Laboratory and animal evidence as well as epidemiologic data suggest that vitamin D status could affect cancer risk. Strong biological and mechanistic bases indicate that vitamin D plays a role in the prevention of colon, prostate, and breast cancers. Emerging epidemiologic data suggest that vitamin D may have a protective effect against colon cancer, but the data are not as strong for a protective effect against prostate and breast cancer, and are variable for cancers at other sites [1,51,52]. Studies do not consistently show a protective or no effect, however. One study of Finnish smokers, for example, found that subjects in the highest quintile of baseline vitamin D status had a threefold higher risk of developing pancreatic cancer . A recent review found an increased risk of pancreatic cancer associated with high levels of serum 25(OH)D (≥100 nmol/L or ≥40 ng/mL) .
Takagi, H., Kakizaki, S., Sohara, N., Sato, K., Tsukioka, G., Tago, Y., Konaka, K., Kabeya, K., Kaneko, M., Takayama, H., Hashimoto, Y., Yamada, T., Takahashi, H., Shimojo, H., Nagamine, T., and Mori, M. Pilot clinical trial of the use of alpha-tocopherol for the prevention of hepatocellular carcinoma in patients with liver cirrhosis. Int J Vitam Nutr Res 2003;73(6):411-415. View abstract.
Bedri, A., Gudetta, B., Isehak, A., Kumbi, S., Lulseged, S., Mengistu, Y., Bhore, A. V., Bhosale, R., Varadhrajan, V., Gupte, N., Sastry, J., Suryavanshi, N., Tripathy, S., Mmiro, F., Mubiru, M., Onyango, C., Taylor, A., Musoke, P., Nakabiito, C., Abashawl, A., Adamu, R., Antelman, G., Bollinger, R. C., Bright, P., Chaudhary, M. A., Coberly, J., Guay, L., Fowler, M. G., Gupta, A., Hassen, E., Jackson, J. B., Moulton, L. H., Nayak, U., Omer, S. B., Propper, L., Ram, M., Rexroad, V., Ruff, A. J., Shankar, A., and Zwerski, S. Extended-dose nevirapine to 6 weeks of age for infants to prevent HIV transmission via breastfeeding in Ethiopia, India, and Uganda: an analysis of three randomised controlled trials. Lancet 7-26-2008;372(9635):300-313. View abstract.
Chintu, C., Bhat, G. J., Walker, A. S., Mulenga, V., Sinyinza, F., Lishimpi, K., Farrelly, L., Kaganson, N., Zumla, A., Gillespie, S. H., Nunn, A. J., and Gibb, D. M. Co-trimoxazole as prophylaxis against opportunistic infections in HIV-infected Zambian children (CHAP): a double-blind randomised placebo-controlled trial. Lancet 11-20-2004;364(9448):1865-1871. View abstract.
Calcium: Health benefits, foods, and deficiency Calcium is essential for living organisms, including humans. It is vital for preserving bone strength and preventing diseases of the skeleton, such as osteoporosis. Find out about calcium's role in human health and foods that contain calcium. Discover also the risks of calcium deficiency and possible remedies. Read now
Ortonne, J. P., Humbert, P., Nicolas, J. F., Tsankov, N., Tonev, S. D., Janin, A., Czernielewski, J., Lahfa, M., and Dubertret, L. Intra-individual comparison of the cutaneous safety and efficacy of calcitriol 3 microg g(-1) ointment and calcipotriol 50 microg g(-1) ointment on chronic plaque psoriasis localized in facial, hairline, retroauricular or flexural areas. Br J Dermatol 2003;148(2):326-333. View abstract.
Mockenhaupt, F. P., Reither, K., Zanger, P., Roepcke, F., Danquah, I., Saad, E., Ziniel, P., Dzisi, S. Y., Frempong, M., Agana-Nsiire, P., Amoo-Sakyi, F., Otchwemah, R., Cramer, J. P., Anemana, S. D., Dietz, E., and Bienzle, U. Intermittent preventive treatment in infants as a means of malaria control: a randomized, double-blind, placebo-controlled trial in northern Ghana. Antimicrob.Agents Chemother. 2007;51(9):3273-3281. View abstract.
Supplementation with beta-carotene, with or without retinyl palmitate, for 5–8 years has been associated with an increased risk of lung cancer and cardiovascular disease in current and former male and female smokers and in male current and former smokers occupationally exposed to asbestos [27,41]. In the ATBC study, beta-carotene supplements (20 mg daily) were also associated with increased mortality, mainly due to lung cancer and ischemic heart disease . The CARET study ended early, after the investigators found that daily beta-carotene (30 mg) and retinyl palmitate (25,000 IU) supplements increased the risk of lung cancer and cardiovascular disease mortality .
Following the final converting step in the kidney, calcitriol is released into the circulation. By binding to vitamin D-binding protein, calcitriol is transported throughout the body, including to the classical target organs of intestine, kidney and bone. Calcitriol is the most potent natural ligand of the vitamin D receptor, which mediates most of the physiological actions of vitamin D.
Villablanca, J. G., London, W. B., Naranjo, A., McGrady, P., Ames, M. M., Reid, J. M., McGovern, R. M., Buhrow, S. A., Jackson, H., Stranzinger, E., Kitchen, B. J., Sondel, P. M., Parisi, M. T., Shulkin, B., Yanik, G. A., Cohn, S. L., and Reynolds, C. P. Phase II study of oral capsular 4-hydroxyphenylretinamide (4-HPR/fenretinide) in pediatric patients with refractory or recurrent neuroblastoma: a report from the Children's Oncology Group. Clin.Cancer Res 11-1-2011;17(21):6858-6866. View abstract.
Two forms of vitamin A are available in the human diet: preformed vitamin A (retinol and its esterified form, retinyl ester) and provitamin A carotenoids [1-5]. Preformed vitamin A is found in foods from animal sources, including dairy products, fish, and meat (especially liver). By far the most important provitamin A carotenoid is beta-carotene; other provitamin A carotenoids are alpha-carotene and beta-cryptoxanthin. The body converts these plant pigments into vitamin A. Both provitamin A and preformed vitamin A must be metabolized intracellularly to retinal and retinoic acid, the active forms of vitamin A, to support the vitamin's important biological functions [2,3]. Other carotenoids found in food, such as lycopene, lutein, and zeaxanthin, are not converted into vitamin A.
Griffiths, C. E., Kang, S., Ellis, C. N., Kim, K. J., Finkel, L. J., Ortiz-Ferrer, L. C., White, G. M., Hamilton, T. A., and Voorhees, J. J. Two concentrations of topical tretinoin (retinoic acid) cause similar improvement of photoaging but different degrees of irritation. A double-blind, vehicle-controlled comparison of 0.1% and 0.025% tretinoin creams. Arch Dermatol 1995;131(9):1037-1044. View abstract.
The body's stores for different vitamins vary widely; vitamins A, D, and B12 are stored in significant amounts, mainly in the liver, and an adult's diet may be deficient in vitamins A and D for many months and B12 in some cases for years, before developing a deficiency condition. However, vitamin B3 (niacin and niacinamide) is not stored in significant amounts, so stores may last only a couple of weeks. For vitamin C, the first symptoms of scurvy in experimental studies of complete vitamin C deprivation in humans have varied widely, from a month to more than six months, depending on previous dietary history that determined body stores.