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Research Newsletter-Fall/Winter 2009


Michael Holick, M.D., Ph.D.

The 2009 LPI Prize for Health Research, consisting of a medal and $50,000, was awarded at the Diet and Optimum Health Conference on May 15th to Michael Holick, M.D., Ph.D. Dr. Holick is Professor of Medicine, Physiology, and Biophysics at Boston University School of Medicine. He earned his B.S. degree in biology at Seton Hall University and his Ph.D. and M.D. degrees at the University of Wisconsin-Madison. He completed his internship and residency at Massachusetts General Hospital in Boston. He has held academic positions at Harvard, MIT, and Tufts, and been at Boston University since 1987, conducting research and caring for patients. Dr. Holick has published over 320 scientific papers and over 209 reviews and book chapters and has written or edited nine books. He joins Drs. Bruce Ames (2001), Walter Willett (2003), Paul Talalay (2005), and Mark Levine (2007) as recipients of the LPI Prize.

Dr. Holick's entertaining plenary lecture consisted of hundreds of slides illustrating, often very humorously, the importance of vitamin D in health. Perhaps more than any other individual, Dr. Holick has championed the benefits of vitamin D above and beyond its vitamin role in preventing rickets. A number of nominators compared Dr. Holick's advocacy of vitamin D to Linus Pauling's advocacy of vitamin C. Both vitamins have been shown to carry out critical functions unrelated to their vitamin roles in preventing deficiency diseases; the intake or blood/tissue status of each is marginal in many people in the United States; and both Drs. Holick and Pauling faced tremendous skepticism, even from their colleagues, about their claims and recommendations. As one nominator wrote, "I well remember Linus Pauling standing up to criticism and skepticism, a trait of Holick as well." Another nomination letter catalogued Dr. Holick's original contributions to vitamin D science—he was the first to isolate and identify 25-hydroxyvitamin D3 in human blood; the first, with Hector DeLuca, to chemically synthesize 1,25-dihydroxyvitamin D3; the first to identify how vitamin D is produced in the skin; and the first to demonstrate that vitamin D is safe and effective for treating psoriasis. He also demonstrated how skin pigmentation, the use of sunscreens, and latitude affect vitamin D synthesis, concluding that supplemental vitamin D is necessary for most people living in northern latitudes or shielded from the sun in the summer. Indeed, his studies stimulated general acceptance among health professionals for a change in the threshold for vitamin D deficiency or sufficiency from <10 ng/ml in blood to <30 ng/ml. Blood levels of vitamin D can be raised 1 ng/ml by every 100 IU of ingested vitamin D.

LPI Prize for Health Research Medal

Dr. Holick stated that vitamin D deficiency is the most common micronutrient deficiency in the world, occurring in over 50% of the people in the U.S., Europe, China, India, and elsewhere. Vitamin D deficiency is linked to an increased risk for cancer, diabetes, autoimmune diseases, bone disease, multiple sclerosis, rheumatoid arthritis, infectious illnesses, upper respiratory tract infections, tuberculosis, and the risk of dying from cancer or heart disease. Dr. Holick noted that the highest intake of vitamin D correlates with the least incidence of cancer. Antimicrobial activities of vitamin D may also improve resistance to influenza.

Upon exposure to sunlight, previtamin D3 is formed in the skin from cholesterol and, after another chemical modification, enters the circulation. In the liver, vitamin D3 (cholecalciferol) is converted to 25-hydroxyvitamin D (calcidiol), which is then hydroxylated in the kidney to its biologically active form, 1,25-dihydroxyvitamin D (calcitriol). Both vitamin D2 (ergocalciferol, made in plants) and D3 raise blood levels of 25-hydroxyvitamin D. Calcidiol persists in the blood for several weeks, whereas calcitriol disappears after hours. To determine vitamin D status, Dr. Holick noted that laboratory tests for the major circulating form of vitamin D—25-hydroxyvitamin D—not 1,25-dihydroxyvitamin D, which is the test often ordered by physicians, should be performed. Dr. Holick related the story of his own work in identifying vitamin D3 in human blood and its synthesis and the isolation of vitamin D from chicken organs, a particularly unpleasant task.

Almost all cells in the body have vitamin D receptors, indicating that the vitamin plays a very important role in cellular biology. Even reptiles in captivity become vitamin D deficient without sun or UV light exposure. Historically, vitamin D has been recognized for its requirement for normal bone growth. There are still a few cases of rickets in Boston, owing to the lack of vitamin D in breast milk. To achieve satisfactory vitamin D status in infants, Dr. Holick recommends an intake of 4,000 IU/day for lactating mothers to ensure adequate vitamin D status in nursing infants. Compounding the problem of vitamin D insufficiency, virtually no vitamin D is synthesized in the skin in latitudes north of Atlanta, Georgia, in the winter. In the summer, use of an SPF-30 sunscreen decreases endogenous synthesis of vitamin D by 99%. Recognizing the increased risk for skin cancer with excessive sun exposure, Dr. Holick advises sun exposure of arms and legs for 5-15 minutes about two or three times per week in northern latitudes like Boston. He suggests about 15-30 minutes of sun exposure two or three times per week for the elderly, about two to three times more for the obese, and about five to ten times more for people with dark skin. Generally, Dr. Holick recommends at least 400 IU/day of vitamin D2 or D3 for children and 1,400- 2,000 IU/day for adolescents and adults. Toxicity is very rare and doesn’t occur until at least 10,000 IU of vitamin D have been consumed daily for at least five months.

The LPI Prize for Health Research recognizes and honors Dr. Holick's fundamental and provocative contributions to our knowledge about the critical importance of vitamin D in human health.

A brief interview with Dr. Holick is posted on the LPI Web site as a podcast. To learn more about vitamin D, please visit LPI's Micronutrient Information Center.

Last updated November 2009