Crous-Bou, M., et al. 2014. Mediterranean diet and telomere length in Nurses’ Health Study: Population based cohort study. British Medical Journal, 379, G6674; doi: 10.1136/bmj.g6674.
The conventional Mediterranean diet features a high intake of fruits, vegetables, legumes, nuts and unrefined grains. It encourages a low intake of saturated fats with a high intake of olive oil. The diet promotes a somewhat high intake of fish and a low intake of dairy products, meat and poultry. And it is well known for supporting moderate consumption of alcohol, specifically wine with meals.
The Mediterranean diet is linked to several major health benefits (see Figure 1). A new study offers promising results indicating that this diet may also lead to longer life.
The Study Population
This new research evaluated data from 4,676 healthy middle-aged women (average age 59, ranging from 42 to 70) involved in the Nurses’ Health Study, which has tracked the health of more than 120,000 U.S. nurses since 1976. Every other year the participants complete questionnaires on health information, lifestyle activities and diagnoses of diseases. And every 4 years since 1984, researchers have asked participants to complete food-frequency questionnaires on 116–130 food items to track dietary data (Crous-Bou et al. 2014). This study cohort included women who were free of major chronic diseases, including cardiovascular disease and cancer. Researchers were interested in measuring specific DNA biomarkers known as telomeres, which are related to life expectancy.
What Are Telomeres, and Why Did the Researchers Measure Them?
Telomeres (from the Greek telos, meaning “end,” and meros, meaning “part”) are the end sequences of chromosomes, the threadlike structures that house DNA (see Figure 2). DNA molecules contain the biological instructions for the development and functioning of all living organisms. Crous-Bou et al. (2014) note that telomeres protect chromosomes by keeping them from unraveling. The authors say oxidative stress—the harmful reactive oxygen species or free radicals that damage cells—and chronic inflammation reduce the strength and protectiveness of telomeres. Oxidative stress has been shown to be highly linked to aging and age-related diseases (Chung et al. 2010).
Crous-Bou and colleagues explain that telomere length is considered a bio-marker of aging, as shorter telomeres are associated with a decreased life expectancy and increased susceptibility to chronic diseases. Telomeres vary considerably among people, a fact that dietary patterns and lifestyle practices may partially explain (Crous-Bou 2014).
Crous-Bou et al. (2014) say the Mediterranean diet has been shown to have antioxidant (counteracting free radicals) and anti-inflammatory effects. Since both of these processes affect telomere length, the researchers hypothesized that greater adherence to the Mediterranean diet would correlate with longer telomere length. Consequently, the main objective of this study was to examine the relationship between telomere length and higher adherence to the Mediterranean diet in this subset of U.S. women within the Nurses’ Health Study.
For comparison, the authors evaluated the correlation between other dietary patterns and telomere length. They also collected information on body mass index, cigarette smoking, physical activity and total calorie intake, as these factors can also impact telomere length. The researchers followed strict standardized laboratory techniques to measure telomere length (which they repeated three times for reliability of the measurement) with laboratory technicians who were blinded to the participants’ characteristics.
Even in healthy people, telomeres shorten with age. And in line with other research, the younger women in this study had the longer telomeres (Crous-Bou et al. 2014). Shorter telomeres are related to lower life expectancy, aging and age-related diseases such as liver disease, atherosclerosis and certain cancers (Crous-Bou et al. 2014). Impressively, the study results indicate that participant adherence to the Mediterranean diet is significantly associated with longer telomeres. These results positively support the benefits of adherence to the Mediterranean diet for promoting health and longevity.
Which Mechanisms of the Mediterranean Diet Promote Longevity?
The researchers (Crous-Bou et al. 2014) propose that the anti-aging and beneficial effects of the Mediterranean diet, as illustrated via telomere length, may result directly from the diet’s ability to help the body overcome oxidative stress and chronic inflammation. The scientists suggest that the nutrient-rich foods included in the Mediterranean diet are likely to improve the metabolic pathways that help to prevent or delay heart disease, stroke, diabetes and insulin resistance. This means it’s unlikely that any one food in the Mediterranean diet promotes these health benefits; it’s more likely they can be attributed to dietary combinations of all the foods.
What Are the Study’s Limitations?
Importantly, Crous-Bou et al. (2014) note that the Nurses’ Health Study population primarily includes women of European lineage. Diet-induced changes in telomere length may differ between genders and among other ethnicities, so the results of this study cannot (at this time) be generalized to all people in the world.
How Does Physical Activity Affect Telomere Length?
Perhaps one of the first studies to measure telomere length and physical activity was Krauss et al. (2011). Measuring maximal aerobic capacity, the researchers found a strong correlation between physical fitness and telomere length in 944 male and female patients with coronary heart disease. The researchers showed that people with a low exercise capacity had 94% greater odds of having short telomere length than those with high exercise capacity.
The authors concluded that the data signaled a clear, direct linkage between longer telomere length and higher aerobic fitness.
In discussing the mechanisms by which inactivity leads to shorter telomeres, Krauss and colleagues cited animal research, which has revealed that inactivity in mice alters the proteins that regulate telomere length. In addition, the authors cited other research showing that aerobic exercise activates anti-inflammatory processes, which help to prevent or inhibit telomere shortening. Furthermore, Crous-Bou et al. (2014), in their discussion, cite other research demonstrating that physical activity (even in moderate amounts) is associated with longer telomeres.
Technologically advanced research in molecular biology is unraveling exciting results in health, diet and fitness. The understanding of telomeres—and how a Mediterranean diet may influence them and thus lead to a longer, healthier life— is highly valuable to personal trainers intent on encouraging clients to know that lifestyle makes a difference. It is also quite reassuring to read how aerobic exercise improves telomere length. Future research will surely reveal more impactful health information in the complex structures of the human genes.
Chung, H.Y., et al. 2010. Molecular inflammation: Underpinnings of aging and age-related diseases. Ageing Research Review, 8 (1), 18-30.
Krauss, J., et al. 2011. Physical fitness and telomere length in patients with coronary heart disease: Findings from the Heart and Soul Study. PLOS ONE, 6 (11), e26983. doi:10.1371/journal.pone.0026983.
Sofi, F., et al. 2010. Accruing evidence on benefits of adherence to the Mediterranean diet on health: An updated systematic review and meta-analysis. American Journal of Clinical Nutrition, 92 (5), 1189-96.