Why diet is important for health

Hello, my name is Andrea Devecchi, medical doctor in Clinical Nutrition at the University of Turin. It is a pleasure to welcome you to this three-week Healthy Diet Course. Our first lesson will focus on diet and health. Food is an extraordinary tool for keeping us healthy, as well as representing a necessary element for living. This lesson will introduce the main issues related to diet and health. First, we all know that we need energy for living. Food represents the means through which we all obtain the necessary energy to survive.

Food contains three kinds of energy nutrients: the first ones are carbohydrates, Carbohydrates are the sugars, starches and fibers found in fruit, grains, vegetables and dairy products. They are the body’s main source of energy. They are called carbohydrates because, at the chemical level, they contain carbon, hydrogen and oxygen. Carbohydrates provide the energy for the most obvious functions of our body, such as moving or thinking. The brain and the red blood cells are especially dependent on glucose as their source of energy.

Let’s now talk about dietary fibers: they are the portion of plant-derived food that cannot be completely broken down by human digestive enzymes.

They have two main components: soluble and insoluble ones. Vegetables and fruit are rich in fibers. There is scientific evidence which proves that dietary fibers, in the context of a healthy diet, are connected to the decreased risk of hypertension, cardiovascular diseases and type 2 diabetes. Proteins are the second kind of energy nutrient. Proteins are large-size molecules (macromolecules), that is polymers of structural units called amino acids. Pulses and cereals are good sources of protein coming from plants. Animal foods, such as fish, meat, dairy and eggs, are also important sources of proteins for our diet. Let’s then continue with proteins. They do most of the work in cells and are required for the structure, function and regulation of the body’s tissues and organs.

Proteins are made of of amino acids. As our body is unable to produce some amino acids, which are called essential amino acids, we have to introduce them through our diet. Fats are the third kind of energy nutrient. Fish and vegetable oils, such as olive oil, are good sources of fats. Fats are important energy sources. Moreover, they have a crucial structural role since they are used by the organism to produce hormones. They are also carriers of the fat-soluble vitamins A, D, E and K, hence supporting their absorption in the intestine.

Fats are typically divided into two main categories: unsaturated and saturated fats. Unsaturated fats are further divided into mono- and polyunsaturated fatty acids. Essential fatty acids, or EFAs, are fatty acids that humans must ingest because they cannot synthesize them. They are linoleic acid (LA) - an omega-6 fatty acid, and alpha-linolenic acid (ALA) - an omega-3 fatty acid.

Both omega-3 (ω-3) and omega-6 (ω-6) fatty acids are polyunsaturated: they are important components of cell membranes and are precursors to many other substances in our body, such as those involved in regulating blood pressure and inflammatory responses. Let’s now move on and talk about micronutrients, that is vitamins and minerals.

Micronutrients can be divided into four categories: water-soluble vitamins, fat-soluble vitamins, microminerals and trace minerals. Although they’re only required in small amounts, micronutrients are not produced inside our body but must be derived from our diet. Micronutrients have many functions, such as the regulation of growth, development, the immune system and the reproductive system. Micronutrient deficiencies can have devastating consequences. Micronutrient deficiency is one type of malnutrition (in addition to undernutrition and obesity) and the United Nations recognize the need to eradicate it worldwide. Finally, I would like to brefly talk about polyphenols. They are neither macro nor micronutrients. They are a class of active compounds contained in some types of food like fruit, vegetables, chocolate and olive oil.

They are interesting because of their potentially beneficial role for human health. We have seen the complexity of nutrition and how much it affects our body. However, the western diet (the diet of developed countries) differs greatly from good eating habits (too many calories, too much sugar, salt, meat and poor in vegetables and fruit). The outcome of this is too many obese people and many diseases linked with obesity. It is widely known that diet plays an important role in preventing chronic diseases like hypertension, type 2 diabetes and cancer, called non-communicable diseases. It is also evident that obesity is one of the major risk factors for chronic diseases.

It has been estimated that cardiovascular diseases, stroke and even type 2 diabetes can be reduced with healthy food choices together with regular physical activity and refraining from smoking. Diabetes is a disease which occurs when blood glucose (often called blood sugar) is too high. Type 2 diabetes occurs when the body becomes resistant to insulin. We can reduce the risk of type 2 diabetes with a combination of lower-calorie intake and exercise. High salt intake is linked to the increased risk of hypertension and cardiovascular diseases. The WHO recommends a salt intake of less than 5 grams per day for adults. Changing the type of fats consumed (i.e.

saturated fat replaced by unsaturated fat) or changing their type in combination with an overall reduction of fat are protective measures against cardiovascular events. We have seen the principles of nutrition The important role of each macro and micronutrient The importance of a balanced diet, the role of carbohydrates, lipids and proteins. The importance of a diet rich in fruit and vegetables, containing fibers, micronutrients and beneficial-action substances such as polyphenols. The need to introduce limited quantities of saturated fats, simple sugars, salt, involved in the pathogenesis of chronic pathologies.

We can find all these features in two types of diet: the Mediterranean and the Okinawa diet.