Helen Rasmussen has been with the federal government’s Human Nutrition Research Center on Aging since it began in 1982.

Twenty years later, she can say with certainty there are distinct lessons to be learned about nutrition as adults age, not the least of which is accepting new ideas.

“People gravitate to what they know,” said Rasmussen, a research dietitian at the center, at Tufts University in Boston. “It is an extra step to eat fresh fruits and vegetables, eat more whole foods overall. But it is worth the effort.”

Nutritional needs do evolve as adults age, and sometimes eating challenges develop. Fortunately, the research from Tufts and other respected sources provides a specific set of guidelines that didn’t exist when Rasmussen and her colleagues began at the center.

Rasmussen was part of a three-person team that created a modified food-guide pyramid for “70-plus adults” in 1999. She worked with Robert Russell, associate director of the U.S. Department of Agriculture’s center at Tufts, and Alice Lichtenstein, a Tufts heart disease researcher.

The eating guide consume liberally from the base, sparingly from the top addresses a growing segment of U.S. adults, largely ignored in previous research.

“The comparison or control groups were always people in their 20s and 30s,” Rasmussen said. “Over the last two decades, we have gathered more data about people 70 and older.”

For starters, the 70-plus food pyramid’s foundation contains eight glasses of water, to emphasize the importance of hydration as adults age.

“Believe it or not, adding water (to the pyramid) caused the most controversy among some doctors and consumers,” Rasmussen said. “They worried that some folks would be drinking too much water and not (eating) enough food, or people would be experiencing incontinence.

“We find many older individuals start drinking more water and they don’t have as many headaches, dizzy spells or constipation,” often caused by medications, she said.

The USDA-Tufts pyramid is narrower than the USDA’s original pyramid for all adults the very one under fire from some researchers for advocating too many simple or processed carbohydrates to emphasize that older adults tend to eat less.

Consequently, some older people are susceptible to what’s called “the dwindles,” or compromised health from malnutrition.

The Tufts 70-plus pyramid cleverly addresses both concerns by focusing on nutrient density.