General guidelines for buying and taking supplements
A well-balanced multivitamin supplement is usually better than several single supplements. Such supplements contain approximately 100 per cent to 300 per cent of the RDA for those vitamins and minerals which may have protective effects or are often lacking in the diets of many people. These include vitamins A (preferably in the form of beta carotene), E, C, thiamin, riboflavin, niacin, B6, folic acid, pantothenic acid, biotin, calcium, copper, iron, magnesium and zinc. However, many multivitamin and mineral supplements do not contain sufficient calcium or magnesium, and additional single supplements may be useful for those who need higher doses, such as postmenopausal women.
Some supplements group vitamin A and beta carotene together, making it difficult to tell how much of each is present. A supplement which provides vitamin A as beta carotene only may be best. Most multivitamin supplements contain only small amounts of beta carotene so it may be worth taking a separate supplement; although probably not if you are a smoker.
It may be beneficial to choose a supplement that provides minerals in the following amounts: chromium 50 to 200 mcg, manganese 2.5 to 5.0 mg, selenium 50 to 200 mcg. Amounts much higher than this may be toxic.
Supplements which contain useless or potentially harmful substances should be avoided. Most experts feel that ingredients which have not been shown to be necessary in the diet may merely increase the price of a supplement. It is also best to avoid products which contain artificial flavor, preservatives and color.
Expensive supplements are not necessarily better. It is more important to check the nutrient content of the supplement. Supplements with the same ingredients which are priced much lower than various reliable brands may not be high quality and those which are priced considerably higher may be too expensive.
Avoid expensive supplements sold through multilevel marketing (MLM). These include multimineral and spray vitamins. There is almost no scientific evidence to support the claims that are often made, and the products are over-priced.
Vitamins should be stored in a cool dry place away from direct sunlight in a closed container. If they are kept sealed, in these conditions they should last for two or three years. Once they are opened, they usually have a 12- month shelf life.
If you are unsure whether the products you are buying will break down in your stomach in time to be absorbed, try dropping the tablet into a glass of vinegar. If it dissolves in 30 minutes it is likely you will be able to absorb the nutrients it contains.