(CNN) -- Niki Gianni was 11 or 12 when she found a video on YouTube called "Meet Your Meat." Saddened and disgusted by the footage from a slaughterhouse, the Chicago girl announced she was no longer going to eat meat. Her parents were less than thrilled. 

"When she first said she wanted to be a vegetarian, we were just looking at each other and we said, 'We can't be switching meals for you. You are not going to get your protein.' We were not educated in the health benefits," said Gianni's mother, Julie Gianni. 

While many parents worry whether their vegetarian or vegan children will receive adequate nutrition for their growing bodies, the American Dietetic Association says such diets, as long as they are well-planned, are appropriate for all phases of life, including childhood and adolescence. "Appropriately planned" vegetarian or vegan diets are healthful, nutritionally adequate and may provide health benefits in the prevention and treatment of certain diseases, the dietetic association says. 

"You can really feel the difference when you are eating something from the ground and something from a factory," said Niki Gianni, an animal activist who became a vegan shortly after embracing the vegetarian lifestyle. 

10-year-old: Why I became vegetarian in first grade 

Now an 18-year-old college freshman, Niki Gianni said her eating habits expanded her palate and turned her away from processed foods. Her food choices also influenced her family: Her mother is now a vegan and her father and sister are vegetarians. 

The number of vegetarians in the United States is expected to increase over the next decade, according to the dietetic association. A vegetarian diet is associated with a lower risk of death from ischemic heart disease, and vegetarians also appear to have lower overall cancer rates, lower blood pressure and lower rates of hypertension than nonvegetarians. 
Is she in school?
ow an 18-year-old college freshman, Nik