Foods of plant origin (I)

Foods of vegetable origin are generally characterized by being rich in carbohydrates, dietary fiber, proteins of lower biological value than those of animal origin and provide little fat, although oils and fats are obtained from seeds and fruits.

They contain practically all minerals, although the iron they contain is not very usable; they contain all the water-soluble vitamins -except vitamin B12-; they also provide the fat-soluble vitamins E, K and provitamin A (carotene) and do not contain vitamin D. They are also rich in bioactive components that help reduce the effects of aging and prevent some chronic diseases.

In this presentation we will study the most important nutritional characteristics of the following food groups of plant origin: cereals, legumes, fruits, vegetables and greens.

Cereals and cereal products

Cereals include wheat, rice, corn, maize, barley, oats, rye, sorghum, millet and canaryseed among others. Cereals contain about 75% carbohydrates and dietary fiber, 8-10% protein and 1-2% fat. Cereal derivatives are flours, bread, pasta, cookies, sweets, etcetera.

Cereals contain a set of proteins of lower quality than animal protein because they do not have sufficient quantities of all the essential amino acids; however, when they are consumed with milk, eggs, meat or legumes - lentils, chickpeas, beans, etc. - the quality of the protein improves notably.

Some people present a permanent "intolerance" to gluten, a protein present in wheat, barley, rye, oats, etc. This disease, known as celiac disease or celiac disease, when not strictly treated, can cause serious health complications. Celiac individuals can only consume cereals or their derivatives that do not contain gluten, for example rice and corn.

Vitamins B1, B3, B6 and B9 predominate in cereals; they do not contain vitamin B12 or vitamin C. Of the fat-soluble vitamins, only wheat germ and corn contain vitamin E and provitamin A -carotenes-. They contain iron, magnesium and zinc minerals; however, the iron in cereals is not easily absorbed.

It is recommended to encourage the consumption of four to six daily servings of cereals, preferably whole grains, without added sugar and enriched with vitamins and minerals.

Legumes

Legumes include lentils, chickpeas, beans, etcetera. They are very complete foods: they contain between 60 and 65% of carbohydrates and dietary fiber; between 1 and 5% of fats and between 18 and 24% of proteins of low biological value; for this reason it is recommended to combine legumes and cereals in meals to obtain higher quality proteins.

Legumes provide calcium, magnesium, zinc, potassium, iron and phosphorus; they also contain practically all vitamins, except vitamin B12 and vitamin D.

It is recommended to include at least three to four servings of legumes in the weekly diet.

Fruits

Fruits are characterized for being very healthy since they provide few calories -with the exception of bananas and avocados- and considerable amounts of water, dietary fiber; minerals such as magnesium, potassium, calcium, etc.; vitamins of the B group, vitamin C, provitamin A (carotenes) and bioactive substances.

Fruits do not provide proteins or fats, except for coconut, which contains mainly saturated fats, and avocado and grapes, both rich in monounsaturated fats.

It is recommended to include in the diet at least three daily servings of fresh fruits, preferably whole.

Vegetables

Within this food group are included different parts -leaves, stems, roots, flowers, fruits and seeds- of a wide variety of plants -lettuce, spinach, watercress, chard, cabbage, asparagus, carrots, turnips, potatoes, cauliflower, artichokes, tomatoes, peppers, peas, etcetera.

Vegetables, like fruits, are very healthy as they provide few calories -with the exception of potatoes-, and considerable amounts of water, dietary fiber, minerals, vitamins and bioactive substances.

Vegetables do not provide protein or fat. They contain minerals such as calcium, zinc, and iron, although the latter is not as well absorbed as that contained in meats. Green leafy vegetables - spinach, chard, cabbage - are rich in folic acid (vitamin B9); while carrots, pumpkins and tomatoes are rich in carotenes or provitamin A.

It is recommended to include in the diet at least two daily servings of vegetables, preferably raw or steamed, to prevent their vitamin and mineral contents from being lost in water or due to excess temperature.