Vitamin D Is For Cancer Defense

[Guest guest]

Vitamin D Is For Cancer Defense

 

by Bill Sardi

http://www.knowledgeofhealth.com/report.asp?story=Vitamin%20D%20Is%

20For%20Cancer%20Defense & catagory=Vitamin%20D,%20Cancer

 

From time to time news reports surface about a " cancer cluster "

among workers in a building. Often the workers have been assigned to

dark basement offices or sealed clean-rooms where they must wear

space-suitlike garb. After an indoor environmental examination,

investigators often are unable to correlate any factor in the

building with the cancer cases. But what if, rather than a cancer-

causing agent, the cancer cases are attributable to a missing

protective factor? Given a growing body of evidence linking cancer

with vitamin D deficiency, a question surfaces: Are indoor workers

getting sufficient sunlight to make enough vitamin D to protect them

from cancer?

 

Vitamin D is formed in the skin of animals and humans by the action

of short-wave ultraviolet light, the so-called fast-tanning sun

rays. Precursors of vitamin D in the skin are converted into

cholecalciferol, a weak form of vitamin D3, which is then

transported to the liver and kidneys where enzymes convert it to

1,25-dihydroxycholecalciferol, the more potent form of vitamin D3.

 

Fat-soluble vitamin D supplements are available in two forms.

Vitamin D3 is believed to exhibit the most potent cancer- inhibiting

properties and is the preferred form of the vitamin. More than 10

substances belong to a group of steroid compounds that exhibit

vitamin D activity. Vitamin D2 (ergocalciferol), derived from plants

and yeast, is a form of the vitamin commonly added to milk and some

nutritional supplements. The first vitamin D to be discovered was a

crude mixture called vitamin D1; it is not available as a

supplement.

 

Although the list of vitamin-D-rich foods is limited, it is acquired

from foods such as egg yolks, butter, cod liver oil and from cold-

water fish such as salmon, herring and mackerel.

 

Cancer Prevention

 

Evidence of vitamin D's protective effect against cancer is

compelling. For more than 50 years, documentation in the medical

literature suggests regular sun exposure is associated with

substantial decreases in death rates from certain cancers and a

decrease in overall cancer death rates. Recent research suggests

this is a causal relationship that acts through the body's vitamin D

metabolic pathways. For instance, some evidence points to a

prostate, breast and colon cancer belt in the United States, which

lies in northern latitudes under more cloud cover than other regions

during the year. Rates for these cancers are two to three times

higher than in sunnier areas.1

 

Dark-skinned people require more sun exposure to make vitamin D. The

thickness of the skin layer called the stratum corneum affects the

absorption of UV radiation. Black human skin is thicker than white

skin and thus transmits only about 40 percent of the UV rays for

vitamin D production. Darkly pigmented individuals who live in sunny

equatorial climates experience a higher mortality rate (not

incidence) from breast and prostate cancer when they move to

geographic areas that are deprived of sunlight exposure in winter

months. The rate of increase varies, and researchers hesitate to

quote figures because many migrant black populations also have poor

nutrition and deficient health care that confound statistics

somewhat.2

 

Although excessive sun exposure may give rise to skin cancer,

researchers as early as 1936 were aware that skin cancer patients

have reduced rates of other cancers. One researcher estimates

moderate sunning would prevent 30,000 annual cancer deaths in the

United States.3

 

Vitamin D may also go beyond cancer prevention and provide tumor

therapy. Much ado has been made of pharmaceutical angiogenesis

inhibitors--agents that help inhibit the growth of new, undesirable

blood vessels that tumors require for nutrient supply and growth.

Laboratory tests have shown vitamin D to be a potent angiogenesis

inhibitor.4

 

Vitamin D also works at another stage of cancer development. Tumor

cells are young, immortal cells that never grow up, mature and die

off. Because vitamin D derivatives have been shown to promote normal

cell growth and maturation, drug companies today are attempting to

engineer patentable forms of vitamin D for anti-cancer therapy.5

 

D Is for Strong Bones

 

Up until now, vitamin D has been better known for its ability to

promote bone strength by increasing calcium absorption. Supplemental

vitamin D has been shown to reduce hip fracture risk among elderly

women when combined with supplemental calcium. In one study of 3,270

healthy women, mean age 84, 1,634 received 1.2 g calcium and 800

international units (IU) vitamin D3, while the other 1,636 received

placebo. During the 18-month study, the supplemented group

experienced 43 percent fewer hip fractures, 32 percent fewer

nonvertebral fractures, and a 2.7 percent increase in bone density

of the proximal femur vs. the 4.6 percent bone density decrease seen

in the placebo group.6

 

Other studies bear out vitamin D's importance to bone health, to the

point where it's now widely known that vitamin D deficiency is

associated with hip fractures, and supplementation helps.

Unfortunately, not everyone is getting enough vitamin D. A recent

study reveals that about 10 percent of retirees in Boston social

clubs are vitamin-D deficient (< 15ng/mL serum vitamin D) compared

with 21 percent of hip-fracture patients at the Massachusetts

General Hospital.7 So experts now suggest people take 600 IU vitamin

D daily, and up to 800 IU a day for elderly patients who do not

produce vitamin D from sun exposure as easily as they did when

younger.8 A recent study showed that 37 percent of adult hospital

patients were deficient in vitamin D upon admission. Two-thirds of

these patients did not consume enough vitamin D from dietary

sources. Surprisingly, 46 percent of those who took daily

multivitamins (most of which provide 400 IU) were also in a state of

deficiency.9

 

How Much Vitamin D?

 

The U.S. Recommended Dietary Allowance (RDA) of vitamin D is 200 IU.

Yet, studies have shown that 200 IU/day has no effect on bone

status.10 Reinhold Vieth, Ph.D., of the University of Toronto,

recently published a landmark review of vitamin D in the May 1999

American Journal of Clinical Nutrition. Vieth says adults may need,

at a minimum, five times the RDA, or 1,000 IU, to adequately prevent

bone fractures, protect against some cancers and derive other broad-

ranging health benefits.

 

Vieth says the 1989 RDA of 200 IU is antiquated, and the newer 600

IU Daily Reference Intake (DRI) dose for adults older than 70 is

still not adequate. Even the 2,000 IU upper tolerable intake, the

official safety limit, does not deliver the amounts of vitamin D

that may be optimal, Vieth says. On a sunny summer day, total body

sun exposure produces approximately 10,000 IU vitamin D per day. As

a result, concerns about toxic overdose with dietary supplements

that exceed 800 IU are poorly founded, Vieth says. His review

indicates a person would have to consume almost 67 times more

vitamin D than the current 600 IU recommended intake for older

adults to experience symptoms of overdosage.11 Vieth believes people

need 4,000-10,000 IU vitamin D daily and that toxic side effects are

not a concern until a 40,000 IU/day dose.11

 

Harvard researchers agree with Vieth. They suggest that older

adults, sick adults, and " perhaps all adults " need 800 ? 1,000 IU

daily. They indicate that daily doses of 2,400 IU--four times the

recommended intake--can be consumed safely.10 Robert P. Heaney, a

noted expert on vitamin D and calcium dynamics at Creighton

University in Nebraska, says that even though the recommendations

for vitamin D have recently been updated to account for increased

needs among the elderly, Vieth's review may stir policymakers to

further upgrade current dietary reference intakes. Heaney says

whatever the increase in the recommended allowance turns out to

be, " it seems inescapable that it will be substantially higher than

the current values and possibly higher than nutritional policymakers

may be prepared to accept. " 12

 

Those who do follow the suggestion to consume more vitamin D may

want to watch for toxicity symptoms of headache, nausea, dizziness,

vomiting, loss of appetite and dry mouth--though these are not

usually seen outside of underlying health conditions such as kidney

or parathyroid hormone dysfunction.

 

Vitamin D is not prevalent in foods. A study conducted at the Bone

Research Laboratory at Boston University School of Medicine revealed

that fortified milk may not be a reliable source of vitamin D. Only

29 percent of commercial milk samples tested were within 80?120

percent of the amount stated on the label. Most milk products were

overfortified, and a few milk cartons contained no vitamin D at

all.13 Vitamin D milk fortification procedures vary widely from

dairy to dairy. Some dairies place their vitamin D preparations in

refrigerated storage, and others do not, which may affect the

vitamin D content of the final product.14

 

Few vitamins can provide such an array of health benefits as vitamin

D. Sunshine is still the most economical and beneficial way to

improve circulating vitamin D levels. In addition, the lack of

sunlight exposure could lead to more than thinning bones and an

increased risk for cancer--there is the added benefit of controlling

cholesterol. Since vitamin D is produced naturally within the body,

technically it is a hormone. Vitamin D precursors require

cholesterol for conversion into the hormone-vitamin. Without

adequate sun exposure, vitamin D precursors turn to cholesterol

instead of the vitamin. The increased concentration of blood

cholesterol during winter months and the fact that outdoor activity

(gardening) is associated with lower circulating cholesterol levels

in the summer, but not in winter, may explain geographical

differences in coronary heart disease incidence.15

 

Sunning before 10 a.m. and after 3 p.m. avoids the sun's harshest UV

radiation. People who live in areas of winter cloud cover, are

homebound, or don't get enough sun should consider naturally

compounded vitamin D3 (cholecalciferol) supplements.

 

Bill Sardi is a health journalist and consumer advocate in Diamond

Bar, Calif. His recent publications include The Iron Time Bomb

(Purity Pub., 1999) and All About Eyes Naturally (Avery Publishing

Group, 2000).

 

References

 

1. Studzinski GP, Moore DC. Sunlight--can it prevent as well as

cause cancer? Can Res 1995;55:4014-22.

 

2.Angwafo FF. Migration and prostate cancer: an international

perspective. J Natl Med Assoc 1998 Nov; 90 (11 suppl):S720-3.

 

3. Ansleigh HG. Beneficial effects of sun exposure on cancer

mortality. Prev Med 1993;22:132-40.

 

4. Shokravi MT, et al. Vitamin D inhibits angiogenesis in transgenic

murine retinoblastoma. Inv Oph 1995;36:83-7.

 

5. Studzinski GP, Moore DC. Vitamin D and the retardation of tumor

progression. In Watson RR, Mufti SI, editors, Nutrition and cancer.

Boca Raton: CRC Press, 1996. p 257-82.

 

6. Chapuy MC, Arlot ME. Vitamin D3 and calcium to prevent hip

fractures in elderly women. New Eng J Med 1992;327:1637-42.

 

7. Neer RM. Environmental light: effects on vitamin D synthesis and

calcium metabolism in humans. Ann NY Acad Sci 1985;453:14-20.

 

8. National Academy of Sciences, Recommended Dietary Allowances,

10th ed., Washington, DC: National Academy Press, 1989.

 

9. Thomas MK, et al. Hypovitaminosis D in medical inpatients. New

Eng J Med 1998;338:777-83.

 

10.Dawson-Hughes B, et al. Rates of bone loss in post-menopausal

women randomly assigned to one of two dosages of vitamin D. Am J

Clin Nutr 1995;61:1140-5.

 

11. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D

concentrations, and safety. Am J Clin Nutr 1999;69:842-56.

 

12. Heaney RP. Lessons for nutritional science from vitamin D. Am J

Clin Nut 1999;69:825-6.

 

13. Holick MF, et al. The vitamin D content of fortified milk and

infant formula, New Eng J Med 1992;326:1178-81.

 

14. Hicks T, et al. Procedures used by North Carolina dairies for

vitamin A and D fortification of milk. J Dairy Sci 1996;79:329-33.

 

15. Grimes DS, et al. Sunlight, cholesterol and coronary heart

disease. Q J Med 1996;89:579-89.