Wednesday January 20 2010
Eating fish is a good way of obtaining omega-3 fatty acids
“Fish oil may really be an ‘elixir of youth’ because of its effects on our biological ageing,” says The Daily Telegraph.
The news is based on a study measuring heart patients’ levels of omega-3 fatty acids, which can be found in fish and supplement pills. Researchers then looked at sections of the patients’ DNA called telomeres, measuring the speed of naturally occuring changes associated with ageing. The results showed that there was an association between higher omega-3 levels and a reduction in the rate at which the patients’ telomeres shortened.
While this study may shed light on the possible actions of omega-3, it did not assess whether these changes affected the health or wellbeing of the participants. This was preliminary research, and further studies are needed to see whether omega-3 fatty acids have a direct effect on telomeres.
Where did the story come from?
This research was carried out by Dr Hamin Farzaneh-Far and colleagues at San Francisco General Hospital and the University of California. The study was funded by the American Heart Association. It used participants from the Heart and Soul prospective cohort study, which had received funding from numerous US research organisations.
The study was published in the peer-reviewed Journal of the American Medical Association.
The research was generally covered accurately by the press. The Daily Express mistakenly referred to telomeres as cells - telomeres are actually regions of DNA found at the end of chromosomes. Telomeres are thought to protect the DNA found in the chromosomes during cellular division.
What kind of research was this?
This was a prospective cohort study looking at a potential link between the levels of omega-3 fatty acids in the blood of heart disease patients and the length of their telomeres. Telomeres are regions of DNA at the end of chromosomes, which are thought to protect the DNA as cells divide. Each time a cell divides, the length of its telomeres reduces slightly. As such, telomere length is often used as a measure of biological age, indicating how many times a cell has divided and how many further divisions it is capable of.
Fish oils and omega-3 supplements have been recommended for the prevention of coronary heart disease following trial results that suggest they may have a protective effect. The underlying mechanism behind this potential protection is unknown.
In this study, the researchers wanted to see whether omega-3 fatty acid levels were associated with telomere length. The participants were given two assessments several years apart to see how quickly their telomeres were shortening in length.
This type of study can only find associations between diseases and factors that may influence them. It cannot directly measure the effect of omega-3 fatty acids on telomere length, or on any measure of disease or wellbeing.
What did the research involve?
The participants were part of the Heart and Soul study, a prospective cohort study that followed people with stable heart disease to test the effects that psychosocial events had on their risk of cardiovascular events.
The participants were recruited from outpatient clinics in California. All had at least one major symptom of heart disease, which was defined as a narrowing of at least one heart artery, poor heart functioning after exercise, changes in the heart blood vessels, or previous heart attack. As the study was looking at stable heart disease, the researchers excluded anyone who had suffered a heart attack in the previous six months.
From 2000-02 the participants enrolled in the study, undergoing a medical examination and providing blood samples. Demographic data, body measurements and medical histories were obtained from the participants. They also had their exercise capacity on a treadmill assessed.
The researchers measured blood levels of the types of omega-3 oils obtained from fish: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The amount of ‘good’ cholesterol (HDL) and ‘bad’ cholesterol (LDL) were also measured. The researchers then isolated white blood cells from the blood, extracted its DNA and measured the length of its telomeres.
The participants were followed up for an average of six years. They were examined again at the end of the study, and the researchers compared how their telomeres had shortened since their first blood test.
What were the basic results?
The researchers found that at baseline (entry into the study) higher omega-3 levels were associated with older age, white ethnicity, higher income, higher education level and higher ‘good’ cholesterol levels. Higher levels of omega-3 were also associated with a lower incidence of heart attacks, diabetes and smoking, plus lower levels of inflammatory markers and smaller waist-to-hip ratios.
At baseline there was no association between omega-3 levels and telomere length. However, when researchers looked at changes in telomere length over the five-year study period, they found that the baseline omega-3 levels were associated with the extent of telomere shortening during this period. Participants whose omega-3 levels were in the lowest quarter showed telomere shortening of 0.13 telomere units, whereas participants who were in the highest quarter of omega-3 levels showed telomere shortening of 0.05 telomere units.
The researchers then analysed their results but made adjustments to take into account factors that may affect heart disease. After adjustment for demographics, age, blood pressure, other fats in the blood, medications, markers of inflammation and baseline telomere length, they found that there was still an association between omega-3 levels and the length of telomeres.
How did the researchers interpret the results?
The researchers said “baseline levels of marine omega-3 fatty acids were associated with decelerated telomere attrition over five years. The association was linear and persisted after adjustment for potential confounders”. They say their findings “raise the possibility that omega-3 fatty acids may protect against cellular ageing in patients with coronary heart disease”.
This was an interesting preliminary study, which found that high omega-3 levels were associated with reduced telomere shortening over time in a population who had stable heart disease. However, interpretations should be made with care:
- This association suggests a potential mechanism by which omega-3 fatty acids may be protective to cells. However, the researchers suggest that a randomised placebo controlled trial would be necessary to determine whether omega-3 fatty acids directly reduces the rate of telomere shortening.
- The researchers say there are many other things that may contribute to telomere shortening, such as other dietary components and the number of free radicals a person is exposed to. These were not measured in this study.
- The researchers only looked at telomere length in white blood cells. They suggest that further studies should look at the telomere length of cells in the heart and blood vessels, which are relevant to heart disease. They also suggest that the research could be repeated in different populations, because the participants were predominantly males suffering from coronary artery disease.
- It has not been assessed whether the reduction in telomere shortening had any impact on the person’s general health and wellbeing or on the cardiovascular disease process.
Fish oils containing omega-3 fatty acids are recommended for a healthy heart. This preliminary study suggests that reducing telomere shortening is a potential mechanism by which omega-3 fatty acids might be protective. However, this study has only shown an association. Further research is needed to test this theory directly.