Vitamin D and DiseaseBy Pamela A. Williams, MPH, R.D
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When we think of preserving the health of our bones, one of the nutrients that immediately comes to mind is vitamin D. We know we get it from fortified milk, certain fish such as salmon, and from a stroll out in the sunlight. Outside of this basic knowledge, we don’t think too much about this vitamin. But researchers have taken another look and what they are finding might be surprising.
Vitamin D Status
What we have known most about vitamin D is that it helps the body place calcium within the bones. Today, we are learning that there is a higher occurrence of vitamin D deficiency among those with certain conditions and chronic disease when compared to individuals without them. So researchers are scratching their heads trying to figure out if the deficiency of vitamin D causes heart disease, high blood pressure and/or diabetes or; does it exist because of the disease.
One thing they know for sure is that over half of the adults in the United States are suspect for vitamin D deficiency. They report that those further away from the equator are at higher risk for vitamin D deficiency. Those with darker skin are at a greater risk than those with lighter skin because darker skin filters out sunlight. Those who take prescription drugs such as glucocorticoids and anti-seizure medications may experience vitamin D deficiency because they may interfere with absorption of this vitamin.
The older crowd may be at increase risk too. For example, the skin contains a substance called cutaneous 7-dehydrocholesterol and when the skin is exposed to the ultraviolet rays of the sun, the body ultimately converts this substance into vitamin D3. The skin of a70 year-old contains about 25% of cutaneous 7-dehydrocholesterol when compared to young adults and this reduced level adds to the risk of vitamin D deficiency.1 Breastfed infants and teens are at risk as well. Also, those who do not consume enough vitamin D rich foods are at risk.
Vitamin D deficiency and Chronic Disease
Within the past ten years, scientists have published a plethora of vitamin D studies. These studies suggest a possible link between vitamin D deficiency and chronic diseases. However, there is much more to discover to understand this link. Here are examples of what researchers have found.
One way researchers are able to tell how much vitamin D (25-hydroxy-vitamin D) is in the body is to measure the concentration in nanograms/milliliters (ng/ml).
In the Framingham Offspring Study, researchers examined vitamin D blood levels and followed the subjects for 5.4 years. They learned that those who had low levels (less than 15 ng/ml) were 53% more likely to experience some type of cardiovascular problem. And those with even lower (less than 10 ng/ml) were 80% more likely to experience a cardiovascular problem.2 And, in the US Health Professionals’ and Nurses’ Health Study, researchers found that low levels were associated with 3 times the risk for high blood pressure. There is not enough information to say that low levels of vitamin D cause high blood pressure but there is enough to continue studying the link between heart disease and this vitamin.3
Studies show that those who live at high altitudes have a greater risk of certain diseases such as type 1 diabetes. A couple of years ago, researchers gave type 1 infants 2,000 IUs of Vitamin D for the first year of life and followed them for 31 years. They reported that the incidence of Type 1 diabetes decreased by 78%.4 Other researchers report that vitamin D may play a role in preventing diabetes type 2 and glucose intolerance.5
About 80 years ago, researchers connected the idea that those who live at high altitudes developed common cancers. Fifty years later, they confirmed that high altitude dwellers developed and died from colon, prostate, breast, lung and other cancers. They also observed that the higher the altitude, the lower the vitamin D levels in the body. They concluded that there might be a correlation between low vitamin D levels and an increased risk of cancer. Researchers have also reported that those in these regions who get adequate sun also have a lower incidence of cancers than those who do not.6
Vitamin D is carried by fat cells in the body. Researchers have noted that those who store an abundance of fat in their bodies are at risk for vitamin D deficiency. This is because fat cells continue to hold on to vitamin D and it becomes unavailable for use in the body.7
Food Sources & Recommendations
Very few foods are considered to be good sources of vitamin D but fish is a natural and rich source. Fish such as salmon, tuna, herring, trout or halibut can contribute significantly to meet vitamin D needs. Recently, a company introduced a brand of mushrooms that have been exposed to ultraviolet light under controlled conditions. These mushrooms may contain up to 400 IUs of vitamin D per serving. Fortified foods such as milk, yogurt, certain brands of soymilk, some orange juice brands, cereal, pudding and others can be good to fair sources of vitamin D. Reading the label will help us determine how much vitamin D is in the product.
Experts recommend that we expose our skin to the sun for 5 to 30 minutes at least two times a week and the best time of day to do this is between 10:00am and 3:00pm. However, there can be quite a bit of interference with this process. Clouds, smog, and smoke can interfere. Windows do not allow ultraviolet rays to pass through to reach those who stay inside. The winter months have a lower level of ultraviolet rays. The use of sunscreen can drastically block ultraviolet rays. Also, too much UV radiation increases the risk of certain types of skin cancer. Although sun exposure is a good way to get vitamin D, our exposure may not be enough to contribute to the vitamin D levels we need.
Supplements are another way to insure that we get enough vitamin D. There are two forms of vitamin D – D2 and D3. These two forms have been thought of as equals but recently, scientists say that D3 is more effective at raising concentrations in our blood. Choose a supplement that has the D3 form.
How much do we need? (Adequate Intakes for vitamin D)9
Children - Recommended intake
Birth to 13 yrs old - 5 mcg (200 IU)
Men and Women* - Recommended intake
14-18 yrs old - 5 mcg (200 IU)
19-50 yrs old - 5 mcg (200 IU)
51-70 yrs old - 10 mcg (400 IU)
71 and over yrs old - 15 mcg (600 IU)
*includes pregnant and lactating women
There is so much more to discover about vitamin D and our health. But until then, making sure we get adequate levels can help us stay healthy and possibly reduce our risk of chronic disease.