Food sources of vitamins include plants and animals. Vitamins are only found in living things; however, there is not one food source that can provide all the vitamins needed for growth and development of a healthy body. A variety of foods, therefore, must be eaten. For example, potatoes are a good source of Vitamin C, but they are not a good source of Vitamin D. Restricting a diet to foods that are limited in their vitamin content or variety can lead to deficiencies. Because vitamins are essential to the body's utilization of energy, deficiencies can cause a wide range of health problems, ranging from brittle fingernails to heart failure. The seriousness of the effects is due mostly to the length of time that a person has had a deficiency. Cells can function for a period of time without the needed vitamins. Cases of life-threatening deficiencies are rare in nations such as the United States because of the abundance of food sources available to people of all economic levels.
