The bone-building benefits of vitamin D have been known for decades. However, there's a host of other reasons for a daily dose of D. Studies show that it could help to prevent life-threatening conditions, ranging from heart and lung disease to diabetes and cancer.
Vitamin D can protect against cancer. The German Cancer Research Center found that higher levels of vitamin D can cut the risk of colorectal cancer by up to 60 per cent (Aliment Pharmacol Ther, 2009 Apr 16; Epub ahead of print). Similar risk reductions have also been seen for breast and prostate cancers (Clin J Am Soc Nephrol, 2008; 3: 1548-54). Also, one review found that not getting enough vitamin D could be responsible for several thousands of premature deaths from cancer each year (Am J Public Health, 2006; 96: 252-61).
Vitamin D's anticancer activity is thought to be due to its role as a 'nuclear transcription factor' that regulates cell growth, differentiation, apoptosis (cell death) and other cellular mechanisms necessary for the development of cancer (Curr Med Res Opin, 2008; 24: 139-49).
High doses of vitamin D can reduce levels of prostate-specific antigen (PSA)-a marker of cancer severity-by half in 80 per cent of prostate cancer patients (Urol Oncol, 2003; 21: 399- 405). The vitamin can slow progression of breast cancer, too (J Clin Pathol, 2006; 59: 1334-6). Although more research is needed, vitamin D may be a useful weapon against this deadly disease.
Vitamin D also brings benefits to the heart. Looking at vitamin D levels in 1739 older adults in relation to blood pressure and other cardiovascular risk factors, those with low levels of the vitamin had a 62-per-cent greater risk of a cardiovascular event compared with those who had higher levels (Circulation, 2008; 117: 503-11).
Also, low levels of vitamin D are associated with a higher incidence of peripheral arterial disease (PAD), or narrowing of the arteries. On looking at nearly 5000 participants in the National Health and Nutrition Examination Survey (NHANES) from 2001 to 2004, those with the lowest vitamin D levels were 80-per-cent more likely to have PAD than those with the highest levels (Arterioscler Thromb Vasc Biol, 2008; 28: 1179-85).
One of the various theories as to how vitamin D exerts its heart-protective effects is that it inhibits inflammation, known to contribute to the development of atherosclerosis (fatty buildup in arteries). Vitamin D also appears to regulate the renin- angiotensin system, which plays an important role in hypertension and cardiovascular health (Kidney Int, 2005; 68: 1973-81).
It's known that vitamin D plays a key role in glucose homeostasis, and in insulin release and response, and is linked with the development of both type 1 and 2 diabetes (Prim Care Diabetes, 2009 Apr 21; Epub ahead of print; Diabetologia, 2005; 48: 1247-57). In a Finnish study of more than 12,000 babies followed for over 30 years, the children who regularly took vitamin D supplements had a lower rate of type 1 diabetes than those who did not, while those suspected of having rickets-another condition linked to vitamin D deficiency-had a threefold increased risk of diabetes (Lancet, 2001; 358: 1500-3).
Additional research from Finland reported that men with the highest vs lowest levels of vitamin D had a 70-per-cent lower risk of type 2 diabetes (Epidemiology, 2008; 19: 666-71).
As more and more research is being done, scientists are discovering that vitamin D may help to protect against a variety of other conditions, such
as dementia, depression, asthma, multiple sclerosis, and bacterial and viral infections (J Alzheimers Dis, 2009; 17: 151-9; J Cell Biochem, 2008; 105: 338-43; Curr Opin Allergy Clin Immunol, 2009; 9: 202-7). Considering the dangerous drugs commonly used to treat these conditions, we should all be making sure that we're getting enough of this essential vitamin.
Getting enough vitamin D
As many of us-especially children and teens-aren't getting enough of this vitamin (CMAJ, 2007; 177: 161-6; Curr Opin Pediatr, 2009 Jun 4; Epub ahead of print), how can we ensure that we're not D-deficient?
- Sunshine. The body naturally produces vitamin D when the skin is exposed to sunlight, and just 10-15 minutes of sunshine a day, without sunscreen, is enough (BMJ, 2003; 327: 1228). Sensible exposure, and supplementing with antioxidants such as selenium, lycopene, beta-carotene, and vitamins C and E, will allow you to enjoy the sun without the need for potentially harmful chemical sunscreens (see also WDDTY vol 19 no 3, pages 20-1).
- Supplements. For those who don't get much sun, supplementing with 600-1000 IU of vitamin D3 (the natural form) is a good idea. Regularly taking as much as 10,000 IU/day poses no risk of adverse effects in adults (Ann Epidemiol, 2009 Apr 11; Epub ahead of print). In children, 800-1000 IU/day is recommended for fighting disease by US vitamin D expert Adrian Gombart (http://wcbstv.com/national/vitamin.d.kids.2.838828.html).
- Diet. Vitamin D is also found in a number of foods, including milk, yoghurt, eggs and fatty fish. However, watch out for the high mercury content in some fish (see also WDDTY vol 17 no 10, pages 20-1).
Vol. 20 04 July 2009