Although vitamins are needed for thousands of bodily reactions every day, they are required in very small amounts. The total amount of vitamins one person needs each day for maintaining good health measures less than 1/8 teaspoon. Such small amounts are sufficient because vitamins are not usually depleted in doing their work for the body. Instead, the body “recycles” vitamins, releasing and reutilizing them until they are replaced by new ones.
The two units of measure commonly used to express vitamin amounts are milligrams and micrograms. To understand these units, think of an ounce – which equals 28.3 grams. A milligram is 1/1,000 of a gram, or slightly less than .03 ounces. The recommended allowance for the average adult is only 60 milligrams of vitamin C per day, for example. The recommended allowance of some vitamins, such as B12, is even smaller.
These are measured in micrograms, that is 1/1,000 of a milligram or 1 millionth of a gram. Thus, a single ounce of B12would be enough to supply one day’s requirement for nearly 9 million people. Until recently, international units (IU) were the common measure used to express the biological activity of fat-soluble vitamins.
But since these vitamins are found in nature in different forms, with varying degrees of biological effect, this imprecise system has created confusion. To help clear matters, fat-soluble vitamins are now measured in their pure form according to weight (micrograms and milligrams). However, during this period of transition, both systems of measurement will continue to be employed simultaneously.