A Path to a Longer and Healthier Life

SQ SPRING INSIDER 2020

COVER ILLUSTRATION BY YICHEN WANG

A Path to a Longer and Healthier Life

written by Lilit Vardanyan

illustrated by Phoebe Ahn

What if opting for a lower-calorie meal instead of calorierich food decreased your chances of disease and increased your lifespan? Although one meal may not be the gamechanger, it could be the beginning of a healthier life.

For years, scientists have been exploring the molecular processes behind aging and the human body’s overall degradation. Dr. Clive Maine McCay, a prominent researcher in the field of aging, published a study on caloric restriction (CR) and its impact on life extension in 1935. Today, CR is theorized as a possible longevity enhancer and continues to be a discussion topic in the future of aging research.

CR, as defined by The National Institute on Aging, involves reducing daily calorie intake by 30 to 40 percent while still providing the nutrients needed to sustain a healthy life. This eating habit does not put boundaries on when one can eat, but rather how much one should consume in a day.

Cellular carbohydrate metabolism involves the breakdown of a simple sugar–glucose–in an individual cell. Glucose breakdown begins during a process called glycolysis, which is followed by further processing in the cell’s mitochondria via the Krebs cycle and the electron transport chain (ETC). Through this cellular journey, one molecule of glucose is completely broken down into carbon dioxide and water, and in the process, generates energy for the cell through moving electrons around. Removing electrons from molecules is known as an oxidative process, and this is the primary form of electron-shuffling that occurs throughout glucose breakdown. Dr. McCay states that CR may combat the pitfalls of this oxidative activity during metabolism, ultimately promoting longevity in the cells and the organism itself.

While metabolism is necessary to sustain life, certain parts of this energy production can hurt the cells. In particular, the ETC segment of the glucose-breakdown process can lead to some dangerous byproducts. In his paper “What is Oxidative Stress?,” Dr. John Betteridge describes oxidative stress as a process that occurs when byproducts such as reactive oxygen species (ROS) accumulate in the cell. These molecules can easily react with important cellular structures, such as cell membranes, proteins, and DNA. Considering this, one established theory proposes that CR improves cell lifespan by decreasing the need for ROS-producing metabolism and lessening cell damage.

Applied physiologist Dr. John O. Holloszy, M.D. and physician scientist Dr. Luigi Fontana, M.D. significantly contributed to the field of aging studies through the paper “Caloric restrictions in humans.” Primary aging is the gradual deterioration of the body due to the accumulation of damaging biochemical products, whereas secondary aging is caused by disease and illness. According to Holloszy and Fontana, CR restriction in mice and rats has shown to slow primary aging and protect against secondary aging.

Although reducing the calorie intake of mice and rats shows results consistent with the ideas behind CR, the process must also be investigated in humans before full treatment plans are built. CR studies have not been performed on humans yet; however, researchers have collected enough information from long-term observations to suggest that CR protects against secondary aging in humans, much like it does in mice and rats.

Throughout our busy lives, it is easy to lose track of what we eat and how it might impact us in the future. Investigating the details of metabolic processes and long-term health impacts can provide insight into what it means to live a healthier life through small, everyday changes. Swapping a high-calorie meal for a low-calorie salad is hard, but consistently making small changes can help decrease disease and increase lifespan.

This aging and CR research also highlights the need to support disadvantaged communities facing food insecurities. While a healthy and balanced diet is ideal, lower-calorie fresh foods are often not viable purchasing options for low-income people– sometimes, they are not even available in grocery stores. In crafting a path to a longer, healthier life, we must find equitable solutions. Our understanding of human metabolism, nutrition, and healthy lifestyles is ever-growing; however, we do know that lifelong results arise from lifelong commitment.

Read feature articles, check out our photo gallery, and meet our bloggers. sqonline.ucsd.edu

Find us on Facebook: www.facebook.com/SaltmanQuarterly

Instagram: @saltmanquarterly

Twitter: @sqatucsd

Email our editors: saltman@biology.ucsd.edu