All research suggests either inconclusive evidence OR that vegan/plant-based infants and/or those born from vegan/plant-based mothers, have the identical recommendations for vitamin D supplementation to all other infants.
From Dr Neal Barnard and PCRM:
“Breast-fed infants also need about two hours a week of sun exposure to make vitamin - a great motivator for Mom to get back into a walking routine. Some infants, especially those who are dark-skinned or who live in cloudy climates, may not make adequate amounts of vitamin D. In these cases, vitamin D supplements may be necessary.”
See the infant section here: http://support.pcrm.org/site/DocServer/Vegetarian_Start_Kit.pdf?docID=261
I would check your own vitamin D status throughout pregnancy and breastfeeding and try and keep yours at least in the middle of the normal range (in range of 75 ng/mL is considered optimal in pregnancy).
However, the American Academy of Pediatrics recommends:
“To avoid developing a vitamin D deficiency, the American Academy of Pediatrics recommends breastfed and partially breastfed infants be supplemented with 400 IU per day of vitamin D beginning in the first few days of life. Vitamin D supplementation should be continued unless the infant is weaned to at least 1 liter per day (about 1 quart per day) of vitamin D–fortified formula. Any infant who receives <1 liter or 1 quart of formula per day needs an alternative way to get 400 IU/day of vitamin D, such as through vitamin D supplementation.”
They also recommend minimizing sun exposure in babies under 6 months
Per the National Institute of Health:
“Vitamin D requirements cannot ordinarily be met by human milk alone, which provides <25 IU/L to 78 IU/L. (The vitamin D content of human milk is related to the mother’s vitamin D status, so mothers who supplement with high doses of vitamin D may have correspondingly high levels of this nutrient in their milk).”
“In supplements and fortified foods, vitamin D is available in two forms, D2 (ergocalciferol) and D3 (cholecalciferol) that differ chemically only in their side-chain structure. Vitamin D2 is manufactured by the UV irradiation of ergosterol in yeast, and vitamin D3 is manufactured by the irradiation of 7-dehydrocholesterol from lanolin and the chemical conversion of cholesterol. The two forms have traditionally been regarded as equivalent based on their ability to cure rickets and, indeed, most steps involved in the metabolism and actions of vitamin D2 and vitamin D3 are identical. Both forms (as well as vitamin D in foods and from cutaneous synthesis) effectively raise serum 25(OH)D levels. Firm conclusions about any different effects of these two forms of vitamin D cannot be drawn. However, it appears that at nutritional doses vitamins D2 and D3 are equivalent, but at high doses vitamin D2 is less potent.”
As I strongly support breastfeeding and breast milk as much as possible, it is most likely the safer option to consider a vitamin D supplement. It is difficult to count sun exposure or measure vitamin D in an infant, and rickets can be a real risk. So from a vegan or plant-based option, a vegan D3 form, OR D2 would be the choice that is not animal derived. I have zero affiliations to any supplement companies, and in reality I tend to prescribe whichever brand/formulation is covered by insurance for my patients, unless the ability to pay out of pocket, which is extremely rare.
I personally do prescribe ‘D Vi Sol’ in clinic as that is what is covered by my patients insurance (would have to contact them to confirm, but I don’t believe this is plant-based/vegan), but if the patient can pay out of pocket (rare), then whilst I have no particular affiliation to any product, I do suggest these as a vegan D3 option (https://www.nordicnaturals.com/en/products/vitamin-d3-vegan/156/?ProdID=1673), and I usually look at this range, as they are stocked at True North (https://www.pureformulas.com/vitamin-d3-liquid-225ml-by-pure-encapsulations.html), and I have have heard this is a good brand (https://nz.iherb.com/pr/Garden-of-Life-MyKind-Organics-Vegan-D3-Vanilla-Spray-1-000-IU-2-oz-58-ml/58127), obviously adjust dose for infants!!! Most adult forms provide 1,000 IU (check the label!) and so an infant could take just under 1/2 this dose. Liquid forms only!
Some books I’d recommend reading:
And this article:
Conclusion: The risk of appropriate vitamin D supplementation for infants is considered low, with benefits outweighing risks at this stage in research (2018), and thus almost all pediatricians and medical professionals recommend supplementation for infants in a reliable way, usually a vitamin D supplement, or supplemented formula providing 400 IU daily from the first few days of life.