with the best balance of benefits and risks. But currently there are many unanswered questions.