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This summary is adapted from ‘The role and requirements of digestible dietary carbohydrates in infants and toddlers’ by Stephen et al. 2012
Digestible carbohydrates are sugars and starches which can be broken down by the body for energy. They are one of the main sources of energy in infants, and therefore are essential for growth and development. The goal of the paper summarised here was to give an overview of digestible carbohydrates and their role in health and disease, particularly in infants and children.
There are a wide range of different types of sugars with many terms used to refer to slightly different molecules. The sugar content of foods can be investigated as total sugars (all sugars present), added sugars (which are added in processing), free sugars (all sugars which have been added), refined sugars (isolated sugar preparations used or added during production), non-milk extrinsic sugars (total sugars minus lactose in milk and sugars in fruit and vegetables) and caloric sweeteners. Starch can be broken up into rapidly digestible starch (freshly cooked foods), slowly digestible starch (raw cereals, pasta), and resistant starch (not digested).
The EU Directive 2006/141/EC stated that infant formula should have a minimum of 9g of total carbohydrates and a maximum of 14g/100 kcal. The approved carbohydrates to be used to achieve this are lactose, maltose, sucrose, glucose, maltodextrins, glucose syrup, precooked starch and gelatinised starch. For follow-on formula, the minimum total carbohydrate should be 9g/100 kcal and the maximum is 14g/100 kcal. There are also requirements for processed baby foods for infants and foods intended for young children.
All of the identified studies looking at carbohydrate intake were pooled. For infants aged 1 year or less, around 50% of their energy was provided by carbohydrates. Values for total sugars were around 30-35% energy, whereas starch intake was 15-18% energy. This is reflective of the values in breast milk and infant formula. Values were also similar in children over 1 year. Added sugars accounted for 4 to 13% of energy in infants and young children. Non-milk extrinsic sugars represented 11-19% of energy. Few studies were found to report the levels of lactose, despite its major contribution to carbohydrate intake in infants due to high concentration in breast milk. There has been a limited amount of studies looking at the major food sources of carbohydrates in infants, however we can assume the greatest source in infants under 12 months is milk products.
There is limited data in infants and young children investigating adequate carbohydrate and sugar recommendations for these age groups. In infants it is thought that the minimum carbohydrate intake should be close to that provided by breast milk, 40% of total energy with lactose as the main digestible carbohydrate. After 6 months and until 2 years of age, intake of digestible carbohydrates should be increased, with lactose remaining the major carbohydrate. There is no data to support an official recommendation, but based on what is known in adults, added sugars should be discouraged in infants. Carbohydrate has an important role in the development of food preferences, and therefore in the feeding behaviour of infants and young children. There are indications that food preferences during infancy are maintained into childhood and adolescence. Infants have an innate preference for sweet substances, and we have an ability to learn to like foods that are relatively energy dense. Therefore, complementary foods without added sugars will likely benefit the infant later in life
The consumption of the sugar sucrose (table sugar) should also be limited as it is the most likely to cause tooth decay1. High intakes of fructose (the primary sugar in fruit) may not be well tolerated in young infants in high levels as it is not efficiently absorbed, potentially leading to discomfort and diarrhoea. Starch is not present in breast milk, but can be present in infant formulas in low levels. At weaning, the infant will be exposed to increased and more complex forms of starch, and biological mechanisms are increased at this point to cope with this.
A link between sugars and cognition has been investigated. Glucose is the primary energy source in the brain, which takes a particularly large portion of ingested energy in infants, at 60% of dietary energy intake. Unfortunately studies have only been undertaken in children of 6-7 years of age, which have suggested areas of cognition that might be affected by glucose intake in young age groups. More study is needed in this area to elucidate a link here. However, infants have been studied directly in the role of sugars in aspects of behaviour. It has been shown that different types of sugar have different abilities to calm infants who are crying spontaneously. Sucrose and fructose were equally effective calming agents, whereas lactose had no more effect than water1. This is not indicative of brain function or cognition, but it does show that sugars are capable of different effects on the infant’s behaviour, and specific sugars may be found to have beneficial effects in future research.
There had been fears that excessive sugar consumption in infants would impair nutrient levels due to diluting their potential effect, but this was seen to be untrue except in extreme cases. For the association between sugar intake and infants or children becoming overweight and obese, there was a lack of research on infants and the results of the studies including children were largely mixed. We can, however, assume that limiting sugar-containing foods in infants will reduce the likelihood of excessive consumption later in childhood. Due to the strong link between obesity and the consumption of sugar-sweetened drinks, it was recommended that infants should not be fed juice or other high sugar drinks when weaning.
The conclusions of this review stated that there were a limited number of studies related to carbohydrate intakes in infants, and of these studies there were differing approaches to the analysis of the carbohydrate and a wide variety of terms used to describe intakes of sugar components. This limits our ability to draw concrete conclusions to inform infant feeding best practices. There was also very minimal information about starch intakes, appearing to result from general disinterest in this nutrient and therefore a lack of basic information about the starch content in foods. There was also a noted lack of attention paid to the complementary feeding period in comparison to studies on breast-feeding infants and older children. Future research will hopefully fill these gaps.
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