Here are some of the 100 or more medical conditions that have been associated with decreased blood levels of vitamin D: arthritis, asthma, colon cancer, emphysema, dementia, depression, diabetes, coronary heart disease, fibromyalgia, hypertension, infections, multiple sclerosis, muscle weakness, obesity, Parkinson’s Disease and psoriasis.
But how many of these links have been proven by scientific studies?
A report from the University of California says most of them are the result of “observational studies.” This means that over a period of years, patients have been followed to see whether low levels of vitamin D are associated with a particular disease. Many researchers now say the bandwagon of “associations” of vitamin D should be slowed down.
The Institute of Medicine echoes this warning. It states the claims of benefits of vitamin D are inconsistent and inconclusive. Some researchers also report that most people are getting sufficient amounts of vitamin D. However, others contend that about half of the people in the U.S. and Canada have blood levels of vitamin D that are considered low. So who do you believe?
This is what we know for sure. In the past, very low levels of D caused rickets. This explains why milk was fortified with vitamin D in the 1930s.
We also know for a fact that adequate amounts of vitamin D are needed in the bowel to absorb calcium. Vitamin D also acts on bone cells to release calcium to maintain normal blood levels. Growth and remodelling of bone is determined by blood levels of D.
It’s also a fact that where you live makes a big difference in whether you get adequate amounts of D. For instance, residents of cities at a latitude above 35 degrees north — which include Boston, Philadelphia and every town in Canada — have a sun problem. These citizens could stand out naked in the noonday sun from October to February and not manufacture one bit of vitamin D due to the angle of the sun’s rays during that time.
Nutritionists also tell us that wherever people live, few foods contain adequate amounts of vitamin D. Most of D comes from oily fish, cod liver oil, egg yolk, some types of mushrooms and fortified foods.
Deciding for or against the value of taking vitamin D supplements is hard, but it’s prudent to assume some may be beneficial. For instance, Dr. Jo Ann Manson at the Harvard Medical School, believes there is strong evidence that higher blood levels of vitamin D help to protect against colon cancer.
Dr. Michael Holick, a world authority on vitamin D at Boston University, reports that people living in higher latitudes show an increased risk of dying from almost all types of cancer, but particularly colon, breast, prostate and skin cancer.
It would also be foolish to ignore D’s protective role in infection, particularly if you happen to be in the midst of a flu epidemic. Vitamin D has been labelled the “antibiotic vitamin” for a good reason. For example, Dr. John Cannell, a U.S. psychiatrist, noted that when the 2005 flu epidemic struck a hospital for the criminally insane in California, the infection spared those patients who were receiving vitamin D. And remember, flu usually strikes in the dark winter months when vitamin D levels are low.
Dr. Edward Giovannucci at the Harvard School of Public Health reported that low levels of vitamin D were linked to increased risk of heart attack. Dr. Thomas Wang, another Harvard researcher, says that low levels of D also increased the risk of stroke.
Add it all up and it appears to be prudent to take a vitamin D supplement. How much is debatable. The University of California researchers suggest 800 to 1,000 IU of D. Others suggest from 1,000 to 3,000 IU.
But all researchers agree that vitamin D is essential for bone health. It will require more studies to determine how many of the 100 other conditions listed really need vitamin D.
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