Protein, carbs, and fats may trigger different insulin responses in people.
- Carbohydrate intake has long been known to
affect blood sugar levels, resulting in insulin release by pancreatic
cells more than other nutrients.
- Novel laboratory research now suggests that
individuals might actually exhibit unique insulin responses to different
nutrients, with some showing larger reactions to proteins or fats.
- It’s unclear if the findings translate to
living humans, but experts are optimistic that further clinical research
will enhance personalized nutrition strategies for managing blood sugar.
A groundbreaking study published in
The study examined insulin responses in pancreatic
islets from deceased human donors with and without type 2 diabetes, as well as stem cell-derived
pancreatic islets.
Pancreatic islets are small clusters of
pancreatic cells, including beta cells, crucial in
regulating blood sugar levels by producing hormones like insulin and glucagon in response to
nutrient intake.
It has long been understood that carbohydrates
significantly contribute to blood sugar levels, prompting insulin release,
while proteins have a moderate effect, and fats have minimal immediate impact.
However, this study suggests that insulin secretion in
response to nutrients may actually be more complex and individualized than
previously believed.
For the
first time, researchers identified subsets of human pancreatic islets
exhibiting larger insulin responses to proteins or fats than carbohydrates.
Although lab studies on pancreatic islets might not
directly translate to living humans, the findings could greatly influence
future personalized nutrition strategies for better blood sugar management, ultimately
improving overall health outcomes.
The effects
of each macronutrient on insulin responses
Researchers at the University of
British Columbia studied how human pancreatic islets secrete
insulin in response to different nutrients.
Between 2016 and 2022, the researchers examined
pancreatic islets from 140 deceased donors of various ages, including those
with and without type 2 diabetes.
They exposed the islets to glucose (carbohydrates), amino acids (proteins), and fatty acids
(fats) while monitoring insulin secretion.
The researchers also analyzed gene expression changes
in pancreas cells from donors with and without type 2 diabetes to understand
their impact on insulin production.
Using
Macronutrients
produce unique insulin responses in pancreatic cells
Aligned with current
understanding, most donors’ islets showed the strongest insulin response to
glucose, a moderate response to amino acids, and little response to fatty
acids.
As expected, compared to islets from donors without
diabetes, islets from donors with type 2 diabetes had fewer insulin-producing
beta cells, a delay in their peak insulin time in response to high glucose, and
a lower insulin response to glucose overall.
While much of the findings were anticipated, there
were some surprising results.
About 9%
of donors’ pancreatic islets responded more strongly to proteins than
carbohydrates, and 8% responded more strongly to fats.
Islets that reacted more to proteins often came from
donors with type 2 diabetes but had similar long-term blood sugar levels
(measured by HbA1c) as others. However,
this heightened protein response was linked to longer lab culture times.
On the other hand, islets that reacted more to fats
were usually from donors with worse HbA1c levels but were otherwise similar to
other donors. The researchers suggest this reaction to fat might be due to beta
cell immaturity, as observed in immature stem cell-derived islet cells.
In exploring the source of the variations, they
compared donor characteristics and found no differences based on body mass
index (BMI) or age. However, they did observe sex differences in insulin
responses.
Specifically,
compared to males, female donor islets secreted less insulin in response to
moderate glucose exposure, meaning their cells were not as efficient in
producing insulin.
This might be due to known sex differences in diabetes,
but the underlying reasons have yet to be determined.
Overall, the results suggest that insulin responses to
different nutrients may vary among individuals. However, the authors note that
it’s unclear if this variability is actually due to natural differences in
pancreatic islet cell responses or if adaptations to lab conditions were behind
the differences.
Notably, they did not observe the same level of varied
responses to different macronutrients in male and female mouse pancreatic
islets of various ages. This potentially lends support to the idea that lab
conditions may have influenced the responses of human islets.
How might
the findings apply to living humans?
Medical News
Today spoke with Jason Fung,
MD, a physician and New York Times bestselling author of The Obesity
Code and The Diabetes Code, who was not involved in the study.
Discussing the potential relevance to living humans,
Fung remarked, “Deceased donors are presumed to be reflective of the general
population. It’s a reasonable assumption, but not necessarily true.”
Thomas M. Holland, MD, MS, a
physician-scientist and assistant professor at the RUSH Institute for Healthy
Aging, RUSH University, College of Health Sciences, who was also not involved
in the study, provided further details.
“[T]he study’s findings from pancreatic islets of
deceased donors offer sincerely valuable insights into insulin production in
response to different macronutrients [but] there are limitations when
translating these findings directly to living humans,” he told MNT.
The environment in living
bodies, including factors like blood flow, hormone levels for signaling, and nervous
system interactions, can affect insulin response and might differ from the
“isolated” beta-islet cell environment. While the study highlights the
variability among individuals, living humans experience additional influences
such as lifestyle factors like diet, stress, and physical activity that can
further modulate our insulin responses.— Thomas M. Holland, MD, MS
“Additionally, deceased donors may not perfectly
represent the healthy population, especially if they had underlying health
conditions that might have influenced pancreatic function,” he pointed out.
The study authors, too, acknowledged limitations in
applying their findings, such as the lack of confirmed type 2 diabetes
diagnoses in organ donors and the absence of any human clinical trials to
support their findings.
They hope their research will inspire clinical studies
involving larger and more diverse groups, enhancing the applicability of their
results to real-world settings.
What are the
implications for practitioners and the public?
“The findings from this
research open the door for the possibility of a more customized dietary care
plan for diabetes treatment,” said Sheri Gaw, RDN, CDCES, a
registered dietitian, certified diabetes care and education specialist, and
owner of The Plant Strong Dietitian, who was not involved in the study.
Fung also emphasized that this study’s findings could
hold significant importance for dietary choices.
“Insulin can cause weight gain, and for most people,
cutting refined carbs is a
very good method of reducing insulin and provoking weight loss. But for some
people, a low fat diet may be
more effective,” he explained.
The study authors, on the other hand, proposed that protein-rich diets could benefit
individuals with type 2 diabetes based on their findings. However, they
emphasized the need for further research.
Ultimately, “traditional diabetes diets focus on controlling carbs,
based on the well-established link between glucose and insulin secretion,
specifically refined grains and sugar,” but this study suggests the need for
personalized approaches based on individual insulin responses to different
macronutrients, said Holland.
“The difference is largely genetically determined, as
pointed out by the study,” Fung agreed.
To this point, Gaw said, “In the future, there may be
genetic tests that a practitioner can use to determine a macronutrient ratio that is best for an
individual’s insulin response.”
In the meantime, Holland advises individuals to follow
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