Protein quantity plant-based diets is shown not to be an issue. Inadequate amino acid supply is not an issue with most cereal-based diets.
When used to score plant-based diets in India, no marked deficiencies are identified. All regions score > 1 for adults, whilst for children scores range from > 1, (Tamil Nadhu) from 6 months of age to 0.78 (West Bengal), rising to 0.9 in the 2-5 year old, consistent with reports that high-lysine maize supports similar weight and height growth to that of casein.
Digestibility is identified as a problem for some cereals (millet (Panicum miliaceum) and sorghum (Sorghum sp.)) and generally is poorly understood.
A new maintenance requirement pattern is developed, with higher values than those of Food and Agriculture Organization / World Health Organization / United Nations University (1985) but lower values than the Massachusetts Institute of Technology pattern (Young et al. 1989).
Calculations of age-related amino acid requirements are based on most recent estimates of human growth and maintenance protein requirements, a tissue amino acid pattern and the new maintenance amino acid pattern. These values appear valid when used to score plant proteins, since they indicate values similar to or less than the biological value measured directly in young children.
Vitamin C, or L-ascorbic acid, or ascorbate, is an essential nutrient for humans, a water-soluble vitamin. Humans, unlike most animals, are unable to synthesize vitamin C, so it is an essential dietary component.
- Vitamin C is required for the biosynthesis of collagen (an essential component of connective tissue), L-carnitine, and certain neurotransmitters, it is also involved in protein metabolism.
- Vitamin C is also an important physiological antioxidant and has been shown to regenerate other antioxidants within the body, including alpha-tocopherol (vitamin E). Vitamin C regenerates vitamin E by reducing vitamin E radicals formed when vitamin E scavenges the oxygen radicals.
- Vitamin C plays an important role in immune function and improves the absorption of nonheme iron, the form of iron present in plant-based foods.
Approximately 70%–90% of vitamin C is absorbed at moderate intakes of 30–180 mg a day. At doses above 1 g a day, absorption falls to less than 50% and absorbed, unmetabolized ascorbic acid is excreted in the urine.
Insufficient vitamin C intake causes scurvy, which is characterized by fatigue or lassitude, connective tissue weakness, and capillary fragility.
Cells accumulate vitamin C. The total body content of vitamin C ranges from 300 mg (at near scurvy) to about 2 g.
- High levels of vitamin C are maintained in cells and tissues, and are highest in leukocytes (white blood cells), eyes, adrenal glands, pituitary gland, and brain.
- Relatively low levels of vitamin C are found in extracellular fluids, such as plasma, red blood cells, and saliva.