As with medications, taking high doses of certain vitamins can put stress on the liver and even cause in liver damage. Some vitamins, such as B-3, are especially hard on the liver, such that your physician may recommend periodic liver function tests during vitamin therapy. Due to risk of liver damage and other harmful side effects, it is important to get your doctor's approval before taking vitamin supplements.
Fat-soluble vitamins, including vitamins A, E, D and K, are stored in the liver and fatty tissues of the body. Since excess amounts of these vitamins are not quickly removed from the body as with water-soluble vitamins like vitamin C, fat-soluble vitamins can accumulate in the liver and cause health problems if consumed in excess. According to Colorado State University, over-consumption of vitamin A can cause enlargement of the liver and high doses of vitamins K and D can cause liver damage and toxicity.
Certain B-complex vitamins also affect the liver. Unlike other water-soluble vitamins, the liver can store B-12 for up to several years for later usage. B-complex vitamins, in general, are also necessary for maintaining the overall health of the liver. However, like fat-soluble vitamins, certain B-vitamins can cause liver damage if you consume them in excess. Specifically, vitamin B-3, or niacin, may cause liver damage in high doses -- and timed-release preparations are more likely to cause damage than regular niacin, according to the University of Maryland Medical Center.
Vitamins and Liver Disease
People with liver disease may require vitamin supplementation, as liver damage can impair your body's ability to absorb certain vitamins. For example, liver disease may inhibit the absorption of vitamins B-12 and B-1, causing deficiencies of these nutrients and necessitating long-term, high-dose supplementation. There is also some evidence that certain vitamins can help treat liver disease. A study published in "The New England Journal of Medicine" in May 2010 indicates that daily vitamin E doses of 800 IU may improve symptoms of nonalcoholic steatohepatitis, or fatty liver disease.
Eating a wide variety of healthy foods is the best way to obtain all the vitamins you need, according to MedlinePlus. Unlike vitamin supplements, foods typically do not contain vitamins in amounts high enough to pose health risks such as liver damage. However, if you are pregnant, have insufficient dietary intake of certain vitamins, or have a medical condition such as liver disease, which inhibits vitamin absorption, you may need to take vitamin supplements as prescribed or recommended by your doctor.