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Lack of vitamin D increases your risk of breast cancer

- and worsens the odds for women who have the disease

Lack of vitamin D increases your risk of breast cancerDecades of research show that there is a link between lack of vitamin D and an increased risk of breast cancer. Vitamin D deficiencies are especially common at the northern latitudes because the sun sits too low in the sky for humans to be able to synthesize the vitamin during the winter. However, even in the southern hemisphere, many women have too little vitamin D because of spending too much time indoors, using too much suncream, or veiling themselves. Vitamin D has many anti-cancer properties, and postmenopausal women with too little vitamin D in their blood, who are diagnosed with breast cancer, have worse odds, according to a study of Brazilian women. In other words, it is not enough to treat breast cancer with surgery, chemotherapy, and radiation. You also need to optimize your blood levels of vitamin D and other nutrients, which the body needs in order to function optimally.

The aim of this Brazilian study was to take a closer look at how having low vitamin D levels before normal breast cancer therapy affected the prognosis. One-hundred-and-ninety-two women aged 45 to 75 years took part in the study. All of them were passed their menopause and had recently been diagnosed with breast cancer.
Around 20 days after receiving their diagnosis, the women’s blood levels of vitamin D (as 25-hydroxyvitamin D) were measured. Levels above 30 ng/ml were classified as “normal”, while levels between 20-29 were classified as “insufficient”, and levels lower than 20 ng/ml were classified as “deficient”.
Thirty-four percent of the women had sufficient levels of vitamin D in their blood, 48 percent had insufficient levels, and 18 percent were vitamin D-deficient. The scientists also gathered data on the type of breast cancer and its severity, lymph node status, hormonal status (estrogen and progesterone) and other data with relevance to breast cancer progression.

Lack of vitamin D affects tumor size, lymph nodes, and hormone balance

The study revealed that those women who were vitamin D-deficient or -insufficient generally had a tendency to develop larger tumors with more metastases. Also, they suffered more lymph node attacks. After adjusting for BMI, age, and the amount of time that had passed since menopause, the scientists also observed a significant correlation between lack of vitamin D and the presence of negative estrogen receptors. They concluded on behalf of this that lack of vitamin D generally gave a worse prognosis for breast cancer sufferers.

Large quantities of vitamin D may lower the estrogen levels

An earlier study has shown that vitamin D supplementation may reduce estrogen levels in the blood, thereby lower the risk of breast cancer. This even applies to overweight women, who often have elevated estrogen levels in their blood.
The study was conducted at the Fred Hutchinson Cancer Research Center in Seattle, the United States. It was a randomized, controlled clinical trial of 218 overweight and obese women, who had low blood levels of vitamin D at baseline. For a whole year, half of the women took part in a weight loss program and received a 50-microgram vitamin D supplement every day. The other half followed the same weight loss program and took matching placebo.
The scientists could see that the women with the largest increase in vitamin D blood levels had the largest reduction in blood levels of estrogen. Potentially, this lowers their risk of breast cancer, as it is known that having too much estrogen in the form of estradiol increases the risk of this cancer form.
Because it takes years for breast cancer to develop, it is most likely an advantage to have plenty of vitamin D in your blood together with normal estrogen levels to help long-term prevention of the disease.

Is vitamin D a new alternative to antiestrogens?

Earlier research shows that weight loss significantly lower levels of estrogen. Now, scientists have shown that vitamin D has a similar effect, provided you get enough of the nutrient to bring blood levels into their normal range. However, the scientists still disagree when it comes to determining optimal levels. According to the study from the Fred Hutchinson Cancer Research Center, the scientists observed a positive effect with a daily supplement of 50 micrograms, but they do not know at this point whether even larger doses of vitamin D has an even more positive effect on the hormone balance.
It is even possible that large quantities of vitamin D may be a new, safe alternative to antiestrogens such as tamoxifen, a drug with with quite a few side effects.

Vitamin D deficiencies are much more common now because of

  • More time spent indoors
  • Increased number of overweight people
  • Fear of the sun
  • Excessive use of sun factor cream
  • Prolonged use of cholesterol-lowering medicine (statins)
  • Ageing processes

Your ability to utilize vitamin D depends on your age and magnesium status

We humans produce a vitamin D precursor when cholesterol in our skin is exposed to sunlight. However, our ability to utilize the vitamin from that point onward depends on several factors. First, vitamin D must be converted into 25-hydroxyvitamin D3 in the liver. After that, it is converted into an active form by the kidneys. These enzyme processes depend on the presence of magnesium Lack of magnesium may therefore impair our ability to properly utilize vitamin D from sun exposure or from supplements. With increasing age, it may become increasingly difficult to utilize vitamin D. Therefore, even if older people get plenty of sun, they may have too litle active vitamin D in their blood.

Vitamin D, supplements, and absorption

Vitamin D is lipid-soluble. Therefore, it is best to take supplements where vitamin D is dispersed in some sort of oil. Leading scientists say that it is perfectly safe to take 50-100 micrograms of vitamin D daily as a supplement. This is about the same amount as our skin is able to synthesize on a hot summer’s day.

Because it takes many years for breast cancer to develop, it is a good idea to make sure to get enough vitamin D on a daily basis, all year round and throughout life, for the sake of long-term prevention. It is also essential to get plenty of selenium, a nutrient that many people lack, and which a lot of scientific studies have looked into.


De Sousa Almeida-Filho B et al. Vitamin D is associated with poor breast cancer prognostic features. J Steroid Biochem Mol Biol 2017

Hutch News. High blood levels of vitamin D linked to reduced estrogen – and potentially lower breast cancer risk
Study found the hormone-lowering effect to be independent of weight loss. 2016 |
By Kristen Woodward / Fred Hutch News Service

Susan Scutti: High Blood Levels Of Vitamin D Help Protect Women Over 50 From Cancer: Study

Anne Marie Uwitonze, Mohammed S Razzaque. Role of magnesium in Vitamin D Activation and Function. The Journal of the American Osteopathic Association. 2018
Harris HR, et al. Selenium intake and breast cancer mortality in a cohort of Swedish women. Breast Cancer Res Treat. 2012.

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