Vitamin D After 50: An Expert Says Fatigue Isn't Always a Deficiency, and Big Doses "Just in Case" Aren't Harmless

The days are getting shorter, we spend more time indoors, and the skin - the main factory for vitamin D - gets less and less UVB radiation. In autumn and winter, at certain latitudes, the sun simply isn't strong enough for the skin to produce it. And that's the moment many people reach for the box at the pharmacy without knowing whether they need it at all.

Vitamin D is involved in the metabolism of calcium and phosphorus, in the health of bones and teeth, and in how muscles and the immune system work. Andrea de la Puente, a specialist in integrative medicine, advises people at higher risk to check their levels in time rather than wait for symptoms.

Fatigue isn't a diagnosis. "It's important not to automatically attribute fatigue to a vitamin D deficiency," she says. Tiredness has many causes: poor sleep, stress, anaemia, the thyroid, lifestyle. Low vitamin D can produce vague symptoms - muscle weakness, pain in the muscles and bones - but many people with a deficiency have no complaints at all. If the fatigue persists, you look for the cause and do a blood test, instead of taking supplements blindly.

After 50, the bones. Around and after menopause, the drop in oestrogen speeds up bone loss and raises the risk of osteopenia and osteoporosis. Vitamin D helps the absorption of calcium and phosphorus and the normal function of muscles, but the expert is clear: strength training, a varied diet and enough protein are just as important, and a pill doesn't replace them.

Which test. The most reliable test is serum 25-hydroxyvitamin D, 25(OH)D. Not everyone needs it, but it's worth it for people who are rarely in the sun, for older people, for those with intestinal absorption problems, with certain diseases or treatments, and with a higher risk of bone loss. Anyone with good levels and no risk gets little benefit from high doses "just in case." "Not everyone needs a supplement, and not everyone needs the same dose," says de la Puente.

More doesn't mean better. Vitamin D is fat-soluble and builds up in the body. "Just because it's a vitamin doesn't mean high amounts are harmless," the expert warns. Overdosing leads to hypercalcaemia: nausea, vomiting, weakness, loss of appetite, thirst, frequent urination, neurological changes. In severe and prolonged cases come kidney stones, kidney damage and calcium deposits in tissues.

In practice: take it with a meal that contains some fat, because it's absorbed better that way, and regularity matters more than the time of day. The dose and duration depend on your starting level and don't have to last forever. Movement, daylight when possible, oily fish, eggs and fortified foods on the plate. So, are we taking it because we need it, or because it's October?