(CNN)If you're wondering how your child might fare on a vegetarian diet, a new study offers some factors to consider. Children eating a vegetarian diet and children who ate meat were similar in terms of growth, height and nutritional measures, but vegetarian children had higher odds of being underweight, according to a study published Monday in the journal Pediatrics.
Vegetarian and meat-eating children have similar growth and nutrition but not weight, study finds
"Over the last 20 years we have seen growing popularity of plant-based diets and a changing food environment with more access to plant-based alternatives, however we have not seen the research into the nutritional outcomes of children following vegetarian diets in Canada," said Dr. Jonathon Maguire, the study's lead author and a pediatrician at St. Michael's Hospital of Unity Health Toronto, in a news release.
The authors used data from nearly 9,000 children who were between 6 months and 8 years old and had participated in the TARGet Kids! Cohort between 2008 and 2019. TARGet Kids! is a primary care practice-based research network and cohort study in Toronto. Details on the diets these children ate were according to their parents, who answered whether their children were vegetarian (which included vegans) or non-vegetarian.
During each health supervision visit over the years, research assistants for TARGet Kids! measured participants' body-mass index, weight, height, cholesterol levels, triglycerides, vitamin D levels and serum ferritin levels. Ferritin is a cell protein that stores iron and enables the body to use iron when needed, so a ferritin test indirectly measures blood iron levels, according to Mount Sinai Health System.
At the beginning of the study, 248 children (including 25 vegans) were vegetarian, and 338 more children had become vegetarian sometime later during the study. Children were followed up with for nearly three years on average. There weren't any significant differences between vegetarian and non-vegetarian children regarding standard BMI, height, serum ferritin levels and vitamin D levels.
However, vegetarian children were nearly twice as likely to be underweight than non-vegetarian children.
Being underweight can be a sign of malnutrition and can indicate that one's diet isn't enough to support appropriate growth, according to the study news release. Specific details about dietary intake or quality, and physical activity, weren't available to the authors -- which could influence growth and nutrition.
Studies with longer follow-up periods and information on motivations for eating vegetarian -- such as socioeconomic status -- would also be helpful for understanding links between children's development and vegetarianism, the authors said.
The findings highlight "the need for careful dietary planning for children with underweight when considering vegetarian diets," Maguire said.
"The kids that were underweight both in vegetarian and non-vegetarian (groups) were similar and were younger in age and of Asian descent," said Amy Kimberlain, a registered dietitian nutritionist and Academy of Nutrition and Dietetics spokesperson. Kimberlain wasn't involved in the study.
"Ethnicity could certainly have played a part in the weight finding," said Dr. Maya Adam, a clinical assistant professor in the pediatrics department at Stanford School of Medicine, who wasn't involved in the study.
The Asian children "were likely of East Indian descent, because this subset of the 'Asian' demographic box (which I also end up choosing as a person of Indian heritage) is much more likely to practice vegetarianism," Adam said via email. "In India, children's growth charts differ from US growth charts. An average 5-year-old girl in India is expected to weigh 17 kilograms and stand about 108 centimeters tall. In the US, an average 5-year-old girl of the same height is expected to weigh 18 kg."
Regardless, "it's important for kids to be monitored for their growth, regardless of their diet," Kimberlain said. "A vegetarian diet can be a healthy choice for all kids. The key is making sure that it is well planned out. With the help of a registered dietitian nutritionist, kids' growth can be monitored as well as their nutrients needs to ensure they are being adequately consumed."
If you and your children are experimenting with eating vegetarian or vegan, having alternative options is important "in case one day they like something and the next day they don't," Kimberlain said.
When feeding babies and children a vegetarian diet, parents should ensure regular consumption of eggs, dairy products, soy products and nuts or seeds, in addition to vegetables, fruits, beans and lentils, grains and oils, the current US Dietary Guidelines for Americans recommend.
Be extra careful to include foods rich in iron and vitamin B12, since plant-based sources of those nutrients are less bioavailable compared with animal foods. Different beans, dark leafy greens and sweet potatoes are iron-rich. And nutritional yeast, dairy products and cereals are some vitamin B12 sources. The guidelines have a graphic table on appropriate servings of each food group per day.
Canadian guidelines say a vegetarian diet can be adequate for children when milk and eggs are included.