One of the most underappreciated areas of health care is also instrumental for human development. Baby formula isn't exactly a market that many investors would consider a growth industry -- but that could be about to change.

The United Nations estimates that the world's population could hit 11 billion by 2100, up from a current 7 billion. That's many more mouths to feed. One of the biggest markets for baby formula is China: With 1.3 billion people and a birth rate of 1.2%, that's 15.6 million babies a year.

The baby formula market is huge and growing -- so what's the best way to invest in it?

Mead Johnson Nutrition (NYSE: MJN) is the only pure-play pediatric nutrition company, and one that has a strong presence in China, to boot.

Mead covers all stages of pediatric development, from newborns to 5-year-olds. It generates over 75% of its revenue from outside the U.S., most notably from China, which accounts for over 25% of its revenue. Infant formula makes up around 60% of revenues, with children's nutrition accounting for the other 40%. Mead's major products are sold under the Enfa brand.

Mead was spun off from Bristol-Myers Squibb (NYSE: BMY) in 2009. It hasn't been easy for Mead investors over the past couple of years, but things may be about to change: A cycling out of bad news could lead to a relief rally, while a rising middle class in China is driving long-term growth.

MJN has been on a roller-coaster ride over the past few years, with the latest pressure coming from a U.S. inquiry into Mead's China business.