Vitamin D is essential for keeping your bones, teeth and muscles strong as it regulates calcium and phosphorus levels in the body. It also plays a key role in immune function, and research suggests that adequate vitamin D intake may reduce the risk or severity of viral infections, including influenza and HIV.
Despite its importance, about 20% of the UK population has low vitamin D levels. The European Food Safety Authority recommends an intake of 15µg per day for everyone over the age of one year.
How we get vitamin D:
Our bodies produce most of our vitamin D when the skin is exposed to ultraviolet B (UVB) light. Sunlight triggers its synthesis, which is then activated in the liver and kidneys.
• During spring and summer, most people can get enough vitamin D from sunlight alone. Around 30 minutes twice a week is usually sufficient.
• Skin tone affects synthesis: darker skin requires longer exposure, while lighter skin produces vitamin D more quickly.
• Always protect your skin during prolonged sun exposure to reduce the risk of damage and skin cancer.
During autumn and winter, when sunlight is weaker, dietary sources or supplements become important. Public Health England recommends a daily supplement of 10µg during these months.
Who might lack vitamin D?
Some people struggle to get enough vitamin D from sunlight alone:
• Older adults, especially the frail or housebound
• People who cover their skin for cultural or religious reasons
• Those with darker skin - higher levels of melanin reduces vitamin D synthesis
In these cases, a vitamin D supplement can be very beneficial.
Dietary vitamin D sources
Vitamin D exists in two forms:
• D2 (ergocalciferol): found in fungi and yeast
• D3 (cholecalciferol): found in animal-based foods
Good dietary sources include:
• Oily fish (herring, mackerel, salmon)
• Liver and red meat
• Egg yolk
• Cottage cheese
• Wild mushrooms
• Fortified spreads and breakfast cereals
Cooking can reduce vitamin D content by up to 30%, so variety is key.
Risks of vitamin D deficiency
Insufficient vitamin D can lead to serious health issues.
In children:
• Rickets (soft, deformed bones, bowed legs)
In adults:
• Osteomalacia (softening of bones, spinal deformities, increased stress fracture risk)
• Muscle weakness, fatigue and pain
• Low bone mineral density, contributing to osteoporosis
Low vitamin D has also been linked to poor sleep quality, low mood and depression, weight gain and difficulty losing fat.
Too much vitamin D
While rare, excessive supplementation can lead to hypercalcemia, causing:
• Nausea, increased urination and thirst
• Calcium deposits in the kidneys, liver or heart
• Potential long-term organ damage
Certain conditions, such as primary hyperparathyroidism, may increase sensitivity to vitamin D and risk of hypercalcemia.
Vitamin D during pregnancy
Adequate vitamin D intake during pregnancy may:
• Reduce the risk of pre-eclampsia
• Support healthy fetal growth
Pregnant or breastfeeding women should consult a doctor before taking supplements.
Digestive health
Vitamin D deficiency can both cause and result from gastrointestinal issues. Conditions like Crohn's disease, ulcerative colitis and irritable bowel syndrome are associated with lower vitamin D levels, as it is a fat-soluble vitamin and requires proper fat absorption.
Vitamin D is vital for strong bones, healthy muscles and a robust immune system. Most people get enough in summer, but supplementation is often necessary in winter or for those with limited sun exposure. Maintaining healthy vitamin D levels supports overall wellbeing, protects against bone and muscle problems and may even improve mood, sleep and immunity.
Important note
This information is for guidance only and is not a substitute for professional medical advice. If you are pregnant, breastfeeding or taking medications, consult a qualified healthcare professional before making changes to your diet or supplements.
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