Written by Tatjana Djakovic, Staff Writer. Vitamin E up to 1600IU/day and vitamin C up to 2000 mg/day have been found safe in a summary of 19 researches.
The health benefits of vitamins C and E are mainly due to their anti-oxidative properties and protection from free radical damage. When vitamin E works as an antioxidant, it is oxidized to a harmful radical that needs to be reduced back to α-tocopherol by vitamin C (1). In clinical trials, vitamins C and E have been shown to be helpful for diabetes, bone health, mental aging and even increasing chance of survival of breast cancer patients. Some clinical trials have found vitamins C and E to be ineffective, often these studies were performed in subjects that already had a high antioxidant intake (2).
The inconsistencies are also due to differences in study populations, the type of antioxidants and the outcome measures (3). For example, one meta-analysis study which combined 19 clinical trials reported that adults that took 400IU of vitamin E daily were 6% more likely to die of any cause than those who did not take vitamin E. Upon a closer look, it was found that the higher risk of death was only significant for those that were taking 2000 IU per day, which is well above the safety level (4).
The above normal intake of these supplements has put the safety of these supplements in question. The purpose of the current study (5) is to evaluate the available literature to address the issue of safety and the levels in the body that are shown to be beneficial without causing any harm. The researchers list a substantial amount of evidence for both vitamins C and E, some of which are highlighted below.
Safety Evidence for Vitamins C and E
- In a study of 20, 536 adults from the United Kingdom with heart disease or diabetes that were randomly assigned to receive 250 mg of vitamin C daily, along with 600 mg vitamin E and 20 mg beta carotene daily or placebo for 5 years showed no clinically important safety issues (6).
- A study of 2002 patients with cardiovascular disease were randomly assigned to receive placebo or vitamin E at 400 IU or 800 IU daily. After a follow-up of 16 months, no significant adverse effects of vitamin E supplementation were reported among these patients (7).
- In a study of 9541 patients with cardiovascular disease risk factors who were given 400 IU of vitamin E daily, the supplement was found to be well tolerated over a period of 4.5 years (8).
On the basis of the human evidence, the researchers determined the safety levels of vitamins C and E that do not cause any adverse affects or pose significant harm to the general population. Those levels include 1600 IU/daily for supplemental vitamin E and 2000 mg/daily for supplemental vitamin C. In conclusion, the benefits of vitamin C and E are crucial to our health when taken in recommended dosages, however, if taken in above the recommended dosages they might pose harm.
Source: Hathcock, John N., et al. “Vitamins E and C are safe across a broad range of intakes.” The American journal of clinical nutrition 81.4 (2005): 736-745.
© 2005 American Society for Clinical Nutrition
Posted March 4, 2014.
