The Big Picture
In 1827, British scientist William Prout suggested that humans need three macronutrients to survive. These are carbohydrates,fats and proteins. Ever since, people from the best nutritionists to the general public have been trying to figure out exactly how much of each macronutrient we should include in our diet to optimise our health.
However,people have been arguing about nutrients so much that we might have forgotten that we don’t simplly eat nutrients,it is food we eat. It’s understandable, because we tend to break things down to a simple level, and nutrients is what’s revealed when we break foods down. Scientists do need that information for research,but food is a much more complicated combination of all these nutrients we talk about. It’s hard to apply what we know about a single nutrient in daily life when we’re facing food and ingredients. So try to think of food as a whole somtimes.
Carbohydrates
Dietary carbohydrates are combinations of sugar units, they can come in simple or complex forms.
Simple carbohydrates,also called sugars,include monossaccharides and dissaccharides. Monossaccharides are sugars made from one sugar unit. The prefix mono- means “one”. Some common monossaccharide are glucose,fructose(commonly found in fruits) and galactose. The prefix di- means “two”,so you might be able to guess that dissaccharides are sugars made from two sugar units combined. Some common dissaccharides are sucrose(common table sugar),maltose and lactose(commonly found in milk).
Complex carbohydrates are polyssaccharides,with the prefix poly- meaning “many”,which are made from more than two sugar units. There are the dietary starches which the human body can digest to release energy,and the indigestable dietary fibers. We don’t break down and absorb fiber,but it’s good for the digestive system. We’re not going to delve into that in this article.
Carbohydrates are the main energy sorce of the human body. All the digestable carbohydrates are broken down into single sugar units,and converted to usable energy in the form of ATP. If not all of the sugar is used up for energy,then the rest is converted into adipose tissue,the fat storage of the human body.
Proteins
Proteins are made of smaller units called amino acids. These amino acids have many important functions in the body,but when consumed in excess,the can be used for energy and contribute to fat storage as well.
Lipids
Lipids can be catagorised into fats(solids at room temperature) and oils(liquids at room temperature). Lipids can be broken down into glycerol and fatty acids. They can also be used to release energy or be stored as adipose tissue.
Energy Density
Energy density describes the amount of energy a certain substance contains each unit mass. Fat is the most energy dense storage form,providing 9Cal/g. The energy density of alcohol is 7Cal/g. We talk about alcohol because glycerol,one of the building blocks of lipids we mentioned before,is a kind of alcohol. In contrast,carbohydrates and proteins only provide 4Cal per gram. This explains why the human body uses fat as energy storage——it takes up the least space.
Suming up
When we consume more energy than we need,the unused energy is stored as fat. This is basically how people gain weight. For those who want to lose weight,try to take in less calories,burn more caloreis through exercise or both. However,if we wish to be healthy,simply controlling how many calories we eat isn’t enough. We need to choose the foods that benefit our health,and not those that work against it. How to do this? We will talk about it in my next post.
Excellent