For some years now, the ‘Mediterranean’ diet has been said to have broad advantages to health, particularly with regard to ‘cardiovascular’ diseases such as heart disease and stroke. A key element in the Mediterranean diet is olive oil, which is rich in ‘healthy’ monounsaturated fat. However, in recent times some scientists have begun to suggest that olive oil may have benefits not just for our circulation, but in terms of cancer protection too. Studies have found that high olive-oil consumers tend to be at a reduced risk of several cancers, including those of the breast, ovary and prostate.
These so-called ‘epidemiological’ studies are interesting, but in no way prove that olive oil consumption can protect against cancer. However, scientists have gone on from these studies to look at what it might be about olive oil that might be cancer-protective [1]. This week, saw the publication of one such study. In it, 182 men spread across five countries were given 25 mls (5 teaspoons) of olive oil to consume each day for two weeks. The urine of these men was analysed for levels of chemicals that measure the amount of damage wreaked in their DNA by chemical entities known as ‘free radicals’. DNA damage is thought to be a key process in the triggering of cancerous change in the body’s cells. The consumption of olive oil for two weeks was found to reduce the level of one marker of DNA damage (8-oxo-deoxyguanosine, for the technically-minded) by 13 per cent.
The authors of this study speculated on what it is about olive oil that might account for this effect. Olive oil is known to contain what are known as ‘phenolic’ compounds that have the ability to quell free radicals. To study this, the researchers used olive oils with different phenolic contents. The amount of DNA damage protection seen seemed to have no relationship with the phenolic content of the olive oil, which suggests that the phenolic compounds were not responsible for the protective effect.
The researchers went on to suggest that it is monounsaturated fat itself that might be the relevant factor here. The notion that monounsaturated itself might be cancer-protective comes in the form of a study published last year which found that oleic acid (the most plentiful monounsaturated fat in olive oil) has the capacity to mute the effects of a common breast cancer gene [2]. What all this adds up to is that olive oil has biochemical effects within the body that could account for the association it has with reduced cancer risk.
The authors of the FASEB study published this week have suggested that their work helps to explain why it is that rates of certain cancers, including those of the breast, ovary and prostate are less common in Southern Europe than Northern Europe. This of course is true. Another likely, and often overlooked, factor is sunlight.
The action of sunlight on the skin generates vitamin D, which is known to have a number of cancer-protective effects. This is supported by a wealth of evidence showing that incidence of several types of cancer is lower in areas of the globe that get plenty of sunshine. For more information about this, you might like to visit Dr William Grant’s website at www.sunarc.org. Here, you’ll find a stack of information on the importance of sunlight and vitamin D on cancer risk.
References:
1. Machowetz A, et al. Effect of olive oils on biomarkers of oxidative DNA stress in Northern and Southern Europeans. FASEB 2006 Nov 16 [Epub ahead of print]
2. Menendez JA, et al. Oleic acid, the main monounsaturated fatty acid of olive oil, suppresses Her-2/neu (erbB-2) expression and synergistically enhances the growth inhibitory effects of trastuzumab (HerceptinTM) in breast cancer cells with Her-2/neu oncogene amplification. Annals of Oncology 2005 16(3):359-371