Vitamin D – The Neglected Supplement

By Laurie Borst

While everyone knows that “milk does a body good,” because calcium is required for bone health, not everybody knows about the important role vitamin D plays.

And not just in bone health…

Mounting evidence points to inadequate supplies of vitamin D contributing to incidence of type 1 diabetes, cancers, hypertension, and multiple sclerosis.

The government’s guideline for vitamin D intake is between 200 IU and 400 IU per day. Comparatively, a three-ounce serving of salmon provides 425 IU and 3.5 ounces of canned sardines provide 270 IU.

For many people, however, fish is not a large component of their diet due to concerns about pollution and biomagnification of heavy metals. But milk, fortified with vitamin D for decades, only has about 100 IU per 8-ounce glass.

Many researchers are now saying the governmental guideline is woefully inadequate, recommending 1,000 IU per day, according to webmdhealth.com. The National Institute of Health’s website, nih.gov, suggests 1,000 IU as the upper intake limit for infants and 2,000 IU as the upper limit for older children and adults.

Dr James FitzGibbons, of Merritt Orthopedists and on staff at St Vincent’s Medical Center, sees the results of calcium deficiency in his patients who develop osteoporosis. Osteoporosis, or thinning of bone, can lead to an increase of bone fractures as patients age.

“Vitamin D aids in the absorption of calcium in the intestines,” Dr FitzGibbons said. “There are factors that can prevent absorption like glucocortocoids [e.g. prednisone] or rheumatoid arthritis. And some people have underlying diseases which prevent them from getting outside for adequate sun exposure.”

Compounding the challenge, vitamin D is not found in large amounts in most foods.

In fact, a major source of vitamin D comes from exposing the skin to sunlight. But, sunlight has gotten a bad rap due to the deleterious effects of ultraviolet (UV) light.

The same UV rays people block with sunscreen stimulate the skin to produce vitamin D. Five to 10 minutes of unprotected sun exposure two or three times per week on your hands, legs and arms will meet vitamin D requirements.

Unfortunately, living north of 40 degrees latitude means that in the winter, the sun’s rays are not strong enough to stimulate the necessary production. The National Institute of Health’s website also cites cloud cover, smog, and time of day for filtering out UV light waves.

Of course, use of sunscreen negates the healthful effects of sun exposure.

Dr Michael Gazsi, a naturopathic physician practicing in Danbury, suggests cod liver oil as a winter source of vitamin D. He also urges people to get a blood test to check the vitamin D levels.

“If you are not getting sun exposure, you may need 2,000 IU per day to reach normal levels,” he said.

Vitamin D is a fat-soluble vitamin, which means it is stored in the cells. One can overdose on vitamin D, but it is unlikely.

With so little in foods, and people avoiding the sun, most Americans do not have to worry about building up an excess in the body.

“As people tan, the build up of melanin blocks UV light from penetrating the skin,” said Dr Gazsi. “The darker the skin becomes, the less it produces vitamin D.”

Dr James Reiley described the functions of vitamin D. “Vitamin D makes the protein the binds calcium and moves it out of the intestine into the bloodstream. Vitamin D also increases renal reabsorption of calcium.”

Dr Reiley is a naturopath who practices with his wife, Dr Vicky Crouse, a family therapist and massage therapist at Physical Medicines Family Wellness Center on Glen Road. They have created a website, naturalopinion.com, which contains a wealth of information on diseases and disorders and natural approaches to treating them.

But remember, if you are heading out to soak up the sun, or to your local store to stock up on massive quantities of vitamin D supplements, people should consult their primary care physician before making significant changes to their diets or medications.

According to the textbook, Review of Medical Physiology, by William F. Ganong, vitamin D is classified as a vitamin because a dietary source is needed to provide for the body’s needs. On a broader scope, “vitamin D” is a generic name for a group of steroid-like compounds — vitamin D acts like a steroid hormone, but it is neither a steroid nor a hormone.

Steroid means lipid, or fat, soluble. Hormones are made in glands and diffuse out of those glands into the bloodstream, the text states.

The blood transports them to their target organs. Lipid-soluble compounds are able to pass through a cell’s membranes because lipids make up a large part of the membrane.

Once in the cell, the hormone travels to the nucleus where it binds with DNA to stimulate genes to produce another chemical.

The text goes on to say, in the presence of sunlight, the skin acts like an endocrine gland. Ultraviolet light stimulates skin cells to convert cholesterol into vitamin D. The vitamin diffuses into the blood and travels around the body.

In the small intestine, vitamin D stimulates cells lining the intestine to produce calcium binding protein. This binding protein then carries calcium through the intestinal wall and into the bloodstream.

In the kidneys, vitamin D increases reabsorption of calcium and returns it to the bloodstream.

Calcium is stored in bone tissue, and a small amount circulates in the blood.

Calcium is necessary for proper muscle contraction and for the transmission of nerve impulses. When more blood calcium is required, bone is broken down and calcium released.

Not only is osteoporosis a concern with calcium deficiency, but communication within the body as well as movement can be impaired. Vitamin D’s role in getting calcium into the body is critical.