All foods possess certain amounts of both macronutrients and micronutrients (vitamins). The makeup and availability of these two nutrient forms determine the degree of which foods are better or worse for our health (36). For example, iceberg lettuce is predominantly composed of water and fiber (~95%), making it practically crunchy water. The nutrients available in the lettuce are not readily accessible since our body must sift the nutrients from the water resulting in nutrient loss (38). Additionally, the number of nutrients present within a food source can affect its nutritional value. Meat has little or no carbohydrates; it’s just protein and fat. As a result, a nice ribeye steak can provide an excellent source of protein and fats, which are necessary for our bodies basic function. However, if someone only eats steak, they are no longer receiving an adequate amount of carbohydrates, which can result in potential health problems. However, while it is important to consume all three of the macronutrients, the quantity in which they can be consumed can vary drastically. Humans are generalists; we can adapt to very diverse environments (31). The Hadza populations consume a 95% carbohydrate based diet, while the Northern Inuit populations subsist on a 95% protein and fat based diet (29). The morphology of our gastrointestinal system, dental morphology, and tool technology have allowed us to consume a wide array of foods while maintaining health across vastly different environments (31). So, whether you eat more like a Hadza, Inuit or somewhere in-between, let us look into how each of the three macronutrients function.
“You can run, but you can’t hide!” If carbohydrates could talk, that’s what they’d say. The most common of the three macronutrients, carbohydrates can be found almost in everything. From fruits to dairy products, this macronutrient carries important nutrients, such as vitamins, minerals, dietary fiber, etc. into the diet (38).
Carbohydrates are composed of three subgroups: monosaccharides, disaccharides, and polysaccharides. Often considered to be the building blocks of carbohydrates, Monosaccharides are simple sugars (glucose, fructose, and galactose). This means that they do not require any form of catabolic reactions in order to be digested and absorbed into the body. Disaccharides are two bonded simple sugars (sucrose, lactose, and maltose.) which require hydrolyzation in the small intestine to be digested. Polysaccharides create the longest chemical chain of bonded sugars. They come in two forms: starchy and non-starchy polysaccharides. Starchy polysaccharides are commonly found in the underground portions of plants, such as potatoes, and store the plant’s nutrients. To digest these, the body must use amylase enzymes located in the pancreas and saliva to help reduce the starch into simple sugars which are then hydrolyzed in the small intestine. Non- starchy polysaccharides or fiber, provide the plant with overall body and cell structure (36). They are the most abundant of all forms of carbohydrates, coming in four different forms: pectin, hemicellulose, cellulose & lignin (38). While pectin & hemicellulose can be digested, cellulose & lignin require bacteria located in the stomach to break them down through fermentation.
Lipids, also known as fat, and protein, although not as common as carbohydrates, are just as important. Lipids help to create long-term energy stores (Triglycerides) through anabolic reactions, carry vitamins, and influence our neurotransmitter levels which help regulate reproductive hormones in our body (38). There are four types of lipids: saturated, cholesterol, mono/polyunsaturated, and trans unsaturated. Both saturated lipids and cholesterol are mainly found in animal fats. Both monounsaturated & polyunsaturated are commonly found in vegetable oils and can have positive effects on our heart health (like Omega-3). Trans unsaturated lipids are the bad guys of lipids. They are unsaturated fats that have been altered by adding hydrogen and are known to cause unhealthy changes in cell membranes.
Protein helps with tissue replacement and is critical for growth and reproduction (32&36). It is composed of different types of amino acid chains.There are a total of 20 different types of amino acids, 9 of which are essential for us that we can’t produce them in our bodies, and 11 which are non-essential that we can produce in our bodies (36). There are two types of protein sources: complete and incomplete. While there are many ways in which we can find all 9 essential amino acids in our diets, all 9 can be found in animal protein and soybeans. So, now that you know all about macronutrients and why butter is not a carb, we must next look at how macronutrients have helped mold us into the Homo sapiens we are today.