January 02, 2007
Olive Oil Lowers Oxidative Stress Marker

The ability of olive oil to lower a marker for oxidative damage of DNA in cells suggests that olive oil might lower the risk of cancer.

If you want to avoid developing cancer, then you might want to add eating more olive oil to your list of New Year's resolutions. In a study to be published in the January 2007 issue of The FASEB Journal, scientists from five European countries describe how the anti-cancer effects of olive oil may account for the significant difference in cancer rates among Northern and Southern Europeans.

The authors drew this conclusion based on the outcomes of volunteers from Denmark, Finland, Germany, Italy, and Spain, who consumed 25 milliliters (a little less than a quarter cup) of olive oil every day for three weeks. During this time, the researchers examined urine samples of the subjects for specific compounds known to be waste by-products of oxidative damage to cells, a precursor to cancer. At the beginning of the trial, the presence of these waste by-products was much higher in Northern European subjects than their Southern European counterparts. By the end of three weeks, however, the presence of this compound in Northern European subjects was substantially reduced.

"Determining the health benefits of any particular food is challenging because of it involves relatively large numbers of people over significant periods of time," said lead investigator Henrik E. Poulsen, M.D. of Rigshospitalet, Denmark. "In our study, we overcame these challenges by measuring how olive oil affected the oxidation of our genes, which is closely linked to development of disease. This approach allows us to determine if olive oil or any other food makes a difference. Our findings must be confirmed, but every piece of evidence so far points to olive oil being a healthy food. By the way, it also tastes great."

I'd like to see more dietary studies using oxidative stress markers as a quicker way to guess at the likely long term effects of various food choices.

The polyphenols in olive oil surprisingly do not look like the cause of the lowered oxidative stress marker.

Another interesting finding in the study suggests that researchers are just beginning to unlock the mysteries of this ancient "health food." Specifically, the researchers found evidence that the phenols in olive oil are not the only compounds that reduced oxidative damage. Phenols are known antioxidant compounds that are present in a wide range of everyday foods, such as dark chocolate, red wine, tea, fruits, and vegetables. Despite reducing the level of phenols in the olive oil, the study's subjects still showed that they were receiving the same level of health benefits.

I'd like to see studies done using different high phenol foods that are low in fat to see if any of the foods can lower oxidative stress using the same marker (8oxodG - sounds like an oxidized form of the nucleic acid guanine) that these researchers used.

The researchers measured the compound 8oxodG in the urine as an indicator of oxidative stress and damage and found olive oil lowered 8oxodG.

Oxidative damage is a process whereby the metabolic balance of a cell is disrupted by exposure to substances that result in the accumulation of free-radicals, which can then damage the cell.

The men were found to have around 13% less 8oxodG compared with their levels at the beginning of the study.

At the beginning of the study, men from northern Europe had higher levels of 8oxodG than those from southern Europe, supporting the idea that olive oil had a reductive effect.

I've started eating more olives and olive oil. The olive oil is displacing canola oil. But we need a comparative study of the effects of olive oil and canola oil on urine 8oxodG. Ditto for fish oils.

The bigger story on olive oil has been the suspected heart benefit. A September 2006 paper published in the Annals of Internal Medicine found olive oil boosts heart healthy HDL cholesterol while lowering triglycerides and lowering oxidized LDL cholesterol.

Results: A linear increase in high-density lipoprotein (HDL) cholesterol levels was observed for low-, medium-, and high-polyphenol olive oil: mean change, 0.025 mmol/L (95% CI, 0.003 to 0.05 mmol/L), 0.032 mmol/L (CI, 0.005 to 0.05 mmol/L), and 0.045 mmol/L (CI, 0.02 to 0.06 mmol/L), respectively. Total cholesterol–HDL cholesterol ratio decreased linearly with the phenolic content of the olive oil. Triglyceride levels decreased by an average of 0.05 mmol/L for all olive oils. Oxidative stress markers decreased linearly with increasing phenolic content.

When you can lower heart disease and cancer risk with the same dietary practice that sounds like a winner to me.

Share |      Randall Parker, 2007 January 02 10:48 PM  Aging Diet Cancer Studies

Bob Badour said at January 3, 2007 6:48 AM:

Randall!! You have known for at least a decade that canola is poison. Why on earth would you have that stuff in your diet in the first place?

Dr Jane Karlsson said at January 4, 2007 5:12 AM:

Hi Randall,
I am wondering if the magic ingredient in olive oil could be manganese. I read in a plant physiology book once that most of the manganese partitions into the lipid fraction. Manganese is crucial in protecting mitochondria from oxidative stress, both as a cofactor for manganese superoxide dismutase, and by activating the enzyme systems that produce NADPH for reduction of glutathione (isocitrate dehydrogenase, malic enzyme, and the first two enzymes of the hexose monophosphate shunt). Mitochondria are very sensitive to (reduced) glutathione deficiency, as you will know.

Did you see my post about copper? If not, look up Martha Morris's paper on transfats and copper, and look at Table 1. It shows that people with the highest intake of copper had a global cognitive score no less than six times higher than people with the lowest intake. The really remarkable thing is that the authors imply that copper is bad for the brain, not good. I have discussed this with a colleague here in Oxford who works on Alzheimer's, and he thinks they made a major mistake analysing their data.

Best wishes, Jane

Randall Parker said at January 4, 2007 5:39 PM:


I saw your comment about copper and was puzzled. Meant to say so there. I do know what a global cognitive score is but wonder how someone can be 6 times higher than someone else. I do know about IQ scores and know that we do not have a factor of 6 difference between functioning people on them. I rather doubt that a single mineral could have that big an impact on the rate of brain aging since so many factors influence the rate of brain aging.

As for manganese from olive oil: Seems an easy thing to test for. Give people manganese and see if the same oxidative stress marker goes down as was used in the olive oil study above.

Dr Jane Karlsson said at January 9, 2007 6:47 AM:

Hi Randall,

Here is the table, hope I get it right: http://archneur.ama-assn.org/cgi/content/full/63/8/1085/NOC60041T1

I agree with you. It is very strange indeed. My colleague who works on Alzheimer's has emailed the authors but so far has not received a sensible reply.

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