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The complementary feeding period is a “window of opportunity” for acclimatizing infants to the taste of a wide variety of foods. Early learning about flavors continues during the complementary feeding period through the introduction of solids and changing exposures to a variety of new foods. In this particular time of the child’s life, there is the transition from breastfeeding/formula feeding to a complementary solid diet, and infants discover the sensory (taste, flavor, and texture) and nutritional properties (energy density) of the foods that will ultimately compose their adult diet [27]. Infant acceptance of new tastes and flavors develops during the so-called “sensitive period” between 4 and 6 months [28]. This period is crucial in influencing the development of later food preferences. The period from 6 to 10 months is favorable for the introduction of more complex textures [28]. The early and easy acceptance of new foods at a slightly younger age in the period of the introduction of complementary foods (4–6 months) has been observed in many studies. It has been shown that the earlier fruits and vegetables were introduced, the better their acceptance both in infancy and at a later age in childhood. This possibly reflects the difficult nature in terms of texture and tastes shared by many fruits and vegetables, both properties which children find aversive. The only texture the infant has experienced before complementary feeding is thin, liquid, warm milk, and thus new textures like soft-cooked vegetables and even thick yogurt will feel wildly different. The oral motor skills are usually learnt between 6 and 12 months of age (the period in which the tongue learns to move solid food around the mouth in preparation for swallowing), and this ability is dependent upon the experience of textured food within the mouth rather than on any particular age or developmental stage [28]. It has been observed that if 12-month-old infants were given pureed and chopped carrots, they consumed more of the pureed carrots, but there was variability in the infants’ willingness to take the chopped carrots. The strongest predictor of the acceptance of chopped carrots at 12 months – other than the presence of teeth – was earlier experience with textured foods [29]. In addition, children who were used to a high variety of different foods in their diet ate more of the chopped carrots; this again reflects the generalization effect, the greater the experience, the greater the willingness to try. Furthermore, infants who are introduced earlier to lumpy foods tend to be easier to feed by their mothers than children introduced to lumpy solids after the age of 10 months. Children introduced to lumpy solids after the age of 10 months were reported as having more feeding problems at 7 years. They were also reported as eating fewer portions of fruits and vegetables at 7 years [30].

At the onset of complementary feeding, many infants dislike vegetables, and there are various reasons for this, including the taste, appearance, and texture, often influenced by how they are prepared. Being exposed to a variety of foods during the complementary feeding period helps modulate the acceptance of new foods, especially vegetables, in the first year of life and later on [1, 10, 11]. It has been shown that experience with a variety of vegetables (changing the vegetable offered each day) at the very onset of weaning increased intake of new foods a few weeks later [10] but also a few years later [1]. Breastfeeding and early experience with variety interacted, in that infants who had been breastfed and had then experienced a high variety of vegetables at weaning showed the most marked acceptance of new foods [10]. In a follow-up study, it has been shown that the benefit of introducing a variety of vegetables maintains at least up to the age of 6 years [1]. At 6 years, children who had been exposed to a high level of variety consumed more of the new and known vegetables, were more willing to taste vegetables, and had higher liking scores for new or familiar vegetables [1].

At present, the first weaning food in many European countries (e.g., Germany), such as vegetables, potatoes, and meat, is thus increasingly competing with the variety and, following the Mediterranean model, also fatty sea fish. The long-held view that only 1 or 2 vegetables per week should be fed has become obsolete. Monotonous nutrition offers no protection against allergies and better food intake. On the contrary, infants who receive a varied complementary diet are also better and less complicated eaters later in life. Parents should, therefore, pay attention to a variety of fruits and vegetables at the beginning of the complementary feeding. Offering the infant a variety of flavors and textures from the start of complementary feeding is the best way to help them to enjoy a variety of foods as they grow up.

In conclusion, a preference for varied flavors should ultimately increase the range of nutrients consumed and the likelihood that a well-balanced diet is achieved. In other words, the variety effect may reflect an important adaptive mechanism in the regulation of food intake among omnivores.