Liver and liver-based foods

Vitamin A and liver

What is vitamin A

Vitamin A is an essential nutrient that plays a vital role in many functions of the body. Vitamin A influences e.g. vision, cell growth and diversification, the defence mechanisms of the body, and foetal development. The body is not capable of producing vitamin A itself, which means we must obtain it from our food. In products of animal origin, vitamin A is found in the form of retinoids, while plants contain vitamin A as carotenoids, which are converted into retinoids in the body. Vitamin A is a generic name for retinoid compounds with the biological activity of retinol. The vitamin A activity is given in retinol equivalents (RE). In foods, the carotenoid with the highest vitamin A activity is beta carotene.

Sources of vitamin A

Vitamin A is a fat-soluble vitamin that is stored in the liver. For this reason, liver has higher vitamin A content than any other food (Table 1). Other foods with high vitamin A content include fatty milk products, dietary fats and eggs. Dark green leafy vegetables as well as orange and red vegetables, fruit and berries are good sources of carotenoids.

Table 1. Average vitamin A content of foods. Foods of animal origin contain vitamin A in the form of retinoids, and plants in the form of carotenoids.

¹Source: Finnish Food Composition Database Fineli ^®,  www.fineli.fi

Deficiency and excessive intake of vitamin A

As far as vitamin A is concerned, both deficiency and excessive intake may cause health problems. Deficiency of vitamin A is, however, rare in western countries. The risk of excessive intake of vitamin A in retinoid form, on the other hand, does exist. Excessive intake is in children and adults manifested as vitamin A toxicity and during pregnancy as foetal development abnormalities. The symptoms of excessive intake of vitamin A can be general symptoms, such as headache and fatigue, or symptoms of the digestive tract, skin, the nervous system and the musculoskeletal system. Toxicity cases caused by food are rare, but continuous excessive consumption of liver, food supplemented with vitamin A or food supplements containing vitamin A can cause vitamin A toxicity.

The cartenoids contained in plants have not been found to have detrimental effects even in large quantities. However, long-term consumption of beta carotene, in particular, may cause yellowing of the skin, but this is completely harmless.