Taking numerous supplements means you're at risk of overdosing on a certain vitamin or mineral. For example, if your diet is already high in iron, an additional supplement could lead you to exceed the necessary threshold. Too much iron can cause nausea, stomach cramps, and diarrhea. Too much vitamin C or zinc can cause nausea, diarrhea, and stomach cramps.
Too much selenium can cause hair loss, gastrointestinal distress, fatigue, and mild nerve damage. Vitamin A toxicity occurs when there is too much vitamin A in the body. Symptoms may include nausea, vomiting, loss of appetite, abdominal pain, dizziness, irritability, drowsiness, headache, rash, increased intracranial pressure, coma, and even death. The maximum limit for adults is 3000 mcg per day.
Just because supplements are safe in moderation doesn't mean that more is better. Combining several supplements or taking doses higher than recommended may increase the risk of them causing harm, Kitchin said.
