Cardiologist warns against vitamin D 'mega doses' ahead of NHS winter supplement push

As the days shorten and people spend less time outdoors, the NHS begins its annual push for vitamin D supplementation. Between October and March, the health service recommends that most people take a daily supplement of the so-called sunshine vitamin—a nutrient that becomes harder to obtain naturally when cloud cover dominates and temperatures drop. But before reaching for a bottle, one cardiologist is asking people to pause and ask themselves a crucial question: do they actually need it?

Dr Osman Najam, a consultant cardiologist, has been vocal about the gap between what people assume about vitamin D and what the evidence actually supports. Speaking on social media, he laid out the basic facts: vitamin D deficiency is real, particularly in the UK where winter sun is scarce. The nutrient does matter for heart health—it influences blood pressure, inflammation, and calcium regulation, all of which affect cardiovascular function. The problem, he argues, is not that vitamin D is unimportant, but that people often take it without knowing whether they need it.

The critical step Najam emphasizes is testing. If someone is genuinely deficient—actually tested, not guessed at—then supplementation makes sense. But if vitamin D levels are already healthy, taking more provides no additional protection. The excess simply accumulates; it does not prevent heart disease, cancer, or autoimmune conditions, despite what many people believe. Most guidelines suggest that adults need between 1,000 and 2,000 international units daily, though individual requirements vary based on baseline levels and other factors.

What often gets overlooked, Najam points out, is that vitamin D is available from food sources. Fatty fish, egg yolks, fortified milk, and mushrooms all contain meaningful amounts. Even modest sun exposure—15 to 20 minutes a few times a week—contributes significantly. People with darker skin require longer sun exposure to produce equivalent levels, a biological reality that affects recommendations for different populations. The real problem he observes is not deficiency itself, but the tendency to take mega doses in hopes of preventing multiple diseases, when the evidence for such broad protection is weaker than commonly assumed.

The NHS guidance remains consistent with Najam's core message, even if the emphasis differs. Health authorities recommend that people consider taking a daily supplement during the winter months, and they note that low vitamin D can cause fatigue, aches, and in severe cases, softening of the bones. Pharmacists are available to discuss appropriate dosing, and low-cost supplements are widely available. For families qualifying for the Healthy Start scheme, vitamin D supplements containing the nutrient are provided free.

Beyond supplementation, the health board recommends practical steps: spending time outdoors during daylight hours, even on cloudy days, and eating a balanced diet that includes foods naturally rich in vitamin D. Thirty minutes of daily outdoor activity can help, though the exact amount needed varies by skin tone and latitude. Fortified foods—certain spreads, plant-based milks, orange juices, and breakfast cereals—offer another route to adequate intake.

Najam's final point reframes the entire conversation. Vitamin D is not a cure-all; it is a supporting player in a larger picture of health. What actually moves the needle, he argues, are the fundamentals: movement, sleep, and stress management. For people who are deficient, supplementation fills a genuine gap. For everyone else, the focus should remain on the lifestyle factors that have proven effects. The winter supplement push is not wrong—it is simply incomplete without the prerequisite question: do you actually need it?