Dehusked, unpolished rice grains are covered by the nutrient-rich bran and aleurone layers. Because these layers are rich in lipids they oxidises rapidly when exposed to air, hence the grains turn rancid and untasty during storage. Polishing, on the other hand, produces rice grains devoid of the nutrients contained in the outer layers but not susceptible to changes in colour, odour and taste.

Parboiling is a process applied to rice to preserve some of the nutrients contained in the outer grain layers, which are normally lost during polishing (the bran and aleurone layers). After a short hot steam treatment part of the nutrients diffuse into the starchy endosperm, thus enhancing the nutritive qualities of the rice. The treatment results in rice that is slightly yellow, hence some parboiled rices carry the name "Golden Rice", which must not be confused with the one produced by genetic modification, as in the project described on this web site.

Vitamin A is stored in the liver and deficiency of the vitamin occurs only after prolonged lack of dietary intake. An early symptom of vitamin A deficiency is night blindness. Additional early symptoms include follicular hyperkeratinosis, increased susceptibility to infection and cancer, and anemia equivalent to iron- deficiency anemia. Prolonged lack of vitamin A leads to deterioration of the eye tissue through progressive keratinization (hardened cell layers) of the cornea, a condition known as xerophthalmia. The increased risk of cancer is thought to be the result of a depletion in vitamin A reserves. β-carotene is a very effective antioxidant and is suspected to reduce the risk of cancers known to be initiated by the production of free radicals. Of particular interest is the potential benefit of increased β-carotene intake to reduce the risk of lung cancer in smokers. However, caution must be exercised when increasing the intake of any of the lipid soluble vitamins. Excess accumulation of vitamin A in the liver can lead to toxicity which manifests itself as bone pain, hepatosplenomegaly (enlarged liver), nausea and diarrhea.

The potential impact of Golden Rice depends on rice consumption patterns in a given country. Target countries for Golden Rice deployment have been selected based on dietary patterns by country. It is important to also calculate how much pro-vitamin A is obtained by consumers from other nutrient sources in their diet. This allows us to calculate the gap that must be filled by Golden Rice or else.

The data presented in the tables below are for adults. Children under 6 eat in average about half as much as an adult.