Nutrition in pregnancy and proteins: what is there to know?

The importance of healthy nutrition in pregnancy

During pregnancy it is important to satisfyincreased need daily nutrients without experiencing a marked increase in energy intake.

The pregnant woman can choose between one variety of nutrient-rich foods, ie nutritionally dense. In this sense, the nutrient density describes the relationship between the amount of proteins, carbohydrates, fats, vitamins, antioxidants, mineral salts and fibers present in a given food with respect to its energy content. Of all foods, the most nutrient dense are those of vegetable origin.

It is important at the same time to limit the intake of calories from simple sugars, refined starches and saturated fats: the latter must not exceed 5-10% of the calories consumed daily. The salt it should be taken in moderate amounts, not exceeding 2-3 grams per day.

Essential amino acids

Proteins represent one essential component of the diet and serve to support growth processes and maintain constant muscle mass. Specifically, within living organisms, proteins play a structural role (see collagen, keratin, actin, myosin) or a functional role (enzymes, transport proteins, hormones).

Our proteins are made up of a combination of 21 different amino acids. This means that, for the purposes of protein synthesis, all 21 amino acids must be present at the same time in certain relative ratios to each other. The amino acids that we define as essential, that is, those that we cannot synthesize independently and that we must necessarily derive from the food we eat.

The essential amino acids are 9, in particular:

• Phenylalanine
• Isoleucine
• Histidine
• Leucine
• Lysine
• Methionine
• Threonine
• Tryptophan
• Valina

Food sources of protein

Protein foods are those of animal origin (meat, fish, eggs, milk and dairy products), legumes and cereals (especially in their integral version). In the meats the protein content varies according to the cut and is influenced by the breed, the age of the animal and the farming method:

• beef has a protein content ranging from 20 to 22%;
• white meat from 18 to 24%;
• lamb, rabbit and pork has a protein content of around 20%;
• in fishery products the protein content is 13-22% in fish and 10-13% in shellfish.

As regards the plant sources, most cereals have a protein content of 7-28%, i legumes dry have a percentage of proteins equal to 20-24%, fresh ones around 5-6%. By appropriately combining the various sources, you can choose to follow a vegetarian diet during pregnancy without fear of going into a state of malnutrition.

A very important concept is that of protein quality of a food. This varies according to two factors: the digestibility of the proteins contained in it and its composition in essential amino acids.

For protein digestibility it is meant in what percentage a given protein is digested and to what extent its amino acids are absorbed in the gastrointestinal tract. There digestibility it is high for foods of animal origin and is lower for those of vegetable origin, especially if consumed in their integral form. In this case, in fact, digestion can be hindered by the presence of intact plant cells and substances that inhibit the activity of enzymes responsible for the digestion of proteins (proteases).

Another very important concept is that of protein requirement. By protein requirement we mean the lowest protein intake with the diet such as to guarantee the maintenance of the body’s protein mass in the presence of adequate energy supplies, a normal body composition and an adequate level of physical activity. As you can imagine, the protein requirement increases during pregnancy: this happens because on the one hand the pregnant woman must maintain and increase her protein mass and on the other hand because the developing fetus also increases its protein mass.

For example, a woman who begins pregnancy under normal weight conditions will undergo a gradual weight gain. In the middle of the first trimester it could have increased by 0.7 kg, in the middle of the second by 4.2 kg and in the middle of the third by 9.6 kg. It will come to termination of pregnancy with 12 kg more. For the purpose of maintaining the protein mass, increases are estimated equal to:

• 0.5 g protein / day in the first trimester;
• 2.8 g protein / day in the second trimester;
• 6.3 g protein / day in the third trimester.

The use of proteins from food and their deposition at the level of the forming tissues are two processes that occur with energy expenditure. Therefore it should be emphasized the importance of fully covering not only the protein requirement but also the energy one so that the pregnancy can be brought to term in full health. It is estimated that a woman consumes during the entire pregnancy about 77,000 kcal more compared to her non-pregnant condition.

The energy cost of pregnancy it is not distributed evenly throughout the gestational period:

• during the first quarter, energy and protein requirements increase negligibly;
• a little more is consumed during the second trimester;
• the highest consumption is concentrated in the third and last trimester, when the fetus tends to increase significantly.

Precisely for this reason the nutritional recommendations during pregnancy they must be specific for gestational age.

Effects of protein-energy malnutrition in pregnancy

If it is true that the genetic information relating to fetal development is already set at the moment of conception, it is equally true that, through the mom’s nutritional choices during the entire course of pregnancy, genetic expression can be modulated. On the basis of current knowledge, the hypothesis is put forward that protein and energy malnutrition during pregnancy can increase the risk in the newborn to face the pathologies of well-being once he becomes an adult. The studies conducted during the great Dutch hunger contributed to support this hypothesis.

In the time of World War II, the western part of the Netherlands was excluded from food supplies. From November 1944 to May 1945, food rations were so scarce that they provided just 400 to 800 kilocalories per day. The daily menu consisted of sunshine two potatoes, a slice of bread and half a sugar beet. Despite the tremendous challenges to be faced in this period of war and famine, data relating to prenatal hospital visits and the size of newborns at birth. The analysis of these extremely valuable data showed that the health status of the offspring differed considerably depending on the gestational time in which the mother had faced the famine. If the deprivation of energy and protein occurred shortly before conception and during the first trimester of pregnancy, the incidence of obesity, diabetes and cardiovascular diseases during adult life increased significantly. This was not the case when exposure to hunger did occur in late pregnancy.

Today we know that if the woman arrives at the birth with a low body weight increases the risk of premature births. Women, but also men of reproductive age, should be encouraged to consume a healthy diet as recommended for the general population. On the other hand, it makes no sense to suggest to pregnant women acarbohydrate-free diet with the sole aim of maintaining a low weight at the time of delivery. In this case, the thinness of the mother will be one of the reasons why the baby will show a tendency to gain weight. Having experienced some sort of famine during his intra-uterine life, the child not only will it show greater voracity but will also develop a greater capacity to assimilate energy and nutrients.

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