A few minutes a day of midday sun ca raise most fair-skinned people’s vitamin D levels to sufficient, though not optimal, levels.
The skin’s production of vitamin D, upon exposure to ultraviolet B radiation in sunlight, is the body’s main source of nutrient, which is scarce in most foods, Dr Lesley Rhodes of Salford Royal NHS Foundation Hospital in Manchester and colleagues noted in their report.
Vitamin D is requited for healthy bones and muscles, the researchers added, and there is also evidence it may help reduce the risk of cancer, high blood pressure, diabetes and other diseases.
To test whether such casual exposures would be enough, the researchers exposed 109 fair-skinned men and women to light equivalent to 13 minutes of midday summer sun three times a week for six weeks.
The study was done during the winter months, when people would be getting very little vitamin D from sunlight, to focus on the effects of the sun baths. All participants had low vitamin D intakes and none were taking vitamin D supplements.
Participants’ average blood level of vitamin D rose from around 18 nanograms per millilitre to 28 nanograms per millilitre.
Recent studies have suggested that 20 nanograms per millilitre and above is sufficient, while 32 nanograms per millilitre and above is optimal.
The findings do not apply to darker-skinned people, who need longer stretches of sun exposure because their skin colour acts as a natural sunblock.