An insider with the guts to oppose mainstream guidelines on exposure to sunlight, the best way for most people to make vitamin D, and on taking more than 400 IU of vitamin D per day in supplements, Dr. Holick has followed in Dr. Linus Pauling's footsteps, doing for vitamin D what Pauling did for vitamin C. Here is a fearless quotation describing some of the advice you may have believed:
"So desperate is the anti-sun lobby to convince you of the dangers of the sun so that you will buy its products year-round, the representatives will tell you with a straight face that if it's February in Boston and you're planning to walk to the corner store to buy a quart of milk or sit outside on your lunch break, you should wear [smear on] sunscreen. This is wrong-headed and alarmist. Even on the sunniest February day, the sun isn't strong enough in New England or New York to increase your risk of skin cancer significantly... The scare tactics of the cosme-ceutical industry have been embraced by most of the dermatology profession. These groups have worked in concert and frightened the daylights out of people - or, to put it more accurately, frightened people out of the daylight." (pp12-13)
Evidence is given from Dr. Holick's own work and others that vitamin D levels are too low in a large fraction of the world's humans, especially those with dark skin and living more than 30° from the equator. This deficiency causes more osteoporosis, rickets, high blood pressure, stroke, heart attacks, arthritis, multiple sclerosis and cancer than had been believed just 20 years ago. The types of skin cancer caused by excessive sunlight are easily treated and are rarely fatal.
With the greatest care, Dr. Holick explains how to obtain the UVB rays from the sun (or tanning parlor lights) without receiving too much UVA or becoming burned. He does advocate the use of sunscreens, the ones that absorb UVA as well as UVB, after you have had all the sun exposure that is safe. For the very pale-skinned or for arctic dwellers, supplements are advocated.
This easy-to-read book, backed by 120 citations to papers in peer-reviewed journals (unfortunately not numbered), has an index and a glossary. Dr. Holick is no outsider, having published over 200 peer-reviewed papers, and with a lifetime of research in dermatology and endocrinology.
Not all is perfect. The little diet advice is misinformed (p55) , pretty much the low-fat low-cholesterol nonsense that has been discredited for years (http://www.thincs.org/unpublic.Joel4.htm). The Atkins diet is hardly a fad with 60,000,000 people using some form of it in the USA alone [Joel M. Kauffman, Low-Carbohydrate Diets, J. Scientific Exploration , 18(1), 83-134 (2004)]. In fact, vitamin D is made by the action of UVB on cholesterol in the skin! A large number of clinical studies showed that total cholesterol levels <180 were associated with depression, accidents, suicide, homicide, antisocial personality disorder in criminals and Army veterans, cocaine and heroin addiction, and high relapse rates after detoxification (Buydens-Branchey, L., Branchey, M. Association Betwee Low Plasma Levels of Cholesterol and Relapse in Cocaine Addicts. Psychosomatic Medicine, 2003;65:86-91). One wonders whether some of the effects of low cholesterol levels, especially increased cancer rates, are due to vitamin D deficiency.
Some very fine data from two studies was given on the use of vitamin D supplements to prevent bone fractures (pp85-86). One study used 800 IU of vitamin D daily and the other 760 IU daily in the elderly. Both cut the bone fracture rate in half in both men and women. These studies are not cross-referenced under the Section on vitamin D supplements (pp151-153), or found in the index under vitamin D supplements.
We are warned not to overdose on vitamin A from multivitamin capsules in order to obtain the vitamin D in them and we are warned about vitamin D toxicity, yet Dr. Holick wrote that people over 1 year old could take up to 2000 IU of vitamin D supplements daily without medical supervision. The superiority of sunlight for vitamin D production is reinforced (pp151-153).
Despite the caveats, this is an excellent book.