The ideal that we can get all the nutrients we need from the food we eat is very appealing. Unfortunately, no dietary survey to date has shown this ideal to be a reality. The truth is that poor dietary habits are the norm, not the exception. Most people don't eat right and even those who do may be lacking in some nutrients. In fact, statistics about food intake indicate that most people need supplements.  For example, the National Research Council (NRC) has advised that individuals eat five or more servings a day of fruits and vegetables, especially green and yellow vegetables and citrus fruits. However, data from a large national nutritional survey showed that 15-25 percent of the population ate no fruit or vegetables serving on the survey day. Of the approximately 80 percent of the participants who did eat some fruit or vegetable, only about one in five (20 percent) reported eating food considered cancer protective. Vitamin are usually distinguished as being water-soluble or fat-soluble. The water-soluble vitamin B-complex, C, and the compounds termed "bioflavonoids," are usually measured in milligrams. The fat-soluble vitamins, A,D,E and K, are measured in units of activity known as :international Units" (I.U). An exception is beta-carotene, a water-soluble form of vitamin A, which is expressed in IU also.