[Nov. 29, 2023: JD Shavit, The Brighter Side of News]
Restricting the intake of a specific essential amino acid, isoleucine, can significantly slow the aging process. (CREDIT: iStockphotos)
In a groundbreaking study, scientists have discovered that restricting the intake of a specific essential amino acid, isoleucine, can significantly slow the aging process and extend the lifespan of mice. These findings have ignited intrigue among researchers, sparking questions about whether similar strategies could be applied to enhance the longevity and overall quality of life in humans.
Isoleucine, one of the three branched-chain amino acids vital for constructing proteins within our bodies, plays an indispensable role in our survival. However, since our cells cannot synthesize isoleucine from scratch, we must obtain it from dietary sources such as eggs, dairy products, soy protein, and various meats. This amino acid is undoubtedly essential, but as with many things in life, moderation is key.
Previous research, drawing data from a 2016-2017 survey of Wisconsin residents, revealed a link between dietary isoleucine levels and metabolic health. It was observed that individuals with higher body mass indexes (BMIs) tended to consume significantly greater quantities of this amino acid.
Dudley Lamming, a metabolism researcher from the University of Wisconsin who was involved in both studies, emphasizes, "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."
What makes this discovery particularly intriguing is the possibility that a dietary change, such as restricting isoleucine intake, could have a substantial impact on both lifespan and "healthspan," even when implemented later in life. This revelation opens doors to potential interventions that could improve the well-being of aging individuals.
The study involved a genetically diverse group of mice, which were divided into three dietary groups. The first group received a diet containing the standard twenty common amino acids, serving as a control. The second group had all amino acids reduced by approximately two-thirds, while the third group had only isoleucine reduced by the same proportion. The mice, equivalent in age to a 30-year-old human, were free to eat as much as they desired, but only from the specific type of food provided to their respective groups.
Remarkably, restricting dietary isoleucine led to a host of positive effects on the mice's health and longevity. It increased their lifespan, improved their overall healthspan, reduced frailty, and promoted leanness and glycemic control. Male mice experienced a remarkable 33 percent increase in lifespan compared to their counterparts whose isoleucine intake was not restricted, while female mice enjoyed a 7 percent increase.
Study graphical abstract: Low-protein diets promote health and longevity in diverse species. (CREDIT: Cell Metabolism)
These mice exhibited significant improvements across 26 health measures, including enhanced muscle strength, endurance, better blood sugar control, improved tail function, and reduced hair loss. Notably, male mice in the low isoleucine group demonstrated less age-related prostate enlargement and a reduced likelihood of developing cancerous tumors—a common occurrence in diverse mouse strains.
An unexpected twist in the study was that the mice with restricted isoleucine consumption actually consumed more calories than their counterparts. Despite the increased caloric intake, they managed to burn more energy and maintain leaner body weights, even though their physical activity levels remained unchanged.
Low Isoleucine Reduces Cancer Prevalence in Males. Compared to mice fed a normal diet (Control), cancer prevalence was reduced by about 25% in male (left) mice fed a low isoleucine diet (Low Ile). However, this did not occur in females (right). (CREDIT: Cell Metabolism)
The implications of this research extend beyond the world of mice, raising the tantalizing prospect of similar anti-aging effects in humans. However, as with all studies involving mice, there are significant challenges to overcome before translating these findings into practical human applications.
Diet is a complex chemical reaction within the body, and it is likely that other dietary components play crucial roles in achieving the observed results. General protein restriction, for instance, has been shown to have detrimental effects on both mice and humans. Therefore, applying these findings to the real world is more intricate than merely reducing the consumption of high-protein foods, despite its simplicity in limiting isoleucine intake.
Low Isoleucine Reduces Frailty. Compared to mice fed a normal diet (Control), mice fed a low isoleucine (Low Ile) or low protein (Low AA) diet scored lower on the frailty index (FI), suggesting reduced frailty. For males this occurred at 24, 28, and 30 months of age. For females this occurred at 24 months of age. For 22-month-old females, the Low Ile, but not Low AA group had a lower FI score than the Control group. (CREDIT: Cell Metabolism)
The researchers highlight that the amino acid restriction level remained constant in all experiments. They acknowledge that further fine-tuning may be necessary to optimize the effects across different strains of mice and genders, emphasizing that when it comes to diet, one size does not fit all.
Dudley Lamming underscores the complexity of the issue, stating, "We can't just switch everyone to a low-isoleucine diet." However, he remains hopeful, suggesting that isolating the benefits to a single amino acid brings us one step closer to understanding the underlying biological processes and the potential development of interventions for humans, such as isoleucine-blocking drugs.
Beef is another good source of isoleucine, with one cooked beef steak containing about 2.4 grams of isoleucine. (CREDIT: Getty Images)
10 common foods that contain significant amounts of isoleucine:
Chicken: Chicken is a rich source of isoleucine, with one cooked chicken breast containing about 2.7 grams of isoleucine.
Beef: Beef is another good source of isoleucine, with one cooked beef steak containing about 2.4 grams of isoleucine.
Pork: Pork is also a good source of isoleucine, with one cooked pork chop containing about 2.2 grams of isoleucine.
Fish: Fish such as salmon, tuna, and cod are good sources of isoleucine. One cooked salmon fillet contains about 2.3 grams of isoleucine, one cooked tuna steak contains about 2.1 grams of isoleucine, and one cooked cod fillet contains about 1.8 grams of isoleucine.
Fish such as salmon, tuna, and cod are good sources of isoleucine. One cooked salmon fillet contains about 2.3 grams of isoleucine. (CREDIT: Creative Commons)
Eggs: Eggs are a good source of isoleucine, with one large egg containing about 1.4 grams of isoleucine.
Dairy: Dairy products such as milk, cheese, and yogurt are good sources of isoleucine. One cup of milk contains about 1.2 grams of isoleucine, one ounce of cheese contains about 1.0 gram of isoleucine, and one cup of yogurt contains about 0.8 grams of isoleucine.
Legumes: Legumes such as beans, lentils, and peas are good sources of isoleucine. One cup of cooked beans contains about 1.5 grams of isoleucine, one cup of cooked lentils contains about 1.3 grams of isoleucine, and one cup of cooked peas contains about 1.1 grams of isoleucine.
Nuts and seeds: Nuts and seeds are good sources of isoleucine. One ounce of almonds contains about 1.4 grams of isoleucine, one ounce of sunflower seeds contains about 1.2 grams of isoleucine, and one ounce of peanuts contains about 0.9 grams of isoleucine.
Legumes such as beans, lentils, and peas are good sources of isoleucine. One cup of cooked beans contains about 1.5 grams of isoleucine. (CREDIT: Creative Commons)
Whole grains: Whole grains are good sources of isoleucine. One slice of whole-wheat bread contains about 0.5 grams of isoleucine, one cup of cooked oats contains about 0.4 grams of isoleucine, and one cup of cooked brown rice contains about 0.3 grams of isoleucine.
Avocados: Avocados are a good source of isoleucine, with one avocado containing about 0.6 grams of isoleucine.
The groundbreaking findings, published in Cell Metabolism, have opened up new avenues for research into aging and longevity. While the road to applying these discoveries to humans may be challenging and uncertain, the prospect of enhancing healthspan and extending lifespan through dietary interventions has never seemed closer to realization. As scientists continue to unravel the mysteries of aging, the promise of a longer, healthier life remains a tantalizing possibility on the horizon.
For more science news stories check out our New Innovations section at The Brighter Side of News.
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