Vitamin D and Cancer
by Carolyn Grobe
|Carolyn Grobe is a Holistic Health Practitioner and researcher working from her home in Crystal Lake, IL. She offers clients a wide array of natural treatment options based on individual diet and lifestyle choices.|
Scientists are now beginning to understand how sunlight activates the body to produce vitamin D and produces far-reaching health benefits. Vitamin D is not actually a vitamin, but a potent repair and maintenance neuro-steroid hormone responsible for the regulation of over 2000 genes. The potential adverse health effects of vitamin D deficiency are cancer, type 1 diabetes, multiple sclerosis, rheumatoid arthritis, cardiovascular disease, osteoporosis, and autism development (caused by prenatal deficiency).
It was recently discovered that all endothelial cells in the body (main cells which line blood and lymph vessels and the heart) are capable of converting 25-hydroxyvitamin D into its active form on their own. This conversion helps control tumor growth and cell death, and may also hinder the growth of blood vessels that feed a tumor.
A 2006 paper, Solar ultraviolet-B exposure and cancer incidence and mortality in the United States, 1993–2002, by Francis Boscoe and Maria Schymura, concluded there is an inverse relationship between solar ultraviolet-B (UV-B) exposure and non-skin cancer mortality, including gastrointestinal cancers. “The evidence is clear that exposure to solar UV-B affords protection against numerous cancers, and that current public health recommendations that advocate little or no sunlight exposure should be revisited.”
Exposure to UV-B rays in the form of sunlight is the way nature intended us to get vitamin D:
- Sunlight converts a compound in skin cells into vitamin D3.
- The liver converts D3 into 25-hydroxyvitamin D (or calcidiol), which is the major circulating form of vitamin D that clinicians use to determine vitamin D status.
- Conversion by the kidneys to the hormone 1,25 dihydroxyvitamin D (or calcitriol).
Adequate vitamin D is different for everyone and depends on where a person lives, their lifestyle, skin color, age and overall health. A young, light-skinned person in a bathing suit on a sunny summer day synthesizes as much as 20,000 or 30,000 units of vitamin D. People with very dark skin need about 10 times as much sun exposure to synthesize the same amount.
Obese people may need more vitamin D because it is sequestered in fat, and so do people who can’t readily absorb nutrients from their gut into their blood stream. People need more as they age because their skin and kidneys gradually become less efficient at synthesizing vitamin D and converting it into its active form. Those living through winter require a tropical vacation every 4-6 weeks (which is the half life of vitamin D through sunlight synthesis!)
Tips for safe sun exposure to optimize Vitamin D levels:
1. Start slowly with sun exposure. There are many medications which may cause sensitivity to sunlight. For some, Gleevec has increased sunburn potential, possibly due to the report of thinning skin, especially for those who have taken the drug for longer periods. At the beginning of the season, go out gradually, exposing as much skin as possible, working up to 15 minutes a day. Never get a sunburn. You do not need to be out during peak sun times in order to synthesize vitamin D.
2. Don’t put on hats, clothing or sunscreen until you’ve been in the sun 15 minutes. SPF-15 sunscreen will absorb 99.9% of beneficial UV-B rays. Also, car and home windows block the majority of UV-B.
3. Don’t shower immediately after sun exposure. Since the conversion is made within your skin cells up to 30-60 minutes after exposure, it is possible that soap may interfere with this process.
What if you can’t get adequate sun exposure? Reaching therapeutic ranges can be a challenge, and some people may require up to 20,000 IU per day to reach their optimal levels. It is imperative that your vitamin D levels be monitored, and it is recommended that your doctor also check serum calcium levels as a rise may indicate vitamin D toxicity.
The most accurate test to measure vitamin D is a blood test which measures total 25-hydroxyvitamin D. Another option is a home test kit where a blood spot is sent back to the lab. Either of these tests, which require a prescription, are more accurate than the measurement of 25-hydroxyvitamin D2 and D3 separately, which on average are 40% higher and may falsely reassure that your levels are optimal when they are deficient.
Dr. Michael Holick of Boston University Medical Center recommends getting blood levels of vitamin D measured once a year, in late fall. He contends if you are deficient then, you will remain so throughout the winter. The appropriate values are somewhat controversial because this area is not well defined, but these general guidelines are currently used in monitoring 25-hydroxyvitamin D levels:
Deficient: Under 40-50 ng/ml*
Optimal range: 50-65 ng/ml*
With Cancer: 65-90 ng/ml*
Excess: Over 100 ng/ml*
*1 ng/ml = 2.5 nmol/l (if your measurement is in nmol/l)
Holick believes that anytime you become vitamin D-deficient, you put yourself at increased risk of potentially developing a malignancy because you’ve lost the policing ability of vitamin D to help keep cell growth in check. He personally, as well as most of his family members, now takes 1,000 IU of vitamin D3 a day.
Relying on dietary sources alone will most likely not raise vitamin D levels significantly. There’s essentially no naturally-occurring vitamin D in our diet, and very few foods are fortified with vitamin D. Fortified milk or orange juice have only about 100 IU per glass. And Holick found that milk very often doesn’t have as much as it says it does on the label. Eating wild salmon will contribute as much as 1,000 units a serving, but you’d have to eat it every day. The addition of cod liver oil to your diet will increase your intake of vitamin D3 as well as provide the well-documented health benefits of omega 3 fatty acids.
So, eat lots of wild salmon or take cod liver oil and have your doctor check your total 25-hydroxyvitamin D to see if you require further supplementation to bring you up to therapeutic levels. If you are in a sunny climate, take advantage of prudent sun exposure. If you are living through a winter season, take that tropical vacation of your dreams!
A Kauai vacation bolsters our levels of Vitamin D. Even though Jeff had been on Gleevec for 18 months, he was fortunate to not have any photosensitivity!
References used for the article above
Boscoe FP, Schymura MJ.
Solar ultraviolet-B exposure and cancer incidence and mortality in the United States, 1993-2002.
BMC Cancer. 2006 Nov 10;6:264.
PMID: 17096841 (free article - click title to link to full text)
Additional recent vitamin D medical papers:
Click the titles to link to abstracts in PubMed. Free access is available to the full papers where noted. A few sentences summarizing the main points are shown below each reference.
Vitamin D status: measurement, interpretation, and clinical application.
Ann Epidemiol. 2009 Feb;19(2):73-8. Epub 2008 Mar 10.
Dr. Holick suggests 25(OH)D of <20 ng/mL is considered to be vitamin D deficiency, whereas a 25(OH)D of 21-29 ng/mL is considered to be insufficient. The goal should be to maintain both children and adults at a level >30 ng/mL to take full advantage of all the health benefits that vitamin D provides.
Vitamin D and cancer incidence in the Harvard cohorts.
Ann Epidemiol. 2009 Feb;19(2):84-8. Epub 2008 Mar 4.
Dr. Giovannucci states about a 30% reduction in risk observed for breast cancer comparing the highest with lowest quintiles of 25(OH)D levels. Vitamin D intake also was associated with a lower risk of pancreatic cancer in both men and women. Results also suggest that the poor vitamin D status generally in African-Americans contributes to their higher incidence and mortality from various malignancies.
Janssens W, Lehouck A, Carremans C, Bouillon R, Mathieu C, Decramer M.
Vitamin D Beyond Bones in COPD: Time to Act.
Am J Respir Crit Care Med. 2009 Jan 22. [Epub ahead of print]
Dr. Janssens and coauthors speculate that vitamin D may down-regulate the inflammatory immune response in the airways whilst boosting innate immune defense against different micro-organisms. Apart from its effects on osteoporosis, vitamin D may also aid in areas of skeletal muscle weakness, cardiovascular disease, and cancer.
A brief history of vitamin D and cancer prevention.
Ann Epidemiol. 2009 Feb;19(2):79-83.
Dr. Mohr discusses those with skin cancer having lower prevalence of non-skin cancers, and that lower overall mortality rates from all internal cancers combined existed in sunnier areas.
Vitamin D and intervention trials in prostate cancer: from theory to therapy.
Ann Epidemiol. 2009 Feb;19(2):96-102. Epub 2008 Jul 10.
Dr. Schwartz asserts that the hormonal form of vitamin D (1,25(OH)(2)D) exerts pro-differentiating, antiproliferative, anti-invasive, and antimetastatic effects on prostate cancer cells.
Stroud ML, Stilgoe S, Stott VE, Alhabian O, Salman K.
Vitamin D - a review.
Aust Fam Physician. 2008 Dec;37(12):1002-5. Full Text available free access.
Dr. Stroud discusses the actions, sources and measurements of vitamin D, and the treatment of established deficiency.