Having too little vitamin D isn't just bad news for immune system and bone health — it could also destroy intimate relationships, new research suggests.
Toxicologists have discovered that a deficiency in the nutrient could fuel erectile dysfunction, and even make libido-boosting drugs less effective.
Spanish scientists found that those with diagnosed vitamin D deficiencies had reduced function in their corpora cavernosa — the spongy tissue in the penis that is crucial for maintaining erections.
Writing in the medical journal The British Journal of Pharmacology, the researchers suggested administering vitamin D to these patients could be an effective treatment for the distressing condition.
Studies suggest that around one in 10 caucasian people in the UK are deficient in vitamin D, along with a third of those with black skin, and half of people of Asian origin.
The nutrient, which helps bones absorb vital calcium, is created by the body the skin interacts with sunlight.
Those who live in the UK are thought not to produce enough in the winter months, although it is possible to get the necessary dose from foods like salmon, mackerel and eggs.
The new research, by specialists from the Complutense University of Madrid, involved taking samples of corpora cavernosa tissue from 12 human donors with vitamin D deficiency.
Erectile dysfunction is the inability to get or keep an erection for long enough to have sex and affects 40 percent of men over the age of 40
The scientists then stimulated the tissue using an electrical probe to test the function of the nerves.
Researchers found that donors with the lowest blood levels of vitamin D had the weakest responses to electric stimulation.
The study also found that the deficient men had lower than average levels of a protein called SLPI in their blood, which can help to repair tissue damage in the intimate area.
In a seperate experiment, the same researchers fed rats a diet free from vitamin D, and found these animals were less responsive to the erectile dysfunction viagra vision changes, compared to rats not on the diet.
'Our results suggest that vitamin D deficiency may contribute to the lack of response to this first-line treatment of erectile dysfunction', said Dr Miguel Olivencia, a researcher at Complutense University and co-author of the study.
'The findings raise the possibility that restoring vitamin D in patients with vitamin D deficiency and erectile dysfunction would improve sexual performance.' Erectile dysfunction is medically defined as the inability to achieve or maintain erection long enough for satisfactory sexual intercourse.
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It is an increasingly common condition, estimated to affect half of all men over the age of 40.
Common triggers include high blood pressure, diabetes, stress, nerve damage and drinking too much alcohol.
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Lifestyle changes — including embarking on a healthy diet — can sometimes help with erectile dysfunction, experts say.
Risk factors for vitamin D deficiency — defined as levels below 25 nanograms per millimeter of blood — include being overweight, suffering from certain inflammatory conditions such as diabetes, and not spending enough time outdoors.
Those with darker skin are also far more vulnerable as their skin is less able to synthesize the vitamin.
Government guidelines recommend taking vitamin D supplements daily during the autumn and winter.
Taking too much vitamin D over an extended period of time however can be dangerous, researchers say.
Excess vitamin D can cause too much calcium to build up in the body, weakening the bones and damaging the kidneys and heart, NHS doctors warn.