Recommended Nutrient Intakes for Vitamin and Minerals

Arsenic

Functions

Arsenic is known as an ultra-trace element which means that it is required in extremely small amounts (i.e. <1mg/g dry diet).

The precise function and essentiality of arsenic in humans has not been elucidated. It may function as a methylated compound.

A provisional maximum tolerable intake of 2mg/kg body weight per day has been set for inorganic arsenic.

The major food sources for arsenic are seafoods. They contain arsenobetaine which is the non-toxic organic form of arsenic.  Inorganic arsenic is very toxic.

Typical dietary intakes of arsenic range from 10mg to 20mg/day.

To date, the essentiality of arsenic is unknown in humans. Deficiency symptoms such as impaired growth and abnormal reproduction have been described in some animal models.

The inorganic form of arsenic is very toxic. A provisional maximum tolerable intake of 2mg/kg body weight per day has been set for inorganic arsenic, by the WHO/FAO Joint Committee on Food Additives.

Vitamin E is a fat-soluble vitamin. There are 8 naturally occurring forms of vitamin E found in plants. Four tocopherols and four tocotrienols.

Functions

Vitamin E is a powerful antioxidant. It protects lipids and cell membranes from free radical damage. Vitamin E is especially effective in preventing the oxidation of polyunsaturated fatty acids. Most of the vitamin E in the body is found in cell membranes where it functions to protect polyunsaturated fats against free radical damage. Plasma lipoproteins (complexes of lipids and proteins which transport lipids around the body) also contain vitamin E. This is particularly important for the low density lipoproteins (LDL). If LDL becomes oxidised it accumulates in the walls of arteries at a greater rate than non-oxidised LDL, thus accelerating the development of atherosclerotic plaques.

Vitamin E also exerts an especially antioxidant effect in the lungs where the exposure of cells to oxygen is maximal. Vitamin E is important for protecting red and white blood cells which pass through the lungs, as well as the lung cells themselves. Vitamin E also protects the lungs form air pollutants such as nitrogen dioxide or ozone that can initiate damaging reactions.

Recommended Intakes

Table 9: Recommended Intakes for Vitamin E (mg alpha-tocopherol equivalnts/day)

Food Sources

Vitamin E is widespread in foods. Foods high in fat, particularly polyunsaturated fats are the best food sources of vitamin E. Wheatgerm oil is the richest source. Corn and soybean oils rank second.

Around about 20% of dietary vitamin E is derived from vegetable oils and products made from them, e.g. margarines. A further 20% comes from fruits and vegetables. Other sources include fortified cereals and grains, meat, poultry, fish, eggs, nuts and seeds.

Deficiency

Dietary vitamin E deficiency is rare. It is usually associated with diseases of fat malabsorption such as cystic fibrosis.

When the concentration of vitamin E in the blood falls below a critical level the red blood cells tend to break open and spill their contents, probably due to oxidation of the polyunsaturated fat in their membrane. This is known as erythrocyte hemolysis and is seen in premature infants born before the transfer of vitamin E from the mother to the infant which takes place in the last weeks of pregnancy. Vitamin E corrects this.

Prolonged vitamin E deficiency also causes neuromuscular dysfunction involving the spinal cord and retina. Some symptoms include loss of muscle coordination and reflexes and impaired vision and speech.

Toxicity

Vitamin E appears to be the least toxic of the fat-soluble vitamins and reports of toxicity are rare. Extremely high intakes of vitamin E may interfere with the blood clotting action of vitamin K and enhance effects of drugs used to oppose blood clotting, causing hemorrhage.