Ask most people what they know about vitamin D and you’ll probably get an answer that includes milk, sunlight, or bone growth in children. Until recently, that answer would have been right, or at least close to right. Now, it seems vitamin D is important for immune system functioning, preventing osteoporosis, lowering blood pressure, regulating cholesterol levels, and may even protect against some cancers including breast and prostate cancer. One study has even identified an association between Alzheimer’s disease and vitamin D deficiency.

Almost all fungi, plants, and animals produce a form of vitamin D that absorbs ultraviolet light. In humans, ultraviolet light from the sun along with special processes in the liver and kidneys helps our bodies produce a useable, active form of vitamin D. We can also absorb vitamin D from supplements and the foods we eat. Experts consider the active form of vitamin D a hormone because vitamin D is similar in structure to the body’s steroid hormones like estrogen and testosterone, and in this role vitamin D increases phosphorus and calcium absorption from the intestines and promotes bone mineralization for stronger bones.

Early scientific research on vitamin D sought to understand an increase in two bone diseases, rickets and osteomalacia, that became epidemic during the industrial revolution when families left their farms to live in the city and work in factories. Rickets is a condition in which the bones in growing children do not mineralize properly and become weak, misshapen, and soft. Osteomalacia is similar but affects the bones and muscles of adults. Minimal sun exposure and poor diets led to an epidemic in vitamin D deficiency. Scientists in the late 1800’s discovered that giving children cod liver oil reversed rickets, and by the 1930’s, the United States began to fortify milk with Vitamin D which made rickets a rare disease in this country. However, recent reports are showing a resurgence of rickets and vitamin D deficiency in the United States. The are many reasons for vitamin D deficiency in our modern world.

Ten Common reasons for Vitamin D deficiency:

1) Aging—Studies have revealed that aging can decrease the skin’s ability to create vitamin D.

2) Melanin—Higher melanin levels in dark-skinned individuals blocks ultraviolet light and limits the skin’s ability to create vitamin D.

3) Higher Latitudes and Seasonal changes—In Northern cities like Boston, Massachusetts, skin can only produce vitamin D from March to October due to low levels of wintertime ultraviolet light reaching the ground.4) Sunscreens and clothing—Block ultraviolet light and interfere with the skin’s ability to produce vitamin D. Studies have shown that sunscreen with SPF of 8 or more will block the skin’s ability to make vitamin D. But it is important to wear sunscreen to prevent premature wrinkling, DNA damage to the skin, and skin cancer.

5) Glass—Blocks the UV-B light waves that the skin uses to make vitamin D. (***Please note glass does not block UV-A which also has been associated with causing skin cancer and premature skin aging. UV-A does not create vitamin D in the skin.)

6) “9-to-5 jobs”—Indoor work environments during peak sun hours prevent the skin from absorbing ultraviolet light to produce vitamin D.

7) Avoidance of dairy products—Since milk is fortified with vitamin D, avoiding milk and milk products can lead to vitamin D deficiency. Vegetarians who do not drink milk or eat fish may be at the greatest risk of vitamin D deficiency if they do not take a supplement.

8) Breastfeeding—Vitamin D is not found in breast milk and infants who exclusively receive breast milk for a prolonged period of time without vitamin D supplementation can develop vitamin D deficiency.

9) Dermatologists and skin cancer prevention—Being married to a dermatologist who specializes in skin cancer has personally decreased my ultraviolet light exposure. Since ultraviolet light exposure is associated with developing skin cancers, I am constantly “encouraged” to wear hats, long sleeves, and sunscreen. Avoiding ultraviolet light helps lower my risk of developing skin cancer, prevents premature skin aging, and keeps my wife happy. It also necessitates taking a vitamin D supplement.

10) Butt Sitting–(The not so politically correct reason for vitamin D deficiency in our modern world). Staying indoors, watching television, and playing video games does not help our skin create vitamin D. Light from a television set does not generate vitamin D.

As you can see, most of us have one or more of the above risks for developing vitamin D deficiency. This deficiency is exacerbated by the fact that the natural food sources of vitamin D are not as prevalent in our modern diet. The Food and Drug Administration’s recommended daily amount of vitamin D for people under 50 years old is 200 IU per day. (A cup of vitamin D fortified milk provides half of this.) And, the required daily amount of vitamin D increases after age 50.

Food sources of vitamin D include:

• Cod Liver Oil—contains 1,360 IU in one tablespoon
• Salmon, cooked—contains 360 IU in 3.5 ounces
• Mackerel, cooked—contains 345 IU in 3.5 ounces
• Tuna Fish, canned in oil—contains 200 IU in 3 ounces
• Sardines, canned in oil and drained—contains 250 IU in 1.75 ounces
• Milk, vitamin D fortified—contains 98 IU in one cup
• Egg (vitamin D is found in the yolk)—contains 20 IU in one egg

Many experts on vitamin D and nutrition are saying that the FDA’s recommendations are not enough and that people < 50 years old should try to get 400 to 800 IU per day and people over 50 years old should get at least 1000 IU per day. Sun and ultraviolet light exposure is still an option for getting enough daily vitamin D, but the associated risk between ultraviolet light exposure and skin cancer is enough to discourage sun exposure as the primary source for vitamin D. The same ultraviolet exposure that creates vitamin D in the skin can cause aging, DNA damage, and skin cancer. The logical alternative to dangerous sun exposure is instead to encourage food sources and supplements.

Who Cares?

The better question is why should we care about vitamin D deficiency? Many researchers are beginning to evaluate possible links between common medical conditions and vitamin D deficiency. Why are we more likely to get sick during the darker times of the year (winter)? Why does cholesterol tend to be higher during the winter months? Why do people with a higher risk of developing elevated blood pressure have lower levels of vitamin D in their blood? Could the muscle and joint pain of fibromyalgia be an early form of osteomalacia and vitamin D deficiency? Why do premenopausal women with higher intakes of calcium and vitamin D have a lower risk of breast cancer?

We have known for some time that bones have a receptor for vitamin D that improves their mineralization and strength. Only recently have we realized that other tissues also have vitamin D receptors. It now seems that these receptors can regulate cell growth, prevent the development of cancer, control blood pressure in the kidneys, and modulate the immune system. The importance of vitamin D throughout the body is becoming increasingly clear.

One example of low vitamin D levels affecting the body relates to cholesterol levels. The first steps in the creation of vitamin D occurs using cholesterol and energy from ultraviolet light. The body will actually raise cholesterol levels when there is not enough vitamin D. Raising cholesterol levels during times of low vitamin D helps ensure that the skin can easily make vitamin D with small amounts of ultraviolet light. Additionally, recent scientific data have shown that low levels of vitamin D in the elderly hasten the development of osteoporosis and bone loss, making vitamin D an important part of any osteoporosis treatment plan. Also, some nutritional experts feel that fibromyalgia is actually an early form of osteomalacia. Physicians are encouraged to ensure that fibromyalgia patients are getting enough vitamin D. Multiple other disease states are being evaluated for a possible link to vitamin D deficiency.

Vitamin D deficiency may also provide an explanation for why people living in higher latitudes (where there is decreased ultraviolet exposure) have an increased risk of developing hypertension and of dying from many common cancers. Furthermore, immunologic diseases like type I diabetes, psoriasis, rheumatoid arthritis, and multiple sclerosis are also more prevalent in higher latitudes where there is less ultraviolet exposure and vitamin D deficiency is more common. Likewise, prostate cancer is more common in African-American men who have difficulty absorbing ultraviolet light due to the increased melanin in their skin.

There is not evidence that vitamin D supplementation will cure any of the above-named conditions. Instead, it seems that low levels of vitamin D can play a part in triggering diseases in certain people. Most disease states are multi-factorial and have complicated genetic and environmental triggers.

Too much of a good thing is NOT good…

Vitamin D toxicity can occur with consuming too much vitamin D. Diet and sun exposure are unlikely to cause toxicity. Toxicity has been documented with consuming large amounts of cod liver oil and vitamin D supplements. Toxicity can cause nausea, vomiting, loss of appetite, weakness, and constipation. Vitamin D toxicity can also raise calcium levels in the blood to dangerous levels that can cause confusion or heart palpitations. Toxicity typically occurs above 1000 IU per day in infants, and 2000 IU per day in children and adults

Recommendations

I recommend consuming foods high in vitamin D and taking a supplement that includes vitamin D. For people under 50 years old, I recommend getting 400 to 800 IU a day. For people over 50 years old, I recommend getting at least 1000 IU a day. Up to 2000 IU is generally safe. I advise using vitamin D in the cholecalciferol (D3) form instead of the D2 (ergocalciferol) form. D3 is more active and has better scientific data to support its usage.

My wife would kill me if I didn’t mention that I also advise wearing sunscreen daily on the face and neck. I do not think that trying to get vitamin D from the sun is safe. The risks of ultraviolet exposure to the skin are well-documented and just not worth it when there are safer alternatives to getting enough vitamin D.