Lots of parents worry about the nutritional quality of their breastmilk. I hear mothers stress that their diets are terrible so their breastmilk must be awful! I even have experience myself of being told by a paediatrician that my son’s faltering growth was due to my vegan diet. I couldn’t possibly be making calorie dense, plentiful milk if I don’t drink cow’s milk! This is, as I later learned, complete bullsh**.
Is there any evidence that the quality or quantity of milk is affected by the lactating parent’s diet? The short answer is no. But it is a little bit nuanced. We can’t really consider the influence of maternal diet on milk production without knowing the diet and nutrient history of the lactating parent. There are so many variables to how diet influences our own nutrient profile, and in the Western world, the likelihood of undernourishment even on a very ‘poor’ diet is low when so many of our foods are calorie dense and fortified.
What does the evidence show?
Vitamin content of mik is generally responsive to increased maternal intake among malnourished women, and less so among well-nourished women. Vegans and vegetarians who do not supplement with vitamin b12 are at risk of b12 deficiency, and infants may become symptomatic before their mothers. (Hale & Hartman, 2007)
Vitamin D – everyone in the UK should take a vitamin D supplement because we don’t get enough sunlight. Formula milk is fortified with Vitamin D which is why formula fed babies don’t need a supplement, not because breastmilk is deficient but because most UK residents are deficient. Mum should supplement too.
Total milk fat content is unaffected by maternal dietary fat intake, but the fatty acid profile can change with maternal intake (so if you eat more polyunsaturated fats, breastmilk will have a higher volume of polyunsaturated fats) – but there’s no evidence to say whether this matters.
Milk mineral content was not influenced by maternal exercise in a randomized crossover trial comparing phosphorous, calcium, magnesium, sodium and potassium content of milk from women during a rest period with milk from the same women before, and 10, 30 and 60 mins after maximal graded exercise (Fly et al, 1998)
Essentially, if you are already malnourished then your nutrients may be impacted, and this can in turn influence breastmilk nutrient profile. The solution to this is to ensure you supplement and eat well – and probably if you’re malnourished then you need to see a doctor and ensure you are taking good care of yourself, because you’ll probably feel quite unwell! The easiest solution is to ask for a blood count, to check whether you have any deficiencies, and then supplement or improve your diet to help you.
As always, your milk is perfect for your baby, and it is the health of the lactating parent that will suffer before the quality or quantity of milk is impacted by your nutrient intake.