The 37-year-old has tried to bring attention to the millions of children suffering with stunted growth and development due to malnutrition in a host of poor countries.
"Stunting is what happens when a child doesn't get the right nutrients in their first 1,000 days of life," said Beckham.
"The damage to a child's brain and body is permanent. They will never learn as much as they could if they had received the right food from the start. It can mean up to three years' loss of schooling."
The former England captain is one of 60 UNICEF ambassadors.