According to Varney, which mineral should be supplemented for breast-fed infants after 6 months of age?

In the context of infant nutrition and development, fluoride supplementation is recommended for breast-fed infants after 6 months of age to help prevent dental caries. Breast milk typically contains inadequate levels of fluoride, which is essential in the formation of healthy tooth enamel. As the introduction of solid foods begins around this age, the dietary fluoride intake may not be sufficient to protect against cavities, especially in infants who do not consume fluoridated water.

It's important for caregivers to be aware of the need for fluoride supplementation as part of a broader approach to oral health in young children. The recommended fluoride can come from supplements or other sources, and it is crucial to monitor the total fluoride exposure to avoid excess, which could lead to dental fluorosis.

This recommendation reflects a focus on dental health, particularly in light of increasing evidence linking fluoride exposure to a reduced incidence of cavities in children. As such, fluoride's role becomes increasingly vital once infants start eating more solid foods and are at risk for higher sugar intake, thus needing additional protection for their developing teeth.