For thousand and thousand of years, people got all the vitamins and minerals they needed from the foods they ate. However, in today's world there is processed foods, drugs, cigarettes, and alcoholic beverages that interfere with adequate nutrition.

Because of this, for some people even a reasonably well-balanced and varied diet can't supply enough certain nutrients needed for the body. Theses people would need to increase their consumption of foods rich in certain vitamins to compensate and possibly add supplements of one or more vitamins to make it beneficial.

Pregnant and Nursing Women:
Vitamin supplements are given to women who are pregnant or nursing and in the ideal situation this should not be necessary –except for extra iron – since both pregnancy and lactation increase a woman's need for calories and because she is eating extra food, she naturally consumes extra vitamins. However, women who have morning sickness beyond the morning, or who have diets for weight control the pregnant women will often have reduced blood levels of vitamins A, C, B6, B12, and folacin. If this should happen, then vitamin supplements would be prescribed. Generally a multivitamin and mineral supplement are prescribed to all women who are pregnant and nursing.

Infants:
Infants that are given vitamin supplements are usually not needed because the RDAs for infants are based primarily on the vitamin content of breast milk which is the ideal complete food for infants for the first six months of life. There are however some differences in vitamin content between breast milk and cow's milk and a vitamin supplement may be important for babies who are not breast fed.

Women using oral contraceptives:
Using the birth control pill will often found to have reduced blood levels of thiamin, riboflavin, B6, B12, folacin and vitamin C, B6 deficiency while on the pill has be linked with mental depression and a vitamin supplement will be needed.

Smokers:
Those who smoke one and a half packs of cigarettes a day have 30% - 40% less vitamin C in their blood than nonsmokers and this is because the Vitamin C is being used up when their body attempts to repair damage to the cells caused by the toxic elements in tobacco smoke. This vitamin C deficit can be made up by either consuming and 8-ounce glass of orange juice per day or a vitamin C supplement.

Drinkers:
A heavy drinker will require more thiamin, niacin, folacin and B6 than person who drink only socially or not at all even if their diet is extremely good. Alcohol damages the liver and interferes with its ability to store needed vitamins, especially folacin and to convert the vitamins to their active chemical forms. Drinking alcohol also leads to poor absorption of vitamins from foods, and it will increase the requirement for vitamins by using some to metabolize the alcohol and to repair the tissue damage it has caused. A heavy drinker usually does not eat properly cause they substitute nutrient –deficient alcohol calories for nutrient rich food calories and compromise their vitamin intake. You will need to daily multivitamin supplement if you will need to daily multivitamin supplement if you drink the equivalent of four or more shoots (2 ounces of pure alcohol) of alcohol a day.