Why do babies love applesauce and hate broccoli?
In the next couple of posts I’m going to talk a bit more about how kids develop preferences for certain foods and how parents can work with this developmental process to familiarize children with different foods in a positive way. I wanted to start today with a brief discussion of innate taste preferences, because understanding the preferences that kids are born with makes it easier to think about how they can be modified through different experiences.
Babies learn about new tastes and textures through their experiences with food and eating, and these experiences can shape how they respond to different foods as they get older. However, babies do not start out as a blank slate - they show specific preferences and aversions even before they have had any experience with milk or food. It seems as if kids are born loving sweets, and in fact this is true. Babies across different cultures and environments favor sweet tastes, and this preference is evident from birth. A couple of studies have even examined how fetuses respond to sweet vs. bitter tasting substances in amniotic fluid and demonstrated that the ability to taste – and the preference for sweetness – is present even before birth. This makes sense, as taste buds are pretty well-developed by the second trimester of gestation.
Throughout history, this innate preference for sweetness has helped babies to survive by attracting them to their natural source of nutrition, breast milk, which has a sweet taste, as well as other energy-rich foods that support the fast growth and development happening during infancy and childhood. The preference persists into mid-adolescence, and then declines resulting in lower preference for sweet taste during adulthood. There are a lot of other factors that determine individual preference for sweetness at different ages, but research has found repeatedly in different populations and cultures that kids like more sweetness in their food and drinks than adults.
Babies and children also tend to prefer salty foods, but this preference emerges a little later at around 4 months of age. This is thought to have a similar evolutionary basis to sweet preference - saltiness indicates high mineral content in a food, which helps ensure that nutrient needs are met. Similar to sweetness, this preference generally declines into adulthood.
So what do babies not like? Vegetables - no surprise there. More specifically, babies have an innate dislike of foods that taste bitter, which again has an evolutionary basis – it helps them to survive by discouraging them from eating toxic plants or other substances that could be harmful. A rejection of vegetables by a young baby is not indicator that the child is “picky” or doesn’t like vegetables - this is a completely natural and expected response. This is why babies will usually spit out broccoli or peas but happily eat applesauce - they are wired to consume sweet foods and reject bitter foods.
Tolerance to bitter taste generally increases with age, but sensitivity to bitterness is more variable between individuals than sensitivity to other tastes. Bitter sensitivity is determined by different variations of a gene called TAS2R28. Both children and adults with a certain variation of this gene are more sensitive to bitter tastes and may be more likely to dislike bitter-tasting vegetables, as well as foods such as coffee, green tea, and even cheddar cheese, than those without this gene variation. Since genes don't change, a child who is more sensitive to bitter tastes is likely to become an adult who is sensitive to bitter tastes. However, just as the preference for sweetness and saltiness is heightened in childhood and declines with age, children also seem to become less bitter-sensitive as they get older. But this doesn’t mean that little ones can’t learn to accept and even like the taste of many vegetables. In fact, research has suggested that while genetic variability does impact sensitivity to certain bitter tastes, it does not strongly influence food preferences or day-to-day intake of certain foods.
While babies are pre-wired for certain preferences and aversions, they are also very receptive to new experiences, including foods (note: this is a generalization and some babies may have other things going on that impact their early experiences with food and eating that can be discussed with an appropriately trained clinician). There is fascinating research demonstrating how the mother’s diet during pregnancy, feeding with different types of formula and/or breast milk in early infancy, and the introduction of different complementary foods and beverages can reshape these innate preferences and help children become more accepting of foods such as green vegetables as they get older. In the next post (or maybe 2), we’ll discuss different ways that children can be exposed in a positive way to different flavors and foods to help modify their preferences to better align with a varied and nutritious diet.