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Vitamin D and the Cancer Connection

by Hans R. Larsen, MSc ChE

Hans Larsen A team of Dutch and Swiss researchers recently reported that vitamin-D deficiency is widespread in Europe. They found that 36 per cent of elderly men and 47 per cent of elderly women suffer from a lack of vitamin-D during the winter months(1). Researchers from the Johns Hopkins School of Medicine in Boston report similar findings(2).

Why a deficiency?
Our main source of vitamin-D is sunlight. It is estimated that at least 75 per cent of our supply comes from photochemical conversion of 7-dehydrocholesterol in the skin(3). This conversion occurs when we are exposed to the sun's UVB rays (290-320 nm wavelength). Vitamin D itself is biologically inactive, but is converted in the liver and kidneys to 1,25-dihydroxycholecalciferol [1,25(OH)2D3] which is a powerful hormone with many functions(4). Most foods contain very little vitamin D with the main sources being eggs, fish, and fortified milk(3,5).

Lack of exposure to sunlight is the main cause of vitamin D deficiency. In recent years medical authorities have exhorted us to avoid the sun and apply sunscreen before we venture outside. This advice is aimed at reducing the astronomical increase in the incidence of skin cancer and melanoma. Recent research, however, has shown that relying on sunscreens to prevent skin cancer and melanoma is counterproductive(6). Research has also shown that regular use of sunscreens completely eliminates the body's synthesis of vitamin D and can lead to a serious vitamin D deficiency(7,8).

Sun avoidance by itself leads to vitamin D deficiency. Windowpanes effectively screen out UVB rays(9). Clothing, whether it be a light cotton shirt or a heavy jogging suit, eliminates or seriously reduces the synthesis of vitamin D(10). Air pollution (ozone and sulfur dioxide) cuts out a large portion of the sunlight needed for vitamin D synthesis and many medications (anticonvulsants, steroids) also interfere with vitamin D formation(2,5,8,9). Vegetarians are at particular risk for vitamin D deficiency because of their high fiber intake and lack of dairy products in the diet(11).

Health authorities have attempted to ensure that people get enough vitamin D through the diet by fortifying milk. This approach, however, is ineffective. Recent research studies have shown that the vitamin D content of milk is highly erractic and many of the samples tested in two recent surveys done in Canada and the United States contained no vitamin D at all(12,13).

Consequences of vitamin D deficiency
The consequences of vitamin D deficiency are many and varied. Drs. Cedric and Frank Garland of the University of California suggested as early as 1980 that a lack of vitamin D could be a major cause of colon cancer. The Garland brothers found that the incidence of colon cancer was almost three times higher in New York than in New Mexico. They attributed this to a vitamin D deficiency caused by the relative lack of sunshine in the northern United States(14). Another survey carried out in Chicago reached the conclusion that men whose daily vitamin D intake was 150 IU or more had a 50 per cent lower risk of developing colon cancer than did men with a lower intake(15).

Vitamin D deficiencies have also been implicated in the development of breast cancer, melanoma, ovarian cancer, prostate cancer, and of course, osteoporosis and hip fractures(2,3,16-26).

Breast cancer rates in the northeastern part of the United States are almost twice as high as in the south and southwest(3). The incidence of ovarian cancer among women aged 45 to 54 years is five times higher in Indiana than in North Carolina. Researchers ascribe this difference to a vitamin D deficiency in northern states caused by a lack of sunlight(18).

Osteoporosis affects about 24 million people in the United States alone and costs about 10 billion dollars a year to treat. One third of postmenopausal women suffer from osteoporosis and, as a result, experience a total of about 1.3 million bone fractures a year(19). Deficiencies in calcium and vitamin D intake have both been implicated in the development of osteoporosis(19,20,21). Recent research has shown that elderly people receiving a single, large, oral dose of vitamin D (100,000 IU) at the start of the winter had 20 per cent fewer bone fractures than a control group(27).

It is clear that vitamin D deficiency is widespread and can have serious, even fatal consequences. Regular, prudent, unprotected exposure to sunlight is the most effective way of maintaining an adequate vitamin D status(4,9,17). However, during the winter months, elderly people and people who spend most of their time indoors should supplement with vitamin D. Recommendations vary from 400 IU (10 micrograms) to 800 IU per day(2,9,22,24,25,28). An adequate vitamin D supply significantly reduces the risk of breast cancer, colon cancer, ovarian cancer, prostate cancer, osteoporosis, and hip fractures.

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  1. van der Wielen, Reggy P.J., et al. Serum vitamin D concentrations among elderly people in Europe. The Lancet, Vol. 346, July 22, 1995, pp. 207-10
  2. Gloth, F. Michael and Tobin, Jordan D. Vitamin D deficiency in older people. Journal of the American Geriatrics Society, Vol. 43, No. 7, July 1995, pp. 822-28
  3. Garland, Frank C., et al. Geographic variation in breast cancer mortality in the United States: A hypothesis involving exposure to solar radiation. Preventive Medicine, Vol. 19, 1990, pp. 614-22
  4. Fraser, D.R. Vitamin D. The Lancet, Vol. 345, January 14, 1995, pp. 104-07
  5. Webb, Ann R., et al. An evaluation of the relative contributions of exposure to sunlight and of diet to the circulating concentrations of 25-hydroxyvitamin D in an elderly nursing home population in Boston. American Journal of Clinical Nutrition, Vol. 51, 1990, pp. 1075-81
  6. Larsen, Hans R. Sunscreens: Do they cause skin cancer? International Journal of Alternative and Complementary Medicine, Vol. 12, No. 12, December 1994, pp. 17-19
  7. Matsuoka, Lois Y., et al. Sunscreens suppress cutaneous vitamin D-3 synthesis. Journal of Clinical Endocrinology and Metabolism, Vol. 64, No. 6, 1987, pp. 1165-68
  8. Matsuoka, Lois Y., et al. Chronic sunscreen use decreases circulating concentrations of 25- hydroxyvitamin D. Archives of Dermatology, Vol. 124, December 1988, pp. 1802-04
  9. Holick, Michael F. Environmental factors that influence the cutaneous production of vitamin D. American Journal of Clinical Nutrition, Vol. 61, No. 3, March 1995, pp. 638S-45S
  10. Matsuoka, Lois Y., et al. Clothing prevents ultraviolet-B radiation-dependent photosynthesis of vitamin D-3. Journal of Clinical Endocrinology and Metabolism, Vol. 75, No. 4, 1992, pp. 1099-1103
  11. Lamberg-Allardt, Christel, et al. Low serum 25-hydroxyvitamin D concentrations and secondary hyperparathyroidism in middle-aged white strict vegetarians. American Journal of Clinical Nutrition, Vol. 58, No. 5, November 1993, pp. 684-89
  12. Holick, Michael F., et al. The vitamin D content of fortified milk and infant formula. The New England Journal of Medicine, Vol. 326, April 30, 1992, pp. 1178-81
  13. Chen, Tai C., et al. An update on the vitamin D content of fortified milk from the United States and Canada. The New England Journal of Medicine, Vol. 329, No. 20, November 11, 1993, p. 1507
  14. Garland, Cedric F. and Garland, Frank C. Do sunlight and vitamin D reduce the likelihood of colon cancer? International Journal of Epidemiology, Vol. 9, No. 3, September 1980, pp. 227-31
  15. Garland, Cedric F., et al. Dietary vitamin D and calcium and risk of colorectal cancer: A 19-year prospective study in men. The Lancet, February 9, 1985, pp. 307-09
  16. Gorham, Edward D., et al. Acid haze air pollution and breast and colon cancer mortality in 20 Canadian cities. Canadian Journal of Public Health, Vol. 80, March/April 1989, pp. 96-100
  17. Ainsleigh, H. Gordon. Benefical effects of sun exposure on cancer mortality. Preventive Medicine, Vol. 22, 1993, pp. 132-40
  18. Schneider Lefkowitz, Ellen and Garland, Cedric F. Sunlight, vitamin D, and ovarian cancer mortality rates in US women. International Journal of Epidemiology, Vol. 23, No. 6, December 1994, pp. 1133-36
  19. Tolstoi, Linda G. and Levin, Robert M. Osteoporosis - The treatment controversy. Nutrition Today, July/August 1992, pp. 6-12
  20. Tilyard, Murray W., et al. Treatment of postmenopausal osteoporosis with calcitriol or calcium. The New England Journal of Medicine, Vol. 326, February 6, 1992, pp. 357-62 and 406-07 (editorial)
  21. Guillemant, Josette, et al. Age-related effect of a single oral dose of calcium on parathyroid function: Relationship with vitamin D status. American Journal of Clinical Nutrition, Vol. 60, No. 3, September 1994, pp. 403-07
  22. Dawson-Hughes, Bess, et al. Rates of bone loss in postmenopausal women randomly assigned to one of two dosages of vitamin D. American Journal of Clinical Nutrition, Vol. 61, May 1995, pp. 1140-45
  23. Jacobsen, Steven J., et al. Seasonal variation in the incidence of hip fracture among white persons aged 65 years and older in the United States, 1984-1987. American Journal of Epidemiology, Vol. 133, No. 10, 1991, pp. 996-1004
  24. Chapuy, Marie C., et al. Vitamin D-3 and calcium to prevent hip fractures in elderly women. The New England Journal of Medicine, Vol. 327, No. 23, December 3, 1992, pp. 1637-42
  25. Chapuy, Marie C., et al. Effect of calcium and cholecalciferol treatment for three years on hip fractures in elderly women. British Medical Journal, Vol. 308, April 23, 1994, pp. 1081-82
  26. Skowronski, R.J., et al. Actions of vitamin D-3, analogs on human prostate cancer cell lines: Comparison with 1,25-dihydroxyvitamin D-3. Endocrinology, Vol. 136, No. 1, January 1995, pp. 20-26
  27. Khaw, Kay-Tee, et al. Single-dose cholecalciferol suppresses the winter increase in parathyroid hormone concentrations in healthy older men and women: A randomized trial. American Journal of Clinical Nutrition, Vol. 59, May 1994, pp. 1040-44
  28. Gloth, F. Michael. Vitamin D. The Lancet, Vol. 345, May 6, 1995, pp. 1185-86

This article was first published in the November 1995 issue of International Health News

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