The role of your cancer health professional is to create an environment of openness and trust, and to help in making informed decisions about alternative/ complementary therapies. Collaboration will improve the safe integration of all therapies during your experience with cancer. The "Summary" and "Professional Evaluation/ Critique" sections of this Unconventional Therapies manual are cited directly from the medical literature, and are intended to help in the objective evaluation of alternative/ complementary therapies.
Summary
There is no definitive evidence that vitamin D is effective as a preventive agent or as a treatment for cancer in humans. Further study is necessary. The use of vitamin D may be limited by its toxicity.
"High doses of vitamin D are toxic which may cause an excess of calcium in the blood. Extreme cases may lead to death." (Ontario)
Description/ Source/ Components
Vitamin D is found in natural sources such as herring, mackerel, "fortified milk, fish liver oils, and liver. Vitamin D is also made by the body upon exposure to sunlight." (Ontario)
"Vitamin D compounds are important components of the endocrine system - being largely responsible for calcium metabolism." (Rigby)
The adult daily recommended intake for vitamin D is 2.5-5ug (or 100-200 international units). 1 ug vitamin D = 40 IU's. (Health and Welfare Canada)
Proponent/ Advocate Claims - Use in Preventing Cancer
"The likelihood of developing colon cancer is higher in areas where people have limited exposure to sunlight (the necessary factor for production of vitamin D in the skin) than in areas where the sun shines frequently." (Somer)
Proponents believe vitamin D helps to inhibit the growth of cancer cells. (Ontario)
"New studies indicate that vitamin D reduces the number of colon tumors that develop in the presence of carcinogen. Vitamin D also inhibits the growth of premalignant cells in the lining of the colon, which might prevent colon cancer." (Somer)
"Based on examples in many different malignant cells, vitamin D appears to be antiproliferative and promotes cellular maturation. It must be viewed as an important cellular modulator of growth and differentiation in addition to its classical role as regulator of calcium homeostasis. 1,25-D3 [calcitriol] and its analogs may prove useful in cancer chemoprevention." (Ren)
Professional Evaluation/ Critique - Use in Preventing Cancer
"The data currently available provide the basis for an optimistic view on the possible use of vitamin D as a cancer chemopreventive agent, although further investigation is clearly warranted to better define its potential chemopreventive utility in humans." (Ren)
"High doses of vitamin D are toxic which may cause an excess of calcium in the blood. Extreme cases may lead to death." (Ontario)
Proponent/ Advocate Claims - Use in Treating Cancer
There have been recent studies published that show that calcitriol and cholecalciferol can inhibit the growth and metastasis of induced tumors in rodents. (Lokeshwar) (Yudoh) (Evans) (Fujioka) (Getzenberg)
Gross and colleagues performed an open label, non-randomized pilot trial to determine whether calcitriol therapy is safe and efficacious for early recurrent prostate cancer. Their hypothesis was that "calcitriol therapy slows the rate of rise of prostate specific antigen (PSA) compared with the pretreatment rate." [Note: After primary treatment with radiation or surgery, the rise in blood levels of prostate specific antigen (PSA) can indicate a recurrence of prostate cancer activity.] "The pilot trial study provided preliminary evidence that calcitriol effectively slows the rate of PSA rise in select cases, although dose dependent calciuric side effects limit its clinical usefulness. The development of calcitriol analogues with decreased calcemic side effects is promising, since such analogues may be even more effective for treating prostate cancer." (Gross)
"Calcitriol may have therapeutic use as an immunoregulatory agent." (Rigby)
Professional Evaluation/ Critique - Use in Treating Cancer
There have been no studies published in any peer-reviewed journal [according to a literature search done in Medline and Cancerlit (June 1999)] that prove the efficacy of vitamin D or its analogues as a cure for cancer in humans.
"...the use of 1,25(OH)2D [calcitriol] in vivo is limited by the risk of hypercalcemia" (Lokeshwar)
Dose dependent calciuric side effects of calcitriol limit its clinical usefulness. (Gross)
Toxicity/ Risks
"Vitamin D is the most toxic of all the vitamins. As little as 2,000 IU a day - only five times required amounts - can be toxic to children." (McDonald)
"Vitamin D overdose becomes evident in elevated blood calcium levels causing symptoms of anorexia, nausea and vomiting, polyuria [the passage of a large volume of urine], polydipsia [chronic excessive intake of water], weakness, pruritus [itching], and nervousness, potentially with irreversible calcification of soft tissue in the kidney and liver. As newer, more highly active forms of vitamin D are developed, it becomes imperative to monitor even more carefully for this potential toxicity." (Spencer)
"Large doses of vitamin D also are linked to increased risk for premature heart attack, atherosclerosis, and possibly kidney stones in people who are predisposed to kidney problems. Vitamin D overdose develops over time and there is wide variation among individuals in their tolerance to toxicity." (Somer)
"Prolonged exposure to sunlight does not cause vitamin D toxicity. The body has an efficient feedback system and reduces the production of vitamin D with increased exposure to sunlight." (Somer)
References
Evans SR, et al. Growth inhibition effects of 1,25-dihydroxyvitamin D3 and its synthetic analogue, 1alpha,25-dihydroxyvitamin-16-ene-23yne-26,27-hexafluoro-19-n or cholecalciferol (Ro 25-6760), on a human colon cancer xenograft. Clin Cancer Res 1998;4:2869-76.
Fujioka T, et al. Inhibition of tumor growth and angiogenesis by vitamin D3 agents in murine renal cell carcinoma. J Urol 1998;160:247-51.
Getzenberg RH, et al. Vitamin D inhibition of prostate adenocarcinoma growth and metastasis in the Dunning rat prostate model system. Urology 1997;50:999-1006.
Gross C, et al. Treatment of early recurrent prostate cancer with 1,25-dihydroxyvitamin D3 (calcitriol). J Urol 1998;159:2035-9.
Health and Welfare Canada. Nutrition recommendations. The Report of the Scientific Review Committee 1990.
(deleted quote)Lokeshwar BL, et al. Inhibition of prostate cancer metastasis in vivo: a comparison of 1,23-dihydroxyvitamin D (calcitriol) and EB1089. Cancer Epidemiol Biomarkers Prev 1999;8:241-8.
McDonald A, et al. Complete book of vitamins and minerals. Publications International, Ltd., 1996;95,185.
Ontario Breast Cancer Information Exchange Project. Guide to unconventional cancer therapies. 1st ed. Toronto: Ontario Breast Cancer Information Exchange Project, 1994:132-133.
Ren S, Lien E. Natural products and their derivatives as cancer chemopreventive agents. Progress in Drug Research 1997;48:148-51.
Rigby WFC. The immunobiology of vitamin D. Immunology Today 1988;9(2):54-58.
Spencer JW, Jacobs JJ. Complementary/alternative medicine: an evidence based approach. Toronto: Mosby, 1999:148.
Yudoh K, et al. 1alpha,25-dihydroxyvitamin D3 inhibits in vitro invasiveness through the extracellular matrix and in vivo pulmonary metastasis of B16 mouse melanoma. J Lab Clin Med 1999;133:120-8.
Revised February 2000