The recommended dietary allowance (RDA, It is the average daily intake of a nutrient needed to meet the requirements of a healthy person, as explained by the US National Institutes of Health (NIH). The RDA for vitamin C (ascorbic acid or ascorbate) that is set higher than the amount needed to avoid a deficiency. For infants, the measure known as adequate intake (AI) is established by the Food and Nutrition Board (FNB) of the Institute of Medicine because the RDA has not been determined for that age group.
The FNB establishes an AI of vitamin C for infants in 40 mg daily from birth to 6 months and 50 mg daily from 7 to 12 months. This is the equivalent of the average intake of vitamin C in healthy infants who are breastfed. The FNB considers breast milk an adequate source of vitamin C and does not recommend feeding small children with any form of cow's milk. Cow's milk contains very little ascorbic acid and heat can destroy this vitamin. Both boys and girls need a minimum of 40 mg of vitamin C daily from birth to 6 months and 50 mg daily from 7 to 12 months.
Children and adults
Children from 1 to 3 years old have an RDA of 15 mg of vitamin C daily, according to the NIH. Children from 4 to 8 years need 25 mg daily and children from 9 to 13 years need 45 mg daily. Gender considerations begin at the age of 14, in which girls have an RDA of 65 mg of vitamin C daily until the age of 18, and boys an RDA of 75 mg in that age range. From 19 onwards, women require 75 mg of vitamin C per day, although pregnant women have an RDA of 80 to 85 mg and lactating women of 115 to 120 mg. Men 19 years and older have an RDA of vitamin C of 90 mg per day.
Considerations for smokers
People who smoke need 35 mg more vitamin C per day than non-smokers, as noted by the NIH. This is partly because smokers have greater oxidative stress and ascorbic acid is an antioxidant. Regular exposure to secondhand smoke also requires a higher intake of vitamin C, although a specific requirement has not been established.
People with certain health conditions or dietary behaviors may not have vitamin C deficiency if they consume only the RDA for their age group. This includes the elderly, the poor, the homeless, or people with mental illness who consume a limited variety or amount of food. Individuals who abuse alcohol or other drugs or those who are following diets that do not provide adequate nutrition may require vitamin C supplements.Some medical conditions can reduce the absorption of vitamin C, such as intestinal malabsorption, AIDS, end-stage renal disease and certain types of cancer. A study published in the November 2009 issue of "Gastroenterology" noted that some surgical and trauma patients and those who were developing septic shock experienced a drastic drop in blood levels of ascorbate. Patients with critical illnesses and burn victims may also need a higher intake of vitamin C. All of these individuals have increased vitamin C requirements due to oxidative stress and wound healing.