The regular use of sunscreen could be causing people to become vitamin D deficient, a new study suggests.
Vitamin D deficiency, which can lead to muscle weakness and bone fractures, has previously been blamed on spending too much time inside.
But new research claims nearly one billion people worldwide may have deficient or insufficient levels of vitamin D due to chronic disease and insufficient sun exposure related to sunscreen use.
Kim Pfotenhauer, assistant professor at Touro University and contributor to the study said: "People are spending less time outside and when they do go out they're typically wearing sunscreen, which essentially nullifies the body's ability to produce vitamin D.
While we want people to protect themselves against skin cancer, there are healthy, moderate levels of unprotected sun exposure that can be very helpful in boosting vitamin DKim Pfotenhauer, assistant professor at Touro University
Chronic illnesses such as Crohn's or coeliac disease may lead to the malabsorption of the vitamin, while poor diet can also cause deficiency.
Spending between five and 30 minutes in the midday sun twice a week could help to increase and maintain healthy vitamin D levels, the osteopathic association said.
It said it was "important to forgo sunscreen during these sessions because SPF 15 or greater decreases vitamin D3 production by 99 per cent".
In the study published in the Journal of the American Osteopathic Association, Dr Pfotenhauer added: "You don't need to go sunbathing at the beach to get the benefits.
"A simple walk with arms and legs exposed is enough for most people."