Ms. Sheth said it was important for caretakers to make sure that vegan babies, once weaned, got enough of vitamins D and B12, calcium, iron, zinc and heart-healthy fats. The same is true for all babies, but these nutrients are worth paying special attention to for vegans and vegetarians.

She added that vitamin B12, in particular, comes predominantly from animal products.

“So if you don’t have B12 coming from animal products, you want to make sure you’re supplementing it,” she said. Many fortified foods for infants include B12, along with other essential nutrients, like iron and calcium.

Ms. Sheth recommended introducing vegan children to a range of foods, starting with breast milk or formula and perhaps mixing that with fortified cereals before moving on to soft options, like puréed fruits, bean spreads, mashed avocados and tofu, then eventually adding more solid options, like whole wheat breads and cooked and dried fruits.

According to a report published by Global Data, 6 percent of American consumers claimed to be vegan in 2017, up from 1 percent in 2014.

Ms. Sheth and Ms. Mangels said they had noticed a growing interest in diets that included more plants and less meat. Some children are even making the decision to eat this way on their own.

“Many kids do thrive on vegan diets,” Ms. Mangels said, adding that parents who were considering raising their children that way should work with health care providers to come up with a plan.

“Many dietitians know about vegan diets and are open to it,” she said. “Just seek out good quality information so that you can feel like what you’re doing is healthy.”