23 September 2013
A US study proclaiming the health benefits of stress management, gentle exercise and a 'plant-based' diet (conjuring up images of the participants strolling happily round their gardens, feasting on foliage) grabbed the attention of the world's media last week (1). Headlines such as 'New study finds health kick can reverse the ageing process' promised much, but what was novel about the findings, and are the life-extending claims justified?
The scientists studied two groups of men: ten of whom changed their lifestyle as described above, and 25 controls who didn't. Specifically, the researchers were interested in whether the healthy lifestyle intervention would have any effect on their telomeres. These are the protective 'caps' found at the ends of chromosomes, the bundles of DNA that contain the cell's genetic information.
Every time a cell divides, the telomeres become shorter. Once the telomeres reach a critically short length, the cell stops dividing and eventually dies. Telomeres are often likened to the plastic tips found at the ends of shoelaces. If the ends of your shoelaces are frayed and tip-less, it's probably time to buy a new pair. In the same way, cells with very short telomeres are likely to have accumulated widespread DNA damage, marking the end of their useful life.
As more body cells are lost or damaged, signs of ageing start to appear, which may eventually be followed by age-related conditions such as type 2 diabetes and heart disease. It's been known for some time that people who develop these illnesses tend to have shorter white blood cell telomeres than healthy people of the same age. Previous studies have also shown that obesity, smoking and stress are linked to shorter telomeres, while exercise and weight loss are linked to longer telomeres. These findings have lead to telomere length being proposed as an indicator of a person's 'biological age', which may be younger or older than their actual age.
The latest research was the first to directly investigate whether comprehensive lifestyle changes can affect telomere length over time, by measuring white blood cell telomeres at the start of the study and again after five years. They found that the average telomere length of the men in the lifestyle intervention group increased during that time, while the average telomere length of those in the control group decreased.
It's important to note that although overall, the difference in telomere length change between the two groups was statistically significant, there was wide variation within them. There were small increases in some of the control group and small decreases in some of the men following the healthy lifestyle. In fact, only four of the ten men in the intervention group had an increase that was greater than the largest increase seen in the control group.
The authors rightly stress that this was a pilot study, and call for larger, randomised studies to confirm the findings. Longer-term research projects are also required – does having longer telomeres (or at least telomeres that shorten more slowly) translate into extra years of life, and/or lower risk of age-related disease? Further questions remain. Does what is happening in the blood cells after lifestyle changes reflect telomere length in the rest of the body's tissues? Do longer telomeres mean that the cell's DNA is in better shape overall?
One thing is certain – there is a pressing need for new and effective ways of tracking how well people are ageing, and to identify which lifestyle factors influence this process. People around the world are living for longer (at least, those fortunate to have access to adequate food, water and healthcare). In the UK, it's predicted that the proportion of people aged over 65 in will rise from one in six to one in four by 2050, and that average life expectancy will continue to rise. However, given our increasingly sedentary lifestyle and high-calorie diets, we don't yet know if increasing lifespan will be matched by an increase in 'healthspan'. It's a crucial issue for policymakers and individuals alike – living for longer may not be such a good thing if more of our later years are blighted by disease.