In support of a higher RDA for vitamin C
Researchers from Université de Lille 2 and Université de La Réunion in France have written a detailed and extensively referenced review of the current state of vitamin C supplementation.
Here are the highlights of their case for increasing the recommended daily allowance (RDA) of vitamin C supplementation to 1 gram, accompanied by a diet rich in fruits and vegetables.
The article is more than 7000 words. So, what follows is a top line summary.
Functions of vitamin C
- Vitamin C is required for maintenance of normal connective tissue and wound healing.
- It’s also required for bone remodeling and other metabolic reactions, among other needs.
Recommended dietary allowance of vitamin C
- People vary widely in their vitamin C requirements.
- The current RDA for vitamin C is based on twice the amount needed to prevent scurvy and the threshold to spill vitamin C into urinary excretion.
- Many reviewers suggest that intake of vitamin C much higher than the RDA may reduce the risk or risk factors for chronic diseases such as heart disease and certain types of cancer.
- But there’s no justification for routine megadose vitamin C, 1–3 grams/day, in the normal population.
Bodily needs in vitamin C
- Needs vary among different people and under different conditions.
- For example, the elderly have reduced concentrations of vitamin C in blood and white blood cells.
- Vitamin C supplementation (500 mg/day for 1 month) enhanced the immune response of T lymphocytes .
- In healthy people with higher concentrations of vitamin C (1 grams/day), white blood cells are more active and could speed their respond to infection or inflammation.
Vitamin C consumption higher than the RDA
- Higher doses of vitamin C (2500 mg daily) taken by mouth result in higher vitamin C blood levels.
- High levels of vitamin C protect against damage to blood vessels and reduce mortality rates in the elderly.
- Taking hourly doses of 1000 mg of vitamin C for the first 6 hours after the onset of cold symptoms and 3 times daily thereafter decreased flu and cold symptoms by 85% vs a control group.
- Although other studies show conflicting results.
- Based on the literature, the authors suggest a minimum vitamin C consumption of 1 gram daily in healthy people in order to complete a prevention program for many diseases.
Safety of vitamin C supplementation
- Gastrointestinal distress is the most common side effect of high vitamin C intake.
- When it occurs, the vitamin C dose is usually at least 2 grams/day.
- Symptoms usually disappear in 2 weeks.
The bottom line?
The authors state that there’s evidence that vitamin C prevents and treats a broad range of diseases. Yet, the current RDA for vitamin C does not cover the need for vitamin C in daily bodily functions.
“Consequently, even if vitamin C requirements vary greatly among individuals, it is suggested that vitamin C supplementation is not only totally safe but also necessary to achieve optimal health. Therefore, in agreement with the current literature, we advise healthy people to consume 5 servings of fruits and vegetables daily, added to 1 gram of vitamin C supplementation divided in 2 or 3 doses during the day, in order to ensure an optimal allowance in vitamin C to achieve optimal health.”
12/3/08 2:30 JR