looking at a mammogram x-ray with a magnifiying glass, overdiagnosis, lower breast cancer risk

Vitamin D levels may be important as a way for women to lower breast cancer risk. That is the conclusion from an epidemiological study (PLOS One, June 15, 2018).

Which Women Had a Lower Breast Cancer Risk?

The study included postmenopausal women from two different randomized clinical trials and a prospective study. Data collection ran from 2002 to 2017 and included data from 5,038 women altogether. All the women were at least 55 years old; their average age was 63. The volunteers had a wide range of vitamin D blood levels, measured as 25-hydroxyvitamin D [25(OH)D]. During the time frame of the study, 77 of the women were diagnosed with breast cancer.

Women with 25-hydroxyvitamin D levels of at least 60 ng/mL were 82 percent less likely to get such a diagnosis than those with 25(OH)D levels of 20 ng/mL or lower. Even after adjusting for factors such as age, smoking and BMI, women with vitamin D levels at 60 ng/mL or above had an 80 percent lower breast cancer risk.

25(OH)D is sometimes measured as nmol/L instead of ng/mL. The equivalent of 60 ng/mL is 150 nmol/L.

How Can You Get Your Vitamin D Levels Up?

Currently recommended levels for vitamin D supplements will probably not raise blood levels of 25(OH)D to 60 ng/mL. US RDA for vitamin D3 is 600 IU/day for everyone from 1 to 70 years of age. Over age 70, the recommended amount is 800 IU/day. Sun exposure of 15 to 20 minutes daily during the summer might suffice, depending on latitude.

However, people planning to get their vitamin D from supplements might need to take as much as 4,000 or even 6,000 IU of vitamin D3 every day to reach blood levels of 60 ng/mL for 25-hydroxyvitamin D. People should ask their doctors to measure 25(OH)D levels so they can adjust their supplementation appropriately. It is possible to take too much vitamin D3 and experience toxicity, so monitoring is helpful.

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  1. Lisa
    Lenox MA

    Can you please amend the title of this article? The research correlated levels of Vit D with breast cancer risk, but it did NOT confirm that taking supplemental Vit D will lower risk. That is the research we really need. Can you please make this more clear to your readers? While we hope supplemental Vit D can mitigate risk, so far the data to support this is lacking. This may be because targets are too low, as well as dose, but it may also be that supplemental Vit D is not equivalent to endogenously produced vitamin D, or because the Vit D levels are an association but not causal.

  2. marciab
    Houston, Tx

    I take 6,000 units of vitamin D a day. My levels were 76.3 ng/ml. I do have breast cancer in the family so I am hoping this will help. I live in the sunbelt but wear sunscreen and probably get my 15 min. of sun a day going to the car etc..

    After reading the article I will continue with the supplements to keep my numbers up.

  3. Shari

    Was there any data on the recurrence of breast cancer for those women who were previously diagnosed with it and were treated?

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