A spot of sunbathing may be just the thing to lift a man's libido, say experts after an Austrian study finds testosterone is boosted by vitamin D

The bulk of this essential nutrient is made by the skin on exposure to sunlight. The rest comes from the diet. A study of 2,299 men found those with enough of the vitamin had more of the male sex hormone than those with less. Blood levels of both dipped in the winter and peaked in the summer. Low testosterone levels can impact on a man's libido as well as zap energy levels. It also performs essential functions in both men and women such as maintaining muscle strength and bone density. The researchers found men with at least 30 nanograms of vitamin D per milliliter of blood had much more testosterone circulating than those lacking in vitamin D. Across the 2,299 men studied, testosterone and vitamin D levels appeared to peak in the month of August, and drop off in the winter, hitting their lowest levels in March.