PHILADELPHIA—Severe malnourishment of mothers and their children can cause lifelong growth deficiencies and health problems, warned scientists at the American Society of Tropical Medicine and Hygiene annual meeting in Philadelphia on Wednesday. But a lack of nutritious food isn’t the only culprit.

Stunting, severe wasting and poor growth while in utero are together responsible for some 2.2 million child deaths worldwide, said Stephanie A. Richard, a researcher at the Johns Hopkins Bloomberg School of Public Health. Additionally, some 178 million kids younger than five in developing countries have stunted growth, said Richard, which has been shown to lead to long-term disability and decreased earning ability later in life.

But simply providing an adequate food supply likely would not be enough to keep these kids growing well. Researchers said that common childhood incidents in the developing world, such as acute diarrhea and infection with a parasite, compound the problem.

One new study of 545 mother-infant pairs in rural Kenya found that about a third of kids had at least one parasitic infection before the age of three. "Paracitism, as you would expect, has an effect on child growth," Desiree LeBeaud, of Children's Hospital Oakland Research Institute, said Wednesday. The infections also affected weight and head circumference, she noted.

And as Peter Hotez, of Baylor College of Medicine, pointed out, not all of the stunting is physical—parasitic infections affect the mind as well. Previous studies have shown that children who have had more hookworms end up with lower IQs.

Even something as simple and common as an episode of acute diarrhea can delay a child's growth. When compared with other children under the age of five who had not had acute diarrhea, those who did showed a significant lag in their height-and-weight scores three months later, according to a recent case-control study from Gambia. "Even after a single episode of diarrhea, [children] are less likely to catch up to their peers," said Debasish Saha, an epidemiologist at the Center for International Health at the University of Otago in New Zealand. Children between the ages of two and five years seemed to suffer the greatest setback by this illness.

Both diarrhea and parasites can lead to malnutrition—and vice versa—so the path to well-nourished, healthy children is not quite as simple as making sure that their families have enough food. Communities require improved sanitation and water supplies as well as better public health education and health care availability. Investment in these changes in the near term should pay off later in improved earning power and an easier ascent out of poverty, which in turn should also lead to better health for the generations to come.