- Researchers have shown that methionine-restricted diets improve the healthspan of some mammals.
- Research has suggested this is because methionine restriction reduces the signaling of the hormone IGF-1.
- Studies also show that selenium reduces IGF-1 signaling in some mammals.
- In the present study, the researchers wanted to see if mice receiving selenium supplementation would experience the healthspan benefits seen in methionine-restricted diets.
Researchers have shown that mice receiving selenium supplementation experience healthspan benefits, including protection against diet-induced obesity.
The study, published in the journal eLife, lays the groundwork for future research to see if similar effects occur in humans.
Human lifespans have significantly increased over the past 200 years. However, there are still inequalities associated with people’s relative lifespans. Further, a person’s health also varies during these additional years.
Researchers have recently focused on the concept of healthspan as a way of talking about the number of relatively healthy years a person experiences.
Given the general increase in lifespans, it is also important to increase peoples’ healthspan. The benefits of a longer life reduce if a person spends those additional years experiencing mental or physical health issues.
One possible way to improve healthspan in mammals is to restrict consumption of the amino acid methionine. Researchers have shown that mammals fed a methionine-restricted diet have increased healthspans, with fewer pathologies that typically develop with age.
For example, researchers found that mice fed a high fat, methionine-restricted diet saw complete protection against obesity. However, they did experience some loss in bone density
Meat, fish, and dairy products contain methionine, so following a vegan diet may be one way humans can restrict their intake of this amino acid.
Despite the significant benefits to human health and environmental sustainability associated with plant-based diets, such as veganism, not all people may be willing or able to make the switch.
As such, researchers want to find out whether it is possible to achieve the benefits of a methionine-restricted diet in other ways.
One potential option is selenium supplementation. Researchers believe that restricting the intake of methionine improves the lifespan of mammals by inhibiting the signaling of the hormone IGF-1. Researchers have shown that selenium supplementation can have similar hormonal effects.
Consequently, the researchers in the present study wanted to see whether they could replicate the healthspan benefits associated with reducing methionine, particularly in protecting against obesity, by using selenium supplementation in mice.
The researchers fed young male and older female mice one of three different high fat diets.
The first, which acted as a control, contained normal amounts of methionine. The second diet restricted methionine, and the third had normal amounts of methionine with selenium supplements.
The researchers found that the mice that consumed the high fat control diet with normal amounts of methionine developed significant white fat tissue.
In contrast, the mice that consumed the methionine-restricted diet and the selenium supplemented diet did not experience this weight gain.
After taking blood samples from the mice, the researchers also found that the mice who ate the methionine-restricted and the selenium-supplemented diets had significantly reduced levels of IGF-1. The mice also had reduced levels of leptin, a hormone that affects metabolism.
The researchers concluded that reduced IGF-1 levels are primarily responsible for improved healthspan benefits and that selenium supplementation is an effective way of promoting this reduction.
To further confirm their findings, the researchers repeated the experiment using yeast. After supplementing yeast with selenium, they found that the lifespan of the yeast improved by 62%, and it produced nine more generations of yeast compared with the control.
According to the senior author of the study Dr. Jay Johnson, Senior Scientist at Orentreich Foundation for the Advancement of Science (OFAS) in New York, “one of the major goals of aging research is to identify simple interventions that promote human healthspan.
“Here we present evidence that short-term administration of either organic or inorganic sources of selenium provides multiple health benefits to mice, the most notable of which being the prevention of diet-induced obesity.”
“In the long term, we expect that supplementation with these compounds will also prevent age-related disease and extend the overall survival of mice. It is our hope that many of the benefits observed for mice will also hold true for humans.”