Foods are defined as “complex matrices” because they are made up of many different components. The main components are nutrients: macronutrients (proteins, carbohydrates and fats), micronutrients (vitamins and minerals) and water. Nutrients can have different qualities and be found in different amounts in different foods, and this defines not only their nutritional value but also their organoleptic qualities. All foods are mixtures of different nutrients, with very few exceptions such as table sugar, which only contains sucrose. Even oils, which are usually thought to consist only of fats, actually contain other nutrients such as vitamin E.
To add the complexity of food matrices, there are also other small components. Some of them are called “bioactive components” because, based on scientific evidence, it is assumed that they can have a positive effect on our body.
The bioactive components belong to many different categories both for their chemical nature and for the type of positive effect they might have on the body. They are not always considered nutritious (in fact they were once called “non-nutritious”), because there is no certain proof of their role in the human body, or of the fact that there is a real need to consume them. Likewise, not consuming them does not lead to signs of deficiency or malnutrition, as is the case for nutrients.
Nevertheless, scientific research in the nutritional field has long looked carefully at these components, because some of them could represent an alternative strategy to maintaining good health.
The largest group of bioactive components are phytochemicals, molecules of various different kinds but all of plant-based origin. Among them, the family of polyphenols, which in turn includes several subgroups, is particularly studied: the anthocyanins of berry fruits, esperidina in oranges, lycopene in tomatoes, the catechins in tea and resveratrol in red wine are all polyphenols. A characteristic all polyphenols have in common is that they are antioxidant substances, and therefore able to counteract oxidative stress. More specific actions than this are carried out by different molecules, which are the basis of other possible positive effects. These positive effects have been studied in vitro and on animals, and it is yet to be confirmed with absolute certainty what their effect is for humans. It is also difficult to establish the “effective dose”, that is, the quantity of this substances that we have to take in order to have the expected effect, considering also the fact that they are poorly absorbed in our intestines.
Although uncertainties still exist, the presence of phytochemicals is definitely one of the many reasons why it is necessary to consume the correct amount of fruit and vegetables (at least 5 portions a day, equal to at least 500 g), possibly each of a different type, because each vegetable has a precise composition of bioactive components, so if we vary our choices we can consume different types of them. The recommendation to take fruits and vegetables of different colours is linked directly to the presence of bioactive components, because most of them, in plants, have a pigmenting function and therefore the colour is affected by the type of predominant phytochemicals contained. This is not only the case for food, but also for flowers.
Although the most known and studied bioactive components are of plant-based origin, it is not true that they are not also found in animal source foods. Conjugated linoleic acid, taurine, carnitine, carnosine, glutathione and lipoic acid are some examples, along with bioactive peptides, which show the importance of having lots of different types of foods in our diet.
Department of Agricultural and Food Sciences
University of Bologna