High vitamin D levels due to supplementation may protect against breast cancer
In epidemiological studies a relatively high vitamin D level protects against breast cancer, but supplementation with vitamin D doesn't seem to have much effect. [PLoS One. 2013 Jul 22;8(7):e69269.] However, the doses in these trials are often modest, and the concentration of vitamin D in the blood does not get much higher. What happens if women take a larger amount of vitamin D?
PLoS One recently published an American meta-analysis in which researchers try to answer this question. The researchers used the data from two trials, in which a number of women were given vitamin D supplements for several years. In one trial women received 1100 IU of vitamin D daily, in the other 2000 IU of vitamin. That amounts to 27.5 micrograms and 50 micrograms of vitamin D per day respectively.
Those dosages are on the high side. According to American and Canadian doctors, consumers can safely use supplement with 50 micrograms of vitamin D on a daily basis. At higher doses, regular blood tests are a necessity.
The researchers also used data collected in an epidemiological study, in which women - who were free to use vitamin D supplements - were followed for several years.
In total, the researchers had access to data from 5038 women. They were all 55 or older.
During the trials and the study, 77 women were diagnosed with breast cancer. This happened less often in women with a lot of vitamin D in their blood.
In the women with vitamin D levels of 60 nanograms per milliliter or higher [that is the same as 150 nanomoles per liter or higher] the risk of breast cancer was 80 percent lower than in women with less than 20 nanograms of vitamin D per milliliter. in their blood [the same as less than 50 nanomoles per liter]. In the Northern Hemisphere, these high vitamin D levels are only possible through supplementation.
The researchers also looked at the effect of the vitamin D level at baseline. High baseline levels protected against breast cancer, but the protective effect was less strong than the effect of the vitamin level during the trials or the epidemiological study.
"The current National Academy of Medicine recommendation of 20 ng/ml (50 nmol/L) is based solely on bone health, yet it is widely used as the target level for all health conditions", write the researchers. "The findings from this study suggest that breast cancer incidence could be substantially reduced by increasing 25(OH)D concentrations well above 20 ng/ml (50 nmol/L)."
"Vitamin D status is a modifiable risk factor for breast cancer, and increasing 25(OH)D concentrations via supplementation at the population level is safe and affordable."
PLoS One. 2018 Jun 15;13(6):e0199265.
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