Alright, this is going to be the crash course necessary for any further discussion in this topic. It is the bare minimum that one needs to know about nutrition.
Though it is the very short version, it probably isn’t classified as a short blog post. If you want the long version, just pick up any University-level physiology textbook. Fortunately, there’s no reason to fret, for anyone can understand the basics!
There are 2 classes of nutrients: Macronutrients and Micronutrients
Macronutrients are the sources of food whereby we derive energy and are needed to function daily with. As the name suggests, they are needed in relatively large amounts (measured in grams)
Micronutrients generally do not have any energy value, but are necessary for the maintenance of good health. Examples would be minerals like calcium, sodium, iodine, etc. As the name suggests, they are needed in small amounts (typical milli or even micro grams)
First we need a unit for energy. In nutritional terms, that is the calorie. The strict definition of the gram calorie is:
The amount of energy required to raise the temperature of one gram of water by 1 °C. The gram calorie was once commonly used in chemistry and physics. Equal to exactly 4.184J
You don’t need to know that really, all you need to know is that calories measure the energy content of food.
Every day, the body needs energy to sustain itself. It draws upon this from the food that we eat or stored body fuel deposits like fat and glycogen.
Rule number 1 as a result of this is: If you eat more than you need, your weight increases. If you eat less than you need, your weight decreases
Despite of what you have heard about calories from carbs being evil, or what not in the media, this rule is sacred. It holds true as long as extremes are not considered. Such extremes involve things like complete starvation for 5 days, or eating the entire buffet table in one sitting. I will get to those topics in the future, but for now, let us assume that people are eating sensibly.
So what is sensibly?
Clearly, there is a certain amount of energy that the body needs each day. Many equations and calculators attempt to estimate this.
Below are 3 examples:
If you input your values into those, you will find that the value will be very different. And that’s the point! Everyone is different and one formula can only say so much. I will be bold enough to say that calorie calculators have potentially a 25% error margin, which will be the difference of blowing up or shrinking to nothing.
The only true method of knowing how many calories you need, is to write down the approximate energy values of everything you eat for 2-4 weeks. If your weight remains the same, that is how much energy you need, and is referred to as your maintenanace caloric intake.
Men can typically do this by 2 weeks but women typically need longer (Due to the menstrual cycle and water balance issues – will do an article in the future)
There are 4 macronutrients:
They provide 4 calories per gram. Fiber is classified under carbohydrates, but it is technically not digestable. It is possible to derive some energy from fiber, about 2+ calories per gram, however, the generally low fiber intake will make this contribution pretty insignificant. (Assuming 30g of fiber/day, that is 60 calories out of at least 2000)
In the USA, fiber is listed under total carbs, so you need to substract that for the total amount of digestable carbs. This is not so in most other countries, though it is always worth at check.
Carbohydrates are basically used as a fuel in the body. The most common sources are from grains, legumes, fruit, vegetables, and any starchy source. So potatoes, bread, rice, quinoa, etc all are good sources of carbohydrates.
What is probably is most important nutrient and the second most abundant substance in the body. Proteins make up everything from your bones, to nails to skin. It must be important then.
Many food sources contain protein. There are some protein in grains, rice, and oats. There is also protein in vegetables, legumes and more notably, soy. Of course, meat is the most obvious source of protein, as with any animal derived products like milk.
I will not go into a detailed discussion of protein, it would take far too long. But I do want to raise 2 points.
The first point is the amount of dietary protein. Frankly, many people do not eat enough protein, especially so of the overly appearance-conscious female. Most of the time, we see that protein intakes can be as low as 30-40g per day. As a rule of thumb, athletes and bodybuilders have always used the arbitrary value of 1g of protein per pound of bodyweight per day. (if you weigh 160lbs, then eat 160g of protein a day). This seems to be relevant to the average person looking to maintain muscle mass. As low as 0.5g/lbs may be alright for non exercising sedentary individuals.
Some groups argue that protein is unimportant, but studies have basically shown that higher dietary protein does not seem to have a negative impact on health, whereas a low protein intake is reflected in reduced lean mass, and probably more pertinent, decreased bone density.
One note though, if you do have an existing kidney problem, then this recommendation does not hold. Consult with your doctor.
As you can see, the main problem I find here is that much of the actual proof of the discussion is loaded with scientific jargon. We just have to take it as a given that sufficient protein is necessary for good health.
I shall not go into any discussion regarding fat other than stating that it has a caloric value of 9 calories per gram. Too much controversy has been stirred over this topic, which you would probably have noticed unless you’ve been under a rock all your life.
What I will say though, is that the conventional knowledge is false. The fact is that we are unsure. We do not know exactly how each type of fat eaten in different ratios affect our health, and how much our genetics plays. Research is being done but not enough at the moment.
Alcohol gives 7 calories per gram.
It is metabolised directly in the liver, and obvious negative impacts are seen by overconsumption. I will not comment much here either. I will add though that some alcohol consumption may be beneficial.
I must say that the baseline requirements for most nutrients like sodium, calcium, iodine, zinc, magnesium, etc are pretty well established and deficiencies are typically not a problem if a whole food diet (not protein shakes and bars and all sorts of supplements) is consumed. There is room for debate over some nutrients, but I will not comment here. After all, these are the basics.
Vegetarianism and Veganism
I do however want to mention this topic.
To summarise, vegetarians and vegans are prone to consuming inadequate protein.
More importantly, the nutrients Vitamin B12 and iron to a certain extent are lacking. Vitamin B12 is unique in the sense that it is not produced by animals nor plants, but rather by bacteria. Animals store it in their tissues, especially the liver, whereas plants typically do not. The exception comes in the form of some fermented foods like tempeh, but it is still subject to the bacterial culture. incidentally, Marmite has Vitamin B12.
Supplementation is recommended acoording to the guidelines on Vitamin B12 and Iron on WHfoods.
Generally, most people are not in danger of lacking any nutrition as long real food is eaten.
The topic of nutrition is debatable yes, but what has proven to work over and over again (for thousands of years) is a diet containing all macro and micro nutrients derived from whole foods without overeating.