Dodie Captiva, 84, says as she's gotten older, her appetite has waned. "Then I ask myself, what have I been doing?, and I take out my whip and say, 'you've got to eat,'" she said.

So to help older American's make every calorie count, researchers at Tufts University have modified the current U.S. Food Guide pyramid for people over 70 years old.

"The differences really have to do with making sure within each category, you pick nutrient-dense foods," said Tufts registered dietician Alice Litchtenstein.

Tuft's pyramid also suggests dietary supplements calcium, vitamins D and B-12. Recently, the calcium recommendation for older women nearly doubled and the suggested vitamin D dose tripled.

"An older person would have to drink a quart and a half of milk in order to get that much vitamin D -- that's totally unrealistic," said Tufts gastroenterologist Dr. Robert Russell. "So a vitamin supplement is really the only way to go."

It's estimated as many as a third of older Americans can't get enough vitamin B-12 either. A deficincy in B-12 can lead to falls and dementia.

"We recommend elderly people ensure they get enough B-12 either by eating fortified cereals with B-12 or actually taking a supplement that contains B-12," Russell said.

Researchers stress everyone should get nutrients from foods first, and some are more packed with vitamins and minerals than others.