The World Health Organization advocates zinc supplementation for severe malnutrition and diarrhea – nearly two billion people in the developing world are deficient in zinc, groups at risk include children in developing countries and elderly with chronic illnesses; in children, it causes an increase in infection and diarrhea and contributes to the death of about 800,000 children worldwide per year.

The U.S. Institute of Medicine (IOM) updated Recommended Dietary Allowances (RDAs) for zinc in 2001 – RDA for pregnancy is 11 mg/day, RDA for lactation is 12 mg/day, for infants up to 12 months the RDA is 3 mg/day and for children ages 1–13 years the RDA increases with age from 3 to 8 mg/day; RDA for adults 19+ years is 11 mg a day for men and 8 mg for women. 

The Daily Value of zinc is 36-45% in 100 gram amount of air-popped popcorn (no salt or other additives).

To make popcorn the Zea mays everta variety of maize is used, this particular variety of corn kernel has the ability to pop – Popcorns for Snack

A popcorn kernel’s strong hull contains the seed’s hard, starchy shell endosperm with 14–20% moisture, which turns to steam as the kernel is heated. Pressure from the steam continues to build until the hull ruptures, allowing the kernel to forcefully expand, to 20 to 50 times its original volume, and then cool.

Popcorn as a breakfast cereal was consumed by Americans in the 1800s and generally consisted of popcorn with milk and a sweetener.

Popcorn is a popular snack food at sporting events and in movie theaters, where it has been served since the 1930s. Cinemas have come under fire due to their high markup on popcorn; Stuart Hanson, a film historian at De Montfort University in Leicester, once said, “One of the great jokes in the industry is that popcorn is second only to cocaine or heroin in terms of profit.”

Popcorn is included on the list of foods that the American Academy of Pediatrics recommends not serving to children under four, because of the risk of choking.

(Ref. Wikipedia & hsph.harvard.edu)