CANCER SUPPORTVitamin D for Cancer Treatment and Prevention
If I had to choose a favorite vitamin it would probably be the ‘sunshine vitamin’, aka vitamin D. I love the concept that sunlight provides humans with an essential vitamin which then helps the body in so many ways.
What is vitamin D?
Vitamin D is unique among essential vitamins as it can be synthesized by the body through exposure to sunlight. Our skin, when bathed in the sun’s ultraviolet B (UVB) rays, undergoes a transformation, converting 7-dehydrocholesterol into vitamin D3. This naturally occurring form is then transported to the liver and kidneys, where it is converted into its active, hormonal state, calcitriol. In addition, smaller amounts of vitamin D are absorbed from foods, particularly foods that have been supplemented.
Vitamin D plays an important role in maintaining healthy bones by aiding absorption of calcium and phosphorus. It has also been found in laboratory studies to play a role in reducing cancer cell growth, help with controlling infections, and reducing inflammation.
Vitamin D insufficiency is a global problem. It is estimated that 50% of the world’s population has vitamin D insufficiency! It is particularly prevalent in countries which are at a higher longitude with less sun exposure throughout the year. Between 75% to 97% of Canadians are believed to have vitamin D insufficiency.
Vitamin D and Cancer Prevention
The link between vitamin D and cancer prevention has been a subject of investigation for decades. Numerous observational studies have suggested an inverse relationship between vitamin D levels and the risk of various cancers, including breast, colorectal, prostate, and pancreatic cancers. A meta-analysis published in the Journal of Clinical Endocrinology and Metabolism in 2018 pooled data from numerous observational studies, revealing that higher vitamin D levels were associated with a reduced risk of colorectal cancer.
A meta analysis of randomized controlled trials in 2019 found that vitamin D supplementation significantly reduced total cancer mortality but did not reduce total cancer incidence. Another randomized controlled trial randomized adults to receive 2000 IU of vitamin D per day or placebo, for 5 years, and did not reveal any difference in cancer outcomes.
Cancer prevention studies are always difficult to conduct, as it is believed that 20 years of follow up is required to truly see if an exposure (vitamin D) can help reduce subsequent cancer risk.
Vitamin D with cancer treatment
I would like to emphasize that vitamin D is not recommended as a stand-alone cancer treatment. But there are clinical studies which have found that when it is used in conjunction with convention chemotherapy it may help enhance the effects of the chemotherapy. The SUNSHINE phase II randomized control trial compared metastatic colon cancer patient who received chemo and either standard dose vitamin D (400 IU) or high dose vitamin D (4000 IU). The study results found that the high dose vitamin D group had a longer progression-free survival (13 vs 11 months) and were 36% less likely to have disease progression or death during the follow-up period of 22.9 months. The SUNSHINE phase III study is being conducted in many centres across the US and the results will be very interesting.
Vitamin D has also been shown to help reduce side effects of chemotherapy and also improve the quality of life of cancer patients undergoing conventional cancer treatment.
What is the best dose of vitamin D supplementation?
This is a hard one. The answer is likely to be different for each individual depending on baseline vitamin D levels, ethnicity, environment, age, sex, and genetics.
Sunlight exposure
Regular, moderate exposure to sunlight is a natural and effective way to boost vitamin D levels. Aiming for 10-30 minutes of sunlight exposure several times per week is a good starting point. Don’t forget to wear sunscreen!
Supplements
The recommended daily allowance (RDA) for vitamin D is 600-800 IU for adults but it seems that larger doses are likely required for cancer prevention benefits. The SUNSHINE study found that 4000 IU per day improved cancer outcomes, but not 400 IU per day. However, higher doses should only be administered under the guidance of a healthcare professional, and regular monitoring of vitamin D levels is important to prevent toxicity.
References
Kimmie Ng et al. J Clin Oncol 35, 2017 (suppl; abstr 3506)
Keum N, Lee DH, Greenwood DC, Manson JE, Giovannucci E. Vitamin D supplementation and total cancer incidence and mortality: a meta-analysis of randomized controlled trials. Annals of Oncology; 30(5) 2019
Manson JE, Cook NR, Lee IM, Christen W, et all. Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. N Engl J Med 2019; 380:33-44
