Lesson 5: Infants and Toddlers – Complementary Feeding

Table of Contents


Introduction

In the last lesson I discussed various aspects of breastfeeding and formula feeding, which are the initial methods of feeding an infant. Regardless if you provide an infant breast milk or formula, eventually you will start introducing foods to complement the primarily liquid source of nutrition. This is termed “complementary feeding”, and there is a a lot of literature describing how this may or may not influence child weight outcomes and health. I will discuss some of the more recent literature here.


Influence of complementary feeding on feeding behavior

In a review of the biological control of appetite, the authors note that infants are generally willing to accept new foods more easily than toddlers, food habits established during infancy track into childhood and adolescence (for both nutrient-dense & nutrient-poor foods), and children in general have a greater desire for sugar and salt flavors prior to developing adult taste preferences in mid-adolescence.(MacLean, 2017) Thus, it may be beneficial to provide infants with a variety of healthy foods repeatedly to increase their acceptance while limiting sweet & salty tastes (as well as high sugar/high salt food products) to help protect against excessive intake later in childhood. These healthy foods should incorporate many different tastes and textures.(D’auria, 2020)

A 2021 review of feeding experiences during infancy and their impact on later child eating behavior noted that the impact of various complementary feeding methods on later appetite & energy intake regulation does not seem to extend beyond toddlerhood.(Pang, 2021) Thus, while the provided foods may influence later food preferences they do not seem to influence later hunger and satiety signals.

Tip: Another reason to support dietary diversity besides increasing food acceptance is due to the risk of contaminants being present in specific foods. A 2021 review of 83 studies attempted to assess the risk of contaminants in foods for infants and toddlers.(Mielech, 2021) The authors note that the youngest children are most at risk of toxic effects due to a prolonged intestinal transit time and an incompletely developed small intestine (leading to greater absorption of toxic elements), immature urinary & biliary systems (decreasing the body’s ability to filter toxicants), and a faster gastric emptying rate (leading to greater peak serum concentrations). The authors provide an overview of a wide variety of potential contaminants in many different food sources, noting this will vary by geographical location.

The authors mention some mitigation measures that you can take. You can soak produce in a solution of baking soda (10 grams to 1 liter) and peel the produce to help decrease the contaminants. Storing them in a refrigerator and cooking them can also be helpful. They note that including a variety of different foods should be helpful as this will minimize the risk of a high level of exposure from specific food items. Thus, dietary diversity will help minimize the risk of excessive contaminant exposure.


Specific food considerations relating to growth

Protein: As mentioned in Lesson 4, high protein intake in infancy can lead to an increased risk of excess weight gain, presumably via inducing higher insulin and insulin-like growth factor 1 levels, and children seem to be most sensitive to this during the first 2 years of life.(Switkowski, 2019; Rolland-Cachera, 2019) A 2021 systematic review and meta-analysis (“SR/MA”) evaluated 16 studies from 9 prospective cohorts examining the impact of protein intake in the first 2 years of life on the subsequent development of childhood obesity.(Stokes, 2021) The authors found total protein intake was associated with an increase in body mass index (“BMI”) and body fat percentage. This was due to animal protein as plant protein did not contribute to the increased risk. The authors note there is no standardized global recommendation for protein intake during infancy, with various guidelines recommending 11-14.9 grams daily. Some guidance advises keeping protein at <15% of total daily energy intake.(D’auria, 2020; Lutter, 2021)

Meat: A 2018 study compared growth with meat vs. dairy-based complementary feeding, both with similar amounts of animal protein, and found the meat-based group had more linear growth between the ages of 5-7 months such that the average length at 12 months was 75.7 cm in the meat group and 73.9 cm in the dairy group. Of note, there were only 32 infants in each group.(Tang, 2018) As iron deficiency is associated with altered neurobehavioral development(Georgieff, 2019) and meat intake is more likely to aid iron and zinc status than dairy intake, a case can be made for incorporating meats early in the complementary feeding process (though not to an excessive degree given the concern for excess protein intake noted above).

Sugary drinks: A 2019 SR of complementary feeding included 49 studies and found that the types and amounts of complementary meats, cereals, and foods/beverages with different fat content did not influence growth.(English, 2019b) However, sugar-sweetened beverage intake did increase the risk of developing obesity and there was limited evidence that 100% fruit juice also contributed to small increases in weight.

Infant & toddler prepared food products: Commercially prepared infant & toddler food products can be too sweet and lack appropriate textures & micronutrients.(Pang, 2021) As mentioned above this may contribute to poor food choices in the child’s future. In addition to the high sugar content, these items may also lack single food flavors and generally do not include bitter vegetables. This is particularly true for foods consumed in pouches; these are associated with an increased risk of dental caries and developing overweight given their added sugar and their method of consumption (via sucking instead of chewing).(Lutter, 2021)


Baby-led weaning (“BLW”)

A 2021 SR on BLW noted there are theoretical concerns of iron and/or zinc insufficiency as well as an increased risk of choking, while it may lead to favorable outcomes for infant weight control and higher levels of satiety responsiveness.(Martinón-Torres, 2021) The authors here found 8 studies with only 2 being randomized controlled trials (1 of which found baby-led weaning helped protect against developing overweight at 12 months, the other found no impact of baby-led weaning). Overall, there was significant variation in the results between the studies which preclude any reliable recommendations. Other reviews have found similar findings regarding BLW associating with a lower risk of child overweight, less demanding of food, increased satiety response later in life, while acknowledging concerns of choking, food wastage, and a delayed introduction of allergenic foods.(Balantekin, 2020; Lutter, 2021)

There is observational data indicating that BLW is associated with decreased food fussiness up to age 3 years, but a confounding factor is that infants who undergo BLW are more likely to breastfeed for a longer period of time.(Pang, 2021) As mentioned in Lesson 4, breastfeeding may select for infants who are less fussy in general, and that may drive this association.


Timing of complementary feeding introduction

The data here refers to term infants (see the note below regarding preterm infants).

General signs of being ready for complementary feeding include maintaining good head control and being able to move food to the back of the mouth, with the earliest developmental skills for pureed foods typically developing at 3-5 months and for finger foods at 5-7 months (occasionally as early as 4 months).(Lutter, 2021) In general, if the infant refuses when you offer a new food then you should withdraw the food and try again at a later point in time as opposed to trying to force the infant to eat it; there is no ideal order to introduce various foods so whenever the infant shows willingness to try something new you can provide it again.

A 2022 SR/MA comparing the initiation of complementary feeding between 4-6 months vs. at 6 months found no differences in health outcomes.(Verga, 2022) A 2019 SR including 81 articles found no difference in weight outcomes when introducing complementary foods at 4 vs. 6 months.(English, 2019a) There was limited and conflicting evidence that the introduction of complementary foods at <4 months may increase the odds of developing overweight or obesity. However, there is evidence that introducing complementary feeding before 4 months may lead to lower satiety responsiveness, higher feeding difficulties, and a lower likelihood of consuming a health-promoting eating pattern.(D’auria, 2020)

Thus, complementary feeding should likely begin between 4-6 months of age, or right at 6 months of age for exclusively breastfed infants. Beginning at this age with a variety of fruits/vegetables/iron-fortified cereals/pureed meats/other foods/flavors/textures also has the advantage of helping with food acceptance and decreasing the likelihood of picky eating as the child ages.(Patel, 2020)

Note: Regarding preterm infants, a 2022 review found no official guidance.(Liotto, 2022) The authors suggest in general it may be best for the infants to be at least 3 months corrected gestational age and between 5-8 months chronological age assuming the infant has demonstrated developmental readiness (reduction of the tongue protrusion reflex and reflexive suck in favor of lateral tongue movement, as well as appearance of a lip seal), but they suggest this should likely be an individual decision based on an individual evaluation.


General advice for complementary feeding

A couple of recent reviews, both already cited above, summarized much of the literature regarding complementary feeding.(D’auria, 2020; Lutter, 2021) While some of the advice and research is not strictly related to weight management, I will still include general advice here as the information is pertinent for generally healthy eating in this age group, and sticking to these recommendations collectively should aid general health and consequently weight management as well.

Calories:

  • The FAO, WHO, and UN have revised total daily energy requirements to ~600 kcal for 6-8mo, ~700 kcal for 9-11 mo, and ~900 kcal for 12-23mo.
  • Aiming for 70-75 kcal/kg/day is reasonable.
  • For breastfeeding infants there will typically be a need of up to 200 calories per day from complementary foods at age 6-8 months, 300 calories per day age 9-11 months, and 550 calories per day age 12-23 months.

Macronutrients:

  • Protein was discussed above. This should likely be kept at <15% of daily calories.
  • Carbohydrates are recommended at 45-60% of total caloric intake; these should be mostly complex carbs, with a preference for starchy alimentary types with a low glycemic index.
    • The WHO recommends keeping free sugars at<10% energy intake, with possible benefit at <5% energy intake.
  • Fats are recommended by the WHO as 30-45% of total energy intake with 3-4.5% being omega-6 polyunsaturated fatty acids.
    • High fat diets do not seem to increase the risk of obesity.
    • There are no strict recommendations for omega-3 polyunsaturated fatty acid intake or saturated fat intake in the first two years.
  • Fiber has no official recommendation by the WHO but other guidelines suggest 10 grams per day age 1-3 years. A moderate and constant amount should not adversely affect energy intake.

Micronutrients:

  • There are no official WHO salt recommendation when <2 years old.
  • The most likely deficiencies are iron, zinc, and vitamin A.
    • Other potential deficiencies include calcium, vitamin C, and several of the B vitamins.
    • In countries where vitamin A deficiency is prevalent very high dose supplementation is recommended beginning at age 6 months.
  • The majority of micronutrients need to be obtained by complementary feeding once beyond 6-9 months of age for breastfed infants.
    • A vegetarian diet will be inadequate at this age; supplementation of iron, zinc, calcium, and vitamin B12 may be needed depending on the amount of animal-sourced food intake.
  • Per a recent review article discussing various health aspects of complementary feeding that listed food options for potential micronutrients of concern(Theurich, 2020):
    • Iron: animal meats are a source of more easily absorbed heme iron, nonheme iron sources include dried beans, peas, lentils, chickpeas, nuts, green leafy vegetables, dried fruit, and other foods that are iron-fortified.
    • Vitamin D: sources include fatty fish and egg yolks.
    • Essential fatty acids: sources include meats, poultry, and eggs, fish, and seafood products.
    • Iodine: sources include fortified foods, if primarily breastfeeding iodine deficiency can be a concern if the mother’s iodine levels are insufficient.

Liquids:

  • Breastfeeding is recommended up to age 2 years. Non-breastfeeding children age 6-23 months should consume 200-400 milliliters daily of milk or formula if other animal-sourced foods (particularly dairy) are consumed regularly, otherwise 300-500 mL/d is advised.
    • Animal milk is not safe the first 6 months of age due to a high renal solute load potentially causing hypernatremic dehydration.
    • Whole cow’s milk is generally not recommended at <12 months of age due to a risk of intestinal bleeding as well as potentially inhibiting iron absorption though some only advise against it at <9 months of age.
      • A recent review supports the notion that animal milk age 6-11 months can increase the risk of iron-deficiency anemia, but the literature base is sparse and it is not clear if providing supplemental iron could mitigate this risk.(Ehrlich, 2022) This may be more relevant in low-middle income countries if well-designed and safe infant formula is not readily available.
    • Whole-fat milk is recommended at <2 years as it is a source of essential fatty acids. Reduced-fat has fewer essential fatty acids & fat-soluble vitamins as well as a high potential renal solute load in relation to energy.
      • There does not seem to be any advantage to using reduced-fat milk for weight management purposes; for an overview of this literature as well as a comparison of whole vs reduced-fat vs skim milk, you can look at this review (Table 2 compares the different types of milk).
    • The WHO and many pediatric societies deem follow-up formulas as unnecessary and not recommended.
      • Thus, after infants turn 1 year old they should be given milk, not formula.
    • Yogurt is considered an appropriate substitution for milk.
  • Some guidance suggests providing 4-8 ounces per day of plain drinking water starting at age 6 months and increasing to 1-4 cups between 12-23 months.
    • Up to 5 cups daily may be needed at age 12-23 months in hotter climates.

Note: For a more comprehensive list of guidelines for calories, macronutrients, micronutrients, and water intake in the first 12 months of life, summarized from different sources, look at this table in PDF format here.(D’auria, 2020)

Tip: To some degree a complementary feeding strategy may differ based on whether infants are receiving breastmilk or formula. This was recently reviewed in the context of protein, calcium, and iron considerations.(Caroli, 2021) The main points made in that article include:

  • Breastfed infants will likely need iron and calcium-fortified foods (ie, fortified cereal) in addition to protein sources (ie, meat and dairy) to meet all of the nutritional requirements.
  • Formula-fed infants will have sufficient protein, calcium, and iron from the formula, but they will not have experienced many flavors at this point. Thus, it will likely be more helpful to prioritize various fruits, vegetables, and other flavored foods to help aid the acceptance of additional foods moving forward.
  • If switching to cow’s milk in the 2nd year of life this will provide plenty of protein and sufficient calcium but not enough iron, so consuming iron-fortified foods without significant additional protein will be helpful to meet nutritional requirements while minimizing an increased risk of obesity from excessive protein intake.

Food types and consistency:

  • The WHO recommends starting with pureed/mashed/semisolid foods at 6 months.
  • Most infants can progress to finger foods by 8 months.
  • By 12 months children can mostly consume adult foods as long as they do not present choking hazards (ie, nuts, grapes and raw carrots would be choking hazards)
  • Honey should not be consumed until children turn 1 year old. Juice should also generally be avoided the 1st year of life.
  • Repeated exposures may be needed for all types of new foods to improve acceptance. At the same time a variety of foods should be offered.

Meals:

  • For breastfed infants, 2-3 meals per day at age 6-8 months and 3-4 meals per day thereafter, while also including 1-2 snacks daily, is reasonable. For non-breastfed infants this may increase to 4-5 meals daily with 1-2 snacks if formula and milk consumption is limited.
  • Having consistent meal times on a daily basis is preferable if possible.

Allergy considerations:

  • It is currently thought that there is no reason to delay allergenic foods beyond 12 months and early exposure (potentially as early as 4-6 months (shown more conclusively with peanut products)) may help decrease the risk of developing food allergies. A couple of trials have found that increasing the diversity of complementary food intake prior to age 1 year is associated with a decreased risk of food allergy onset.
  • The most allergenic foods are generally peanuts, tree nuts, wheat, soy, eggs, dairy, fish, and shellfish. If you are able to introduce these in a safe format (ie, not real peanuts as these would be a choking hazard, instead look for infant peanut products) this may help prevent food allergies. If there are already concerns for food allergies or a child has moderate-to-severe eczema then it may be worth first seeing an allergist prior to introducing these foods; you can discuss this with the child’s healthcare provider.

While individual flavors of food should be introduced initially, when mixing various foods together this may generate a plate such as the following (though with nut products and not nuts themselves as they would be a choking hazard):

an image indicating foods to provide to infants
Reproduced from: D’Auria E, Borsani B, Pendezza E, Bosetti A, Paradiso L, Zuccotti GV, Verduci E. Complementary Feeding: Pitfalls for Health Outcomes. Int J Environ Res Public Health. 2020 Oct 29;17(21):7931. doi: 10.3390/ijerph17217931. PMID: 33137971; PMCID: PMC7662522.

With various portion sizes of some of example foods shown in the following table:

a table of portion sizes for infants
Reproduced from: D’Auria E, Borsani B, Pendezza E, Bosetti A, Paradiso L, Zuccotti GV, Verduci E. Complementary Feeding: Pitfalls for Health Outcomes. Int J Environ Res Public Health. 2020 Oct 29;17(21):7931. doi: 10.3390/ijerph17217931. PMID: 33137971; PMCID: PMC7662522.

Tip: You can additionally look at the 2020-2025 Dietary Guidelines for Americans, which in the appendices at the end contains nutritional recommendations for ages 6 months and older, both in the form of calories/macronutrients/micronutrients as well as food groups. Chapter 2 of the guidelines is specifically devoted to infants and toddlers; looking through that chapter and the appendices at the end will provide a general overview of how many servings of different food groups are recommended, and you can then divide that up into meals and snacks as you see fit.


Conclusion

The key points from this lesson regarding complementary feeding include:

  • This should likely begin between 4-6 months or right at 6 months, with no strong preference on the order of food type introduction but a preference for variety over time.
  • Particularly for breastfeeding infants it is important to prioritize iron and calcium-fortified foods.
  • Allergenic foods (peanuts, tree nuts, wheat, soy, eggs, dairy, fish, shellfish) in a format that is safe for infant consumption (ie, not a choking hazard) should be provided relatively early as this may help prevent food allergies; if there are already concerns for food allergies or a child has moderate-to-severe eczema then it may be worth first seeing an allergist prior to introducing these foods.
  • Honey, juice, and other very sweet substances should be avoided in the first year of life (honey in particular for safety).
  • Baby-led weaning seems acceptable and may have advantages; more research is needed to clarify this.
  • After 1 year of age regular cow’s milk at no more than 2 cups daily is likely ideal, particularly if the child is consuming additional dairy products. If no other dairy is consumed than 2-3 cups daily is appropriate.

In the next lesson I will discuss additional aspects of feeding in infants and toddlers.

Click here to proceed to Lesson 6


References

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