Doctor urges Britons to start taking vitamin D as one in six adults are deficient

A GP has urged people across Britain to begin taking vitamin D supplements as the country moves into the darker months, saying reduced sunlight will limit the body’s ability to produce the nutrient and that about one in six adults are currently estimated to be deficient.

Dr. Donald Grant, a general practitioner and senior clinical adviser at The Independent Pharmacy, told media that vitamin D is essential for normal muscle and immune function and for helping the body absorb calcium, which in turn supports bone and muscle health. He warned that lower daylight hours increase the risk of deficiency, particularly among older people.

Public health guidance differs by jurisdiction on thresholds and dosing. The US Institute of Medicine sets a minimum threshold of 20 nanograms per millilitre (ng/ml), while the NHS cites 12 ng/ml as a healthy baseline. The NHS currently advises that adults and children over one year should consider a daily supplement of 400 international units (IU) of vitamin D in autumn and winter, or year-round for people who have little exposure to sunlight.

Dr. Grant said that while vitamin D is present in foods such as oily fish, red meat and egg yolks, it can be hard to achieve sufficient levels from diet alone, and that supplements taken earlier in the season can help avoid deficiencies through the colder months. He added that many commercially available supplements provide more than the NHS recommendation of 400 IU per day and that, in his view, higher doses may be appropriate to support immune, bone and muscle function.

Public health experts and clinicians typically advise patients to consult their GP before starting higher-dose supplements, particularly those with existing health conditions or on certain medications. Excessive vitamin D intake can cause the body to absorb too much calcium, leading to hypercalcaemia. Symptoms can include nausea, vomiting, constipation, dehydration, bone pain and kidney stones, and in severe cases calcium deposits can affect the kidneys, lungs and heart.

Older adults are a group of particular concern because vitamin D deficiency can contribute to muscle weakness and an increased risk of falls and fractures. Dr. Grant emphasised that maintaining adequate vitamin D is part of promoting healthy ageing, alongside balanced nutrition and physical activity.

Research has also explored links between vitamin D and inflammatory conditions. A 2017 study led by researchers at the University of Birmingham suggested maintaining sufficient vitamin D might help prevent the onset of inflammatory diseases such as rheumatoid arthritis, owing to the vitamin’s role in immune regulation. The study’s authors cautioned, however, that for people who already have rheumatoid arthritis, standard supplementation may not be sufficient and higher doses could be required — points that underline the importance of medical supervision when altering supplement regimens.

Health bodies continue to recommend targeted supplementation rather than blanket high-dose use. Clinicians say the most reliable way to determine deficiency is through testing and clinical assessment, and that patients should discuss individual risk factors such as limited sun exposure, darker skin, obesity, older age and certain chronic conditions with their GP.

As the UK enters autumn and daylight hours shrink, doctors and pharmacies are renewing calls for public awareness about vitamin D, balancing the benefits of preventing deficiency against the risks of excessive supplementation.