Blog

Taking a Second Look at Vitamin D

Our family practice doctors have cautioned in the past about the dangers involved in consuming unregulated supplement products for health. And with good reason! Many supplements—including vitamins—can have side effects, or interact with other medications you may be taking, 

We would be the first to admit, however, that vitamin and mineral supplements from a reliable source have their place in some circumstances.

Take vitamin D, for example. This vitamin is necessary for strong bones. According to the National Institute for Health (NIH), it is also helps reduce inflammation throughout the body, enhances cell growth and immune function, and regulates the metabolism of glucose.

Other possible benefits

“It has long been postulated that vitamin D deficiency can cause other problems besides osteoporosis and immune system dysfunction,” Dr. Len Horovitz, an internist with Lenox Hill Hospital in New York City, told United Press International (UPI).

For example, higher levels of the vitamin may strengthen the immune system and stimulate cell growth. It has also been suggested as a prevention of or treatment for type 2 diabetes, multiple sclerosis, and various other types of cancers, including prostate, pancreatic, colon, breast, and esophageal cancers.

Other studies have found a possible benefit for…

• cognitive function for older adults being treated for dementia.
• a lower risk of cardiovascular disease (CVD) incidence and mortality.
• an aid in helping control hypertension (high blood pressure).

New findings

The problem with research surrounding vitamin D is that its suggested benefits have largely come from observational studies. Clinical studies have often failed to support such findings. Some studies found vitamin D worked as expected. Others found no effect.

But a new clinical study, published this month in the journal BMJ, appeared to show that vitamin D could help prevent respiratory infections such as colds and flu, especially in those who are deficient in it.

Researchers analyzed data from clinical trials, which included nearly 11,000 participants from 14 different countries. Subjects’ ages ranged from 0 to 95.

“Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall,” the authors wrote in the journal. “Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit.” (A bolus is a single large dose of a substance.)

“Our analysis of pooled raw data from each of the 10,933 trial participants allowed us to address the question of why vitamin D ‘worked’ in some trials, but not in others,” Adrian Martineau, a professor at Queen Mary University of London (QMUL) and a lead researcher on the study, wrote in a release.

Those who have the lowest levels of vitamin D in their blood seem to show the largest benefit, he said. Those who took it daily or weekly, as opposed to intermittently also saw a large benefit.

Vitamin D in foods

Vitamin D is found in large amounts in only a few foods: fatty fish, such as salmon, tuna, and mackerel, and beef liver, and egg yolks. This is why it’s often added to such foods as cereals, milk, and orange juice.

Researcher Martineau thinks their new study means more foods should have vitamin D added to them.

“By demonstrating this new benefit of vitamin D,” he wrote, “our study strengthens the case for introducing food fortification to improve levels in countries such as the UK where profound vitamin D deficiency is common.”

Why we see deficiencies 

You would think that the UK and the U.S.—two wealthy, advanced nations—wouldn’t have a problem with vitamin D deficiency.

But the body also makes vitamin D when exposed to sunlight. The amount it makes depends on your distance from the equator, what time of day you’re exposed to the sun and skin pigmentation. Darker-skinned individuals actually absorb less.

In addition, with knowledge sun exposure causes skin cancer, these days most of us wear sunscreen outdoors. This prevents the absorption of vitamin D from what little sunlight we might otherwise receive.

And, since it’s not present in many foods either, we recommend that most people take a multivitamin supplement containing vitamin D. That doesn’t mean, however, that you should consume large amounts of it. Vitamin D is a fat-soluble vitamin. This means it tends to be stored in the body’s fat and can lead to accidental overdoses.

Children over the age of nine, adults, and pregnant and breast-feeding women who receive more than 4,000 IUs a day could experience side effects from supplementing with vitamin D, including nausea and vomiting, constipation, weakness, and kidney damage, among others.

If you think vitamin D supplementation might benefit you, we can test your vitamin D levels to learn whether you are deficient in this necessary vitamin. We can also advise you on the appropriate dosages for you.