The Recommended Daily Allowance or RDA is deemed to be the amount of specific nutrients required for health. People have been led to believe that as long as they eat the RDAs for the major nutrients then their nutritional needs will be satisfied. Against this, increasing numbers of scientists and nutritionists claim that the RDAs are set far too low, and that generally much higher doses of vitamins and minerals are required to maintain optimum well-‐being. So, does eating nutrients in excess of the RDAs really offer tangible health benefits, or do our bodies simply expel them?
The RDAs represent the level of nutrients needed to prevent what is known as deficiency diseases. For instance, scurvy can be prevented with just 60 mg of vitamin C each day, while a daily dose of just 1 mg of vitamin B1 can prevent the condition beri-‐beri. However, while an RDA represents the absolute minimum amount of a nutrient needed to prevent an obvious deficiency, it does not necessarily reflect the dose required to prevent important conditions such as heart disease and cancer. There is a world of difference between the level of a nutrient needed for basic health, and the dose required to ensure optimum health. For instance shows that taking 100 international units (IU) of vitamin E per day seems to reduce the risk of heart attack by a third. 400-‐800 IU of vitamin E per day offered substantial benefits for individuals with heart disease. In the light of these findings, it does seems that taking vitamin E at the RDA level of just 14 IU is unlikely to be effective in preventing and treating Britain’s number one killer.
Another example of a nutrient for which there exists an obvious disparity between its RDA and optimal intake is vitamin C. High intakes of this vitamin have been correlated with a reduced risk of heart disease and cancer, and there is good evidence that supplementing with vitamin C can increase longevity too. More and more evidence suggests that for optimum health, each of us should be consuming at least 200 mg of vitamin C each day. What is more, during infections such as colds and flu, doses around a hundred times the RDA of 60 mg may be required to speed recovery and restore health.
While the RDAs for certain nutrients do indeed appear to be set too low, for many nutrients, no RDA exists at all. It is known that we require about 50 different nutrients to sustain life. Looking more closely at the nutrients with no official RDA level, it does seem as though there has been some glaring omissions. A good example is the antioxidant mineral selenium. A study published in the New England Journal of Medicine in 1996 showed that supplementing with selenium at a dose of 200 mcg per day effectively halved an individual’s risk of dying from cancer. And yet, to this day, no RDA for selenium exists.
One of the things which causes resistance to taking nutrients in doses which exceed the RDAs is a feeling that doing so may lead to problems with overdose and toxicity. For the most part, this is simply not the case. The RDAs are not intended to reflect the safe levels of nutrients at all. There is now a wealth of scientific literature designed to determine the levels of nutrients safe for human consumption. Generally, what we find is that the safe daily intake for a nutrient is many times the RDA. For instance, while the RDA for vitamin B6 is just 2 mg, there is good evidence that suggests its upper safe limit is at least 200 mg. Disappointingly, and despite good evidence science to the contrary, the European Union body responsible for determining safe levels of nutrients (the Scientific Committee on Food) has recently recommended that vitamin B6 be subject to an upper safe limit of 25 mg per day.
There seems little doubt that the RDAs are outdated, inappropriate, and well overdue for review. More emphasis should be placed on the real doses of nutrients required for optimum health. There is now a wealth of scientific and anecdotal evidence which supports the idea that taking nutrients in excess of the RDA can be a safe and effective way to enhance health and prevent illness.
Modified from: Recommended Dietary Allowances – Are they useful? By Doctor John Briffa, 19/10/2000.