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This presentation offers an entertaining, highly informative review of little-known facts about vitamin D and the role of vitamin D deficiency in a long list of health problems – as well as Dr. Holick’s simple suggestions for avoiding deficiency.

Dr. Holick directs Boston University's General Clinical Research Center. He is also a Professor of Medicine, Physiology and Biophysics, and author of The UV Advantage: The Medical Breakthrough That Shows How to Harness the Power of the Sun for Your Health. This presentation was the keynote address at the 34th European Symposium on Calcified Tissues in Copenhagen, May 2007. Note: bone is a calcified tissue.

A Few Takeaway Points from Dr. Holick’s Presentation

People who watch “The Vitamin D Pandemic and Its Health Consequences” (http://www.uvadvantage.org/portals/0/pres/) typically find it so enlightening that they forward the link to friends, but following are a few key points for reference.

What is vitamin D?
It is calciferol - a fat-soluble vitamin that is best known for supporting absorption of calcium and phosphorous into the bloodstream, but plays a role in many other functions and influences the activity of perhaps 200 genes.

How do we get vitamin D?
From the UV rays of the sun (or artificial source of UV light) and from our diet, in foods or supplements. It is hard to get enough vitamin D from foods. Fish oil contains the most significant amounts, followed by fatty fish, and lower levels are found in foods such as beef liver and egg yolks. Fortified (irradiated) milk is an important source. A quart contains about 400 IU of D. However, our skin is designed to convert the energy in the sun’s rays - first to “pre-D” and then to vitamin D3 - and this is naturally our main source of D.

How is vitamin D deficiency defined?
The level of 25(OH)D (25-hydroxyvitamin D) measured in blood (serum) should be at least 50nmol/L, and Dr. Holick advocates 60 to 75nmol/L. Insufficient/deficient is under 50, and toxic upper levels might start at about 150 to 200nmol/L.

How common is this deficiency?
Amazingly common. Perhaps 50% of all Americans, and even higher proportions of darker skinned and older population groups, fall well below 50nmol/L. Dr. Holick’s reports on studies of deficiency in different age groups at different times of the year are eye-opening.

Why is vitamin D deficiency important?
In children it causes “rickets” – bowed, soft bones, muscle weakness, stunted growth, and high risk of low bone density later in life. This is because vitamin D is needed to support absorption of calcium from the gut to the bloodstream. Mother’s milk contains little vitamin D, so other sources can be important for nursing babies.

In adults, deficiency can lead to “osteomalacia” (a defect in the bone building process, by contrast with osteoporosis, which is breakdown of existing bone structures). Osteoporosis is “silent,” but osteomalacia involves aches and pains in the bones & joints, and muscle aches/weakness that can be generalized or isolated. As Dr. Holick explains it, the defective bone matrix absorbs water and expands, causing pain in the bones’ fibrous outer membrane - the periosteum. (This membrane contains the blood vessels and nerves providing nourishment and sensation in the bones.) He says he diagnoses this condition by pressing to test for pain in certain places such as the breastbone and shin.

Patients with these symptoms are often diagnosed as having fibromyalgia. Dr. Holick says that in his practice, 40% to 60% of patients presenting with these symptoms are vitamin D deficient, and of 150 patients presenting with these symptoms in a Mayo Clinic study, 139 were deficient.

“But that is the tip of the iceberg.” Research is demonstrating that vit D deficiency is also associated with susceptibility to type 1 diabetes, multiple sclerosis, rheumatoid arthritis, infections, tuberculosis, psoriasis, high blood pressure, coronary heart disease, and even common cancers. (Dr. Holick offers an impressive series of slides highlighting the vitamin D deficiency link to incidence of these and other illnesses.)

Is vitamin D deficiency often missed?
Yes. Often, if the physician finds normal calcium levels in the blood, he/she may look no further, since ability to absorb calcium into the bloodstream depends on vitamin D. However, the sole purpose of the parathyroid glands is to control calcium levels in the blood (calcium builds bones, but also supports conduction of electrical currents among nerve cells in the muscles, heart, and brain). If the parathyroids determine that blood calcium levels are too low to support the brain’s demands, they make more PTH to transfer calcium out of the bones and into the bloodstream. And if the D deficiency continues, hyperparathyroidism (inability to regulate blood calcium) results.

Ideally, how much vitamin D should one get in the diet?
1,000 IU daily, as a general rule for adults. IU stands for International Units and is a measure of a vitamin or drug’s activity/effect. One IU of vitamin D is 0.025 micrograms.

How much sun exposure is recommended?
During non-winter months, Dr. Holick advocates at least 10 minutes on 10% of the body surface (e.g., arms or legs) “followed by good sun protection,” two to three times a week. This balances the need for vitamin D with need to minimize skin cancer risk.

Can you make any vitamin D in winter?
Little or none, if you live above the 35th latitude north or south of the equator. That's only slightly north of such 'southern' cities as Atlanta, Georgia, which is at 33 north. In a study, subjects exposed to sunlight in Boston (42.19 north) were able to make “zero vitamin D” from November through February. To check the latitude where you live, click here.

How much does sun block reduce the body’s ability to make D from sunshine?
SPF 15 reduces it by 99%.

Do darker skinned people need more sun than lighter skinned to produce vitamin D?
Yes. In studies, darker skinned subjects “couldn’t budge” their serum D levels until they had 5 to 10 times as much sun exposure as caucasians. [Tables in Dr. Holick’s book – The UV Advantage - help people in different parts of the world with five skin types to determine how much unprotected sun exposure to get.

What amount of sun exposure creates "toxic" levels of vitamin D?
This can’t happen, as the body automatically switches off vitamin D conversion when supply reaches a certain level.

Does ability to make vitamin D decline with age?
It takes longer to make sufficient D as we age. One of Dr. Holick’s studies, published in the Lancet, found for example that a 70-year-old would make 75% less than a 20-year-old with the same sunlight exposure time. So the older person would likely benefit from increasing sun exposure from 15 minutes to 30 minutes.

Are obese people more likely to be deficient?
A study of normal weight vs. obese subjects with the same amount of UV exposure found vitamin D levels averaged 55% lower in the obese group.

Does taking supplemental calcium and vitamin D work to counter osteoporosis and osteomalacia?
Yes it does.

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Note: This information has not been evaluated by the FDA. It is generic and is not meant to prevent, diagnose, treat or cure any illness, condition, or disease. It is very important that you make no change in your healthcare plan or health support regimen without researching and discussing it in collaboration with your professional healthcare team.