Plant cell residues that are resistant to digestive enzymes are referred to as “dietary fibre”. Dietary fibres provide no calories or nutritional value, but perform important functions for the human body. Dietary fibres can be subdivided into two broad classes: soluble and insoluble ones.
As the name suggests, these fibres do not dissolve in water, but can absorb a high quantity of water, thus increasing in volume in the faeces. Thus, the faeces become more abundant and softer. When taken with plenty of water, fibres act as a laxative, facilitating evacuation; vice versa, it may lead to constipation. Insoluble fibres can be basically be of two types: cellulose, present in high quantities in fresh vegetables (tomatoes, fennel, celery, carrots etc.) as well as in dried fruit and unrefined (wholemeal) cereal flour, and hemicellulose, present in all vegetables.
When dissolved in water, soluble fibres form a gel that facilitates the smooth absorption of certain nutrients. One example of soluble fibre is pectin, used to thicken jams. Pectin is available in good quantities in fruit (citrus fruits, apples, pears, plums and grapes) and is especially abundant in pulses.
In addition to facilitating the smooth functioning of the intestine, dietary fibre performs many other functions:
- It increases the feeling of satiety because it promotes an increase in the volume of food ingested. Consequently, the stomach empties more slowly.
- The faeces are eliminated faster, thus decreasing the risk of constipation and haemorrhoids.
- It helps to keep blood sugar and blood cholesterol in check, because it partly reduces the absorption of macronutrients such as sugars and fats. By having an impact on the metabolism of these nutrients, dietary fibre reduces the risk of developing major diseases, such as cardiovascular disease and diabetes.
- By reducing the time that waste substances remain in the body, and thus in contact with the intestinal wall, fibre helps to prevent common intestinal diseases and cancers of the colon and rectum.
Recommended Daily Intake
Fibre-rich foods should be consumed every day to achieve the recommended daily intake of the 25-35 g for an adult. To reach the recommended levels established by the nutritional guidelines, your diet should include foods such as:
- Fruits and vegetables: 5 servings a day
- Wholemeal pasta and bread: 1 or 2 times a day
- Pulses: 2 or 3 times a week
- Fibre is present in fruit and vegetables when fresh, dried or frozen, but it is not as present in industrially prepared juices, centrifuged products or extracts.
- The sense of satiety and the purifying action of the fibre greatly increases when drinking plenty of water: 1.5 to 2 litres a day.
- If you are not used to eating foods rich in fibre, you should start increasing the fibres content in your diet gradually to avoid the bloating or intestinal disorders that can arise when starting to add fruit, vegetables and whole grains to your diet.
Minerals, among all the nutrients, are inorganic substances present in nature and in plant and animal food.
They are not always in the form of salt. Minerals are considered essential not only because life cannot be sustained without them, but because our body is unable to synthesize them. Man is forced to eat them with food adopting a varied diet to ensure an adequate intake of the necessary minerals.
Minerals are classified according to the quantity required by the body: Macroelements, Microelements, and Trace elements.
Macroelements: Calcium, Phosphorus, Magnesium, Sodium, Potassium and Chloride, the requirement is more than 100 mg/day.
Microelements: Iron, Copper, Zinc, Fluoride, Iodine, Selenium, Chrome and Cobalt, the requirement is from 1 to 100 mg/day.
Trace elements: Bromine, Chrome, Nickel, Lithium, Silicon, Tin and others.
There are only traces of these in the body and the requirement is below 1 mg/day.
Function of minerals
Minerals are present in all food chains; plants absorb them from the soil and from fertilizers, including animal kind ones.
They pass from the plant to the animal world in a continuous cycle. Minerals make up 6% of body weight, are an essential part of our cells and with other substances they form bones and tissues. Minerals are also part of the metabolic system so they are eaten with fats, proteins and sugars, are essential to synthesize proteins, to keep body temperature and blood pressure stable as well as to supply the cardiovascular system and perform many other vital functions. They are constantly eliminated with urine, feces and sweat so they must be reintegrated daily. Among the many minerals and numerous functions, below we take a close look at the properties of the most important minerals for human beings.
It is the most abundant mineral present in the human body, which contains between 1 and 1.5 kg of calcium.
The majority of bones and teeth are made of calcium, but the mineral also intervenes in other important functions such as the nervous system and cardio-circulatory system. Calcium deficiency can prevent a correct physiological growth in children and cause osteoporosis at an advanced age.
It is a very important micro-nutrient for health because it carries out many functions inside the human body. It is an element of the red blood cells, part of numerous proteins including hemoglobin, myoglobin and cytochromes which are essential for transporting and using oxygen. A shortage of this mineral causes iron-deficiency anemia. Iron deficiency in the blood can be higher in women during childbearing age, pregnancy and breastfeeding.
It works in synergy with calcium and vitamin D forming the material that makes bones.
It is above all an essential part of hormones produced by the thyroid. Iodine deficiency causes goiter and, in pregnant women, can lead to a mentally retarded child.
It intervenes in muscle function, facilitating the contraction of the muscles including the heart.
It is above all important for the proper function and health condition of the nervous and muscle systems, including the heart.
It intervenes in the hydro-saline balance, avoiding excessive water loss.
It is a powerful antioxidant and, like zinc, it reduces the damage caused by excess free radicals.
It has a synergistic effect with vitamin E.
It is a powerful antioxidant; it intervenes in growth, in prostate function, works on the immune system and in healing wounds.
It also intervenes in protein synthesis and in collagen formation.
Tomatoes contribute a large quantity of potassium (approx. 650 mg per 100g of product).
This mineral is part of the plasmatic electrolytes, the minerals which work on blood pressure, muscle strength, and reflexes. Potassium deficiency can cause fainting and muscle cramps. For these reasons tomatoes are an important food in the diet of athletes.
The contents of this article are in accordance with the parameters set out by the European Food Safety Authority - EFSA.