Research from Harvard reports propionate, a widely used
ingredient that helps prevent mould from forming on foods, may pose
an increased risk for obesity and diabetes.
Calcium propionate is found in some baked goods, dairy products,
processed meats, vegetable products, and egg and fat-based
Consumption of propionate, also widely used in animal feeds and
artificial flavourings, appears to increase levels of several
hormones that are associated with risk of obesity and diabetes,
according to new research led by the Harvard TH Chan School of
Public Health in collaboration with researchers from Brigham and
Women's Hospital and Sheba Medical Centre in Israel.
The study, which combined data from a randomized placebo trial
in humans and mouse studies, indicated that propionate can trigger
a cascade of metabolic events that leads to insulin resistance and
hyperinsulinemia, a condition marked by excessive levels of
The findings also showed that in mice, chronic exposure to
propionate resulted in weight gain and insulin resistance.
"Understanding how ingredients in food affect the body's
metabolism at the molecular and cellular levels could help us
develop simple but effective measures to tackle the dual epidemics
of obesity and diabetes," said Gökhan Hotamışlıgil, James Stevens
Simmons Professor of Genetics and Metabolism and director of the
Sabri Ülker Center for Nutrient, Genetic and Metabolic Research at
Harvard Chan School.
More than 400 million people worldwide live with diabetes, and
the rate of incidence is projected to increase 40 percent by
The surging number of diabetes cases, as well as obesity, in the
last 50 years indicate that environmental and dietary factors must
be influencing the growth of this epidemic.
Researchers have suggested that dietary components including
ingredients used for preparing or preserving food may be a
contributing factor, but there is little research evaluating these
For this study, the researchers focused on propionate, a
naturally occurring short-chain fatty acid that helps prevent mould
from forming on foods.
They first administered it to mice and found that it rapidly
activated the sympathetic nervous system, which led to a surge in
hormones, including glucagon, norepinephrine, and a newly
discovered gluconeogenic hormone called fatty acid-binding protein
This in turn led the mice to produce more glucose from their
liver cells, leading to hyperglycaemia (high glucose levels), a
defining trait of diabetes.
Moreover, the researchers found that chronic treatment of mice
with a dose of propionate equivalent to the amount typically
consumed by humans led to significant weight gain in the mice, as
well as insulin resistance.
To determine how the findings in mice may translate to humans,
the researchers established a double-blinded, placebo-controlled
study that included 14 healthy participants.
The participants were randomized into two groups: One group
received a meal that contained one gram of propionate as an
additive and the other was given a meal that contained a
Blood samples were collected before the meal, within 15 minutes
of eating, and every 30 minutes thereafter for four hours.
The researchers found that people who consumed the meal
containing propionate had significant increases in norepinephrine
as well as increases in glucagon and FABP4 soon after eating.
The findings indicate that propionate may act as a "metabolic
disruptor" that potentially increases the risk for diabetes and
obesity in humans.
The researchers noted that while the US Food and Drug
Administration generally recognizes propionate as safe, these new
findings warrant further investigation into propionate and
potential alternatives that could be used in food preparation.
"The dramatic increase in the incidence of obesity and diabetes
over the past 50 years suggests the involvement of contributing
environmental and dietary factors," said Amir Tirosh, associate
professor of medicine at Tel Aviv University's Sackler School of
Medicine, director of the Division of Endocrinology at Sheba
Medical Center, and research fellow at Harvard Chan School.
"One such factor that warrants attention is the ingredients in
common foods. We are exposed to hundreds of these chemicals on a
daily basis, and most have not been tested in detail for their
potential long-term metabolic effects," he said.