by Mark L. Fuerst
If you want to conceive a child, just take a holiday in the sun since sunlight boosts fertility in both men and women by increasing their levels of vitamin D. That’s how the media in the United States and Britain interpreted the results of a recent systematic review of the connection between vitamin D and fertility. The new findings, say the pundits, mean that some infertile couples may be undergoing unnecessary and costly fertility treatments when spending time in the sun could be their answer.
There are some hints that vitamin D, the so-called “sunshine vitamin,” can help balance sex hormones in women and improve sperm counts in men. Other studies show some evidence supporting a role of vitamin D in prostate cancer. However, the evidence for the role of vitamin D in both fertility and prostate cancer is mixed, at best.
The researchers from The Medical University of Graz in Austria reported studies that show vitamin D helps boost levels of the female sex hormones progesterone and estrogen, regulates menstrual cycles, and makes conception more likely. Vitamin D also increases sperm count and improves sperm quality and testosterone levels, according to studies among the results published online at the end of January in the peer-reviewed European Journal of Endocrinology.
In two of the studies reviewed, peak conception occurred during the summer months. And in a study of 2,300 men, levels of testosterone and vitamin D peaked in the summer and were at their lowest in March.
Lead author Elisabeth Lerchbaum, MD, warned that although vitamin D could help to improve fertility, overexposure could lead to skin cancer. She told the media “people could either spend more time outside in the sun -- or they could take vitamin D supplements, which are a safe and cheap way to increase levels.”
Vitamin D and Conception
Does vitamin D really help conception? Let’s take a closer look at the Austrian study. The researchers admit that their systematic review found that there was a lack of human studies, particularly controlled human studies, which had looked at the effect of vitamin D on fertility. So the review mostly examined animal, laboratory, and observational studies. Although sitting in the sun appears to be an easy solution, without controlled, human trials it is not possible to say whether this could reduce the need for fertility treatments.
Because the Austrian study was touted in British tabloids, the British National Health Service issued a “Behind the Headlines” report about the study. “This systematic review took a broad sweep approach to look at the evidence for a link between vitamin D and any aspect of fertility. Although systematic reviews are a good way of comprehensively looking at all of the evidence in an area, there can sometimes be limitations to pooling data if the included studies differ in design. In this systematic review, the researchers included both human and animal studies and care has to be taken in reporting which of the included studies has relevance to humans,” said the NHS report.
“In most systematic reviews, the researchers listed their criteria for including or excluding studies. They may, for example, only include some study designs and not others. However, in this review, the researchers did not say how they decided to include studies. The researchers said that they did not find many human studies and have included animal and laboratory studies that can give information about the basic biology of vitamin D but do not tell us whether vitamin D can help infertile couples.”
In their conclusion, the Austrian researchers admit that the evidence was based largely on animal work and observational studies rather than on intervention trials. “Nevertheless, there are some promising findings deserving further investigation,” they suggest. More studies need to be done to confirm these preliminary results.
Many factors can cause infertility. It’s impossible to say whether spending time in the sun or taking vitamin D supplements can prevent the need for fertility treatments. Couples who are having considerable trouble conceiving would be better served spending their money on fertility workups than on a long holiday in a sunny clime.
Vitamin D Levels and Prostate Cancer Risk
Several studies suggest that sunlight has a direct effect on lowering prostate cancer risks, especially for men who had early-to-midlife sun exposure, because sunlight stimulates the body to produce vitamin D. However, prostate cancer does not appear to depend on a man’s vitamin D levels, according to a recent study by researchers at the University of Bristol, Bristol, UK.
Lead author Rebecca Gilbert and colleagues at Bristol’s School of Social and Community Medicine searched more than 24,000 papers and reviewed and analyzed the literature regarding associations between intake and concentrations of vitamin D and the risk of prostate cancer. Their meta-analysis of 25 papers was published in the journal Cancer Causes and Control.
The review showed that higher or lower levels of vitamin D do not mean men are more or less likely to develop prostate cancer. One study showed that a vitamin D deficiency appeared to increase the risk of developing prostate cancer. Another study found that men who had prostate cancer were more likely to have low levels of vitamin D when compared with men who were disease-free. Yet a review by the International Agency for Research on Cancer has reported there is no evidence that low levels of vitamin D will increase a man’s risk of prostate cancer. The British researchers conclude that there is “little evidence to support a major role of vitamin D in preventing prostate cancer or its progression.”
However, it is still important for men to maintain adequate levels of vitamin D for prostate health. Vitamin D appears to have a role in benign prostatic hypertrophy (BPH) and prostatitis. Studies show that low levels of vitamin D are associated with a greater risk of BPH and that vitamin D’s anti-inflammatory properties may be helpful in both BPH and prostatitis.
Mark L. Fuerst is an award-winning free-lance health and medical writer based in Brooklyn and the co-author of A Baby at Last!
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