Should You Take Vitamin D?
Sunlight is the the body's main source of vitamin D. The energy from the sun changes a chemical in the skin to vitamin D3, which is then carried to the liver and the kidneys where it is made into active vitamin D.
The main function of vitamin D is to increase the intestinal absorption of calcium, which is a process that is crucial for good bone health. Vitamin D also helps strengthen the immune system and aids cell to cell communication in the body. Lastly, according to the Vitamin D Council, it also is important for muscle function, the respiratory system, cardiovascular function, and brain development.
According to the Food and Nutrition Board at the Institute of Medicine of The National Academies, the recommended dietary allowance of vitamin D for people up to age 70 is 600 IU each day and 800 IU for those over 70. According to Harvard Medical School, if the body does not get enough vitamin D, it can absorb only 10 to 15 percent of dietary calcium, compared with 30 to 40 percent with sufficient vitamin D levels.
The simple answer is inconsistency in results. Last year, a study published in the Lancet Diabetes & Endocrinology based on 290 prospective observational studies and 172 randomized trials of vitamin D supplements found no evidence that vitamin D supplementation yields any health benefits.
More recently, the Lancet performed an analysis that tested the effect of the vitamin on bone density. It found that supplements led to a "small but significant" improvement in bone density, but only in the narrow part of the upper thigh bone. The researchers still questioned the finding because no improvement in bone density was found elsewhere. They concluded the use of vitamin D supplements for skeletal protection was not justified.
Despite questions about vitamin D, Berkeley Wellness takes the position that overall, evidence supports the use of vitamin D supplements for bone health and muscle function. Unless you've had your vitamin D level measured and been told it's adequate, it suggests taking 800 to 1,000 IU a day. Of course, always check with your doctor first.