In short:
- Exclusive breastfeeding, when possible, is the most suitable form of feeding for all healthy infants, including the vegan ones, up to 6 months of age (Vegan Society, World Health Organization). "Breastfeeding keeps mother and baby close. Physical contact is important to newborns. It helps them feel more secure, warm, and comforted. Mothers also benefit from this closeness" (Womenshealth.gov).
- Soy-based formula is a nutritionally adequate option for infants who can't be breastfed and for those with rare genetic diseases, such as lactase deficiency and galactosemia (Pediatrics).
- Soy-based formula does not provide health benefits over breastfeeding or cow's milk formula (Childhood Obesity and Nutrition). Soy-based formulas are often made from genetically modified soy and can be high in aluminium, pesticides and phytoestrogens, which may have effects harmful for health, but these have not been clearly documented, so far (Frontiers in Nutrition).
- Plant foods (cereals, etc.) fortified with iron, vitamin B12 and other nutrients or natural plant foods in combination with multivitamin supplements can provide all necessary nutrients for toddlers (1-3 years) (EatRight).
Is a vegan diet nutritionally complete and suitable for babies?
Natural vegan diets for infants containing only plant foods without supplements are not nutritionally complete and are at least vitamin B12 deficient (Vegan Health, Vegetarian Nutrition Dietetic Practice Group) and can be also deficient in calcium, iodine, iron, zinc, vitamin D and protein (EatRight, 2019, Journal of American Dietetic Association, 1985).
Specifically, soy milk, rice milk, almond milk and homemade formulas are not appropriate for babies during the first year because they have the wrong ratio of protein, fat and carbohydrates and do not contain sufficient amount of minerals and vitamins (EatRight, 2019).
Soy-protein based formulas seem to be the only widely available vegan formulas for infants that are nutritionally complete. They are, at least in the US, fortified with certain amino acids, iron, iodine, calcium, zinc, vitamin B12 and D3 and other minerals and vitamins (Pediatrics, 2008; Frontiers in Nutrition, 2016), so all the essential nutrients in the usual amount (1 liter or ~1,000 g) of a given soy formula should meet the Recommended Dietary Allowances for infants.
Note that vitamin D3, also called cholecalciferol, added to many soy formulas, may be derived from sheep’s wool, so not vegan by certain standards (The Vegetarian Resource Group).
Vegan society and German and Swiss nutrition authorities strictly recommend exclusive breastfeeding for infants up to 6 months of age and say that a soy-based formula is only the option for infants who cannot be breastfed or cannot have cow's milk based formula due to allergy to cow's milk, lactose intolerance or galactosemia.
A mother who insists to remain vegan during breastfeeding needs to take vitamin B12 and, possibly, other supplements, as advised by a doctor, to prevent nutrient deficiencies in a baby (CDC.gov).
Some nutrition authorities believe that a vegan diet is not the most suitable option for infants:
Vegan Society: Exclusive breastfeeding is recommended for the first six months of
your baby’s life. Soya-based infant formula can be fed to vegan infants when
breastfeeding is not an option.
German Nutrition Society (DGE), 2016: DGE does not recommend a vegan diet for pregnant women, lactating
women, infants, children or adolescents. Because of their content of phyto-oestrogens and the higher level of
aluminium in comparison to infant formulas based on cows’ milk,
infants who have not been breastfed (or only partially) should only be
given soya products regularly in exceptional and justified cases (e.g.
galactosaemia) and on medical recommendation.
Federal Commission for Nutrition in Switzerland, 2018: Children and pregnant women are advised against adopting a vegan diet. If an infant cannot be breastfed, the only adequate vegan alternative
is a soy-based methionine-fortified infant formula, as recommended by
the ESPGHAN Committee on Nutrition. There are no formula options that
do not contain animal products for those infants, who are intolerant
to soy formula. A lack of data persists to know whether the nutritional requirements
are covered and whether the development of children and adolescents
fed with a vegan diet is secure.
American Academy of Pediatrics, 2008: In term infants, although isolated soy protein-based formulas may be
used to provide nutrition for normal growth and development, there are
few indications for their use in place of cow milk-based formula.
These indications include (a) for infants with galactosemia and
hereditary lactase deficiency (rare) and (b) in situations in which a
vegetarian diet is preferred...Soy protein-based formulas are not designed > for or recommended for preterm infants...The routine use of isolated soy > protein-based formula has no proven value in the prevention or management of > infantile colic or atopic disease.
Nutrition authorities who believe vegan diets can be appropriate for infants in general:
American Dietetic Association and Dietitians of Canada, 2003: Well-planned vegan and other types of vegetarian diets are appropriate
for all stages of the life cycle, including during pregnancy,
lactation, infancy, childhood, and adolescence.
Italian Society of Human Nutrition, 2017: Vegetarian diets that include a wide variety of plant foods provide
adequate nutrient intake for Italians of all ages. However, vitamin
B12 intake may be low, so vitamin-fortified foods/B12 supplements are
advised.
Are soy-based formulas safe?
Health concerns about soy-based formulas are that they can contain genetically modified soy and excessive amounts of phytoestrogens (isoflavons genistein and diadzin), aluminium and pesticides.
In general:
In conclusion, modern SIF [soy infant formulas] are evidence-based safety options to feed
children requiring them. The patterns of growth, bone health and
metabolic, reproductive, endocrine, immune and neurological functions
are similar to those observed in children fed CMF [cow's milk formula] or HM [human milk]. (The British Journal of Nutrition, 2014)
Phytoestrogens:
A global evaluation of the impact of modern SFs [soy formulas] on human development
seems to suggest that their use is not associated with relevant
abnormalities. The negative influence of isoflavones, which has been
repeatedly demonstrated in developing animals, has not been evidenced
with the same relevance in humans. (Frontiers in Nutrition, 2016)
Soy infant formulas are of minimal concern for adverse effects on
development in infants consuming SIF (National
Toxicology Program (NTP) Board of Scientific Counselors (BSC), 2010)
Aluminium:
There is evidence of both immediate and delayed toxicity in infants,
and especially preterm infants, exposed to aluminium and it is our
contention that there is still too much aluminium in infant formulas. (BMC Pediatrics, 2010)
Pesticides:
Tests in Oregon/US, 2014 showed there may be pesticides in some soy infant formulas:
Just as Oregonians are voting on whether to label genetically
engineered foods, Center for Food Safety (CFS) announced today that
genetic testing has confirmed the presence of soy that has been
genetically engineered by Monsanto for heavy pesticide exposure in
infant formula that is being sold in Portland, Oregon... With recent
published studies confirming that genetically engineered soy has
significantly higher levels of chemical herbicides than conventionally
grown soy, the test findings raise concerns about increasing infant
exposure to chemical herbicides. (Center for Food Safety, 2014)
Tests in Brasil, 2012-2017, confirmed the presence of glyphosate in some soy-based formulas:
The presence of glyphosate and AMPA residues in soy-based infant
formulas was evaluated during the years 2012-2017, totalising 105
analyses carried out on 10 commercial brands from different
batches...Among those samples that contained levels above the LOQ, the
variation of glyphosate residues was from 0.03 mg kg-1 to 1.08 mg kg-1
and for AMPA residues was from 0.02 mg kg-1 to 0.17 mg kg-1. (AMPA =
aminomethylphosphonic acid (a derivate of glyphosate); LOQ = limit of
quantification ; Food Additives & Contaminants, 2018)
In conclusion, breastfeeding is the most appropriate feeding for infants for the first 6 months of life. In this period, a vegan diet (soy formula) can be considered therapeutic nutrition for infants who cannot be breastfed and does not need to be promoted as "suitable as a mass diet."