By Lisa Rapaport
(Reuters Health) - Older adults who cut back on the amount of vegetable protein in their diets may be more likely to experience age-related health problems than their peers who increase the amount of plant protein they eat, a Spanish study suggests.
Researchers examined data on 1,951 people aged 60 and older who completed dietary surveys and questionnaires to detect four types of unhealthy aging: functional impairments; reduced vitality; mental health issues; and chronic medical problems or use of health services. Participants provided this information in three waves: from 2008-2010, in 2012 and again in 2017.
Overall, study participants got an average 12% of their calories from animal protein, including meat and dairy, and about 6% from vegetable protein, including sources such as legumes, nuts, grains, root vegetables and green plants.
Compared to people who decreased vegetable protein intake by more than 2% between the first wave and 2012, those who increased their consumption of vegetable protein by more than 2% developed fewer deficits associated with unhealthy aging during the study.
"There is growing evidence supporting a beneficial effect of higher intakes of total protein on muscle mass and strength, physical functioning, hip fracture and frailty," said Esther Lopez-Garcia, senior author of the study and a researcher at Universidad Autonoma de Madrid.
The study offers fresh evidence that the type of protein matters, too.
"If you eat more plant-based sources of proteins, you are also getting a lot of micronutrients and healthy fats, and fiber that help improve your health," Lopez-Garcia said by email. "On the other hand, if you consume animal sources of proteins full of saturated and trans fats, and other substances added during the processing (mostly salt and nitrites), you are getting all the detrimental effects of these substances."
At the start of the study, people got about 5.2% of their calories from meat, 3.3% from dairy, 3% from refined grains and 2.8% from fish. Participants got less than 1% of their calories from legumes, eggs, fruit, vegetables, whole grains, tubers or nuts.
Changes in animal protein consumption during the study didn't appear to influence the potential for people to show more signs of unhealthy aging by the end of the study, researchers report in the American Journal of Medicine.
But adding more vegetable protein was linked to fewer deficits by the end of the study.
"Since substitution of plant protein for animal protein has been associated with lower risk of type 2 diabetes, and all-cause and cardiovascular mortality, it is relevant to understand which source of protein may be more beneficial for a healthy aging," Lopez-Garcia said.
The study wasn't designed to prove whether or how eating more plant proteins may stall unhealthy aging. It also wasn't able to determine which types of vegetable proteins might be best from an aging perspective.
One limitation of the study is that many participants dropped out before the end. It's also possible that results from this study of older adults might not apply to younger people.
"While high protein intake might not be preferable for middle-aged adults, it has been shown that high level of protein intake is protective among those aged 66 years and older," said Yian Gu, a neurology researcher at Columbia University in New York City who wasn't involved in the study.
"It is important to interpret scientific findings on protein intake based on age groups, " Gu said by email. "The current study results are consistent with findings in the elderlies, with further information from innovative analyses of animal and plant based proteins separately."
The sources of protein also matter, Lopez-Garcia said.
Good sources of plant-based protein include lentils, beans, peas, soybeans, nuts, seeds, and whole grains like teff, wheat, quinoa, rice, oats, and buckwheat, Lopez Garcia advised.
Healthy options for animal protein can include poultry, seafood, eggs, as well as dairy in moderation, Lopez-Garcia advised. Protein sources to reduce or limit include red and processed meat.
SOURCE: https://bit.ly/2HjwkKE American Journal of Medicine, online July 31, 2019.