What’s all the fuss with macronutrients? The big three – carbohydrate, protein and fat – are constantly being called out, individually demonized or praised as a panacea for health. In reality, these three nutrients all have important roles to play in the human body and should be valued because of their individual use and synergistic interactions. Food is fuel, food is nourishment, and specific nutrients should not be feared.
Glucose and glycogen (a monosaccharide and a polysaccharide, respectively) are used for roughly 50 percent of all of the energy needs of the muscles and body tissues. The other half of energy needs comes from fat.
The hormone insulin, known most commonly for its role in regulating blood sugar, stimulates the absorption of glucose into the cells for energy after a meal, and also initiates the storage of glucose as glycogen in the liver and muscle cells for later use. Excess glucose is also converted into fat for storage, and insulin is also responsible for this process.
Resistant starch is a dietary fiber (one of the categories of carbohydrate) that passes whole through the small intestine – put simply, it resists digestion and absorption. Studies have also shown that resistant starch specifically can feed and nourish gut bacteria, thereby contributing to robust health.
Amino acids are the building blocks of proteins. There are 20 different amino acids, nine of which are considered “essential amino acids” because the body cannot synthesize them without dietary intake. A “conditionally essential amino acid” is one that is normally nonessential, or synthesized by the body, but in this case must be supplied entirely by the diet when the body’s need exceeds the body’s ability to produce it. This could be in the case of an extreme deficiency or a disease that impairs the digestion and absorption of complete proteins.
The food we eat doesn’t automatically translate into proteins in our body – the food we eat supplies the amino acids out body needs to synthesize its own proteins, to be used in muscle cells, to form hormones and transport molecules, to create collagen, and to develop into enzymes, among other uses.
An important part of understanding protein lies in understanding DNA, as our genetic material is responsible for coding protein synthesis. (Genes to proteins!) A subset of protein/genetics study that I find fascinating is that of nutrigenomics and nutrigenetics, or the understanding of how nutrition and other environmental factors can influence gene expression in individuals.
One of the most important categories of fat is the sterols, which includes bile acids, sex hormones, adrenal hormones, vitamin D and cholesterol. Without fat, most of the body’s delicate hormonal processes cannot occur – fat is our friend!
Cholesterol gets a bad rap, but it’s not the enemy. In the body, cholesterol is substrate for the synthesis of those important aforementioned compounds like sex and adrenal hormones, and it plays a crucial role as a structural component of cell membranes. In fact, more than 90 percent of all of the body’s cholesterol is found in the cells (note: where it is supposed to be), rather than in the arteries where all of the whole-grain cereal commercials would have you believe it lives.
There are two types of cholesterol, endogenous and exogenous. Endogenous cholesterol is produced within the body, while exogenous cholesterol exists outside of the body and is taken in; i.e., dietary cholesterol. The liver makes roughly 800-1500 mg of cholesterol per day, thereby contributing more to total cholesterol levels than dietary cholesterol. This, of course, is influenced mainly by genetics.
“Some people, confused about the distinction between dietary cholesterol and blood cholesterol, have asked which foods contain the ‘good’ cholesterol. ‘Good’ cholesterol is not a type of cholesterol found in foods, but it refers to the way the body transports cholesterol in the blood.” – Understanding Nutrition, 13th ed.