As the baby grows from 6 months onwards, a diversity of micronutrients is required for his growth and development, in addition to macronutrients derived from protein, fats and carbohydrates. While macronutrients, as the name suggests, provide large amounts of amino acids, sugars and fatty acids, it is the trace amounts of micronutrients, including vitamins and minerals, which provide more specific functions in maturing tissues. While they are lower in amount, they are just as important. This is seen in examples of children when a specific mineral become very low, resulting in specific types of health issues.
A mineral is a type of basic element in its simplest form. All foods have some trace amounts of most dietary minerals, although levels will vary depending on the food source. As their name suggests, some are naturally occurring, such as sodium, which is abundant in sea water, while calcium occurs in lime and egg shells. Breastmilk is a balanced source of the dissolved form many minerals required for the first 6 months of development and beyond, in particular, calcium.
This is the most abundant mineral in the body and is important for an infant’s bone and tooth development, for a healthy nervous system and for muscle function. Calcium forms part of the hard component of bones as they begin to change from their softer, cartilage forms, such as the fontanelles at the back of the skull, and the gums as new teeth begin to emerge. As complementary foods are introduced, infants gain calcium from clean dairy sources, including yoghurt, cheese and cow’s milk. While this should not be given as the main drink to infants under 12 months old, cow’s milk and cheese represent one of the most abundant and easily consumed sources of calcium and can be given in moderation as part of a balanced diet. Diets lacking sufficient calcium can lead to problems with skeletal development.
Healthy infants are born with enough iron stores for the first 4 to 6 months of life, most of which has come from maternal stores in late pregnancy via the placenta. Iron is most abundant in red blood cells and muscle, where it binds and transports oxygen throughout the body. From around the 4th month, these stores start to become depleted due to rapid tissue growth and expansion of blood volume. While some iron is absorbed form the breastmilk as lactoferrin, a substantial amount of iron comes from protein sources, such as eggs, red meat, which can be easily incorporated during the weaning process.
Zinc is critical for tissue growth, the production of blood cells, development of immune function and maturation of the brain during infancy. It is even required for the formation of collagen, which forms the flexible component of growing bones. Probably the most surprising thing about zinc is that it controls newly dividing cells in every tissue, as well as the parts of cells that extract energy from macronutrients. So, it works in combination with the protein and carbohydrates that fuel the daily growth processes. As a result, an insufficiency of zinc during the 6-12 month period can result in loss of appetite, slowing of growth and increased susceptibility to illness due to a slower immune system. During complementary feeding, animal products are the best source of zinc, both in their content and bioavailability.
Minerals are trace elements (micronutrients) that are found in small amounts in food and the body, but are essential to infant health. They help growing bodies to process macronutrients and have vital functional roles in growing tissues.
- Specker et al. 2004 https://academic.oup.com/jn/article/134/3/691S/4688688