"You are what you eat" is more than a cliche -- it's fact. Food is made up of compounds called macromolecules -- protein, carbohydrates, lipids and nucleic acids -- that are also the building material for the cells, tissues and organs in your body. Macromolecules are composed of smaller units called monomers.
Protein: More Than Muscle
Colorful packaging on bars and shakes advertises the muscle-building properties of protein, but its role in the human body is much more extensive. Enzymes, hormones and membrane receptors are all made up of protein. Proteins are composed of 20 subunits called amino acids. Your body can make some amino acids, but others must come from dietary sources. Meat and other animal products are known as complete proteins because they supply all the amino acids your body can't make. Most vegetable sources of protein must be mixed and matched, but some -- including soy -- are complete proteins, too.
Carbohydrates: Sweet Energy
Your body converts all carbohydrates into a simple sugar known as glucose. The sugar is in your bloodstream and supplies every cell in your body with energy. Glucose is an example of a simple sugar, or monosaccharide. Larger complex carbohydrates -- like starch -- are composed of chains of monosaccharides. Milk, fruit and vegetables are healthy sources of simple sugars. Whole-grain products such as bread and pasta; starchy vegetables and legumes contain complex carbohydrates.
Good Fats and Bad
Your body is home to many thousands of types of lipids -- some disease-causing and some essential to life, according to the National Institute of General Medical Sciences. Of the various lipids, some of the most familiar are fats. Saturated and trans fats are solid at room temperature and include food items such as butter and lard. Both types of fats are associated with heart disease. Unsaturated fats are liquid at room temperature and are considered the healthier option. Canola and olive oils are examples of unsaturated fats. Two types of lipids -- omega-3 and omega-6 fatty acids -- are considered essential because your body cannot synthesize them; they must come from dietary sources such as fatty fish.
Nucleic Acids for Posterity
Every part of who you are, from your eye color to the shade of your hair, is encoded and stored in the fourth type of macromolecule -- nucleic acids. Deoxyribonucleic acid and ribonucleic acid -- DNA and RNA, respectively -- are the types of nucleic acids found in your cells. They're made up of chains of monomers called nucleotides. Nucleic acids make it possible to pass genetic information from one generation to the next. RNA is also essential for protein synthesis. Nucleic acids are made up of smaller units called nucleotides, which are made in your cells -- you don't need to get nucleic acids in your diet, though they are found in every food.