When I first started traveling to Africa, I would often meet children in the villages I was visiting and try to guess their ages. I was shocked to find out how often I guessed wrong. Kids I thought were 7 or 8 years old based on how tall they were—would tell me that they were actually 12 or 13 years old.

What I was witnessing was the terrible impact of malnutrition in Africa. These children were suffering from a condition known as stunting. They were not starving, but they were not getting enough to eat, leaving them years behind in their development—and it was hard to see how they could ever catch up.

Stunting not only affects a child’s height. It also has an impact on brain development. Stunted children are more likely to fall behind at school, miss key milestones in reading and math, and go on to live in poverty. When stunted children don’t reach their potential, neither do their countries. Malnutrition saps a country’s strength, lowering productivity and keeping the entire nation trapped in poverty.

Worldwide, one in four children is stunted. Three-quarters of them live in South Asia and sub-Saharan Africa. However, while stunting has declined by more than a third in South Asia since 1990, in sub-Saharan Africa, the number of stunted children is still on the rise, up 12 million since 1990 to 56 million. Forty percent of all children in sub-Saharan Africa are stunted.

I run into a lot of people from rich countries who still think of Africa as a continent of starvation. The fact is, that’s an outdated picture (to the extent that it was ever accurate at all). Thanks to economic growth and smart policies, the extreme hunger and starvation that once defined the continent are now rare. As I saw when I was back in Africa last month with best-selling author John Green, today the issue isn’t quantity of food as much as it is quality—whether kids are getting enough protein and other nutrients to fully develop.

As Melinda and I have grown aware of the scale of this challenge, we’ve made improving nutrition a bigger priority for our foundation. One thing we’ve quickly come to appreciate is the problem’s complexity.  There’s no vaccine to prevent stunting. Proper nutrition involves eating enough food, and the right kinds, every day of your life. While the global health community is still working to understand all of the causes and solutions to malnutrition, we do know a lot about how to ensure children get the nutrition they need for a healthy start to life.

We know that getting children the right nutrition in the first 1000 days—from the start of a woman’s pregnancy until her child’s 2nd birthday – is the best down payment on their future, giving them the opportunity to grow and develop physically and mentally. We also know that exclusive breastfeeding in the first six months of a child’s life is the single most effective intervention to help the brain develop and protect against life-threatening diseases. That’s why we continue to research the best ways to address cultural beliefs and other barriers that have kept almost half of all women from using optimal breastfeeding practices.

We know kids have a hard time getting the nutrients they need when fruits, meats, and vegetables are in short supply—so fortifying staple foods like cooking oil, flour, and salt with essential vitamins and minerals can fill the gap. We’re also beginning to develop new crops that are more-nutritious--including a sweet potato that’s enriched with vitamin A—and also produce a higher yield. Not only does this help smallholder farmers earn more income that can be used to diversify their family’s diet, it also puts more nutritious food directly on their table.

Providing better health care can make a difference too. Children who receive the rotavirus vaccine, for example, have fewer bouts of diarrhea, which can drain kids of vital nutrients and make them more susceptible to infection. Likewise, clean water and sanitation play a role in improving nutrition by reducing illness and disease.

We have many great interventions on our side, but with so many factors at play it can be difficult to measure which interventions have the most impact on improving nutrition and why. If I could have one wish, I would want the world to have a better understanding of malnutrition and how to solve it.

We have much more research to do in this area and we will continue to make progress. But what’s not in doubt is the importance of giving all children the nutrition they need for a healthy start to life. Their future depends on it. So does Africa’s.