“In mice, limited intakes of one specific essential amino
acid can slow the effects of aging and even extend their lifespan, research
from the US shows.
Scientists wonder if these findings could help people
improve their longevity and quality of life.
Isoleucine is one of three branched-chain amino acids that
our bodies use to make proteins. It's essential for our survival, but our cells
can't produce it from scratch, so we have to get it from sources like eggs,
dairy, soy protein, and meats.
But there can always be too much of a good thing.
Earlier research using data from a 2016-2017 survey of
Wisconsin residents found dietary isoleucine levels were linked with metabolic
health and that people with higher BMIs were generally consuming much greater
quantities of the amino acid.
In the most
recent study, a genetically diverse group of mice was fed either a diet
containing 20 common amino acids as a control, a diet where all amino acids
were reduced by about two-thirds, or a diet where only isoleucine was reduced by
the same amount.
The mice were around six months old at the start of the
study, which is the equivalent age of a 30-year-old person. They could eat as
much as they wanted, but only from the specific kind of food provided to their
group.
"Different components of your diet have value and
impact beyond their function as a calorie, and we've been digging in on one
component that many people may be eating too much of," endocrinologist
Dudley Lamming from the University of Wisconsin, who was involved in both
studies, explained in 2023 when the newest findings were published.
"It's interesting and encouraging to think a dietary
change could still make such a big difference in lifespan and what we call
'healthspan,' even when it started closer to mid-life."
Restricting
dietary isoleucine increased the lifespan and healthspan of the mice, reduced
their frailty, and promoted leanness and glycemic control. Male mice had their
lifespans increased 33 percent compared to those whose isoleucine was not
restricted, and females had a 7 percent increase.
These mice also scored better in 26 measures of health,
including muscle strength, endurance, blood sugar levels, tail use, and hair
loss.
The male mice in this group had less age-related prostate
enlargement, and were less likely to develop the cancerous tumors that are
common in the diverse mice strains.
Curiously, the mice given low isoleucine food also ate
significantly more calories than the others. But rather than gaining weight,
they actually burned more energy and maintained leaner body weights, even
though their activity levels were no different.
Graphical abstract shows dietary isoleucine was restricted
by 67%, charts showing blood glucose and body weight declining over time / age
respectively, reduced frailty and cancer, increased lifespan (survival improved
by 33 percent)
A visual summary of the impact the reduced isoleucine diet
had on mice in the study. (Green et al., Cell Metabolism, 2023)
The researchers think restricting isoleucine in humans,
either by diet or pharmaceutical means, has the potential to yield similar
anti-aging effects - although, as with all mice studies, we won't know for sure
until it's actually tested in humans.
This is easier said than done. Although the food provided to
the mice was controlled, the researchers noted that diet is an incredibly
complex chemical reaction, and there may be other dietary components involved
in producing these results.
Restricting protein intake in general, for instance, has
detrimental effects on the body, mouse or human. Translating this research for
real-world human use is more complicated than just reducing intake of
high-protein foods, even though this is the simplest way to limit isoleucine
intake.
The amino acid restriction level was constant in all
experiments, and they acknowledge that more fine-tuning may be required for
optimum effects across different mice strains and sexes – when it comes to
diet, one size does not fit all.
"We can't just switch everyone to a low-isoleucine
diet," Lamming said.
"But narrowing these benefits down to a single amino
acid gets us closer to understanding the biological processes and maybe
potential interventions for humans, like an isoleucine-blocking drug."
The research was published in Cell Metabolism.
An earlier version of this article was published in November
2023.”
Eat more gelatin,
rice and greens, all these have less isoleucine.
Foods Low in Isoleucine
To reduce your isoleucine intake, consider incorporating the
following foods, which are naturally lower in this amino acid:
Gelatin:
A protein-rich
food derived from animal collagen, gelatin is a good source of protein but
lower in certain amino acids, including isoleucine.
Rice:
Grains like rice are a good source of carbohydrates and are
naturally lower in isoleucine compared to protein sources like animal products.
Greens and Vegetables:
Fruits, vegetables, and greens are generally lower in
isoleucine and can be a significant part of an isoleucine-restricted diet.
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