Friday, April 24, 2009

Vitamin D: Low Levels can be a Health Risk

Vitamin D deficiency has become the "hot topic" in the news lately - and for good reason. There is mounting evidence that low levels of vitamin D may be associated with increased risk of obesity, weight gain around the waist, cardiovascular disease, insulin resistance, type I and type II diabetes, high blood pressure, arthritis, muscle and joint pain, autoimmune diseases, fatigue and depression, and other diseases, along with the more well known problems with bone density.

According to this article from the April 15th issue of Family Practice News, "(a)recent analysis of data collected by the National Health and Nutrition Examination Survey (NHANES) during 1988-1994 and 2001-2004 even suggests that an epidemic of vitamin D deficiency may have hit the United States."
The article further notes that the "Institute of Medicine is reviewing its 1997 guidelines for vitamin D intake, and will likely recommend increased supplementation when new guidelines are published in 2010..."

Another article in the same issue emphasizes that even teenagers can experience health risks associated with low vitamin D: "Low serum levels of vitamin D were linked to increased blood pressure, hyperglycemia, and obesity in an analysis of more than 3,500 American teenagers, a link previously seen in adults."

According to the article, Dr. Jared P. Reis, a researcher in the School of Public Health at Johns Hopkins University, Baltimore, analyzed data from adolescents aged 12-19 during 2001-2004 in the National Health and Nutrition Examination Survey (NHANES), run by the National Center for Health Statistics, and found that teens with the lowest vitamin D levels were more than fivefold more likely to have a BMI at the 95th percentile. They also " had a significantly higher rate of low levels of HDL cholesterol, high triglycerides, and metabolic syndrome, compared with the teens in the highest vitamin D quartile." Dr. Reis explained that "Vitamin D reduces activation of the renin-angiotensin system, thereby lowering blood pressure. It also reduces insulin release from pancreatic beta cells and raises insulin sensitivity. Low vitamin D levels produce opposite effects, activating renin-angiotensin to raise blood pressure, boosting insulin release, and lowering insulin sensitivity."

How did this "epidemic" come about? What has changed in our lifestyle in this country, that would lead to a widespread lack of vitamin D? The answer may be more simple than one might expect.

Vitamin D comes from three main sources: diet, sunlight, and supplements. Many experts believe that we need 1000-2000 I.U.'s of vitamin D per day, just to keep up a normal D level in our bodies. A glass of milk only has about 100 I.U.'s of vitamin D (and even that amount is destroyed if it is exposed to light). Most people do not drink 10-20 glasses of milk per day, so we can't get all of our D from milk! Very few other foods have a large amount of vitamin D. According to the first article above, “you cannot eat enough vitamin D-containing foods to get anywhere near 1,000 IU of vitamin D per day,” according to Dr. Weaver, who served on the IOM committee for the current guidelines.

So our next option is sunlight. Our skin IS capable of producing vitamin D from the sun, but this ability is blocked if we wear sunscreen. Our skin is also less capable of producing vitamin D as we age, gain weight, or have darker skin tone. Add this to the fact that very few of us spend much time outdoors hunting or gathering anymore, and we have the scene set for vitamin D deficiency.

So the final, and ultimately best option, is going to be supplementation. Many multi vitamins have between 400 and 800 I.U.'s of vitamin D. Calcium and D combination supplements may have anywhere from 100 to 500 I.U. of vitamin D. And there are plain old vitamin D supplements, all by themselves. I do NOT advise trying to guess, all on your own, how much vitamin D you need. It IS possible to take in too much vitamin D; it is fat-soluble, and can build up over time, with high doses. The best route is to check with your primary care physician, and ask about his or her approach to vitamin D. Ask if he or she is aware that the Institute of Medicine is reviewing its 1997 guidelines, and will likely be changing them with the new 2010 guidelines (oh boy, your doc will love me for this one!) Ask if you need to have a blood test to determine your current blood level of vitamin D, and if you need treatment. Be aware that there is no widespread consensus on ideal levels and treatment courses - there is wide variation among physicians. Also be aware that certain people can be at risk of overtreatment with vitamin D - people with hyperparathyroidism, or sarcoidosis, for example.

I will keep you updated, as more information becomes available...