It may seem strange to emphasize the importance of vitamin D if it’s the summer, yet many of us will continue to require supplementation despite the abundance of seasonal sunshine. If your levels are low, a one or two week vacation at the beach probably won’t be enough to replenish this vitamin to adequacy. And, if you work indoors or wear sunscreen religiously when you go outside (and good for you if you do), you should be supplementing with vitamin D.
In addition to its positive effects on bone health and calcium absorption, vitamin D offers powerful cancer protection. Some of the most ground-breaking findings in nutrition science in recent years have been evidence of the vitamin D ability to defend against cancer. More than 800 scientific papers have been published on the relationship between vitamin D and cancers. We now have ample evidence that maintaining adequate vitamin D levels is an effective cancer-protection strategy. Research suggests that vitamin D adequacy reduces the risk of death in breast, colorectal, lung and prostate cancer, leukemia and lymphomas and all cancers combined. A 2014 analysis on vitamin D supplementation found that it was associated with reduced risk of cancer mortality.
Evidence of Vitamin D’s Ability to Decrease Cancer Risk
The idea that vitamin D could protect against cancers originated from observations that colon cancer mortality was highest in areas that got the least amount of sunlight.
Several studies have found an inverse relationship between sun exposure and 24 different types of cancer, including some of the most common—breast, colon, rectum, and prostate. Because most people’s primary vitamin D source is sunlight, and darker skin is less efficient at producing the vitamin in response to UV rays, vitamin D insufficiency is thought to be one reason for the cancer survival disparities that exist between African Americans and white Americans.
Evidence suggesting vitamin D’s involvement in decreasing cancer risk has steadily grown. Additional support for vitamin D’s importance in cancer prevention was provided by randomized controlled trials of vitamin D supplementation that showed reduced cancer risk compared to a placebo. There have also been many reports that vitamin D receptor gene mutations, which interfere with the normal biological actions of vitamin D, were associated with increased cancer risk.
Additional studies have confirmed that vitamin D can block cancer cell growth in a number of ways: Vitamin D alters the expression of genes that control inflammation, cell death and cell proliferation, and also interferes with the growth-promoting actions of IGF-1 and other growth factors. It also enhances DNA repair and immune defenses, and angiogenesis inhibition.
Vitamin D and Healthy Aging
In addition to cancer prevention, making sure that vitamin D levels are adequate may help to reduce the risk of frailty and falls. Falls can be devastating for older adults, a major cause of fractures, head injuries, and accidental deaths in older people. After a fall, it is common for an elderly person to experience an accelerated decline in physical function and a loss of independence.
About 25 percent of elderly Americans who fall die within six months, and more than 50 percent are discharged to a nursing home.
Loss of muscle mass and vitamin D deficiency are two of the risk factors for falls, and these factors are connected. One of vitamin D’s lesser known properties is its beneficial effect on muscle function, by altering gene expression and calcium transport in muscle cells. Low vitamin D is associated with reduced muscle strength in the elderly, and vitamin D supplementation has been found to improve muscle strength and balance.
Very few foods naturally contain vitamin D and achieving adequate levels via sunlight can be difficult, depending on where you live, time spent outside, and your skin color. Plus sun exposure carries risk of skin damage and the risk of skin cancer.
A moderate daily dose of a vitamin D3 supplement (which is the natural form of the vitamin and it is a safer, higher-quality supplement than vitamin D2), is a sensible option for most individuals. As suggested by scientific evidence, aim for a blood level of 30 to 45 ng/ml. For most people, that will mean supplementing with approximately 1000 to 2000 IUs of vitamin D daily.