Vitamin B12 has been shown to improve sperm quality and production. It also may help to boost the endometrium lining in egg fertilization, decreasing the chances of miscarriage. Some studies have found that a deficiency of B12 may increase the chances of irregular ovulation, and in severe cases stop ovulation altogether. B12 also aids in nerve function and is vital for making DNA. It is essential for your baby’s brain development and important to have enough of while breastfeeding. Best sources: Clams, oysters, mussels, fish, crab, lobster, grass-fed beef, New Zealand lamb, cheese, organic eggs.