Nutrition, Aging and Telomeres
How Do We Age?
There is, of course, no simple answer to this complex and intriguing question. However scientists are exploring a number of hypotheses that attempt to explain the underlying mechanisms that affect the aging process. Recent research suggests that there may be a limited number of these mechanisms, providing hope that scientists’ efforts may one day lead to strategies that could help us lead longer, healthier lives.
A number of ‘aging’ hypotheses are being hotly pursued. One hypothesis involves the complex connections between the brain and nervous system and our endocrine glands – the neuro-endocrine system. This system becomes impaired as we age, and can lead to high blood pressure, poor sugar metabolism and sleep problems. Researchers are focusing on a pathway that involves insulin and a substance called insulin-like growth factor. Though reducing levels of insulin-like growth factor extends the lifespan of several species, it’s not yet clear whether it might have the same effect in humans.
Another hypothesis hinges upon free radicals and oxidative damage. Free radicals are one of the by-products of normal cell metabolism, and are normally mopped up and neutralized by antioxidants. But those that escape this clean-up process can damage DNA, proteins and mitochondria – the tiny energy-producing structures in our cells. Mitochondria from the cells of older people tend to be less efficient than those from younger individuals, and too much damage to mitochondria can cause cell death. Because oxidative damage is linked with so many of the problems associated with aging, it remains one of the hottest areas of aging research.
With age, our proteins, DNA and other molecules develop unwanted attachments to one another, referred to as cross-links. The cross-linking hypothesis holds that these attachments disable the function of important proteins and DNA. One of the main offenders is glucose (sugar), which can stick to proteins and form injurious links. Cross-linking of proteins is thought to be partly responsible for wrinkling of the skin as well as age-related cataract.
Another hypothesis arose from the observation that human cells can undergo only a limited number of divisions to make new cells. Most scientists believe that what determines this limit on cell division is the length of a structure called a telomere. Telomeres are positioned at the end of our cells’ chromosomes, and they play an important role in cell division by ensuring that chromosomes don’t fuse together or get rearranged, which can lead to cancer. Every time a cell divides, telomeres get a little bit shorter. And when they are totally gone, the cell self-destructs. Telomere length is believed to be one marker of biological aging.
Nutrition, Aging and Telomeres
Diet can have a profound effect on many aspects of health, including aging. We’ve learned, for instance, that restricting calories can lead to greater longevity in primates. We know that the right diet and lifestyle can help maintain healthy glucose levels, and that dietary antioxidants can help counter oxidative stress. Research is also beginning to shed light on how nutrients affect the expression of our genes.
Preliminary findings from two recent population health studies now raise the question of whether nutrients might be a factor in maintaining telomeres. In the first study , investigators examined multivitamin use, nutrient intakes and telomere length in 586 women aged 35-74. They found that telomeres were modestly longer in multivitamin users compared to non-users. They also observed a positive relationship between dietary intake of vitamins C and E and telomere length.
The second study also looked at the dietary habits and telomeres in nearly 2,000 Chinese participants over 65. The researchers report that the telomeres of people who drank an average of 3 cups of tea (mostly green tea) daily were longer than those drinking on average only a quarter cup per day. Telomeres have been shown to be highly susceptible to oxidative stress, and antioxidant vitamins C, E and the polyphenols in tea could be protective of these structures. While it’s premature to draw conclusions from these findings, they will prompt a new and exciting research direction.
- Xu Q, et al. Multivitamin use and telomere length in women. Am J Clinical Nutr 89:1857-63, 2009.
- Chan R, et al. Chinese tea consumption is associated with longer telomere length in elderly Chinese men. Br J Nutr [Epub ahead of print, Aug 2009]