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You May Live Longer Eating a Mediterranean Diet
Len Kravitz, Ph.D.

Study Reviewed
Crous-Bou, M., Fung, T.T., Prescott, J. 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 is characterized by 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. It is well known to support a moderately regular intake of alcohol, specifically wine with meals. The Mediterranean diet is linked to several major health benefits. A new study offers some promising results indicating this diet may also lead to a longer life.

The Study Population
This new research evaluated data from 4,676 healthy middle-aged women (average age = 59 yrs, with ages ranging between 42 and 70 yrs) involved in the Nurses' Health Study, a continuing study tracking 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 four years, since 1984, researchers complete food frequency questionnaires with participants on 116-130 food items for dietary information collection (Crous-Bou et al., 2014). This study co-hort (group) included women who were free of major chronic diseases, including cardiovascular disease and cancer. Researchers were very 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 (telos is Greek for end and meros means part) are the end sequences of chromosomes, the thread-like structures that house a person's DNA. DNA molecules contain the biological instructions for the development and functioning of all known living organisms. Crous-Bou et al. (2014) note that telomeres offer protection for the chromosomes, by keeping them from unraveling. The authors continue that oxidative stress (i.e., the harmful reactive oxygen species or free radicals that damage cells) and chronic inflammation (See Side Bar 1 on Chronic Inflammation) reduce the strength and protective effectiveness 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 biomarker of aging, as shorter telomeres are associated with a decreased life expectancy and increased susceptibility to chronic diseases. Telomeres vary considerably between people, which may partially be explained by dietary patterns and lifestyle practices (Crous-Bou).Crous-Bou et al. (2014) summarize that the Mediterranean diet has been shown to have antioxidant (i.e., counteracts effects of free radicals) and anti-inflammatory effects. Since telomere length is affected by both of these processes, the researchers hypothesized that greater adherence to the Mediterranean diet would be correlated with longer telomere length. Consequently, the main objective of this study was to examine the relationship between higher adherence to the Mediterranean diet and telomere length in this subset of U.S. women within the Nurses' Health Study.

For comparison, the authors also evaluated the correlation between other existing dietary patterns and telomere length. In addition, the researchers also collected information on body mass index, cigarette smoking, physical activity, and total calorie intake, as these factors have been shown to impact telomere length. The researchers followed strict standardized laboratory techniques to measure telomere length (which they repeated 3 times for reliability of the measurement) with laboratory technicians who were blinded to the participants' characteristics.

Results of the Study
Even in healthy people, telomeres shorten with age. And in line with other research, the younger women 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.). 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.

What are the Mechanisms of the Mediterranean Diet that Promote Longevity?
The researchers (Crous-Bou et al., 2014) propose the anti-aging and beneficial effects of the Mediterranean diet, shown with telomere length, may be a direct result of the diet's positive effect to overcome oxidative stress and chronic inflammation. The scientists suggest the nutrient rich foods included in the Mediterranean diet likely enhance favorable changes in metabolic pathways that help to prevent or delay heart disease, stroke, and diabetes and insulin resistance. So, it is unlikely that there is one food in the Mediterranean diet promoting these health benefits, but more likely the dietary combinations of all of the foods.

What are the Limitations of this Study?
Importantly, Crous-Bou et al (2014) note the Nurses' Health Study population primarily includes women of European lineage. Telomere length changes from diet may differ between genders and other ethnicities, so the results of this study cannot be generalized to all people in the world (at this time).

How Does Physical Activity Effect Telomere Length?
Perhaps one of the first studies to measure telomere length and physical activity was Kraus et al. in 2010. 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 persons 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 signal a clear, direct linkage between longer telomere length and higher aerobic fitness. In discussing the mechanisms why inactivity may prevent shorter telomere length, Kraus and colleagues cite animal research, which reveals that inactivity in mice leads to altered changes in the proteins that regulate telomere length. In addition, the authors cite other research that shows that aerobic exercise activates anti-inflammatory processes, which help to prevent or inhibit telomere shortening. Furthermore, in their discussion, Crous-Bou et al. (2014) cite other research demonstrating that physical activity (even moderate amounts of activity) is associated with longer telomeres.

Final Thoughts
The technologically advanced research in molecular biology is beginning to unravel some exciting results in the area of 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 so valuable to personal trainers encouraging clients that lifestyle makes a difference. It is also quite reassuring to read of the positive effects aerobic exercise has on telomere length. Future research will surely reveal more impacting health information in the complex structures of the human genes.

Side Bar 1. Understanding Inflammation
Inflammation is an immune, self-protection and healing response of the body to remove harmful stimuli, irritants, pathogens and/or damaged cells. In most instances, inflammation is acute, such as when a person sprains an ankle. It is the way the body protects and heals itself. Symptoms of inflammation include swelling, redness, pain and impaired (sometimes) movement or function. Acute inflammation targets the damaged area and mobilizes immune cells to promote healing. Acute inflammation usually lasts a few days and terminates as healing proceeds. Other examples causing acute inflammation are burns, chemical irritants, physical injury, foreign bodies (i.e., dust and environmental debris), scratches and cuts.

Chronic inflammation, on the other hand can last several months or even years (Chung et al., 2010). In some cases the body is not able to resolve what caused the initial acute inflammation. In other cases, the body's immune system attacks healthy tissue, mistaking it for something harmful. As humans grow older, chronic systemic inflammation may have degenerative effects on the body that can result in chronic diseases, dementia, atherosclerosis, cancer, and osteoporosis (Chung et al., 2010).

Additional References:
Chung, H.Y., Cesari, M., Anton, S. et al. (2010). Molecular Inflammation: Underpinnings of Aging and Age-related Diseases. Ageing Research Review, 8(1), 18-30.
Krauss, J., Farzaneh-Far, R., Puterman, E. et al. (2010). 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., Abbate, R., Gensini, G.F., Casini, A. (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, 1189-1196.