The Effects of Calorie Restriction on Aging
For ages, humans have been searching for ways to counteract the aging process. The legendary fountain of youth generated much attention in the past, and more recently, thousands of dollars have been spent each year on creams, pills, plastic surgery, and various forms of therapy designed to make one look and feel younger. So far nothing has been proven to reverse or even retard human aging, but scientists are finally catching a glimpse as to a dietary manipulation technique that might work.
In the 1930s, Clive McCay, a scientist at the laboratories at Cornell University, experimented on his ...view middle of the document...
When calories were restricted by 30 percent, they lived from 56 to 57 months, which is roughly equivalent to 147 years old in human terms (Man Immortal).
Among his findings, Walford discovered that the mice lived about 30 percent longer than average, weighed about 30 percent less than usual, had lower blood pressure, lower levels of serum cholesterol, lower concentrations of circulating glucose, lower triglyceride concentrations, lower insulin levels, and greater insulin sensitivity. In short, their bodies were becoming extremely efficient at utilizing the few calories that were put into it (Weindruch 49). The animals had stronger immune systems, and the onset of common late-life diseases, such as certain cancers, were held off as well (Weindruch 48).
Why It Works
Walford knew that reducing calories was slowing metabolism in the mice and improving their health in general, but he was unaware of exactly what was causing the slowing of the metabolism, and why it caused the extension of life span in the mice. In order to explain what was triggering the results, we first look at worms.
Nematodes have an average life span of 14 days. However, at times when food is scarce, such as when overpopulation occurs, the seemingly simple worms have the ability to switch into a state of suspended animation known as the Dauer phase, “dauer” being the German word for “durable,” during which they can live for two months or more, which is over four times longer than usual. Scientists such as Cynthia Kenyon at the University of California at San Francisco are studying the nematodes and their connection with humans (Roush 897).
Kenyon and her colleagues have found that there is a gene responsible for the worms changing into their Dauer phase. It is called DAF-2, for Dauer-formation defect 2. The gene senses when there is not enough glucose present, and then acts as a switch to begin the Dauer phase. More recently it has been found that the DAF-2 gene shares 35 percent of its amino acid sequence with the human insulin receptor, making it the worm equivalent of our insulin receptor (Roush 897). So when there is insufficient glucose in the human body, there is less insulin secreted in response, and the human insulin receptor detects that there is not enough insulin, and acts as a switch to slow our metabolism and cellular respiration.
Metabolism is defined as the energy-releasing breakdown of molecules. Energy is created through cellular respiration. Cellular respiration takes place in the mitochondria of the cell, and uses oxygen to make energy in the form of ATP. During ATP synthesis, an electron is removed from an oxygen molecule during the electron transport chain, leaving an unpaired electron. These molecules with one unpaired electron are known as free radicals (Kotulak and Gomer).
Free radicals are very unstable molecules. The byproduct of burning oxygen in cells, they severely damage essential enzymes, molecules, organelles, and DNA (Weindruch 49). The...