Longevity Articles

Is it Possible to Reverse Human Aging?

Is it Possible to Reverse Human Aging?

Research shows that aging clocks can be slowed down…and even go backwards.

Everyone ages. But how aging affects health is different for each person. This means that how old someone seems or feels does not always match the number of years they have been alive; in other words, someone’s “biological age” can often differ from their “chronological age.” Although somewhat of an abstract concept, “biological age” intuitively makes sense when you think about why people have different aging trajectories. 

Much research has revealed a link between your health and how quickly your body ages biologically—or your “true” age. On top of that, there is new evidence that biological aging can be slowed down by interventions. To put it another way, it appears that biological aging can be slowed down.

But can biological age be reversed? Can your body, tissues, or cells actually be rejuvenated?

How to Measure Aging

To get at the questions about biological aging reversal, we first need to grasp how biological age is measured and what it can tell us. Biological age is a complex parameter involving the calendar age of a person, their health as relating to their age, and medical signs of when they might die of old age.

The first estimates of biological age were based on markers that could be measured in the clinic (e.g., inflammation, glucose resistance, and endocrine markers) and on functional tests (e.g., cognitive function and cardiorespiratory fitness). Such markers have a clear clinical meaning, but even if they can predict death better than chronological age, it is not clear how well they measure biological aging as opposed to other causes of health decline.

Other approaches, based on a deeper understanding of the molecular and cellular causes of aging, include measuring the levels of markers for cellular senescence—or when a cell stops dividing—and the length of the ends of chromosomes called telomeres.

In 2013, Steve Horvath and Gregory Hannum both published papers about aging clocks that used changes to DNA, specifically a change called methylation, to figure out how old different types of samples were. Since these pioneering publications, a lot of progress has been made in the aging clock field by trying to understand patterns of DNA modifications, or what’s called epigenetics. While less common, other aging clocks have been created using RNA, proteins, and metabolites. The biomedical relevance of these models has been demonstrated by their ability to capture differences in human health, meaning that as the aging clock increases, the health and function of cells and tissues decrease.

You may be thinking, “Well, which aging clock is best? Which one provides the most accurate information for health and mortality”

In 2020, some researchers looked at data on nine different measures of biological age. The risk of deaths among the group during the follow-up period could be explained by using any one of the nine biological age measures, according to Li and colleagues from Sweden's Karolinska Institutet. In other words, when comparing members of the study group who were the same age chronologically, the member with the higher biological age measure was more likely to pass away sooner. The analysis also showed that biological aging appears to speed up as people get older, and that there are distinct differences in aging between men and women. Measuring methylation and frailty (the frailty index) best predicted a person's risk of dying.

Is it Possible to Reverse Human Aging?

Slowing Down Human Aging

Studies have shown that a variety of factors can slow down the human aging clock. According to the epigenetic aging clock, factors like diet, exercise, education, and lifestyle appear to have the ability to affect how quickly you age.

For example, a large study that looked at data from 4575 people found that eating fish, having blood markers for eating fruits and vegetables, and being physically active were all linked to slower biological aging.

Similar associations between dietary elements, physical activity, and other lifestyle choices and a slower aging clock have been made by other groups. Interesting examples to highlight include:

Additionally, studies have shown that specific molecules can slow the aging process in both lab-cultivated cells and lab animals.

Turning Back Human Aging

Only a few aging clock studies have connected a particular intervention or variable to a decrease in biological aging. Dietary changes have been shown to impact the aging process—at least according to the latest aging clocks—in human trials.

For example, there was a study of 120 elderly healthy subjects from Italy and Poland (60 from each nation) that were given a Mediterranean-style diet to follow for a year. Even though the results were different based on gender and where the people lived, the difference between the biological age and the chronological age of the Polish people who ate a Mediterranean-style diet was reduced by 0.84 years. The biological age of Polish women dropped by 1.47 years.

In a cohort of 219 healthy, postmenopausal women, researchers similarly discovered that a changed diet could lower aging clocks. After 24 months of following a diet centered on eating plant foods, the predicted biological age change was 0.66 years less in comparison to controls.

In healthy subjects, combination therapies involving diet and exercise have also been shown to reduce biological age. In one of these studies, after only 8 weeks, a thorough lifestyle intervention significantly reduced biological aging predictions. The regimen for this study included diet, sleep, exercise and relaxation guidance, and supplemental probiotics and phytonutrients. Subjects in the treatment group were predicted to have an epigenetic age that was 1.96 years lower than when they started the study.

Is it Possible to Reverse Human Aging?

In Due Time

In each study reporting a significant reduction in biological aging, an aging clock was used to make a prediction before and after an intervention. When looked at as a whole, the results of these early studies suggest that people might be able to do something to delay the start of biological aging. Even though many of these trials were interesting, they were short and only involved a small number of people.

Time (and clinical studies) will show if any of the many molecules, whether they are natural compounds or synthetic drugs, that have been shown to lengthen the lives of animals or improve their health can safely slow down the aging process in humans.

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