Final answer:
Vitamin D is the recommended supplement for breastfed infants or infants ingesting less than 1 L of fortified formula.
Step-by-step explanation:
The supplement that is recommended for breastfed infants or infants ingesting less than 1 L of fortified formula is Vitamin D.
Breast milk is a valuable source of nutrients for a baby's development and growth, but it may not provide sufficient vitamin D. Therefore, it is recommended to supplement breastfed infants with vitamin D to meet their daily requirement.
Other sources of vitamin D include cod liver oil, fish liver oil, egg yolk, milk, and animal liver. Additionally, sufficient exposure to sunlight can help the body produce vitamin D.