Caloric Demands of Lactation
Lactation is metabolically expensive. Human milk production requires approximately 500 kcal per day above the non-lactating requirement to produce a full milk supply of approximately 750–800ml per day. This energy comes from dietary intake and from mobilisation of fat stores laid down during pregnancy (typically 2–4kg). Most lactating people are advised to consume an additional 330–500 kcal per day, depending on how much fat mobilisation is occurring.
How Diet Affects Milk
Maternal diet has more impact on some milk components than others. Fatty acid composition of milk fat is directly influenced by maternal diet — omega-3 fatty acid intake increases DHA content of milk, supporting infant brain development. Water-soluble vitamins (B vitamins, vitamin C) are influenced by maternal levels. Fat-soluble vitamins (A, D, E, K) and minerals (calcium, phosphorus) are largely maintained at adequate levels regardless of maternal diet, but at the cost of maternal stores. Lactose, proteins, and total fat content are relatively stable regardless of diet.
Key Nutrients
Iodine and vitamin D are the nutrients most commonly deficient in breastfeeding people. Iodine requirements increase substantially during lactation and dietary intake is often insufficient without supplementation. Vitamin D is low in breast milk even when the mother is sufficient — most guidelines recommend infant vitamin D supplementation. Calcium requirements are high but breast milk calcium is maintained at expense of maternal bone (which remineralises after weaning).
What You Don't Need to Avoid
The evidence for blanket dietary restrictions during breastfeeding is weak. Alcohol: small amounts in breast milk (peak ~30–60 minutes after drinking) and metabolised within 1–2 hours; moderate occasional alcohol consumption is considered compatible with breastfeeding. Caffeine: passes into milk in small quantities; up to 200–300mg/day is generally considered safe. Most foods do not cause infant colic or discomfort despite popular belief.
