Exposure to the outside will give your baby vitamin D, even in winter and when the sky is covered. An hour or more exposure during the week will give your baby more than enough vitamin D.
Breast milk contains less iron than formulas do, especially those that are iron enriched. Iron will give the baby added protection against infections, as many bacteria need iron in order to multiply.
The iron found in breast milk is utilized well by the baby, while not being available to bacteria. The introduction of iron should never be delayed beyond the age of 6 months.
Breast milk is the best that your can feed your baby, as it provides everything he will need for probably the first 6 months. After the first 6 months, you can introduce solid foods to your baby if he is taking an interest to them.