All experts agree on the benefit of vitamin D supplements, especially during the winter.
Vitamin D is not a vitamin in the literal sense, but rather a hormone. Specifically, it is a hormone that our bodies produce in response to exposure to sunlight, so when the days are shorter and darker, its production decreases.
Vitamin D can be obtained by eating foods that contain it, but food only provides the body in very limited quantities, estimated at only 10%.
So what happens if sunlight is limited, and only 10% – or perhaps less – of total vitamin D comes from food?
The National Health Service in the United Kingdom – according to an article published by the British newspaper The Independent – explains the following: “Vitamin D deficiency can lead to bone deformities, such as rickets in children, and bone pain resulting from a condition called osteomalacia in adults.”
This is because vitamin D helps the body regulate calcium and phosphate levels, maintains healthy bones, teeth and muscles, and helps regulate mood and sleep.
Low levels have been linked to mood disorders such as anxiety and depression, and a deficiency of this essential hormone can contribute to the symptoms of seasonal affective disorder, which, according to the Royal College of Psychiatrists, affects 3% of the population.
What causes vitamin D deficiency?
Sunlight is the main natural source of vitamin D, so short winter days and cloud cover are the main reasons for low levels.
“We make vitamin D in the skin in response to UV rays,” explains nutritionist Maz Packham.
Exposure to the hot sun without protection is not considered the safest way to increase vitamin D levels, as it can cause damage to the skin and may lead to problems such as sunburn and sunstroke in the short term and skin cancer in the long term.
Dermatologists agree that sunscreens with a sun protection factor (SPF) can block some ultraviolet rays, but they do not block enough to significantly affect vitamin D levels, so it is recommended to use them to protect the skin from sun damage throughout the year.
According to the National Institutes of Health in the United States, individuals with dark skin are more likely to have low levels of vitamin D than those with light skin.
This is related to the level of melanin in the skin. Individuals with lighter skin have less melanin, which allows them to absorb ultraviolet rays more efficiently and produce vitamin D more effectively than those with more melanin-prone skin.
A person’s level of deficiency may depend on their location in the world, their exposure to daylight, their skin color, and their lifestyle.
People at risk of vitamin D deficiency
“Vitamin D plays a role in reproduction and glucose balance,” explains nutritionist and hormone specialist Hannah Alderson.
For this reason, she explains, people with diabetes and those with hormonal conditions like polycystic ovary syndrome are more likely to develop vitamin D deficiency.
“The prevalence of vitamin D deficiency in women with PCOS is about 67-85%,” she says.
While the prevalence of deficiency in the elderly is about 37% for those aged 60 and over, according to a study conducted in 2019, the numbers may be much higher after Covid.
“We can get a little bit of food — like oily fish, dairy products, eggs — but it’s not really enough,” Alderson explains.
“Some people have decreased absorption due to poor gut health and/or conditions like Crohn’s disease and celiac disease, and this makes it more difficult to get vitamin D from food,” explains nutritionist Eve Kalinic.
What are the signs of vitamin D deficiency?
Feeling tired is the first symptom that a person notices. But it can mask circadian clock changes during the winter, sleep disturbances, or perhaps other health considerations such as hormonal fluctuations, or vitamin D deficiency.
Deficiency can appear in many other forms. “Unexplained infections may be a sign of vitamin D deficiency, since vitamin D is an essential component of immune strength,” says Eve.
Signs of deficiency may also appear in the form of bone pain, muscle weakness (because vitamin D helps balance calcium in the body), or even low mood, which is often associated with seasonal affective disorder.
Osteomalacia can turn into osteoporosis, which increases the risk of fractures, a problem that may be life-threatening in later stages of life. In severe cases of deficiency, the patient may suffer from epileptic seizures.