In addition to being essential for healthy bones and teeth, mounting evidence shows that vitamin D significantly reduces the risk for cancer.
The Canadian Cancer Society (CCS) recommends that Canadians increase their intake of vitamin D to 1000 international units (IU) a day during the fall and winter.
The CCS also suggests that adults at risk for lower than normal vitamin D levels take 1000 IU vitamin D a day 365 days a year.
The recommendation by the CCS is based on a growing body of evidence which shows that vitamin D reduces the risk for breast, colorectal and prostate cancers.
The recommendation was based in part on data just published in the American Journal of Clinical Nutrition.
The study shows that “improving calcium and vitamin D nutritional status substantially reduces all-cancer risk in postmenopausal women.”
This study was a randomized, double-blind, population-based trial that took place over four years. During that time the researchers found that “both treatment and serum 25-hydroxy vitamin D concentrations were significant, independent predictors of cancer risk:” meaning the lower the levels of vitamin D, the higher the risk for cancer.
The daily dose of vitamin D in the study was 1100 IU.
Over the past few months several studies have been published indicating a wide range of health benefits associated with vitamin D— not just in cancer.
The Wellcome Trust (United Kingdom) reported findings which indicate that a single 2.5 mg dose of vitamin D could boost the immune system enough to fight tuberculosis.
Also in May, the Journal of the American Medical Association (JAMA) and Archives Journals published findings that linked a lower risk of age-related macular disease with higher intakes of vitamin D. And JAMA and Archives Journals also reported in May that calcium and vitamin D may help prevent weight gain in postmenopausal women.
These are just a few of the many, many studies showing a wide variety of health benefits for vitamin D – from heart disease to obesity and depression. I remember reporting on a study over two years ago that showed a link between increased risk for renal and ovarian cancers in women with low vitamin D levels.
So what does vitamin D do that makes it so special?
Well, in addition to playing an essential role in musculoskeletal growth – bones and teeth specifically – it also bolsters the immune system. Scientist are now discovering that vitamin D appears to promote normal cell growth and differentiation, which is important in maintaining hormonal balance and a healthy immune system.
In truth, researchers are still trying to determine the full range of affects that vitamin D has within the body, but so far it appears to have far reaching and unexpected benefits.
Our bodies don’t store vitamin D. We make it on exposure to sunlight – ultraviolet B (UVB) light specifically. So many of us living in northern latitudes – away from the sunny tropics and subtropics – need to take vitamin D supplements: we don’t get enough natural sunlight during the course of year to maintain adequate levels of vitamin D.
Two years ago I attended an international conference on vitamin D, and learned that many world renowned scientists, including researchers from NASA, have, for several years, been studying the health benefits of vitamin D as they relate to different geographic populations.
What they’ve discovered is that the incidence for cancer increases the farther away from the equator populations are located. In other words, people who live in places that are sunny most, if not all of the year, have lower incidences of certain types of cancer: natural exposure to sunlight (ultraviolet radiation) is associated with a reduced risk for cancer.
What about sun exposure and skin cancer?
Just because vitamin D from sunshine is good for us, doesn’t mean we should abandon our sunscreens and go out into the sun unprotected for large amounts of time.
UV light exposure is well recognized as the leading cause of skin cancer. The two types of UV rays of most concern are UVA and UVB. UVA is associated with penetrating radiation, while UVB causes sunburn. Sunscreens or sun block creams typically block both.
If you’re planning on increasing your vitamin D levels through sun exposure this summer try to find a sunscreen that blocks more UVA than UVB.
It’s also important to note that you don’t need to be out in the sun all day to make vitamin D. Just 15 to 20 minutes twice a day on our arms and face is sufficient for most of us to optimize our vitamin D levels.
What about tanning beds? Are they a safe source of vitamin D?
The short answer is “No”. That’s because sun beds emit both UVA and UVB. While most sun beds can be calibrated to emit different ratios of UVA and UVB, the longer lasting, golden brown tan that people want when they visit a tanning salon is caused by exposure to UVA.
So, typically, sun beds in tanning salons are calibrated to emit more UVA than UVB. If you already go to a tanning salon, ask the manager or operator of the salon what the ratios of UVA/UVB for their beds, and make your decision accordingly.
Vitamin D supplements are the best bet
Because many of us can’t get outside for an hour or so every day, and even if we could there’s no guarantee it will be sunny, vitamin D supplements are likely the best bet. Also, there’s no associated risk of skin cancer with vitamin D supplements.
Vitamin D with calcium, vitamin D3, cod liver oil supplements are all good. If you’re unsure of what to take talk to you health care practioner or a nutritionist about what might be best for you. Many health food stores have dieticians and nutritionists on staff.
Tips for preventing vitamin D deficiency
- Eat a nutrient-dense diet that includes whole foods and complex carbohydrates. Mackerel and sardines – fatty fish – are an excellent source of vitamin D. Fortified organic milk, eggs, and other dairy produces also provide a source of vitamin D.
- Consult your health care professional about taking a daily vitamin D supplement. Fish oil supplements such as cod liver oil are a good source of vitamin D, and if you are already taking a multi-vitamin – you will have increased your daily vitamin D intake. To be on the safe side – 200 IU is a minimum daily recommended intake- and 1000 IU is the current maximum. It is possible to overdose on vitamin D – so don’t exceed 1000 IU a day.
- Get outside in the sunshine. Unless you’ve had skin cancer, try to get some early morning and late afternoon sun exposure between May and September, for a maximum of 15 minutes a day if you are light skinned, and 40 minutes a day if you are dark skinned. This is especially important if you live in northern latitudes.
Risk Factors for Vitamin D Deficiency*
- Exclusively breast fed infants: Babies fed exclusively on breast mild who do not receive vitamin D supplementation are at high risk of vitamin D deficiency, particularly if they have dark skin and/or receive little sun exposure. The American Academy of Pediatrics recommends that all infants that are not consuming at least 500 ml (16 ounces) of vitamin D fortified formula or milk be given a vitamin D supplement of 200 IU/day.
- Dark skin: People with dark skin synthesize less vitamin D on exposure to sunlight than those with light skin. The risk of vitamin D deficiency is particularly high in dark-skinned people who live far from the equator.
- Aging: The elderly have reduced capacity to synthesize vitamin D in the skin when exposed to UVB radiation, and are more likely to stay indoors or use sunscreen.
- Covering all exposed skin or using sunscreen whenever outside: Osteomalacia has been documented in women who cover all of their skin whenever they are outside for religious or cultural reasons (26, 27). The application of sunscreen with an SPF factor of 8 reduces production of vitamin D by 95% (1).
- Fat malabsorption syndromes: Cystic fibrosis and cholestatic liver disease impair the absorption of dietary vitamin D.
- Inflammatory bowel disease: People with inflammatory bowel disease like Crohn’s disease appear to be at increased risk of vitamin D deficiency, especially those who have had small bowel resections.
- Obesity: Obesity increases the risk of vitamin D deficiency. Once vitamin D is synthesized in the skin or ingested, it is deposited in body fat stores, making it less bioavailable to people with large stores of body fat.
* Reference: Oregon State University:
