Is a vegan diet nutritionally complete and suitable for babies?

Question

We have a related question of a more general nature, but there has been a lot of talk in Italy on whether to disallow or otherwise restrict vegan diets to people who are below a certain age.

This has been prompted by multiple cases of babies and toddlers risking death due to malnutrition after their parents adopted a vegan diet for them.

On one side, there are many people who say it's essentially safe or healthy; on the other people that say that a vegan diet for babies and infants requires constant supervision of a pediatrician.

What is the current scientific consensus on the risks and benefits of administering a vegan diet to the very young?

An example of the claim that it is harmful from the links:

Ed è a causa di un’alimentazione sbilanciata che in questi giorni è ricoverata all’ospedale Gaslini di Genova la piccola Chiara di nemmeno 3 anni, giunta in uno stato di salute talmente grave da richiedere subito la rianimazione.

I medici hanno collegato tutto questo alla dieta vegana che la bambina seguiva dalla nascita.

Baby Chiara, not even 3 years old, has been hospitalized for a few days because of an unbalanced diet. She was in such a bad state to require emergency reanimation. The physicians connected all this to the vegan diet that the child followed since birth

An example of the claim that it is healthy:

It is the position of the American Dietetic Association that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases

Answer 1

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).

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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)

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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."

Answer 2

If you're talking about small babies, here's a review of soy formulas: https://www.ncbi.nlm.nih.gov/pubmed/24507712 (emphasis mine)

The present review includes cross-sectional, case-control, cohort studies or clinical trials that were carried out in children fed SIF [soya-based infant formulas] compared with those fed other types of infant formulas and that measured safety. The databases that were searched included PubMed (1909 to July 2013), Embase (1988 to May 2013), LILACS (1990 to May 2011), ARTEMISA (13th edition, December 2012), Cochrane controlled trials register, Bandolier and DARE using the Cochrane methodology. Wherever possible, a meta-analysis was carried out. We found that the anthropometric patterns of children fed SIF were similar to those of children fed CMF [cows' milk-based formulas] or HM [human milk]. Despite the high levels of phytates and aluminium in SIF, Hb, serum protein, Zn and Ca concentrations and bone mineral content were found to be similar to those of children fed CMF or HM. We also found the levels of genistein and daidzein to be higher in children fed SIF; however, we did not find strong evidence of a negative effect on reproductive and endocrine functions. Immune measurements and neurocognitive parameters were similar in all the feeding groups. In conclusion, modern SIF 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 or HM.

That would present soy formulas as a suitable alternative to breast milk for babies if breast milk is unavailable for whatever reason. Just please don't make it yourself at home, or you and your baby may end up in a newspaper. If you search hard enough, there are infant formulas that are vegan, just use those if you must.

For older babies, many doctors and medical institutions give advice about what would a healthy vegan diet look like. Take for example NHS: https://www.nhs.uk/conditions/pregnancy-and-baby/vegetarian-vegan-children/

Babies and young children on a vegetarian or vegan diet can get the energy and most of the nutrients they need to grow and develop from a well-planned varied and balanced diet. But they might need specific supplements (such as vitamin B12) in addition to the usual vitamin supplements recommended for all babies. Talk to a health professional for advice.

Based on that, I see no reason why an appropriately planned vegan diet would not be nutritionally complete or suitable for babies.

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Edit: when initially writing this post, included NHS's advice as scientific evidence because I thought there wouldn't be any proper studies on vegan babies. In the meantime I have found this study, which would supersede the NHS paper on weight of evidence. The NHS paper is still relevant thought, as it details some risks and benefits of administering a vegan diet that are not explicitly covered in the next study. The study: https://academic.oup.com/ajcn/article-abstract/48/3/822/4716540

The growth and development of children born of vegan mothers and reared on a vegan diet has been studied longitudinally: All of the children were breast-fed for the first 6 mo of life and in most cases well into the second year of life. The majority of children grew and developed normally but they did tend to be smaller in stature and lighter in weight than standards for the general population. Energy, calcium, and vitamin D intakes were usually below the recommended amounts. Their diets, however, were generally adequate but a few children had low intakes of riboflavin and vitamin B-12. Most parents were aware of the need to supplement the diet with vitamin B-12. It is concluded that provided sufficient care is taken, a vegan diet can support normal growth and development.