Vitamin A is a fat-soluble vitamin essential for maintaining vision, strengthening immunity, and cell growth and differentiation. However, just like the philosophy in Korean medicine that 'too much is as bad as too little,' modern medicine also warns that excessive intake of vitamin A can cause serious health problems. This is a condition called 'hypervitaminosis A.' This requires special attention as it can cause particularly fatal damage to the liver.
Vitamin A exists largely in two forms. One is 'preformed vitamin A' in the form of 'retinol' found in animal foods or dietary supplements, and the other is 'provitamin A carotenoids' such as beta-carotene abundant in plant foods. What mainly becomes a problem is preformed vitamin A in the retinol form. Beta-carotene is converted into vitamin A only when needed by the body, so the risk of toxicity is very low, but if retinol is consumed excessively, it accumulates directly in the body and can cause toxicity.
In our body, vitamin A is mainly stored in stellate cells in the liver. The liver is the primary organ storing vitamin A, and at the same time, it makes ceaseless efforts to detoxify excess vitamin A. However, when there is too much vitamin A in the body, it exceeds the liver's processing capacity, and vitamin A accumulated excessively in stellate cells can stress the cells and trigger inflammatory responses. When chronically exposed to high doses of vitamin A, stellate cells become activated and begin to excessively produce collagen; if this process continues, fibrosis progresses in the liver tissue.
Liver fibrosis is a phenomenon in which the liver hardens stiffly, and although there may be no symptoms in early stages, it gradually brings about hepatic hypofunction. If it worsens, it can develop into liver cirrhosis, causing severe damage to the liver's detoxification and protein synthesis functions, and there is also a risk of leading to severe complications such as portal hypertension and hepatic encephalopathy.
Symptoms of vitamin A toxicity can manifest acutely and chronically. Acute toxicity occurs when high doses are consumed over a short period, and headache, nausea, vomiting, dizziness, blurred vision, and muscle pain may appear. Chronic toxicity appears when relatively lower doses are consumed over a long period; in this case, xerosis cutis, alopecia, fatigue, joint pain, osteoporosis, and most importantly, hepatic dysfunction, including elevated liver enzyme levels and hepatomegaly, can appear. The progression of liver injury can be diagnosed by checking liver enzyme levels, including aspartate aminotransferase and alanine aminotransferase, through blood tests, measuring blood vitamin A concentrations, and, if necessary, using imaging studies such as abdominal ultrasonography, computed tomography, and magnetic resonance imaging.
Overusing supplements simply after hearing that they are 'good' can become a toxin to our body. In particular, since the liver is often called a silent organ and symptoms appear late, careful management regarding daily lifestyle habits and supplement intake is necessary.
