• What is aging?
• Aging: It is a process characterized by progressive loss of physiological integrity and work- home disorder, leading to an increased risk of major chronic diseases such as cancer, diabetes, cardiovascular and neurodegenerative diseases. The World Health Organization considers individuals aged 65 and above as elderly.

• What is the relationship between Telomere length and aging?
• Preventing and delaying the occurrence or at least the progression of age-related diseases is of great importance both for the national economy and for the protection of public health. For this reason, the American Aging Research Federation argues that in order to better understand aging, aging biomarkers must be correctly defined. In this context, telomere Length (TL) is considered as an aging biomarker.

• What are telomeres?
• Telomeres are the terminal (terminal) regions of chromosomes that contain DNA and protein. It differs structurally and functionally from other chromosomal DNA sequences. The enzyme telomerase (telomere terminal transferase or reverse transcriptase) is responsible for telomere synthesis. It is a special DNA polymerase with ribonucleoprotein structure responsible for the synthesis of "5-TTAGGG-3" repeats at the chromosomal ends. This enzyme is necessary to maintain the integrity of the terminal region of chromosomes.

• What are the functions of telomeres?
• Telomeres have two important functions. Firstly; to allow the completion of replications at the ends of chromosomes. The second is to prevent these ends from mixing with each other or from reacting with the inner parts of the chromosomes.

• What is the reason for the variable results in telomere length?
• The structures responsible for the extension of the telomere in healthy tissues cannot maintain their activity during cell division and a shortening occurs in their length. Since telomere length also determines the replicative life of the cells, the aging program is activated when the critical size reaches. After this process, cell division stops, but continues to live and function. So, telomere length is considered to be the biomarker of aging. Shorter telomere length is associated with decreased survival and increased rate of development of age-related chronic diseases. Telomere length decreases with age and varies considerably from person to person. In more detail, the wear of telomeres is accelerated in the case of oxidative stress and inflammation. Studies have shown that it is known that the height of the telomers can also be shortened regardless of age and that the wear of the telomeres has variable consequences. These variable results are associated with individuals' eating habits and lifestyles.

Studies on the relationship between Telomeres Length and nutrition.

• Mediterranean Diet:
• In this study conducted in 2019, the effect of herbal foods and herbal-rich diet on telomere length was examined.
• Firstly, studies on the “Mediterranean Diet”, which is a herbal-rich nutritional model, seed consumption (predominantly hazelnuts, grains) and carotenoid intake, have been examined.
• Secondly; studies evaluating the effect of herbal-rich diet model and herbal-rich nutritional status on telomere length were examined. “Mediterranean diet; it is a diet model characterized by high consumption of grains, legumes, nuts, vegetables and fruits, relatively high consumption of olive oil, moderate fish consumption, moderate poultry consumption, low consumption of red meat and its derivatives, and generally moderate consumption of red wine. Considering that the “Mediterranean Diet” is a diet rich in herbal and antioxidants, it has been focused on whether those who follow the Mediterranean Diet protect against telomere wear for a long time. The first study based on this hypothesis was realized by Trichopoulou et al. for an average sample of 217 Italians of 78 years in which 74% of them were women. Consequently, when the compliance with the Mediterranean Diet was evaluated by creating the Med Diet score, which was observed that the participants with high Med Diet score had high telomere lengths compared to the participants with lower Med Diet scores. In another study, it was concluded that plant-based nutritional components such as vitamin C, vitamin E, Folate, Polyphenols and turmeric would prevent telomere wear.  

• Western Style Nutrition Model:
• According to the study done for the mode of nutrition conducted by Lee et al. which was characterized by high intake of whole grains, legumes, vegetables, seafood and seaweed) applied to middle-aged and high-aged Korean adults who follow a 'Western-style' diet (high consumption of refined grains, refined sugar, processed meat, sugary sodas). It has been reported to those people with this western-style of diet have a shorter telomere length compared to Koreans who follow a diet model.
•  In another study, Chinese women who adhere to a plant-rich diet pattern were significantly more likely than Chinese women who followed the traditional model, which included mostly animal foods, alcohol, rice, red meat, pickled vegetables, sugary drinks, fries, called `` macho '' were observed with long telomeres. In a similar study, it was reported that telomere length was negatively affected as a result of applying the "Western Style" diet of 300 healthy people aged 25-40. As a result, when the relationship between dietary patterns was evaluated, populations following the Mediterranean Diet were found to be associated with longer telomere length compared to populations applying other models.

• NHANES cohort study:
• The abundance of "Guanine" in telomeric DNA repeats (5-TTAGGG-3) makes telomeres suitable for oxidative damage. This has made us wonder whether adding antioxidant-rich foods into the diet will help telomere length. Seeds are foods rich in antioxidants. The nut layer is enriched in compounds that prevent the oxidation of plant DNA and ensure the longevity of the seed. In a 1958 study in Korean individuals, higher nut and legume consumption resulted in longer telomere length. In addition, in the NHANES cohort study, which included 5582 participants, it was found that the consumption of nuts and other seeds was positively associated with telomere length. However, the relationship between grains and telomere length is not strong. This is explained by the lack of fiber and antioxidants that the grain loses during refining. Carotenoids from green leafy vegetables and fruits are phytochemicals known for their powerful antioxidant properties. Higher concentrations of carotenoids in plasma (lutein and zeaxanthin) of 786 elderly Australian participants have been associated with longer telomere length. In a subset of 3660 participants from the NHANES cohort, a significant association was observed between telomere length and the sum of α-carotene, β-carotene, and β-cryptoxanthin: higher blood carotenoid concentrations were associated with longer telomeres.

• What is the standard model of nutrition should be taken for slow down aging?
• Considering that there is a directly proportional relation between oxidative stress and telomer wear, it would be correct to say that a diet rich in plant foods, especially the consumption of antioxidant-rich foods, will help the prevention of telomere wear. It should be kept in mind that telomere length is not only related to a diet rich in herbal and antioxidants, but also to the formation of age-related diseases and premature aging.

• References
• Crous-Bou et al. Plant-Rich Dietary Patterns, Plant Foods and Nutrients, and Telomere Length. Adv Nutr 2019; 10: S296 - S303.

Dyt. İpek CANYAKANLAR

Nutrition and Diet