Does vegan or vegetarian diet have any negative effect on the quality of breast milk?
If so, does a vegetarian or vegan mother need to take any special dietary supplements to improve quality of breast milk?
According to US National Center for Biotechnology Information:
Vegan diet in lactating women can induce vitamin B12 deficiency for their children with risk of an impaired neurological development.
They also provide a real life example:
A 9.5-month-old girl presented with impaired growth and severe hypotonia. She had a macrocytic anemia secondary to vitamin B12 deficiency. MRI showed cerebral atrophy. She was exclusively breastfed. Her mother was also vitamin B12 deficient, secondary to a vegan diet. She had a macrocytic anemia when discharged from the maternity. Vegan diet is a totally inadequate regimen for pregnant and lactating women, especially for their children. Prevention is based on screening, information and vitamin supplementation.
According to kellymom.com:
A vegetarian or vegan mother does not need to take any special dietary precautions as long as she is maintaining a diet with adequate amounts of vitamin B12, calcium and zinc. This is something that mom needs to do for herself, even if she is not breastfeeding.
Specifically for vegetarians:
If you are avoiding meat but eating any other type of animal protein (eggs, milk, cheese or other dairy products, fish, poultry) you will normally get enough vitamin B12.
And finally a quote specific to your case:
If, on the other hand, you are consuming no animal protein at all — no fish, meat, poultry, eggs or dairy products — you will need to make sure you get enough vitamin B12 to prevent your baby (and you) from becoming deficient in this vitamin. Vitamin B12 supplements and vitamin B12 fortified foods are available. Supplementing your baby with vitamin B12 is an option if you are vitamin B12 deficient, but you would still need the vitamin B12 for yourself (and if you’re getting enough, baby won’t need the supplement).
In simple terms, you and the baby may have a chance becoming deficient in vitamin B12.