By Anne Chiavacci, M.S., M.A., R.D., L.D.N.
Brigham and Women's Hospital
Vitamin D is a fat-soluble vitamin, well-known for helping the body absorb calcium and promote bone health. It's now well-established that getting enough vitamin D decreases your risk of getting many cancers, such as colon, prostate, breast, ovarian, pancreatic and digestive tract cancers.
You can get vitamin D from foods and supplements but the best source is from exposure to sunlight, which triggers the production of vitamin D3 (cholecalciferol). D3 is then changed by the liver to the active form of Vitamin D, called 25-hydroxycholecalciferol (25-OH-D). The final step to make the most active form occurs in the kidneys.
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The Cancer Connection
The hallmark of cancer is uncontrolled cell growth. Vitamin D seems to keep abnormal cell growth in check by
- blocking a phase of the cancer cell growth cycle
- hindering angiogenesis, the growth of blood vessels that feed a tumor
- triggering the death of abnormal cells
- stimulating cell differentiation, the development of characteristics of normal cells.
Preliminary research is beginning to suggest that, in addition to cancer prevention, vitamin D may also improve survival and decrease the risk of a cancer returning. Several studies, for example, suggest a better survival rate for people with colon, prostate, breast, lung and Hodgkin's lymphoma when they are diagnosed and treated in the summer and fall months. That's when vitamin D levels are typically higher. Here's a closer look at the research:
- A Harvard-based study reported that people who had the highest vitamin D intake and had non-small-cell lung cancer (NSCLC) surgery during the summer months had a significantly higher 5-year survival rate compared with people who had winter surgery and a low vitamin D intake. This data is intriguing, but doesn't it mean that people should put off cancer surgery until the summer or fall season. However, it may suggest that improving vitamin D status with supplements before surgery could improve survival.
- This same group of researchers also measured vitamin D blood levels in 447 NSCLC study participants at the time of diagnosis to see if they were related to survival. This study is unique and the first to measure blood vitamin D levels directly in relation to cancer prognosis. The researchers grouped patients according to the blood level of 25-OH-D, ranking them from highest to lowest. The results indicate that:
- The survival rate was 26% higher for patients whose vitamin D blood levels were above 21.6 ng/ml compared with patients whose levels were below 10.2 ng/ml.
- Patients with stage IB and IIB lung cancer whose vitamin D levels were above 21.6 ng/ml had a 55% improved survival rate than those with lower vitamin D levels.
- The Health Professional Follow-Up Study of 51,529 U.S. male health professionals looked at cancer risk and cancer death in relation to vitamin D intake from diet and supplements, skin pigmentation, body fat, geographic residence, and leisure-time physical activity. The study found that increasing blood vitamin D levels by 25 ng/ml was associated with:
- a 17% reduction in the number of new cancers
- a 29% reduction in the total number of cancer deaths
- a 45% reduction in death from digestive system cancers (colorectal, pancreatic, esophageal); the strongest benefit was for oral and pharyngeal cancers.
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How Much Vitamin D Do You Need?
Guidelines issued by the Institute of Medicine recommend that people age 70 and younger get 600 international units (IU) per day of vitamin D, and those 71 and older get 800 IU/day. However, some experts suggest higher vitamin D intake to maintain blood levels sufficient for optimum health. People who live in the Northern part of the United States, and those with darker skin pigmentation are more prone to vitamin D deficiency.
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Your "D-Fense" Plan
- Make foods rich in vitamin D part of your diet. Choose from this list:
- salmon – 3.5 ounces (360 IU)
- mackerel – 3.5 ounces (345 IU)
- sardines – 3.75 ounces (250 IU)
- shrimp – 4 ounces (162 IU)
- milk, any type – 8 fluid ounces (100 IU)
- orange juice, D-fortified – 8 fluid ounces (100 IU)
- yogurt, vitamin D-fortified – 6 to 8 ounces (40-80 IU)
- fortified cereal – ¾ cup (40-50 IU)
- Take a supplement. A reasonable and safe starting dose is 1,000 IU of vitamin D3 (cholecalciferol) per day, in addition to food sources. Vitamin D2 (ergocalciferol) is a less effective form. It takes about 1,000 IU of vitamin D3 to increase D blood levels by 10 ng/ml. It’s not clear that a higher dose is needed unless you have proven vitamin D deficiency.
- Get a little sunshine. About 15 minutes of sun exposure daily without sunscreen to 50% of the skin is enough for many people
Your doctor may consider ordering a total 25-OH-D blood test. Based on the results of the blood test (many experts consider between 30 ng/ml to 70 ng/ml is ideal), your doctor or registered dietitian can recommend the right vitamin D supplement dose for you.
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Anne Chiavacci, M.S., M.A., R.D., L.D.N. is a senior nutritionist at Brigham and Women's Hospital and Dana-Farber Cancer Institute. She received her Bachelor of Science in nutrition from the University of Massachusetts at Amherst and her Master of Science in nutrition at Tufts University. Chiavacci completed her dietetic internship at Frances Stern Nutrition Center, New England Medical Center in Boston. She has a Master of Arts in counseling from the Biblical Theological Seminary in Hatfield, Pa.