Natural vitamins, minerals and supplements are known as micro-nutrients as they are only needed in small amounts compared to protein, fats and carbohydrates which are known as macro-nutrients. However they are all essential to our health and need to be taken in the correct amounts to ensure a long and healthy life.
To help us to know how much of each supplement is needed, the Food and Drug Administration (FDA) provide a recommended optimum Daily Value (DV) of various nutrients found in food and supplements. For example, a snack which has 18 grams total fat will provide 26% of the amount needed for someone on a 2,000 calorie diet. Something with 1.7mg Riboflavin will have received 100% of the daily requirement from just one serving. However the government has only set recommended levels for a fraction of the vitamins and supplements available and the optimum requirement for many products is as yet unknown. These products are marked with a ** next to the % daily value.
The Institute of Medicine has also issued its own guidelines, which may or may not be the same as the FDA numbers. Figures available from the Institute of Medicine include the Recommended Dietary Allowance (RDA) and the Adequate Intake (AI) of a product. These figures indicate the amount you need to take daily to stay healthy and are individually tailored to men, women and specific age groups separately.
The less well known figure of Tolerable Upper Intake Level (UL) is the maximum you can take without suffering side effects. This is the total amount of the substance obtained from the diet in addition to that taken as a supplement. These UL figures are not widely published but can be found on government websites.
How Much is Too Much?
Some people think that if something is good for your health, taking twice as much will be twice as good, but this is rarely the case. Some supplements will pass the excess through the body doing no harm, but doing no good either. However, other supplements such as vitamin A, iron and selenium when taken in excess will build up in the body causing toxicity.
In some cases the RDA recommendations have not been updated in line with new research. One such example is vitamin D, where the RDA for a 60-year old is 600 IUs but the National Osteoporosis Foundation recommends 800-1000 IUs for that age group, as shown in research.
Generally, eating a healthy diet and topping it up with a multivitamin is the best way to ensure that you are covering any gaps in your diet, ensuring the best possible health for many years to come.