Researchers at the University of Michigan Health System are finding this often ignored bone-building vitamin can play a significant role in the prevention of heart disease and the function of other critical body systems. And getting enough vitamin D in your system is as easy as soaking up the sun.
"Vitamin D is very important for our bodies, and we're finding out more all the time," says Robert Simpson, Ph.D., professor of pharmacology in the University of Michigan Medical School. "Vitamin D is now recognized to play a role in heart disease. We're finding vitamin D affects the heart's pumping ability and the heart cells' structure, and it's important for prevention of many of the symptoms in animals that humans with heart failure experience."
Simpson hopes to take advantage of this new knowledge to discover useful drugs.
Traditionally, the role of vitamin D, which we can get through direct sunlight, has been understood as helping the body absorb calcium and contributing to strong bones. Without enough vitamin D, bones can become thin, brittle, soft or misshapen, and deficits of D can cause rickets in children.
Researchers now recognize that vitamin D does more than strengthen bones. It also affects immune function, the ability to make insulin, cancer cell growth, skeletal muscle and heart function.
"I think an overall shift in thought on the vitamin D system is in order," Simpson says. "We're getting a signal from sunlight to produce vitamin D. In response to that signal, our body can take actions. We build strong skeletal structure. We build stronger muscle. We make efficient and stronger hearts. We optimize the immune system and the body's utilization of sugar. These effects render an individual more adapted to an out and about lifestyle, a life in the sun."
Simpson's research is in animals, but he notes that other studies have begun in humans and have found significant associations between vitamin D deficiency and congestive heart failure.
The bad news is it's difficult to get enough vitamin D through a normal diet. It's not found in many foods, and those that do contain vitamin D " egg yolks, fish oils " aren't typically part of an everyday diet. Milk is generally fortified with vitamin D, but an adult would need to drink four glasses of milk a day to achieve the recommended amount of vitamin D.
The good news is sunlight is an excellent source of vitamin D. Experts say as little as fifteen minutes of direct sunlight several times a week will get you your recommended dose. It doesn't require sunbathing. If you live in an area that does not get sunshine, including northern climates in the winter months, you may not get enough vitamin D from the sun.
"Recent studies in northern climates out of Boston showed that as many as 35 percent to 40 percent of hospitalized people from the general population in the winter are vitamin D insufficient. So in general, we should all be somewhat concerned if our diets are not providing adequate vitamin D," Simpson says.
Others at risk for vitamin D deficiency include people following vegetarian diets, people with intestinal disease, people with darker skin tones and those who are recommended to stay out of the sun. People at high risk of deficiency should talk to their doctors about taking supplements.
Be careful not to overdue it though: High doses of vitamin D can be toxic. Vitamin D is a fat-soluble vitamin, which means your body will store the extra amount. This could lead to a severe increase in the level of calcium, which can cause mental confusion, heart rhythm abnormalities or calcium deposits in soft tissues such as the kidneys.
Recommended amounts of vitamin D: "¢ 400 international units per day for adults"¢ 800 IU daily for people age 55 or older "¢ 200-300 IU daily for children
Food sources of vitamin D: "¢ Milk is fortified with 100 IU per glass"¢ Eggs"¢ Organ meats"¢ Fatty fish, including salmon, sardines, herring
Sunlight and vitamin D:Vitamin D is manufactured in the skin after direct exposure to sunlight. Exposing the hands, face or arms to direct sunlight for 15 minutes two or three times per week will help produce vitamin D. Sunscreen with SPF 8 or higher will block the UV rays that cause vitamin D to form in the skin. While it's important to get direct exposure for short periods, always use sunscreen when in the sun for longer than 10-15 minutes.
Resources:UMHS Guidelines for calcium and vitamin D: http://www.med.umich.edu/1libr/guides/calcium.htm
NIH Clinical Center: Facts about vitamin D: http://www.cc.nih.gov/ccc/supplements/vitd.html
Calcium and vitamin D to prevent osteoporosis: http://www.nof.org/prevention/calcium.htm
Dietary supplements: http://www.niapublications.org/engagepages/supplements.asp
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