What dietary supplements can cause hepatotoxicity (liver damage) and which ones are at risk of accidental overdosing, and do excess vitamins get excreted in the urine?

From the Guidelines

High doses of vitamin A, niacin, and certain herbal supplements can cause hepatotoxicity, and individuals should be cautious of accidental overdosing, especially with fat-soluble vitamins that can accumulate in body tissues. Several supplements can cause liver damage, including high doses of vitamin A, niacin, green tea extract, and certain herbal supplements like kava, comfrey, and black cohosh 1. Vitamin A is particularly concerning as it's fat-soluble and can easily be megadosed accidentally. While water-soluble vitamins like B and C are generally excreted in urine when taken in excess, fat-soluble vitamins (A, D, E, and K) can accumulate in body tissues, potentially reaching toxic levels. For vitamin A, daily intake should not exceed 10,000 IU (3,000 mcg) for adults, as high doses may be hepatotoxic or teratogenic 1.

Some key points to consider:

• The liver metabolizes most substances we consume, making it vulnerable to toxicity from concentrated supplement ingredients.
• Liver damage from supplements often occurs gradually and may present with symptoms like fatigue, abdominal pain, jaundice, and dark urine.
• If you're taking supplements, stick to recommended doses, avoid multiple products with overlapping ingredients, and consult healthcare providers before starting new supplements, especially if you have existing liver conditions or take medications.
• The U.S. Pharmacopeia has developed reference standards to aid in quality control of dietary supplement production, but the content and concentration of ingredients in commercially available formulations probably vary considerably 1.
• High dosages of antioxidants may lead to health problems, including diarrhea, bleeding, and toxic reactions, and consuming megadoses of dietary antioxidants has not been demonstrated to protect against cardiovascular disease, diabetes, or various forms of cancer 1.
• Vitamin E supplements may induce bleeding risks, and individuals taking anticoagulant drugs like warfarin and those who are vitamin K deficient should not take vitamin E supplements without medical supervision 1.

In terms of excess vitamins, fat-soluble vitamins (A, D, E, and K) can accumulate in body tissues, potentially reaching toxic levels, while water-soluble vitamins like B and C are generally excreted in urine when taken in excess. The tolerable upper intake levels for certain vitamins and minerals are as follows:

• Vitamin A: 3,000 µg/day
• Vitamin B6: 100 mg/day
• Folic acid: 1,000 µg/day from fortified food and supplement intake
• Niacin: 35 mg/day niacin equivalents
• Vitamin C: 2,000 mg/day
• Vitamin E: 1,000 mg/day 1.

Overall, it is essential to be cautious when taking dietary supplements and to consult with healthcare providers before starting new supplements, especially if you have existing liver conditions or take medications.

From the Research

Dietary Supplements and Hepatotoxicity

• The use of dietary supplements has been associated with an increased risk of liver injury, with some supplements causing severe damage to the liver 2, 3, 4.
• Certain dietary supplements, such as green tea extract, have been linked to hepatotoxicity, with cases of liver damage reported in individuals consuming these supplements 5.
• The mechanisms by which these supplements cause liver damage are not fully understood, but it is thought that individual ingredients, as well as interactions between ingredients, may play a role 2, 5.

Risk of Accidental Overdosing

• The use of dietary supplements can also lead to accidental overdosing, particularly when individuals take multiple supplements or combine them with other medications 3, 4.
• Certain supplements, such as vitamin A, can cause liver damage if taken in excess, highlighting the importance of careful dosing and monitoring 2, 6.

Excess Vitamins and Urine Excretion

• Excess vitamins, particularly fat-soluble vitamins like vitamin A, can accumulate in the body and cause toxicity, rather than being excreted in the urine 6.
• Water-soluble vitamins, on the other hand, are generally excreted in the urine if taken in excess, but can still cause adverse effects if consumed in very high amounts.

Supplements Associated with Hepatotoxicity

• Specific dietary supplements associated with hepatotoxicity include:
  • Herbalife products
  • Hydroxycut products
  • Green tea extract
  • Linoleic acid
  • Usnic acid
  • 1,3-Dimethylamylamine
  • Vitamin A
  • Garcinia cambogia
  • Ma huang
  • OxyELITE Pro
  • Kava tea
  • Polygonum multiflorum 2, 3, 5.