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 While previous research has linked low-carbohydrate diets to better
success with short-term weight loss and improvements in risk factors
for premature death like diabetes, less is known about the long-term
outcomes of cutting carbs, or what types of foods people should eat
instead for optimal health.
For the current study, researchers followed more than 15,000 adults
ages 45 to 65 for about 25 years. During this period, 6,283 died.
Participants who got 50 to 55 percent of their calories from
carbohydrates had a lower risk of death from all causes during the
study period than people who had much lower or higher carbohydrate
intake, researchers report in The Lancet Public Health.
With lower carb intake, the types of foods people ate instead of
carbs were associated with very different types of outcomes.
"Low carbohydrate dietary patterns that replaced carbohydrate with
animal-derived protein or fat were associated with greater mortality
risk, whereas this association was reversed when energy from
carbohydrate was replaced with plant-derived protein or fat," said
lead study author Dr. Sara Seidelmann of Brigham and Women's
Hospital and Harvard Medical School in Boston.
"The key message from this study is that it is not enough to focus
on cutting carbohydrates alone, but instead to focus on the types of
food replacing them," Seidelmann said by email.
The study wasn't designed to prove whether or how eating fewer
carbohydrates or more vegetables might directly impact longevity.
But it's possible plant-based proteins help people live longer by
reducing inflammation and so-called oxidative stress, Seidelmann
said. As the body uses oxygen, it produces by-products called free
radicals that can damage cells and tissues. The damage by oxygen
free radicals is known as oxidative stress.
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At the same-time, it's possible the reverse may be true for meats,
and especially for processed meats. Animal proteins and fats might
have negative health effects because they cause inflammation and
oxidative stress, Seidelmann said.
Researchers estimated that from age 50, the average life expectancy
was an additional 33 years for people with moderate carbohydrate
intake, meaning carbs accounted for 50 to 55 percent of their
calories.
High carbohydrate intake - representing more than 70 percent of
calories - was associated with average life expectancy of about 32
years. Low carbohydrate intake - representing less than 40 percent
of calories - was associated with life expectancy of 29 years.
One limitation of the study is that researchers only assessed eating
habits twice, at the start of the study and again six years later,
and participants' diets may have shifted over time.
Even so, the results add to a large and growing body of evidence
suggesting that a balanced diet is best, said Andrew Mente, coauthor
of an accompanying editorial and a researcher at McMaster University
in Hamilton, Ontario.
"The new study shows that a moderate amount of carbohydrates is
optimal, while too low or too high was related to mortality," Mente
said by email.
"This is not really surprising given that most nutrients or foods
have a sweet spot," Mente added. "A moderate amount of carbohydrates
generally translates into a balanced diet that includes fruit,
vegetables, nuts, legumes, fish, dairy and unprocessed meats, all in
moderate amounts."
SOURCE: https://bit.ly/2OVROi8 and https://bit.ly/2MHENwa The Lancet
Public Health, online August 16, 2018.
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