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The idea that you are what you eat has been a prevailing belief in many cultures throughout the history. For example, the ancient Aztecs would eat the brain of their rivals because they believed it gave them the wisdom and knowledge of the enemy. The Nordic Vikings believed that drinking the blood of a bear or a wolf before battle gave them the ferocity those animals possess. These are just two of many examples of bizarre and fascinating traditions which arise from the idea that you embody what you eat. Mystical beliefs aside, this phrase when used in nutrition settings has a pretty straightforward meaning: if you eat healthy, nutrient dense food you will look and feel healthy, if you eat junk food you will look and feel sick. In search for scientific validity to it, first we should answer the question: why do we eat?

We eat to get energy. We aren‘t like plants which produce their own food and need to eat to acquire energy. Therefore, human rely on food chain that starts with photosynthetic plants which captures the energy of the sun to synthesize sugars. The energy from these sugars are taken either directly in the form of fruits, vegetables, grains, legumes or indirectly from eating animals that eat plants. This energy is derived from the chemical bond energy in food molecules and is released during digestion. Then it is used immediately and stored in other molecules that can be broken down to provide energy when the body needs it. The energy that food gives us is measured in kilocalories. A calorie is a measurement unit defined as the amount of energy that is needed to raise the temperature of water by one degree Celsius. Counting calories is like keeping track of the body‘s energy budget. A healthy balance occurs when we put in about as much energy as we lose.

We eat to supply our body with nutrients for cells to grow, repair and divide. Cells are units of structure and function in living things. You can imagine them as bricks from which all your tissues and organs are made. The average adult loses from 50 to 70 billion cells every single day due to a normal process called programmed cell death. To make up for all these lost cells, billions of your cells are dividing constantly. Your body keeps regenerating this way. For example, stomach and intestinal lining cells are fully replaced every few days. Our body has to rebuild itself from the building materials we deliver to it with the food we eat.

From the moment a bite of food enters the mouth, begins the process of digestion which is a series of complex chemical reactions that transform food into components small enough for your body to absorb and use for energy, growth and repair. The foods we eat provide us with nutrients: carbohydrates, proteins, fats, water, vitamins and minerals. The first three are classified as macro nutrients and have a caloric value. If all macronutrients are abundant in the diet, carbohydrates provide energy, fats insulate and store energy, while proteins provide the raw materials to form muscle and connective tissue, hormones, enzymes. Protein synthesis is only possible if you have all the amino acids necessary. There are nine out of twenty which we cannot make ourselves and are called essential amino acids. By eating foods that are high in protein we can digest them down into their base particles and then use these essential amino acids in building our own protein.

By volume water makes up the biggest part (around 60 %) of average human body. And we need to consume a certain amount of water each day to function properly. You constantly excrete water through sweat and urination, so your body needs to replenish the lost fluids. We can last without food for a month, but without water it is just a matter of days.

Vitamins aren‘t used as building blocks or for energy but they are essential in sustaining life. Most vitamins need to come from food because human body either does not synthesize enough or does not synthesize any at all. A deficiency of any kind of vitamin can result in certain medical conditions. For example, deficiency of vitamin D may cause rickets, softening of the bones, emotional disturbance.

Minerals, like vitamins, do not provide energy, but have other vital functions. Minerals make up around 6 % of human body mass but can’t be produced by the body and have to be ingested. Calcium, magnesium and phosphorus are the most abundant minerals in the body which harden bones and teeth. Iron deficiency anemia is the most common nutritional deficiency in the world. Iron is a trace mineral and a crucial part of hemoglobin, which is a protein in red blood cells that carries oxygen.

To sum up, the food we eat affects our wellbeing to a cellular level. All protein, fat and carbohydrates that make up human body comes from the food she or he eats. When we make poor food choices our bodies have hard time manufacturing new healthy cells. If your cells cannot operate efficiently, the functioning of your tissues and organs, which are built of your cells, will be disturbed. When this happens, you experience a decrease in physical functioning and manifestation of primary symptoms of various health conditions and diseases. By keeping your cells well nourished, you are keeping yourself well nourished. 

By Jugnė Jūnė Jonušaitė, nutritionist at HealthState