Urban living has changed the way we experience the sun. We spend long hours indoors, follow white-collar routines and commute in cars, all of which limit our direct exposure to sunlight. While much emphasis and discussion has focused on vitamin D deficiency in children, experts say that adults are at risk too, often without realising it.
“The problem is even worse in low-income urban settlements, where poor planning limits access to open spaces and sunlight, despite these being abundant in many African countries,” explains Jackson Mudengeya, a public health advocate and nutritionist.
Vitamin D helps the body to absorb calcium and maintain strong bones. ‘The vitamin is involved in several important bodily processes, including bone metabolism and maintaining the balance of calcium and phosphorus in the body,’ he says.
Research has also linked vitamin D deficiency to various health conditions, including diabetes, cardiovascular disease, autoimmune conditions, obesity, infections, and cognitive decline. Studies have also shown an association between low vitamin D levels and upper respiratory tract infections, including those caused by the SARS-CoV-2 virus.
One of the biggest challenges, he says, is that deficiency often develops slowly and quietly. Many adults may dismiss symptoms such as muscle weakness, continuous fatigue, bone pain, frequent viral infections such as flu and colds, slow recovery from illness, poor concentration and frequent mood changes.
In severe cases, vitamin D deficiency can lead to osteomalacia, a condition in which the bones become soft due to poor mineralisation.
This can eventually result in bowing of the legs.
“Most people remain asymptomatic, so vitamin D deficiency is effectively a ‘silent epidemic’,” Mr Mudengeya explains.
Older adults, people who work indoors for long hours, children who spend most of their time inside and individuals with chronic diseases such as diabetes and heart disease are at greater risk of vitamin D deficiency because they have limited exposure to sunlight, which is needed to maintain healthy levels of vitamin D in the body.
Individuals with fat malabsorption conditions may also struggle because vitamin D is fat-soluble, meaning the body requires fat to absorb it effectively. Obesity has also been associated with poor vitamin D utilisation. So how much sunlight does the body actually need?
Mr Mudengeya says that this varies depending on factors such as skin tone, geographical location and season. Near the equator, exposure at midday may be sufficient.
“For individuals dressed modestly, estimates are about three minutes for those with a fair skin tone and around 15 minutes for those with higher melanin levels,” he explains.
However, he cautions people to be mindful of harsh ultraviolet rays during the hottest part of the day. One common misconception is that sunlight through windows is sufficient.
According to Mr Mudengeya, however, sitting near a sunny home or office window, or driving in a brightly lit car, does not provide the same benefit. He believes that workplaces and institutions can play a major role in addressing the problem.
‘Simple changes such as encouraging outdoor breaks, walking meetings, open office spaces and outdoor seating areas may help people reconnect with natural sunlight during the day,’ he says.
He adds that diet alone is rarely enough to maintain healthy vitamin D levels. “Sun exposure remains the most readily available and affordable way to improve and maintain vitamin D levels.”
Nevertheless, he acknowledges that supplements may be necessary in certain cases, particularly for individuals with limited sun exposure or at high risk of deficiency. However, supplementation should not be taken lightly.
“In cases of mild deficiency, doctors may first recommend dietary adjustments and increased sun exposure. However, severe deficiency may require supplements under medical supervision to avoid toxicity,” he says. “Dosage recommendations usually depend on blood test results measuring serum vitamin D levels.”
He adds that emerging research has also shown links between vitamin D deficiency and women’s reproductive health conditions, including hormonal imbalances and pregnancy complications. “Some studies suggest that supplementation may improve outcomes in certain cases.”