Doctor warns: Taking supplements too long can destroy your liver

Many people turn to dietary supplements to fight fatigue and boost their health. But experts are warning that taking high doses indiscriminately can actually damage the liver.

Kang Sang-wook, a professor in the Department of Chemical and Energy Engineering at Sangmyung University, and Choi Seok-jae, an emergency medicine specialist at Yeouido St. Mary's Hospital, said on the YouTube channel "Jisik Hansang" that improper supplement use can cause toxic damage to the liver.

Choi said most drugs are metabolized in the liver through an enzyme called cytochrome P450, and that taking supplements on top of other medications already in use raises the risk of liver toxicity.

"If you are on medication, taking two or three supplements may not be a problem, but if you are taking five or ten, you need to watch out for liver toxicity," he said. "Adding herbal juices or decoctions on top of that puts a double or triple burden on the liver."

He added that in severe cases, jaundice — a yellowing of the skin and whites of the eyes — can develop. "Even in the emergency room, when a patient comes in with elevated liver enzyme levels, we always check what medications and supplements they are taking," he said.

Choi stressed that combining multiple supplements does not simply double or triple the strain on the liver and kidneys. "The burden does not increase two or three times — it goes up four or eight times," he said. "It is safer to take only what you need, one at a time."

Kang also said research has shown that high doses of vitamin A and some B vitamins taken over a long period can cause liver toxicity.

Niacin (B3) can cause facial flushing, headaches and nausea at doses above 30 mg per day, and long-term use at 500 mg or more has been flagged as a risk for liver dysfunction. Vitamin B6 has similarly been reported to cause sensory neuropathy — including numbness and tingling in the hands and feet — when taken at doses above 100 mg over an extended period.

Choi also warned of risks associated with omega-3 supplements, which many people take to prevent blood clots. Because omega-3 is derived from fish fat, he said, it is prone to oxidative rancidity — and rancid omega-3 can actually become harmful.

"Even if a soft-gel capsule looks perfect on the outside, it has tiny pores that allow oxygen to enter, and heat makes rancidity even more likely," he said. "Even when nitrogen is added during manufacturing, some oxygen can remain." He recommended buying individually packaged omega-3 supplements with a recent manufacturing date and storing them in a cool place.