Vitamins are essential nutrients for the body to function normally. But consuming them in excess of the body's needs can become toxic rather than beneficial.
According to the medical community on Friday, Megan Nunn, an American pharmacist, said in a recent interview with health media outlet Verywell Health that "vitamin overdose problems are most likely to occur when specific vitamins are taken in high doses over long periods," adding that effects "can range from mild skin rashes and vomiting to seizures, strokes, and organ damage in severe cases."
Health problems caused by excessive vitamin intake can be more serious than commonly thought. According to research from the University of New South Wales in Australia, taking more than 400 IU of vitamin E daily over a long period may increase the risk of death. Some studies have also raised the possibility that excessive intake of vitamins A, B6, and B12 could increase the risk of lung cancer.
Side effects vary depending on the nature of the vitamin. Fat-soluble vitamins A, D, E, and K, which dissolve in fat and accumulate in the body, are not easily excreted when consumed beyond necessary amounts and can build up to cause toxicity.
Excessive intake of vitamin A can cause skin peeling, liver damage, vision impairment, and increased pressure inside the skull. Overdose during pregnancy can also pose risks of abnormal heart and brain development in the fetus.
Excessive vitamin D intake can cause severe thirst, frequent urination, and seizures, and in severe cases can lead to coma. Some research has shown that taking excessive amounts of vitamins A and D together can lower bone density and increase fracture risk. Excessive accumulation of vitamin E can raise the risk of bleeding and stroke.
In contrast, water-soluble B vitamins and vitamin C, which dissolve in water and are excreted in urine, are known to be relatively safer than fat-soluble vitamins. However, overuse can still cause symptoms that are difficult to identify, such as nausea, vomiting, diarrhea, and skin rashes.
Infants, children, pregnant women, the elderly, and people taking multiple supplements at the same time are particularly vulnerable to vitamin toxicity. Children can easily overdose by eating sweet gummy vitamins like candy, while pregnant women face increased risks of fetal deformities from vitamin A overdose.
The elderly also need to be cautious. As people age, the body's ability to break down and excrete vitamins declines, so side effects can occur even at standard recommended doses.
"Most healthy adults who maintain a balanced diet do not need separate vitamin supplements," Nunn said. A study published in the British Medical Journal (BMJ) also found that a significant number of supplement users were already getting enough vitamins from food alone.
Those considering vitamin supplements should first take a blood test to check which nutrients are actually deficient. Those who are pregnant or breastfeeding, follow specific diets, or have chronic illnesses should consult medical professionals before deciding whether to take supplements.
"Vitamins are beneficial to health only in appropriate amounts, and taking more does not increase their effectiveness," Nunn emphasized. "It is most important to accurately understand your body's condition and take only what is truly necessary."
