For a long time fats have been the nutritional “bad guy”, blamed for everything including heart disease, diabetes and obesity. We talked about this in an earlier blog (Go Easy On Fats! ). The food industry picked up on our fear of fats and created a vast array of low fat foods to tempt us. Their marketing departments were also busy with campaigns and slogans like “99% fat free”, “lite”, “no trans fats”, “cholesterol free” and “skimmer”. The not-so-subtle message being the “low fat” food is better for you and will keep you slim. Yet the very same marketing departments were also telling us fats were good for us! We were encouraged to eat certain relatively fatty foods like fish (salmon, herring, and mackerel may have more than 10% fat), avocadoes (10% or more), nuts (more than 50%) and that we needed to take fish or krill oils as fat supplements. With all the mixed messages, no wonder the consumer was confused!
So what about olive oil? Is it good or bad? Olive oil has been a food for a very long time. Indeed, there are references to olive oil in almost all the major religious texts, it was considered a gift from the Gods by the ancient Greeks and is mentioned several times in the works of Homer. There is plenty of evidence a high intake of olive oil, as part of a balanced Mediterranean diet, with its emphasis on grains, fresh fruit, fish, vegetables and pulses is healthy. In the last decade a lot of research has been carried out to better understand why (1). Much of this research has focused on two components of olive oil:
- monounsaturated fats
While both of these are present in abundance in olive oil, there are also a lot of other substances in olive oil which are nutritionally important.
There are lots of claims about the beneficial effects of olive oil on our health and wellbeing. It has for example been said to reduce the risk of heart disease, type 2 diabetes, cancer and metabolic syndrome (1, 2). Metabolic syndrome greatly increases the risk of diabetes, stroke and heart disease. Those with metabolic syndrome have high levels of a particular fat (triglycerides) in the blood, increased body fat, especially at the waistline, high blood pressure and high blood sugar. But what is particularly intriguing about olive oil is the claim that it may reduce the risk of obesity. Yes, you did read that right: Eating a fat may actually stop you from getting fat! What a paradox if it were true? Olive oil is a fat, containing about the same amount of energy as most other fats and oils (34 kjoules per gram or 230 calories per ounce). Olive oil also contains almost double the kjoule or calorie content of the other two principal components of our diet: Carbohydrates and proteins. Because of its high kilojoule or calorie content, you would have thought eating olive oil would increase, not decrease, the likelihood of putting on weight and obesity!
So what is the evidence eating olive oil can stop you getting fat? And how can it be?
Now no one is saying taking a few spoonfuls of olive oil every day will make you lose weight. What is being claimed is a Mediterranean diet, where olive oil is the principal fat, “does not contribute to obesity” or “is not associated with higher weight gain or risk of developing obesity” (3). And these claims are coming from reputable scientists in international scientific journals and not from the latest fad diet book or people growing or selling olive oil. A more recent study published in the European Journal of Endocrinology by a group of Spanish scientists appears to show children (1 – 4 years) can also benefit from an olive oil rich diet (4). Yet another study indicates even those who have an inherited predisposition to putting on weight may also benefit from an olive oil rich diet (5).
While these findings do not prove olive oil is a magic elixir to ward off excess weight, they do suggest, when taken as part of a balanced Mediterranean diet, the body may not treat olive oil in the same way as other fats, like animal fats. So what is it that is different about olive oil?
One very obvious difference is in the very high levels of the so-called “monounsaturated” fats, which make up more than 70% of olive oil. By comparison, animal fats like those in butter only have around 25% monounsaturated fat. The main “monounsaturated” fat in olive oil and butter for that matter, is oleic acid. For quite a while it was considered to be just another fat. We now know better.
We have known for some time oleic acid does not increase blood cholesterol in the same way as saturated fats do. Then, a few years ago, scientists working in a completely different area of research – and this happens quite a lot – made the very interesting discovery. The scientists were working on cannabinoids, chemical substances present in certain plants, in particular marijuana or pot. Marijuana is often called cannabis because of the high levels of cannabinoids it contains. The scientist found the body made its own “cannabinoids”, called “endocannabinoids”. While these molecules were chemically quite different from those found in marijuana, they also had effects on different organs and especially the brain. And one of these endocannabinoids, called oleoylethanolamide, is made in our bodies from oleic acid, the main fat found in olive oil (6). What makes this finding particularly interesting from a nutritional point of view, is oleoylethanolamide seems to be made in the gut and, in ways we do not as yet understand, may be involved in the regulation of food intake (6, 7). So when you eat olive oil, the monounsaturated fat oleic acid in the oil is converted in your gut into something, which suppresses appetite and therefore regulates the amount of food you eat. Could this explain the apparent paradox where eating olive oil does not make you put on weight?
It is probably not that simple because olive oil is a complex mixture, containing a lot more than just oleic acid. There are many other components, just a few of which include:
- Polyphenols: Which act as antioxidants, anti-microbials and anti-inflammatories;
- Fat soluble vitamins: Like vitamins E, K and beta-carotene, a vitamin A precursor;
- Squalene: A fatty substance known to boost the immune response;
- Phytosterols: Which can reduce the blood levels of the “bad cholesterol.
Then there are dozens of other substances, which contribute to the unique odour, colour, and taste of olive oil. If olive oil were involved in lowering the risk of gaining weight, it would be surprising if these additional substances did not contribute in some way.
Consumers are spoilt for choice when it comes to choosing an oil or fat for cooking. Making that choice is confusing however because of the conflicting messages the consumer gets from the media, the internet and the labels on the bottles. What is a saturated, monounsaturated or polyunsaturated fat? What does Extra-Virgin mean? What is a cold pressed oil? How long can I store an oil? Which oil is good for my health and why? Is this a safe oil to cook with? What does “Organic” on the label really mean? These are just some of the questions asked by consumers. To answer this question, and many others, we have written “Olive Oil: Everything You Want to Know”, which is available as both an e-book and as a paperback book on our website.
“Olive Oil: Everything You Want to Know” has been specifically written for consumers and addresses many frequently answered questions about olive oil. Others who will find the book useful include:
- Anyone confused by the terminology surrounding olive oil.
- Those who want to know what the information on the label means or want to know more than what is on the label.
- Those who want to know what olive oil is and what it contains.
- Those who want to know about the health benefits of olive oil, one of the key components of the Mediterranean diet.
- Professional chefs, retailers, foodies, nutritionists, dieticians, health and food journalists.
- The olive oil industry.
- And anyone who wants unbiased and understandable information based on the latest scientific and medical research published in international peer-reviewed journals.
Someone like you! We hope you enjoy it.
Meanwhile, stay healthy.
(1) Lopez-Miranda, J.; et al; Olive oil and health: Summary of the II international conference on olive oil and health consensus report. Jaén and Córdoba (Spain) 2008. Nutr. Metab. Cardiovasc. Dis., 20, 284-294, 2010.
Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/20303720 
(2) Psaltopoulou, T.; et al; Olive oil intake is inversely related to cancer prevalence: a systematic review and a meta-analysis of 13,800 patients and 23,340 controls in 19 observational studies. Lipid Health Dis., 10, 127, 2011.
Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/21801436 
Full article available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3199852/pdf/1476-511X-10-127.pdf 
(3) Bes-Rastrollo, M.; et al; Olive oil consumption and weight change: the SUN prospective cohort study. Lipids, 41, 249-256, 2006.
Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/16711599 
(4) Haro-Mora, J. J.; et al; Children whose diet contained olive oil had a lower likelihood of increasing their body mass index Z-score over 1 year. Eur. J. Endocrinol., 165, 435-439, 2011.
Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/21715417 
(5) Razquin, C.; et al; A Mediterranean diet rich in virgin olive oil may reverse the effects of the -174G/C IL6 gene variant on 3-year body weight change. Mol. Nutr. Food Res., 54, Suppl 1, S75-82, 2010.
Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/20352618 
(6) Gaetani, S.; et al; Role of endocannabinoids and their analogues in obesity and eating disorders. Eat Weight Disord., 13, e42-8, 2008. Erratum in Eat Weight Disord. Mar;16(1):e72., 2011.
Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/19011363 
(7) Thabius, C.; et al; Analysis of gene expression pattern reveals potential targets of dietary oleoylethanolamide in reducing body fat gain in C3H mice. J. Nutr. Biochem., 21, 922-928, 2010.
Abstract available at: http://www.ncbi.nlm.nih.gov/pubmed/19954948