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The Sunshine Vitamin and CancerAn exciting study was published a few of weeks back in the American Journal of Clinical Nutrition that indicates that getting enough Vitamin D is important for reducing one's risk of cancer. Post-menopausal women that took 1100iu on vitamin D daily reduced their risk of cancer by up to 60%, which is nothing short of astounding. Already the Canadian Cancer Society has suggested that all adults should all take 1000iu of Vitamin D a day in the winter months, and that dark-skinned people should take 1000iu of Vitamin D a day year round. Although this level of supplementation is probably safe for the vast majority of people and many may in fact need more, in my opinion, Vitamin D status must be assessed not only before supplementation, but also every six months or so, so that the appropriate dosage for the individual can be established, as at high levels Vitamin D can be toxic. We are all biochemically different, get different amounts of sun, eat different diets, and these individual differences must be taken into account. So go see your doctor for a simple blood test if you are planning to or are supplementing with Vitamin D. Optimal levels of 25(OH)D are 40-50ng/ml. Vitamin D deficiencies are extremely common, and are also linked to osteoporosis, heart disease, Type 1 and Type 2 diabetes, obesity, infertility, fibromyalga, chronic fatigue syndrome, depression, autoimmune diseases like multiple sclerosis, rheumatoid arthritis, Crohns disease, and Sjogren's Disease.
Vitamin D works differently from the other vitamins, as it is converted into and used as a hormone in the body. It controls blood levels of calcium, so if there is not enough calcium in the diet, calcium will be taken from the bones to keep the blood happy. In the opposite scenario, when calcium levels are high and D levels are low, it is believed that the result may be calcification of joints, arteries, and kidneys. Vitamin D is a very potent antioxidant - more potent than Vitamin E, and is also very important in immune function and cell repair.
So why have our levels of Vitamin D dropped? We are told to slather ourselves in sunscreen before going out the door, which blocks our ability to synthesize vitamin D. We are also told to avoid the midday sun, but it is the UV-B rays that are needed to manufacture Vitamin D, and those rays are only potent enough for Vitamin D synthesis between 10am and 2pm in the warmer months. The higher the latitude, the fewer months of the year that UV-B is strong enough for us to make Vitamin D. The guidelines to avoid the sun are to avoid skin cancer, but according to John Cannell of the non-profit Vitamin D Council in California, about 1500 Americans die each year of skin cancer, whereas 1500 Americans die each day of the kinds of cancers that could be helped with adequate sun exposure. And skin cancer is relatively easy to detect and treat. So, are we throwing out the baby with the bathwater? Spending enough time in the sun without letting oneself burn looks to me to be a healthy practice. Many of the food sources of Vitamin D we are wrongly told not to eat, so diets low in saturated fat may also be low in vitamin D. Increased levels of mono-unsaturated fats and omega 6 polyunsaturated fats decrease the assimilation of Vitamin D from the diet, whereas omega 3 fats and saturated fats aid in its assimilation. Those with very low cholesterol levels due to statin drugs or otherwise would have difficulty synthesizing Vitamin D, as it is the cholesterol in the skin that converts the UV-B rays into the health-giving vitamin. I am wondering if it is through this mechanism that statin drugs may be associated with higher risks of cancer.
According to the USDA the best dietary sources of Vitamin D in order of potency include:
- high vitamin cod liver oil (read the label!)
- lard (pork fat)
- pickled Atlantic herring
- eastern oysters
- catfish
- sardines
- mackerel
- chinook salmon
- sturgeon roe
- shrimp
- egg yolk (fresh)
- butter
- liver
How steroids, hormones and neurotransmitters work
Breast / Prostate cancer prevention
Lappe JM et al. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial Am J Clin Nutr Vol 85(6) 1586-1591, June 2007.
Lin J. et al. Intakes of calcium and Vitamin D and breast cancer risk in women Arch Intern Med Vol 167(10) 1050-1059, May 2007.
Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety Am J Clin Nutr 1999;69:842-56.
Glerup H, Mikkelsen K, Poulsen L et al. Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited. J Intern Med 2000;247:260-8.
Webb AR, Kline L, Holick MF. Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J Clin Endocrinol Metab 1988;67:373-8.
Cantorna MT. Vitamin D and autoimmunity: is vitamin D status an environmental factor affecting autoimmune disease prevalence? Proc Soc Exp Biol Med 2000;223:230-3.
Vogelsang H, Ferenci P, Woloszczuk W et al. Bone disease in vitamin D-deficient patients with Crohn's disease. Dig Dis Sci 1989;34:1094-9.
Bettica P, Bevilacqua M, Vago T, Norbiato G. High prevalence of hypovitaminosis D among free-living postmenopausal women referred to an osteoporosis outpatient clinic in northern Italy for initial screening. Osteoporos Int 1999;9:226-9.
Kinuta K, Tanaka H, Moriwake T, Aya K, Kato S, Seino Y. Vitamin D is an important factor in estrogen biosynthesis of both female and male gonads. Endocrinology 2000;141:1317-24.
Gloth FM, III, Alam W, Hollis B. Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder. J Nutr Health Aging 1999;3:5-7.
Sato Y, Kikuyama M, Oizumi K. High prevalence of vitamin D deficiency and reduced bone mass in elderly women with Alzheimer's disease. Neurology 1997;49:1273-8.
Sato Y, Asoh T, Oizumi K. High prevalence of vitamin D deficiency and reduced bone mass in Parkinson's disease.. Bone 1998;23:555-7.
Chiu KC et al. Hypovitaminosis D is associated with insulin resistance and beta cell dysfunction. Am J Clin Nutr. 2004 May, 79(5): 820-5.
Watson KE, Abrolat ML, Malone LL et al. Active serum vitamin D levels are inversely correlated with coronary calcification Circulation 1997;96:1755-60.
Wortsman J, Matsuoka LY, Chen TC, Lu Z, Holick MF. Decreased bioavailability of vitamin D in obesity. Am J Clin Nutr 2000;72:690-3.
Bouillon R, Xiang DZ, Convents R, Van Baelen H. Polyunsaturated fatty acids decrease the apparent affinity of vitamin D metabolites for human vitamin D-binding protein. J Steroid Biochem Mol Biol 1992;42:855-61.
Muller K, Bendtzen K. 1,25-Dihydroxyvitamin D3 as a natural regulator of human immune functions. J Investig Dermatol Symp Proc 1996;1:68-71.
Online at The Miracle of Vitamin D Weston A. Price Foundation.
Online at Vitamin D Council
Copyright 2007 Vreni Gurd