From a nutritional perspective we are finally emerging from the era of everything having to be low fat or fat free. For the last couple of decades the public have been persuaded to be scared of fat in the belief that eating fat made you fat, and gave you heart disease to boot. However the scientific evidence to support these seemingly commonsense assumptions is just not there.
On the contrary we now know that the important message is that it is the type of fat that you eat that is crucial and not the total amount. In fact there are so many good nutritional factors about extra virgin olive oil that it really does earn it’s right to be called a health food. This is why I include it in the Dr Joanna plate and you'll find it used ubiquitously in my recipes and meal ideas.
We shouldn’t really be surprised. After all the Mediterranean diet with olive oil as its staple fat has long been touted as one of the healthiest in the world. Of course there are other factors about this diet that contribute to its healthfulness (high fish intake, lots of fruit and veg etc) but there is little argument that the source of fat plays a major role. Such a diet is associated with a low risk of heart disease and several cancers, and this has led many to try to emulate the diet in other parts of the world.
So how might olive oil be helping to promote these health benefits?
The first factor may simply be the type of fatty acid it contains. Olive oil is unique in having such a high content of oleic acid. This is a monounsaturated fat (MUFA), meaning it has only one double bond, and this in turn makes it a relatively stable kind of fat. Polyunsaturated fats with lots of double bonds are much more unstable and susceptible to free radical damage that is part of the processes leading to heart disease, cancers and other detrimental effects in the body. By having a MUFA as the principal fat in your diet, you potentially protect cells from this damage while avoiding cholesterol raising saturated fats.
Secondly studies from Europe have shown that olive oil added to the diets of Northern European men, who traditionally don’t consume much, reduces their blood pressure (J. Nutr 2007, 137; 84-7). We also know that in terms of improving the cholesterol profile of your blood a low fat diet is not the best approach, but a diet consisting of the right healthy fats.
Finally extra virgin olive oil is a rich source of several antioxidants that are thought to play important effects in protecting cells in the body from damage.
Interestingly given that we have for a long time thought that eating fat makes you fat, more recent research from here in Australia and overseas is showing that high monounsaturated fat diets can in fact assist weight loss. This may be working in part by replacing processed carbohydrates with the healthy fat from olive oil and other high MUFA foods.
It may also be simply because fat tastes good and so such a diet is far more palatable and easy to follow than the traditional low fat regimes. There are also theories, as yet unproven, that MUFA are more easily ‘burned’ as fuel by the body and therefore less likely to be stored as body fat, than saturated animal fats. Whatever the mechanisms most people will be pleasantly surprised and pleased to hear that they can enjoy foods such as olive oil and still control their weight.
So is there a difference between extra virgin (EVOO) and refined olive oils?
Certainly you will be no doubt be aware that there are enormous differences in terms of flavour, but you may be less aware of the differences in nutritional factors. The gentler extraction techniques used to produce EVOO successfully retains many of the phytochemicals (plant chemicals) including antioxidants present in the fruit. By contrast the combination of heat, pressure, filtration methods and/or chemicals used to produce cheaper refined olive oils removes many of these compounds.
One comparison study showed that compared to EVOO, refined olive oil had 20% less squalene, 75% less total phenols, almost 90% fewer simple phenols and almost 80% fewer lignans (Food Chem Toxicol (2000) 38:647-659). All of these compounds are thought to be beneficial to health. Squalene is now sold as a health supplement as it is thought to have chemoprotective effects. In the body the majority is transported to the skin where it acts as an antioxidant preventing free radical damage. It is possible that high levels of squalene from olive oil in the Mediterranean diet are a protective factor in reducing skin cancer incidence. The phenols are potent antioxidants and may help to reduce levels of oxidised LDL-cholesterol in the blood – this damaged cholesterol is what is taken up into artery walls causing atherosclerosis.
The EuroLive study, conducted across 6 centres in 5 European countries has compared the effects of olive oils varying in polyphenol content. 200 healthy men were given 25ml a day of a low, medium or high polyphenol olive oil. The results clearly showed the benefits of the polyphenols with the group of men given the high polyphenol oil showing significantly higher protective HDL-cholesterol and significantly lower oxidised LDL-cholesterol. The authors conclusions were in full support of recommending EVOO over refined oils to achieve all of the cardiovascular benefits that olive oil can bring (Annals Internal Medicine 2006, 145: 333-341).
In terms of cancer EVOO phenols have also been shown to play a protective role. Research in the lab has shown protection at all three stages of colon cancer development (Int J Cancer 2005;117:1-7). Epidemiological research has shown an inverse relationship between olive oil consumption and breast cancer incidence (Lancet Oncol 2000;1:107-112) and the EPIC study reported that women with an olive oil intake of more than 30.5g a day were 30% less likely to be in the high mammographic breast density group (associated with increased breast cancer risk) (Int J Cancer 2006;118:1782-9).
In conclusion there is little doubt that the high MUFA content of all olive oils confers health benefits, but there are additional benefits to be gained from consuming EVOO. Evidence is building to suggest that the phytochemicals, the polyphenols in particular, found in far greater quantities in EVOO may be beneficial in areas ranging from cancer, heart disease, gut health, rheumatoid arthritis and even play a role in slowing the aging process. EVOO truly does deserve to be labelled a superfood.
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