Question

about 90 percent of the people in the united states have enough to eat. why do you think vitamin supplements and vitamin-fortified foods are so popular?

Answer 1

I'm going to phrase it this way:

Even though 90 percent of people in the US have enough to eat, that does not mean that they are getting enough nutrients, vitamins, and minerals. This is why vitamin supplements are popular; because people can eat the food they like and if those foods do not have enough vitamins or minerals, they can take supplements to make up for the missing minerals and vitamins.