Breast cancer is a major health concern. This article explains how Vitamin D might help prevent breast cancer, based on a study by Garland (et al).
This article does not deal with rickets, calcium, bones and teeth, electrolytes or general nutrition.
Explaining Garland's Pooled Study on Vitamin D and Breast Cancer
A "pooled study" reviews previous studies to "pool" the data from those sources. Any findings are more credible because more data was collected, by more original researchers with different methodologies and biases.
Garland's 2006 pooled study, "Vitamin D and prevention of breast cancer: Pooled analysis" reviewed relevant research published from 1966 through 2006, on any relationship between blood Vitamin D levels and the risk of breast cancer.
They reviewed the level of one vitamin D metabolite, "25(OH)D", in the blood. A low value is 10 ng/ml (nanograms of "25(OH)D" per millilitre of blood); a high value is 50 ng/ml.
Garland found two studies to support the following:
If a woman were to increase her blood level of "25(OH)D" from 10 ng/ml to 50 ng/ml, she would reduce her risk of breast cancer by 50%. A rise from 10 to 32 ng/ml provides risk reduction of 31%. The difference in "25(OH)D" levels "accounted for 90% of the variation in risk of breast cancer".
Garland also found one previous study that had a similar result for a different metabolite of Vitamin D, and two that did not find any relationship.
What are Safe Levels for Vitamin D?
The American government's National Institutes of Health (NIH) makes several recommendations about Vitamin D in "Dietary Supplement Fact Sheet: Vitamin D". This fact sheet notes that Vitamin D may aid resistance to cancer (and some other diseases), but also that excessive sunlight leads to skin cancer. The recommended daily Vitamin D dosage varies from 400 to 800 IU.
The fact sheet says that "studies to date do not support a role for vitamin D, with or without calcium, in reducing the risk of cancer". This contradicts Garoland's study.
The toxic threshold of "25(OH)D" is about 200 ng/ml: four times the highest level in Garland's study. The NIH reports that other health risks rise at levels as low as 30 ng/ml., including a higher risk of some other cancers.
The NIH also says that 97.5% of the population has adequate Vitamin D if their blood level is 20 ng/ml. Lower levels increase the risk of deficiency diseases.
Sunshine, Food and Supplements are Sources of Vitamin D
People make Vitamin D when their skin is exposed to sunshine. The NIH claims that sunshine does not lead to a Vitamin D overdose, but they do warn about skin cancer. We all should use common sense about sunburn and long-term skin damage.
Dairy products, fatty fish such as mackerel, salmon and tuna, and some fortified margarines are dietary sources of Vitamin D.
A supplement dosage of 1,000 IU raises the blood level of "25(OH)D" from 10 to 20 ng/ml, but the effect decreases at higher starting levels. In 2006, the American maximum supplement was 2,000 IU per day. It is difficult to accidentally get a toxic Vitamin D overdose with any reasonable amount of diet supplements.
Known Medical Issues About Vitamin D
The NIH fact sheet adds:
- Vitamin D is important for the body to use calcium for bones and to avoid "hypocalcemic tetany": muscle spasms due to a calcium electrolyte imbalance
- Some dietary restrictions, such as lactose intolerance, milk allergies, or a vegan diet, may lead to low Vitamin D intake
- Vitamin D is absorbed with fat, so Crohn's disease (and others) may cause low Vitamin D levels
- Gastric bypass surgery can reduce Vitamin D absorption
- Some diet drugs such as Orlistat, and cholesterol drugs such as Cholestyramine, reduce fat absorption and so may reduce Vitamin D levels
- Some other drugs also change Vitamin D's effectiveness
- Obese people store more Vitamin D in their fat, so less is available for their blood levels
In "Vitamin D: Are higher doses needed?", Milosevich points to hyperparathyroidism as a contra-indication for taking Vitamin D. He also explains that Vitamin D toxicity symptoms include dizziness, dry mouth, headache, loss of appetite, nausea and vomiting.
How to Use Vitamin D to Reduce the Risk of Breast Cancer
Ask your doctor about using Vitamin D to help prevent breast cancer:
- Check your current blood level for the "25(OH)D" form of Vitamin D, and explain why you are interested
- Discuss any risks or concerns based on your own health, allergies, medications, diet and lifestyle
- Ask about the risk trade-off if you decrease your risk of breast cancer but increase other risks
Then buy Vitamin D if your doctor agrees, and take it as directed.
Can taking a Vitamin D supplement help prevent breast cancer? The answer is a cautious "Probably, in moderate doses".
Updated June 28, 2011 regarding Melanoma
In "Combination of calcium, vitamin D reduces melanoma risks in some women", Medical Xpress reported from a Stanford University study that women who had previously had non-melanoma skin cancer, and later began taking 1,000 mg of calcium plus 400 IU of vitamin D daily, "developed 57% fewer melanomas than women with similar histories" but who did not take the supplements. This did not help women who had no history of non-melanoma cancer, and the study did not include men. However, those who fall into the study's category have an extra reason to seek medical advice about taking these supplements.
Disclaimer: The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
References:
Cedric F. Garland et al, Journal of Steroid Biochemistry and Molecular Biology, "Vitamin D and prevention of breast cancer: Pooled analysis", published 2006 (doi:10.1016/j.jsbmb.2006.12.007), PDF referenced March 20, 2011.
Office of Dietary Supplements (NIH), "Dietary Supplement Fact Sheet: Vitamin D", referenced March 20, 2011.
NOTE: the NIH fact sheet uses both "nmol/L" (nanomoles per litre) and "ng/mL". 1 nmol/L = 0.4 ng/mL, so take care reading the numbers.
Dan Milosevich, C.N., "Vitamin D: Are higher doses needed?", referenced March 20, 2011.
Medical Xpress, "Combination of calcium, vitamin D reduces melanoma risks in some women", published June 28, 2011, referenced June 28, 2011.@
Mike DeHaan - Copyright (c) Mike DeHaan, B. Math., of DeHaan Services. Well written and well researched freelance articles; ghost writing for clients.
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