After air and water, we get most of the substances we need to survive from food. We call the substances we need lots of macronutrients (macro for 'big' or 'lots of'), opposed to micronutrients which we only need small amounts of.
The main macronutrients are protein, carbohydrate, and fat.
This classification is a bit blurry, some regard alcohol and some minerals like calcium and iron as macronutrients too, but for our purposes just think of the main three – protein, carbs, and fats. And most foods contain a mix of the three but we usually put them in the group they contain the most of. We categorise foods like this because each of the macronutrients do different jobs so we want a nice balance of all three. Just what constitutes 'a nice balance' is another matter for another page...
So what's what?
Have a quick look at this food table, you'll get an idea of the types of foods in each macronutrient group. Essentially:
Carbs grow from the ground, protein moves around.
Meats, poultry, seafood, and eggs are the main sources of proteins – i.e., animals and animal products. There are plant sources of protein, mainly soybean based foods like tofu.
Proteins are important structural components of muscles and all other body parts, we need to eat them to survive. Proteins themselves are made of amino acids. Different foods contain different amino acids but as long as you're getting protein from a few different sources you should be fine. Vegetarians may need investigate further though, and there are some common misconceptions to look out for.
Foods made from grains like bread and pasta and cereal are obvious examples of carbohydrate sources. Sweet foods containing sugar are also carbs – cakes, biscuits, etc. But maybe you don't know that fruits and vegetables contain carbs too – potatoes have lots, lettuce has hardly any, and the rest fall somewhere in between.
There are a few different types of sugars, and all carbohydrate foods contain one or more of them. These 'simple' sugars can join together in chains - starchy foods like bread and potatoes contain these chains of sugars, they're often called 'complex' carbohydrates. Some foods contain both – cake for example contains starchy 'complex' flour and 'simple' table sugar.
Interestingly, we break up any chains of sugars in our stomach and intestines and only absorb simple sugars, so our bodies can't tell if the sugar in our bloodstream came from apples or ice cream.
We actually don't need to eat sugar as we can make our own but it's generally regarded as healthy to eat some carbs as a source of energy. Fruits and vegetables also contain a lot of the micronutrients we need.
Fats are required by the body and are just as important as proteins, you certainly shouldn't be scared of them. It's worthwhile learning about the different types because changing the types of fat you eat can improve your health a lot. Briefly, avoid foods with lots of polyunsaturated omega 6 fats. This includes a lot of processed foods made with vegetable oils. Olive oil is good though.
Some foods contain roughly equal amounts of 2 or 3 of the macronutrients so can't be easily categorised. Dairy products are a good example – milk and natural yoghurt contain similar amounts of protein carbs and fat, while cheese contains similar amounts of protein and fat but no carbs.
There's other stuff in food too
Most foods are not just made up of these macronutrients – they also contain other things like water and fibre. I just told you above that meats contain proteins, but most meats consist of only about 25% proteins by weight. And the carbohydrate foods have a big range – lettuce is only about 1% carbs, whereas cereals can be over 80% carbs.
A few foods including table sugar and cooking oils do just contain 100% macronutrients.
So that's that
That was the macronutrients. Now you know what we'll be talking about in the rest of the instruction section. And the theory section has more details if you want...
What about micronutrients?
These are the things like vitamins and minerals that we only need small amounts of. There are others too, and they're all just as important as the macronutrients.
As a general rule: heavily processed foods have less micronutrients than whole natural foods. So vegetables and fruits and even meats are much more micronutrient dense than foods like biscuits and soft drink.