Welcome to the first episode of You are what you eat series. As I said in the introduction, I’m going to focus on main nutrients first. This week’s hero is… protein!
Role in our bodies
First things first: proteins are mainly responsible for building muscles – that’s what we learn at school and it’s accurate enough. But it’s good to know that proteins can be found in all cells of our bodies and make the second most abundant type of molecules, after water.
If we look closely (without too much detail though), proteins are polymer chains made of amino acids. There are 8 essential types of acids (9 in case of infants) that a human body needs to be delivered from diet – malnutrition results in death. All of the above should be consumed in certain ratios – one cannot fully replace another. And because different foods contain different acids in varied proportions, the easiest way to have all of them delivered is keeping a balanced, varied diet.
Types & sources
Fortunately, proteins can be found in a wide range of foods, both plant and animal-derived. According to a study research from 1994, the world average is around 60% consumption of protein coming from plants, although there are parts of the world where the proportions are significantly different (for example, the average ratio for North America is said to be 70-30 in favour of animal-derived foods).
There are 2 main types of proteins: complete and incomplete, and they stand for the number and proportions of essential amino acids they contain.
Complete protein is the only one that contains a sufficient amount of all of them. It’s said the best source of it are chicken eggs, which not only supply all necessary acids, but also deliver them in optimal proportions. However, pretty much all other animal-derived products are a good source of complete protein as well. Plant-based foods can also contain complete protein – examples include legumes, grains, seeds or vegetables – soy, beans, quinoa, pumpkin seeds or cashews. The main issue about plants is that in most cases proteins only make a small part of them – a significantly lower fraction than what’s usually found in animal-derived foods.
Incomplete protein lacks in one or more essential amino acids and is found in plant-based products like roots, tubers and fruits, for example: potatoes, yams and cassava. In case of having a diet based on the above, it’s extremely important to eat the most varied combination of protein sources possible, as each type of food supplies only some of the amino acids.
Probably the most common misconception about vegetarians and vegans is saying that they can’t deliver their bodies all essential types of proteins. First things first: there are a lot of reasons why people choose to exclude certain foods from their diets, from health issues like lactose or gluten intolerance to purely ethical reasons. I can’t see the point in arguing with others, trying to force them to follow our own eating habits – if they decide to exclude meat from their diets, it’s a) not our business and b) a lot of work they take on themselves in case they want to stay healthy. Because yes, it is possible to deliver your body all necessary nutrients, even if you’re vegan – for example, as you could see in the previous section, in terms of complete protein beans are a good enough replacement for meat. It’s just a lot harder to keep a healthy diet than when you eat all foods in balanced proportions and, for that reason, I wouldn’t recommend switching to vegetarian or especially vegan diet if you don’t know exactly how to eat to not ruin your body. Even though the effects of having an unbalanced protein economy grow to a noticeable level over a long period of time, once seen, they can already be devastating for the body.
A short reminder from the introduction: 1 g of protein is worth approximately 4 kcal, and around 20% of our daily calorie intake should come from proteins (with 10% being absolutely necessary). Another, simple way of calculating our recommended daily protein intake says that for each kilogram of our body mass 1 g of proteins should be consumed.
Let’s focus on protein deficiency first. Severe cases of protein malnutrition don’t occur very often in developed, industrialized countries and are mainly an issue in countries struggling with hunger in general. The most serious cases lead to death and their symptoms include apathy, flaky skin and edema of belly, legs, fingers or eyelids. In developed countries they’re usually found in small children with milk allergy whose nutritional needs are ignored.
Less advanced deficiency leads to lowered immunity and kidney malfunctions.
Excess consumption is said to be carcinogenic, with animal-derived proteins increasing cancer risk more than plant-based ones. Other possible results of protein excess include kidney diseases, kidney stone formation and osteoporosis (as a result of increased calcium excretion).
For many years it was believed that protein in general increased blood pressure. Currently, studies show no connection between the two. However, it’s been proven that high plant-based protein intake might decrease blood pressure, and therefore it’s recommended that those suffering from hypertension should replace some animal sources of protein with vegetable ones.