Figure 25.1 For humans, fruits and vegetables are important in maintaining a balanced diet. (Credit: modification of work by Julie Rybarczyk)

All living organisms need nutrients to survive. Animals obtain their nutrients by the consumption of other organisms. At the cellular level, the biological molecules necessary for animal function are amino acids, lipid molecules, nucleotides, and simple sugars. However, the food consumed consists of protein, fat, and complex carbohydrates. Animals must convert these macromolecules into the simple molecules required for maintaining cellular functions, such as assembling new molecules, cells, and tissues. The conversion of the food consumed to the nutrients required is a multi-step process involving digestion and absorption. During digestion, food particles are broken down into smaller components; later, they are absorbed by the body.

One of the challenges in human nutrition is maintaining a balance between food intake, storage, and energy expenditure. Imbalances can have serious health consequences. For example, eating too much food while not expending much energy leads to obesity; this in turn will increase the risk of developing illnesses such as type 2 diabetes and cardiovascular disease. The recent rise in obesity and related diseases makes understanding the role of diet and nutrition in maintaining good health all the more important. Many health experts believe that nutrition education will improve the overall health of the entire population. In fact, according to Williams et al. (2014), one nutrition education program, the Supplemental Nutrition Assistance Program (SNAP), focused on pre-school-aged children enrolled in a low-cost childcare setting and found that participating children were significantly more likely to eat more vegetables at home. You can read more about SNAP here.