Source: MEATINGPLACE, 3/5/14

A new study links a high-protein diet to increased cancer, diabetes and mortality in middle-aged people but found higher protein consumption may be protective for older adults.

Those aged 50 to 65 who reported high protein intake from animal sources, including meat, milk and cheese, had a 75 percent increase in overall mortality and a four-fold increase in cancer death risk in an 18-year follow-up period.

High protein intake was associated with reduced cancer and overall mortality in respondents over 65, but it was also linked to a five-fold increase in diabetes mortality across all ages.

The findings were published in the journal Cell Metabolism and funded by the National Institutes of Health’s National Institute of Aging.    

“The research shows that a low-protein diet in middle age is useful for preventing cancer and overall mortality, through a process that involves regulating IGF-I and possibly insulin levels,” said study co-author Eileen Crimmins, a professor of gerontology at University of Southern California. “However, we also propose that at older ages, it may be important to avoid a low-protein diet to allow the maintenance of healthy weight and protection from frailty.”

The American Meat Institute cautioned that consumers should exercise skepticism, saying the study stands in contrast to evidence in other journals about the important role of protein in the diet throughout the lifespan and conflicts with federal recommendations.

In the study, a high-protein diet was defined as deriving at least 20 percent of calories from both plant- and animal-based protein. Across the more than 6,300 people over the age of 50 in the study, the average protein intake was about 16 percent of total daily calories, with about two-thirds from animal protein.

The researchers found that plant-based proteins such as those from beans did not have the same effect on mortality as animal proteins. Rates of cancer and death also were unaffected by controlling for carbohydrate or fat consumption.

“The majority of Americans are eating about twice as much proteins as they should, and it seems that the best change would be to lower the daily intake of all proteins but especially animal-derived proteins,” said co-author Valter Longo, professor of bio-gerontology at USC.  “But don’t get extreme in cutting out protein; you can go from protected to malnourished very quickly.”
AMI, however, said the federal Dietary Guidelines Technical Report in 2010 showed the protein group is the only food group consumed at the proper levels.

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