The Sunshine Vitamin.

Vitamin D is often called the sunshine vitamin because the body can produce it when skin is exposed to sunlight. UVB rays trigger the conversion of 7-dehydrocholesterol into vitamin D3, which is then processed by the liver and kidneys into the active form.

Although called a vitamin, vitamin D behaves more like a hormone. It influences several processes, including bone health and immune function.

Bone health

Vitamin D supports regulation of calcium, phosphate, and magnesium, all of which are important for strong bones and muscles. Deficiency can contribute to rickets in children and osteomalacia in adults, and may worsen osteoporosis risk.

Immune health

Vitamin D also influences immune responses. It is involved in both innate and adaptive immunity and may affect respiratory infection risk and inflammatory pathways.

Sources of vitamin D

Vitamin D3 is found in foods such as oily fish and cod liver oil. Vitamin D2 is present in some sun-exposed mushrooms. Sunlight remains an important source, but production can be reduced by winter months, sunscreen, darker skin tones, ageing, and spending little time outdoors.

Vitamin D in the UK

In the UK, adequate sunlight for vitamin D synthesis is limited during the year. People at higher risk of deficiency include older adults, people with darker skin tones, those with limited sun exposure, and people with conditions affecting absorption or kidney function.

Symptoms to consider

Low vitamin D may be associated with fatigue, muscle weakness, bone aches, frequent illnesses, slow wound healing, mood changes, hair loss, muscle cramps, and sleep disturbance.

Regular blood tests can help monitor and manage deficiency, especially in higher-risk groups.

At London Harley Street Practice, we offer assessment and guidance tailored to individual needs. You can book an appointment or learn more about health checks.