The Mediterranean diet has been all the rage over in recent weeks because of a flurry of reports about new research suggesting that adherence to the diet slows the aging process.
The diet is not a fad and is really not anything new. Just think about Greek or Italian food and that’s the general idea of the Mediterranean diet. Whole grains, vegetables, fruits, nuts and olive oil are emphasized. Moderate fish consumption, some poultry, and very small amounts of lean beef are allowed as protein sources, as are small amounts of alcohol, such as a glass of wine with dinner, but fatty meats are avoided and sugars kept to a minimum.
Because the Mediterranean diet keeps saturated fats at a low and replaces them with monounsaturated fat (as in olive oil) and omega-3 polyunsaturated fats (as in fish), it is known to decrease risk for heart disease and strokes. Part of the reason is thought to involve special particles that carry cholesterol in the blood. Eating more monounsaturated fat and less saturated fat raises the levels of good blood cholesterol, known as HDL, while lowering the level of bad cholesterol, known as LDL. This helps keep arteries in the heart and brain from narrowing. Mild alcohol consumption also may help keep good cholesterol at a high, while low levels of sugar help to protect against diabetes.
But cholesterol and sugar in the blood do not completely explain the risk lowering effect of the diet against heart disease, strokes, and diabetes. Nor do they explain the fact that Mediterranean diet also reduces the risk of certain cancers. Thus, for many years, scientists have suspected that changes in dietary fats, sugars and other foods must do something at the level of cells and DNA, and that’s why the new research is so exciting. But excitement suggest that we should proceed with caution, since anything powerful to affect DNA in a good way also has the ability to do harm.
Some slack for your chromosomes
Most body cells do not live as long as the individual who carries them, but instead divide to produce daughter cells. When cells divide, chromosomes in the nucleus must replicate their DNA. The DNA of each chromosome is a long strand containing thousands of genes. Each time the chromosome replicates, the strand gets cut a little shorter on each end. Over many years, as old cells divide to make new cells, the DNA of each chromosome gets shorter at the ends of each chromosome. Known as telomeres, the ends of the DNA strand of each chromosome do not contain any genes, but are needed as a kind of slack, so they’re expendable as long as they don’t get too short.
Think of telomeres like the ends of shoelaces. You can keep snipping the ends and the laces work perfectly fine, but as you snip them too short they don’t work so well anymore. In the case of chromosomes, when the telomeres get too short, genes near the ends of the strand can get cut out the next time the chromosome replicates, and also chromosomes can start fusing together. These effects–the gene loss and chromosome fusing–are associated with aging, cancer and various medical conditions. In other words, long telomeres are a sign of youthfulness and good general health, while telomere shortening means that things are starting to go wrong.
Aging and disease
Although telomeres of chromosomes get shorter and shorter as cells reproduce throughout a person’s lifetime, science has revealed factors other than the passage of time that can affect telomere length. One major factor is stress. Because it’s fairly easy to take blood samples from people, most human research involving telomeres looks at the telomeres of white blood cells (leukocytes). Over the years, a range of stress types, including radiation exposure, spaceflight and domestic physical abuse in children have been show to shorten telomeres in white blood cells. We’ve always had an idea that physical and mental stress accelerate aging, but now we know why and apparently the Mediterranean diet can work against that effect.
As with anything involving chromosomes and genes, putting a discovery into practical use requires caution. Probably, the Mediterranean diet merely slows telomere shortening modestly, rather than adding length to telomeres. However, the connection between short telomeres and aging and disease underlies some drug development research aimed at increasing telomere length.
This may sound logical, because long telomeres are good for overall health, but last summer researchers at the University of California at San Francisco and the Mayo Clinic found that people with certain genes associated with long telomeres are at increased risk for gliomas–malignant brain tumors. Now, gliomas are very rare compared with heart disease, strokes, and diabetes, and of course aging, which affects everyone. However, the San Francisco/Mayo results suggest that we probably don’t want to go overboard in terms of preventive therapies to make telomeres very long.
“Though longer telomeres might be good for you as a whole person, reducing many health risks and slowing aging, they might also cause some cells to live longer than they’re supposed to,” says Kyle M. Walsh, a neurosurgeon and one of the researchers of the study.
In other words, short telomeres have their uses too, namely the help cancer cells and other cells that we want to eliminate meet their demise before they develop into disease. So let’s be careful as we consider going beyond dietary control to stronger therapies. We do need slack on our shoelaces, but not so much that we might trip over them.
David Warmflash is an astrobiologist, physician and science writer. Follow @CosmicEvolution to read what he is saying on Twitter.