Why healthy adults may not need supplements—and when they do

Many middle-aged people with a balanced diet and regular exercise don't need dietary supplements. Yet self-prescribing high doses of vitamins and minerals can cause serious health problems. Experts warn that unnecessary supplements may do more harm than good for those already in good health.

While some groups benefit from targeted supplementation, others risk side effects from excessive intake. The key lies in understanding individual needs and dietary gaps rather than relying on blanket advice.

Vegetarians and vegans often face deficiencies in iron, zinc, copper, vitamin B12, iodine, and L-carnitine. These nutrients are mainly found in animal products, making plant-based eaters more vulnerable. To compensate, they can turn to legumes, tofu, and tempeh, which provide amino acids, iron, magnesium, and fibre for gut health.

Whole grains like oats, quinoa, and buckwheat are packed with B vitamins (except B12), while nuts and seeds help restore omega-3 levels. Green vegetables such as broccoli, spinach, and arugula offer magnesium, calcium, vitamin K, folate, and sulforaphane. Orange and red vegetables contain beta-carotene, which the body converts into vitamin A, and purple foods deliver polyphenols and anthocyanins.

Common deficiencies in the general population include vitamin D3 in autumn and winter, zinc, magnesium, and omega-3 fatty acids. Supplements are recommended for older adults, teenagers with poor diets, and those recovering from surgery or chemotherapy. However, even seemingly healthy overweight individuals may have hidden issues like high blood pressure or impaired glucose tolerance.

Research shows that excessive vitamin C (3–4g daily) can cause bloating and diarrhoea, while doses above 1g increase the risk of kidney or oxalate stones, especially in those with kidney problems. Too much vitamin A may lead to headaches, liver damage, skin changes, and birth defects. Long-term vitamin D overdoses (over 20µg daily) can trigger nausea, cramps, muscle weakness, or even kidney failure.

For most healthy adults, a varied diet covers essential nutrient needs without supplements. But specific groups—such as vegans, older people, or those with medical conditions—may require extra support. Before taking high-dose vitamins or minerals, consulting a healthcare professional is crucial to avoid harmful side effects. The focus should remain on balanced eating rather than relying on unnecessary supplements.