Healthy and balanced nutrition is one of the key factors in the harmonious growth and development of the baby. It ensures the maturation of organs and body systems, resistance to the action of various unfavorable environmental factors, and also largely determines the quality and duration of the child’s future life.

It’s no secret that the gold standard for infant nutrition is breast milk, which is the source of all easily digestible nutrients a child needs, as well as a wide range of biologically active compounds. However, as the child grows and develops, it becomes necessary to expand his diet and introduce complementary foods (in this case, “complementary foods” should be understood as any products other than human milk and its substitutes (including juices and teas)).

This need is due to the following main factors:

  • the need for the growing body to receive additional calories and a number of nutrients (iron, protein, zinc, etc.), which are no longer supplied with breast milk (or with its substitutes) at a certain stage of development (after 4–6 months);
  • the expediency of expanding the range of nutrients in the diet, including due to various types of carbohydrates, vegetable protein, fatty acids, trace elements necessary for the further growth and development of the child;
  • the need to include in the diet more dense than milk food in order to develop and train the chewing apparatus, digestive system, as well as intestinal peristalsis;
  • the need to socialize the child (transition to a common table), teach him the skills of independent eating, familiarity with the variety of tastes.

Timely introduction of correctly selected complementary foods will contribute to health improvement, nutritional status and physical development of the child during the period of accelerated growth and maturation.

So when does this “timely” come? For a long time in our country there were legal provisions on the introduction of complementary foods from the age of three weeks of age.

Such a system was established in connection with the widespread use of artificial feeding with products not adapted to human milk, which included unchanged cow’s milk protein. As carbohydrates, the baby received mainly sucrose and glucose, and as fats – a mixture of  saturated and unsaturated fatty acids.

With such a diet, children very often developed disturbances in the functioning of the structures of the enzyme system, dysbiosis, allergic dermatitis, rickets and anemia.

In order to improve digestion, as well as obtain the necessary dietary fiber, fiber, vitamins and minerals, it was assumed very slow (starting with a few drops), but very early introduction of complementary foods.

The scheme of introducing complementary foods was approximately as follows: at the age of about 3 weeks, the child was given juices (with drops), then a vegetable broth, gradually adding one component at a time in order to “accustom” the child to these products. At 2 months, fruit puree was introduced, at 3 – kefir, at 4 – porridge, at 5 – vegetable puree and cottage cheese, then – an egg, at 7 months – meat and biscuits.

It should be noted that such an early introduction of products into the baby’s diet existed only in the countries of the USSR.

In 1999-2002. At the initiative of the World Health Organization (hereinafter – WHO), epidemiological studies were carried out ,  as a result of which it was found  that one of the leading causes of the development of  gastroenterological, allergic, immunological diseases among children and adults  is the early introduction of complementary foods.

As a result of these studies, the attitudes regarding the introduction of complementary foods have changed significantly. The modern approach is based on the study of the physiology of the development of organs and systems of a child, his readiness to accept new food. In particular, the ability to consume “solid” food requires the maturation of the neuromuscular, digestive, renal and defense systems.

The neuromuscular system. Many food reflexes appear and disappear at different stages in the development of neuromuscular coordination. Such reflexes can both facilitate and hinder the introduction of different types of food.

So,  at birth, breastfeeding is facilitated due to the reflex of grasping the breast, as well as the mechanism of sucking and swallowing, but the introduction of “solid” food can interfere with the gag reflex.

In addition, up to 4 months of age, infants do not yet have the neuromuscular coordination necessary in order to form a food lump, transport it into the mouth of the pharynx and swallow, therefore, the introduction of even semi-solid food before this time is not physiological. It is still difficult for the baby to control the movements of the head, the support of the spine is not developed, respectively,  it is difficult to maintain a position for the successful absorption and swallowing of semi-solid food.

At about 5 months, children begin to bring objects to their mouths, the “chewing reflex” gradually develops, the vocal reflex moves from the middle to the back third of the tongue. This  allows the baby,  regardless of the presence of teeth, to consume food in the form of puree.

By about 8 months of age, most babies already have their first teeth, can sit without support, and have the flexibility of their tongues to swallow harder lumps of food – pounded or chopped food, and food that can be eaten by hand.

Soon thereafter, infants develop manipulation skills for self-feeding, cup-drinking, holding it with both hands, and chewing skills are improved and they can eat food from a common table.

It is very important to encourage children to develop eating habits, such as chewing and holding objects, at appropriate stages; if these skills are  not acquired on time , behavioral and feeding problems may arise later.

Digestion and absorption.  A newborn is able to fully and effectively digest only breast milk, which already contains the enzymes needed to hydrolyze fats, proteins and carbohydrates (in other words, breast milk digests itself).

By about 4 months, stomach acid helps stomach pepsin digest protein completely. B ost heat treated starches  already digested and absorbed almost entirely by the work of pancreatic amylase (at full contribution to the digestion of starches, it will start to be made only at the end of the first year of baby’s life). 

The microflora of the colon also changes with age and depending on whether the baby is breastfed or artificially fed. It ferments undigested carbohydrates and fermentable dietary fiber, converting them into short-chain fatty acids, which are absorbed in the colon, thereby maximizing energy utilization from carbohydrates.

Thus, the introduction of complementary foods is advisable only after the   baby’s digestive system has matured to the required level in order to   effectively digest the starch, proteins and fats contained in non-dairy foods.   This happens at different times, but not earlier than 4-6 months.

Renal function.  The kidney solute load is the total amount of solutes that must be excreted by the kidneys. Basically, it includes food components that are not transformed during metabolism (mainly sodium, chlorine, potassium, phosphorus), which were absorbed in excess of the body’s needs, as well as metabolic end products, including nitrogen compounds.

The potential load of solutes on the kidney includes solutes of  food and  endogenous origin that are not used in the synthesis of new tissue, as well as not excreted by non-renal routes, respectively, to be excreted in the urine. Potential solute loading is defined as the sum of the four electrolytes (sodium, chlorine, potassium, phosphorus) and solutes derived from protein metabolism, which typically account for over 50% of the potential load on the kidneys.

A newborn baby has too limited kidney capacity to handle a high solute load while retaining fluids. Breast milk has the lowest potential load on the kidneys – 93 mosmol / l, infant formula – 135 mosmol / l. With the introduction of complementary foods, the load increases by two or more times.

By about 4 months, kidney function becomes significantly more mature and babies can  handle higher concentrations of solutes while retaining water. However,  in children who have undergone chronic intrauterine or postnatal hypoxia, maturation can occur at a later date (by about 6 months).

Thus, based on the level of maturation of the   renal system, the  introduction of complementary foods also appears to be safe at the age of 4-6 months. 

Protective system.  The immature intestinal mucosa of infants is not protected from damage by pathogenic microorganisms and is sensitive to the effects of some antigens in food.

Breast milk makes a great contribution to the development of  active defense mechanisms. Under the influence of lymphocytes and partially hydrolyzed immunoglobulin G of breast milk, the intestinal lymphoid system (GALT – Gut associated lymphoid tissue) matures, which is not only the main protective factor, but also reduces the permeability of the intestinal wall. Thus, breast milk  helps prepare the gastrointestinal tract to absorb transitional foods. Unfortunately, even the most adapted formula does not contain many of the substances that are in breast milk, so the maturation of the intestinal lymphoid system in bottle-fed babies can take longer.

Non-immunological defense mechanisms that help protect the intestinal surface from pathogens, antigens and toxins include gastric acidity, gastrointestinal secretions,  peristalsis,  and  mucous membranes . However, in an infant, these protective mechanisms are still poorly developed, therefore, early introduction of complementary foods increases the risk of damage to the mucous membrane of foreign food and microbiological proteins, which can cause direct toxic or immunologically mediated damage, contribute to the development of allergic reactions (in connection with which it seems to me very doubtful recommendations of some doctors on the introduction of early feeding for children with atopic dermatitis, ostensibly to accelerate the process of maturation of the gastrointestinal tract).

Thus, it is advisable to start the introduction of complementary foods no earlier than 4–6 months, since until this time the baby’s body is not yet able to adequately perceive food other than breast milk or its substitutes.

At the same time, the introduction of the first complementary foods later than 6-7 months can also have a number of negative consequences due to the following:

  • insufficient intake of energy and nutrients from breast milk alone (or its substitutes) can lead to stunted growth, malnutrition, delayed maturation of the structure and  functions of the gastrointestinal tract, and the development of constipation;
  • due to the inability of breast milk (or its substitutes) to meet the increased needs of the developing organism, the child may develop a deficiency of iron, zinc, copper and other trace elements;
  • it may be difficult to adapt to foods that are harder than milk (in particular, a delay in the formation of chewing and swallowing skills, as well as a negative perception of the new taste and structure of food).

However,  controversy remains over when to begin complementary feeding. The indisputable fact is  that the optimal age is individual for each specific child, but the question of what age to recommend  remains open. 

There is  almost universal agreement that complementary foods should not be initiated before 4 months of age (assuming that this is the full 4 months of life, i.e. at least 17 weeks) and delayed until over 6 months of age (i.e. 26 weeks of a child’s life).

In the resolutions of the World Health Assembly 1990 and 1992. the recommended age is “4-6 months”, while the 1994 resolution recommends “about 6 months”. The 2001 Guidelines for the WHO European Region, with a particular focus on the republics of the former Soviet Union, Infant and Young Child Feeding and Nutrition, recommend the introduction of complementary foods at around 6 months of age, but indicates that some infants may need to earlier, but not earlier than 4 months of age.

The need to introduce complementary foods before the child reaches 6 months of age is indicated by the fact that the child, in the absence of an obvious illness, does not gain enough weight or looks hungry after unrestricted breastfeeding. Moreover, an insufficient increase should be established as a result of 2-3 evaluations in a row using the standard indicators of physical development established by WHO specifically for breastfed children. In addition, other factors should be taken into account: body weight and intrauterine age at birth, nutritional status of the child, clinical condition and general developmental status.

As a result of a study carried out in Honduras, it was found that feeding breastfed babies with a birth weight of 1500 grams. up to 2500 gr. free high quality complementary foods from 4 months of age did not provide any developmental benefits. In addition, in countries with economies in transition, there is evidence of an increased risk of infectious diseases with the introduction of complementary foods before 6 months and that the introduction of complementary foods before this age does not improve the rate of increase in weight and length of the child. This is due to the fact that for an immature organism it is much harder to assimilate “solid” food than breast milk (or its substitutes), almost all the energy obtained with complementary foods is spent on this. In addition, energy expenditure increases in response to increased morbidity, associated with the introduction of foods and fluids other than breast milk (or milk substitutes). Given that complementary foods partially replace breast milk (or milk substitutes), which are much easier to digest, the potential benefits of complementary foods are generally negated.

Thus, the WHO recommendations boil down to the fact that it is correct to exclusively breastfeed children for about 6 months, even for low birth weight children. At the same time, in order to improve the situation with the baby’s weight gain, it is recommended to revise the mother’s diet for its usefulness (you can read about the diet of a nursing mother  here ).

The main provisions of the theory and practice of introducing complementary foods in the Russian Federation are established in the “National program for optimizing feeding of infants in the first year of life in the Russian Federation”, approved at the XVI Congress of Russian Pediatricians (February 2009).

In accordance with this Program, the optimal timing of the introduction of complementary foods is the age of 4.5-5.5 months. Moreover, when choosing a term, preference should be given not to the calendar age, but to the degree of physical and motor development of the child. With exclusive breastfeeding of healthy full-term babies with normal weight and height at birth, with optimal health and good nutrition of a nursing mother, a later introduction of complementary foods is possible – from 6 months.

It should be noted that the timing of the introduction of complementary foods, depending on the type of feeding (if modern adapted infant formula is used with artificial feeding), do not differ, however, the sequence of introduction of certain types of products may differ.

In connection with the above, I believe that it  is inappropriate to consider the timing of the introduction of complementary foods as a kind of dogma  . When deciding on the introduction of complementary foods (preferably in conjunction with a doctor watching the child), one should take into account the individual characteristics of the child, signs of his readiness to introduce complementary foods, namely: the manifestation of food interest, the ability to maintain a sitting position, extinction of the pushing reflex, increased appetite, etc.

You should be especially careful when determining the timing of the introduction of complementary foods in the presence of an allergic predisposition, manifestations of atopic dermatitis in a child, premature birth, long-term unstable stool, late start of enzymes, etc. In these cases, one should not rush, because the later complementary foods are introduced,  the higher the likelihood that the digestive system and enzymes “ripen”, respectively, new products will be normally absorbed.

However, you should not delay with complementary foods, since when complementary foods are introduced later than 8-9 months, insufficient nutrient intake and a delay in the development of
nutritional skills may occur .

You may be interested in the following entries:

How to start introducing complementary foods to babies?

First food: cook or buy?

How to cook porridge for feeding babies at home

How to cook vegetables and fruits for feeding babies. Part 1 (general rules)

How to introduce complementary foods for atopic dermatitis: mom’s experience