In the previous article in this series, we looked at how different styles of dietary restriction extend lifespan in animals.
There is compelling evidence that adopting such eating patterns can improve biomarkers associated with aging and overall health. And it appears likely that these regimens would extend both lifespan and healthspan in humans. But it’s not all about food (or the lack thereof). In this blog we’ll explore two important questions: First, how does smoking influence aging? Second, what about alcohol and aging?
Smoking and Aging
Just about every single person reading this blog already probably knows that smoking isn’t good for you, so there’s no need to spend too much time belaboring the obvious. Smokers develop lung cancer up to 25 times as frequently as their non-smoking counterparts. They also are at much greater risk for coronary artery disease and stroke – the major killers of the industrialized world. Smoking remains a significant cause of morbidity and premature mortality, and in that respect, it is clearly not a wise choice for those who seek to prolong life and optimize their health.
But smoking may also influence biological aging in a very direct way, and that is what’s new and interesting here. A study by Robert Philibert and colleagues examined the effects of various types of environmental exposure – including cigarette smoke – on epigenetics, which is a process that influences when or how strongly our genes are expressed. DNA methylation is an epigenetic process in which methyl group is added to a gene, mostly to suppress transcription (i.e., production) of new proteins. Prior research has shown that patterns of DNA methylation shift in predictable ways as people age. Some of these changes are associated with age-related pathology – for example, hypermethylation of the genes for estrogen receptors. The Philibert lab had also identified two specific locations in the human genome in which methylation levels characteristically change in response to alcohol and tobacco. This change occurs so reliably that measurement of said methylation levels was found to be a better measure of smoking and alcohol consumption than users’ own self-reported estimates.
The group studied the effects of these substances on biological aging by measuring patterns of DNA methylation throughout the genome, as a sort of epigenetic “clock” that can be used to estimate the biological age of organisms. Perhaps unsurprisingly, they found that smoking was associated with significant premature aging. Importantly, they found that any level of exposure to smoking is associated with significant premature aging – even light or infrequent smoking has detrimental effects. This is generally supported by other prior research, which has shown that occasional smoking carries significant health risks.
Smoking remains the leading cause of preventable death in the United States. It appears unlikely that any dose of smoking is beneficial, so avoiding it outright is pretty much a no-brainer. Examining the effects of consuming alcohol, however, is a bit less straightforward.
Alcohol and Aging
The research on alcohol and its effects on long-term health in humans can appear confusing and seemingly paradoxical. Conventional health organizations recommend moderate drinking – if you drink at all – due to potential beneficial effects for cardiometabolic health. On the other hand, they do not encourage teetotalers to start drinking, on account of the possible risks associated with alcohol consumption.
One basic principle of toxicology to keep in mind is “the dose makes the poison.” This applies to literally all chemicals – including vitamins and minerals that are essential to our survival. Even water can become toxic when too much is absorbed into the body. So, whether or not a substance can be characterized as a toxin is not a simple question. It depends upon the dose, as well as the duration of exposure. Epidemiology and basic science have suggested that alcohol can actually be beneficial to health and longevity – however only in the right amounts. Ethanol appears to work its magic by improving insulin sensitivity and lipid profiles. But these benefits are largely lost in the context of heavy drinking.
Current scientific consensus supports relatively low doses for best results: 2 drinks per day for men, and 1 drink per day for women. Above is what a standard “drink” looks like – depending on your beverage of choice. (source: http://www.niaaa.nih.gov/alcohol-health/overview-alcohol-consumption/what-standard-drink).
The study from the Philibert lab that we discussed earlier appears to support this target level of alcohol consumption as well, specifically with respect to biological aging. They found that moderate alcohol use – around one to two drinks per day – was correlated with an optimal aging rate, as discerned by methylation patterns. Meanwhile, both lower (<1 drink per day on average) and high consumption (greater than 2 drinks per day on average) were linked to accelerated aging.
Other researchers have confirmed the effects of excessive alcohol consumption on the aging process via other molecular methods. Heavy alcohol use (defined as four drinks per day or more) has measurable effects on telomeres, which protect strands of DNA from deteriorating or sticking to each other. Telomeres get a little bit shorter every time that a cell divides. When they finally become too short, the cell dies. And as people age, telomeres tend to decrease in length. Thus, telomere length, like methylation patterns, can serve as a reasonable proxy for biological age. You can actually get your telomere length tested. Here is one place you can get it checked.
Here is a fun 6 min video by Varitasium in which telomeres are described in more detail (and other interesting aspects of aging are discussed, too!).
One study discovered that excessive alcohol can accelerate telomere shortening – and quite dramatically. In some subjects, telomere length was found to be just half as long as telomere length in non-abusing counterparts. So, it is clear that the consequences of excessive alcohol consumption must also be weighed, especially in light of the potential risk for addiction and abuse in susceptible individuals.
The literature has demonstrated overwhelmingly that smoking is detrimental to health and accelerates biological aging, seemingly at any dose. Unlike smoking, the relationship between alcohol and aging is not linear but inverse J-shaped (i.e, a little is better than none, and a little is also better than too much). Epidemiological and biochemical evidence has long suggested that moderate amounts of alcohol may confer benefits to health and lifespan. DNA methylation indices, as measured by the Philibert lab, also appear to support this finding. Certainly, in the near future, we will see more research connecting aspects of lifestyle with methylation patterns predictive of biological aging. For now, to age well, don’t smoke but raise a glass, just not three.
- Beach SR, Dogan MV, Lei MK, et al. Methylomic Aging as a Window onto the Influence of Lifestyle: Tobacco and Alcohol Use Alter the Rate of Biological Aging. 2015. J Am Geriatr Soc. doi: 10.1111/jgs.13830.
- Gonzalo S. Epigenetic alterations in aging. 2010. J Appl Physiol 109: 586–597.
- O’Keefe JH, Bybee KA, Lavie CJ. Alcohol and cardiovascular health: the razor-sharp double-edged sword. 2007. J Am Coll Cardiol 50: 1009–1014.
- Pavanello S, Hoxha M, Dioni L, et al. Shortened telomeres in individuals with abuse in alcohol consumption. 2011. Int J Cancer 129: 983–992.
- Schane RE, Ling PM, Glantz SA. Health effects of light and intermittent smoking. 2010. Circulation 121: 1518–1522. doi: 10.1161/CIRCULATIONAHA.109.904235.
- U.S. Department of Health and Human Services. The Health Consequences of Smoking—50 Years of Progress: A Report of the Surgeon General. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2014.