Nutrients at age
3-6 months

By nature, calcium, phosphorus, and vitamin D play a crucial role in a baby’s healthy growth and development. They are especially important between the ages of 3-6 months as this is when the foundation for strong bones is laid and when teeth begin to grow. Accordingly, more detailed information about the science behind these three nutrients and their function in the human body, as well as their possible sources, is provided in the following.

Lettering "Calcium"


Coinciding with the appearance of their first teeth, calcium (an integral component of the skeletal system, its bones and teeth) is essential for babies aged 3-6 months. Babies receive calcium via breast milk or infant formula, but supplementation might be needed to reach the dosage recommended by scientific institutes. 
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As the second most abundant inorganic element in the human body, phosphorus is extremely important for healthy development. It supports many essential physiological processes, including the cell's energy cycle. A variety of sources for phosphorus intake exist. 
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Lettering "Phosphorus"
Lettering "Vitamin D"
Vitamin D

Vitamin D

Despite the body's ability to produce vitamin D with the help of sunlight, vitamin D deficiency has become a widespread problem due to several reasons. Supplementation has already become common, and is a valuable measure for strengthening bone mineralisation and healthy tissue growth. 
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  • Calcium

    Although calcium is very important during pregnancy, it also plays a major role during infancy and early childhood. More specifically, during the 3rd to 6th months of a baby’s life, calcium supports the mineralisation and strengthening of the first teeth. In addition, it fosters the development of healthy bones, paving the way for healthy future motor and physical development.

    During the first six months of life, babies only have the ability to suck and swallow food. Therefore, the appropriate nutritional elements for a baby from 3-6 months should come from breast milk or infant formula. Although calcium is present in breast milk at a concentration of 264mg/L (Atkinson et al, 1995), calcium can be administered as an additional supplement or as part of infant formula. The recommended daily dosages of calcium may vary according to specific national regulations or guidelines. However, the following is generally accepted by several scientific assessments:

    EFSA (2015) and Institute of Medicine (US) (2011):

    • 0-6 months: 200mg per day 

    WHO/FAO (2004): 

    • 0-6 months, breastfed: 300mg per day
    • 0-6 months, cow's-milk fed : 400mg per day

    When calcium supply is insufficient to meet physiological requirements, calcium is resorbed  from the skeleton to maintain blood concentrations optimal for normal cellular and tissue function. As a consequence, bone mass is reduced, which could lead to osteopenia (reduced bone mineral density), osteoporosis, and increased risk of fracture. The previous conditions, including skeletal disorders such as rickets (also connected with vitamin D deficiency), have been documented during infancy – particularly in preterm infants (EFSA, 2015; Koo and Warren, 2003). Excessive calcium intake – when total calcium serum levels are above 12mg/dL (which is unlikely to be reached through diet alone) – usually leads to hypercalcaemia in infants and children. Signs of this condition include gastrointestinal reflux, nausea, vomiting, and hypertension (EFSA, 2015; Lietman et al, 2011).

  • Phosphorus

    Phosphorus is an essential nutrient – the second most abundant inorganic element in the body – and part of many important compounds and pathways: it is involved in physiological processes such as the cell's energy cycle, the regulation of the body’s acid-base balance, cell signaling and regulation, and teeth and bone mineralisation (EFSA, 2015). Phosphorus makes up about 0.5% of a newborn’s body and 0.65-1.1% of an adult’s body (Institute of Medicine (US), 1997). The body’s phosphorus content is available in bones and teeth (85%), in soft tissues (14%) including the muscles, liver, heart and kidneys, and also in extracellular fluids (1%) (EFSA, 2015).

    Dietary sources of phosphorus include foods with high protein content such as milk and milk products, meat, fish, grains and legumes. Mean phosphorus intake ranges between 265-531mg per day in infants, based on dietary surveys in nine European Union countries (EFSA, 2015). The adequate intake of phosphorus is defined as follows: 

    Institute of Medicine (US) (1997) and EFSA (2015):

    • 0-6 months: 100mg per day, based on a breast milk intake of 780ml per day with a phosphorus of 124mg/L 

    EFSA (2015):

    • 6-12 months: 275 mg per day, based on phosphorus coming from breast milk and solid foods   

    As an alternative to breast milk and mainly during weaning or when unable to provide breast milk, infant formulas and supplementation of phosphorus offer an alternative in order to avoid deficiency states. 

  • Vitamin D

    Vitamin D is a generic term for ergocalciferol and cholecalciferol, named vitamins D2 and D3 respectively. They are formed following a two-step reaction involving ultraviolet-B (UVB) radiation and subsequent thermal isomerisation. Vitamins D2 and D3 are fat-soluble compounds present in foods and dietary supplements but are also synthesised in the skin following the skin’s exposure to UVB radiation (EFSA, 2016). Vitamin D plays an important role in bone metabolism and musculoskeletal health through regulation of the homeostasis of calcium and phosphate – minerals associated with bone development (SACN, 2016; EFSA, 2016).

    Vitamin D is produced by skin exposure to sunlight, but is also found in eggs, oily fish and fortified foods. The absorption  rate of vitamin D when ingested through diet and absorbed along with fat is around 80%. According to WHO, infants are born with low vitamin D reserves and replenishment is dependent on breast milk consumption, sunlight exposure, or dietary supplementation during the first months of life. Vitamin D content of breast milk is highly dependent on maternal diet and is often low. Also, infants are not exposed to sun light frequently, and geographical, climate, and cultural conditions may intensify this problem. These conditions can include latitude, time of year, time of day, length of sunshine hours, the use of clothing and other protective sun care, as well as skin pigmentation and thickness. For these reasons, infants are highly vulnerable to vitamin D deficiency, particularly in some countries in the northern hemisphere (e.g. Germany) and even more so during the winter months if vitamin D stores are not sufficient to last. Vitamin D deficiency, or hypovitaminosis D, is associated with impaired bone mineralisation (causing rickets in children and osteomalacia in adults), seizures and breathing difficulty (EFSA, 2016). Impaired mineralisation is also associated with both calcium and phosphorus malabsorption (Holick et al, 2012). Excessive vitamin D consumption or administration may lead to hypercalcaemia, which may induce soft tissue calcification, and renal and cardiovascular damage (Vieth, 1999; Zitterman and Koerfer, 2008).

    As sun exposure should not be regarded as the primary source of vitamin D, combining it with breast milk administration, infant milk formulas, infant foods, or dietary supplementation offers a valid solution to improve vitamin D levels and avoid its deficiency. Vitamin D supplementation is recommended from birth onwards in the following dosages:

    DGE (2015), Institute of Medicine (US) (2011), Yu et al. (2017): 

    • 0<12 months: 10?g per day

    WHO/FAO (2004):

    • 0-6 months: 5µg per day

More about nutrients for natural growth