- Absorption of fat soluble vitamins
- Polyphenol content of olive oil
- Mediterranean diet and industry funded research
- How to cook without oil
This page is written by Dr Malcolm Mackay and edited by Jenny Cameron
See our recent interview:
There is no place for oil in a whole foods, plant-based diet. Olive oil, coconut oil and other vegetable oils are processed foods that do not support good health. If that sounds controversial then consider the following facts:
- Vegetable oils contain almost no vitamins, minerals or fibre
- Vegetable oils are extremely energy dense and lead to weight gain
- Whole plant foods contain all the essential fats that our bodies require
- Mediterranean diets are healthy because of their whole plant foods
The ultimate junk food – weight gain, nutrient displacement or both?
Vegetable oils, including olive oil, are energy dense and nutrient poor. Foods with these qualities are defined as junk foods and when consumed in significant amounts cause weight gain and/or nutrient displacement.
Vegetable oil is almost pure fat and has the highest energy density of any food, more than twice that of sugar. One Australian tablespoon (20ml) of oil provides 160 calories (670kj), the same number of calories as a can of Coke. Adding oil to a meal adds a lot of calories without any appreciable change in portion size. Most people continue to eat the same portion sizes, but the calorie content of the meal is higher, leading to systematic weight gain over time. Recent olive oil research in Australia (Sarapis et al 2020) had subjects consume 60ml of olive oil per day – that’s 480 calories (2000kj) which is about 20-25% of an average person’s daily energy needs. The study observed that energy intake increased by 428 cal (1800kj) per day when subjects added 60ml of olive oil to their diet. However, in the long term, subjects may partially compensate by eating less of other foods, which leads us to the other half of the junk food problem.
Vegetable oils contain very few nutrients. Most have some vitamin E but virtually zero protein, iron, calcium, dietary fibre, and very little omega 3 fats. The extraction of oil from olives, seeds, etc is a form of food processing that removes most of the nutrients – this includes cold pressed oils. Vegetable oils ‘displace’ nutrients from the diet. When we eat more calories from one source, we tend to eat less calories from other sources: eat more low nutrient ‘junk’ and you are likely to eat less nutrient rich whole foods. If 20ml of olive oil were to displace equal calories of wholemeal wheat pasta the nutrient ‘displacement’ would include 4.9g fibre, 2mg iron, 31mg calcium, 0.7mg zinc and 42mg magnesium.
Consuming vegetable oil adds a lot of calories but very few nutrients. If you reduce food intake to compensate for the extra calories you will have less nutrients. If you maintain food intake to conserve nutrients you will gain weight. It’s either weight gain, nutrient loss or a combination of both.
This 144g serve of cooked brown rice has the same number of calories as a 20ml tablespoon of olive oil (160 calories).
A tablespoon of olive oil also has the same number of calories as a 375ml can of Coke.
Note that the Australian tablespoon is larger than in North America (where it is 15ml)
The term ‘good fats’ is often applied indiscriminately with little consideration to its meaning. One could call ground flaxseed a ‘good fat’ because it is in the context of a complete whole food package, and its fatty acid composition is favourable. But what about olive oil? Olive oil consists predominantly of omega 9 monounsaturated fats which are a source of calories but are not a required nutrient. It may surprise you that olive oil is moderately high in saturated fats – 15% – and therefore no amount of olive oil added to the diet will bring the proportion of saturated fats down to a target of less than 10% of calories.
We need some dietary fats – the omega 6 and the omega 3 essential fatty acids. The omega 6 series are abundant in grains, nuts, seeds and seed oils and it is thought that the Australian diet provides far too many omega 6’s relative to omega 3’s compared to the suggested optimal ratio of 4:1 or less. Olive oil contributes excessive omega 6’s with less than 1% omega 3’s and an omega 6 to 3 ratio of 13:1. See also Omega-3 Essential Fatty Acids
Coconut oil deserves a special mention because its one of the few plant fats that are made up of predominantly saturated fats – fats that tend to raise cholesterol and promote insulin resistance. The MCTs (medium chain triglycerides) in coconut oil may not have the same adverse effects but represent only 15% of the fat content.
Olive oil contains vitamin E. Many vegetable oils are high in vitamin E because it’s a fat soluble vitamin that is retained when the fats are extracted from their whole plant-food source. Vegetable oils appear high in vitamin E because they are a food concentrate – on a per calorie basis, they are no higher than the plants from which they were made. Many whole plant foods, including whole grains, are rich in vitamin E, and its not a nutrient that’s associated with deficiency states.
Absorption of fat soluble vitamins
We do not need to add oil to our meals to absorb fat soluble vitamins and phytonutrients. Nutrition research has overturned the decades old belief that fat soluble nutrients are only absorbed in association with large amounts of dietary fat. A 2014 nutrition textbook stated that the carotenoids in a salad would not be absorbed without the addition of a high fat salad dressing and gave one reference of a study that was funded by a salad dressing manufacturer (Brown et al 2004). When the subjects ate the low-fat salad alone, with no other food, blood measurements suggested that the carotenoids in the salad were not absorbed without the dressing. This concept has led some dietitians to recommend adding olive oil to vegetables and salads to boost the absorption of fat-soluble nutrients.
Research in the Phillipines (Ribaya-Mercado et al 2007) found that only 2.4g fat per meal was needed for optimal utilization of vitamin A and concluded that the “poor or marginal vitamin A status observed in the study participants at baseline cannot be attributed to insufficient fat intakes, but rather to insufficient intakes of food sources of vitamin A.” Just to put it into context, 2.4 g fat can be provided by the whole grains alone in a meal of rice and vegetables, or oats and fruit.
More recent research has found that vitamin E, a fat soluble vitamin, is well absorbed regardless of the fat content of the meal (see Reboul 2019). Traber et al 2019 showed that after gaining entry into the enterocytes (cells lining the small intestine), vitamin E is kept in storage until there is enough fat to package it into chylomicrons (fat/cholesterol particles) and release it into the blood. Short term studies such as the salad dressing study missed this delayed appearance in the blood and mistakenly assumed that none was absorbed. We don’t have to worry about getting enough fat to form chylomicrons as a low fat, whole foods, plant-based diet still provides about 10% of calories from fats (>20g per day), which is more than enough.
Other fat-soluble vitamins/phytonutrients are likely to follow a similar pattern. Enterocytes have ‘cholesterol transporter’ proteins on their surface that transport a broad range of fat-soluble nutrients including vitamin E, carotenoids, vitamin D, vitamin K, phytosterols and lutein. Hopefully, future nutrition education will recognise that large amounts of ‘healthy fats’ are not necessary for nutrient absorption and Australians can stop pouring olive oil on their salad and vegetables.
Polyphenols are phytochemicals, with anti-inflammatory and antioxidant properties, that are found in many different plants. Oleocanthal, the main polyphenol in olive oil, has been the subject of much research in isolation from the broader context of other plant sources of polyphenols. It is the polyphenols in olive oil that are alleged to give it cardioprotective qualities.
Not all olive oil has a high polyphenol content. In a recent Australian study (Sarapis et al 2020), the ‘high polyphenol olive oil’ had 36mg/100g polyphenols while the ‘low polyphenol olive oil’ had only 8.6. (These values are lower than the analyses listed in the table below). The public health message that ‘olive oil is good for you’ (because of the polyphenols) is at odds with the reality that most of the olive oil consumed in the community is the cheaper low polyphenol products.
The polyphenol content of olive oil needs to be put into perspective and compared with other food sources. The table below compares the polyphenol content of common plant foods – olive oil compares poorly with many whole plant foods. 100g strawberries has 235mg of polyphenols compared to only 12mg in a 20ml tablespoon of extra-virgin olive oil. The inferior polyphenol content of olive oil becomes more pronounced when we adjust for its ultra-high calorie content and express polyphenol content in milligrams per calorie. 100 calories of strawberries has 960mg polyphenols whereas 100 calories of EVOO has only 7.6mg. The oleocanthal in extra-virgin olive oil would need to be orders of magnitude more biologically active than other polyphenols for olive oil to qualify as a good source of polyphenols.
Polyphenol content of food
Mediterranean Diet and Olive Oil Industry
Much of the ‘evidence’ for olive oil comes from Mediterranean diet studies. Adherence to a Mediterranean diet is associated with a lower incidence of cardiovascular and other diseases. But the key qualities that make a Mediterranean diet are not olive oil, fish or red wine but rather the whole plant foods – legumes, whole grains, vegetables and fruit. It is these components that are most strongly associated with better health outcomes. Follow up studies of the people of Crete found that individuals who consumed the most olive oil had the most heart disease (Vrentzos et al. 2007).
The PREDIMED study has been misrepresented as evidence that a Mediterranean diet with olive oil or nuts is more heart healthy than a low-fat diet. However, the ‘advice to eat a low fat diet’ group was not low fat (at 37% calories from fat), received less counselling than the other groups, and at the end of the study averaged less legumes, vegetables and fruits than the other groups (although not statistically significant). Whenever we read of studies that report benefits from a particular diet, we ask “compared to what?”. PREDIMED found no significant reduction in cardiac events or mortality but did find a reduction in strokes, particularly in the nut eating group. No Mediterranean diet studies have demonstrated the regression of heart disease observed in research by Ornish and Esselstyn which used a low fat, whole foods, plant-based diet.
The booming olive oil industry has become a major sponsor of nutrition research (and Lifestyle Medicine). Research seems to have been focussed on drawing out the benefits of olive oil rather than comparing it to whole plant foods or putting the findings into context – for example, investigating the pharmacological properties of oleocanthols (phytochemicals in extra virgin olive oil). Some studies report statistically significant benefits that are of little clinical significance – eg. an Australian study that found a minimal improvement in blood pressure for EVOO (extra-virgin olive oil) compared to lower quality olive oil (Sarapis et al 2020). A recent study from Greece had an abstract that reported great improvements in cognitive function in subjects with early dementia but had used a dozen measures of cognition, most of which showed no significant improvement (Tsolaki et al 2020).
The ‘processed food’ label could damage the image of olive oil but industry has found a solution – a new term has emerged, ‘ultra-processed food’, which does not seem to include olive oil.
See also our blog post discussing recent research on Olive Oil and Mortality
Saturated fats, unsaturated fats and carbohydrates
The vegetable oil saga began in the 1960’s when the association between saturated (animal) fat intake and heart disease became widely accepted. The first error was to attribute the entire blame on a single nutrient – fat – rather than the ‘whole’ animal product ‘package’. The second was to try and solve the problem by simply adding more fat to the diet in the form of polyunsaturated vegetable oils. The polys had a favourable effect on blood cholesterol, but long-term heart outcomes did not reflect this and they were implicated with cancer. Enter the mono-unsaturated fats, particularly olive oil, the answer to the quest to find a fat we could add to our food without compromising our health.
Large observational studies often crunch the data set to try and tease out individual foods or macronutrients. Some studies suggest that unsaturated fats are healthier than carbohydrates. This may be true when the ‘carbs’ are sugar and processed food but the comparison is irrelevant when the carbohydrates are whole plant foods.
Effects of oil on arteries
Vegetable oils and high fat meals are harmful to arteries.
Flow mediated dilation is a well validated test for measuring the impact of food on endothelial function. Impaired flow mediated dilation is predictive of future cardiovascular events. A single high saturated fat meal can impair flow mediated dilation for up to 6 hours. A reduction in flow mediated dilation is also observed after ingestion of polyunsaturated vegetable oils and olive oil. A study by Dr Robert Vogel (Vogel et al 2000) on the effect of vegetable oils on the arterial flow found that olive oil reduced flow mediated dilation by 31% and canola oil by 10%, suggesting that ordinary olive oil is more harmful to endothelial function than canola oil (which contains less saturated fats and more omega 3 fats).
Some olive oil studies have used ischaemic reactive hyperaemia as a measure of endothelial function, but this is not a well validated measure and fails misses some conditions associated with impaired endothelial function. We should regard studies that have used this method to assess the impact of olive oil on artery function as inconclusive. Studies using the gold standard flow mediated dilation method have shown extra virgin (high polyphenol) olive oil to have a more neutral effect, neither worsening blood flow nor protecting against the adverse impact of a subsequent high animal fat meal. In contrast to the negative or neutral effects of olive oil, fruits, vegetables (and, in one study, walnuts) have a strong protective effect, reducing the impact of a high fat meal on flow mediated dilation.
The EPIC study (Spanish cohort) found that neither ordinary olive oil nor extra virgin olive oil significantly reduced heart attack rates after controlling for other healthy lifestyle behaviours like vegetable intake. The heart healthy components of the Mediterranean diet seem to be the antioxidant rich foods – fruits, vegetables, and some varieties of nuts – rather than the olive oil.
Olive oil and polyunsaturated oils raise HDL cholesterol, however changing the value of a biomarker for disease does not always translate into reduced disease risk. For example, a clinical trial of an HDL raising drug was stopped prematurely due to an increase in cardiac events. Past animal studies, a research method that is no longer considered ethically acceptable, found that olive oil was just as bad as saturated fat for promoting heart disease in monkeys (Rudel et al 1995).
Adding vegetable oil may raise cholesterol by causing weight gain and by displacing fibre-rich foods (e.g. oats) that block the absorption of cholesterol.
Australian Dietary Guidelines
The Australian Dietary Guidelines do not support the high intake of olive oil that many of our health professionals are advocating. The guidelines recommend that we choose foods from the five food groups, none of which include vegetable oil.
In respect to weight gain the guidelines state that “Foods with a higher energy density encourage energy intake above requirements”, and that Australians limit the consumption of “energy-dense, nutrient-poor discretionary foods”. Vegetable oils, including olive oil, fit all these criteria – maximum energy density, nutrient poor and discretionary in being outside of the five food groups.
We recommend that you aim to eliminate all vegetable oil from your diet including oil in food products. A ‘little bit of oil’ can add a lot of calories and displace important nutrients. Using oil at home may desensitise you so that you do not notice the high oil content when eating out. We need more people to request no oil or minimal oil so that restaurants know consumers want this option.
- Why do we recommend a low-fat diet?
- How to cook without oil
- Omega-3 Essential Fatty Acids – discusses omega-6 to omega-3 ratios
- Energy density – this is the key to making a WFPB diet work
- Nutrient density – gives vegetable oil a minus number for nutrients
- Energy Pie – explains why low carb means high fat
- Eating out and the Guide for Chefs
- Is Oil Healthy? – Caldwell B. Esselstyn (2019)
- NO OIL! Really, NO oil! Webinar 03/17/16 – (55 min video) Dr John McDougall
- Salt, Sugar and Oil: What You Need To Know (video) – Dr Michael Klaper, available through Vimeo
- Blood Sludge: Blood Flow, Before & After Eating a Fatty Meal – (1 min. video) footage of animal arteries provided by Roy Swank, MD
- Lipemic Plasma. The Importance of LOW Fat Plant Based Foods – (video) Randy Kreill discusses how his high-fat plant based food choices (including not avoiding added oils) led to lipemic plasma (fatty blood)
- Don’t Be Duped By Bad Science – Part 1 of Fats (34 min video) – Jeff Nelson
- You Don’t Need Added FAT to Absorb Nutrients (Part 3 of Nuts) – Jeff Nelson looks at the science behind the claims regarding absorption of fat soluble vitamins
- Fat Soluble Vitamins Do Not Need to be Consumed With Fat – (video, starts at 5m 35sec) Pam Popper
- The Truth About Olive Oil – Jeff Novick, RD
- No Oil — Not Even Olive Oil! – (4 min video) Dr Caldwell Esselstyn Jr, is adamant that we should use “no oil” and gives his reasons in this excerpt of a longer talk.
- The Myth of Moderation Pt 2: The Impact of “Just A Little Oil!” – Jeff Novick, RD
- Olive Oil Is Not Healthy – (10 min. video) Michael Klaper, MD. This is a short excerpt of his longer talk at the 2012 Healthy Lifestyle Expo
- Oil to Nuts: The Truth About Fats – (6 min. video) Jeff Novick, RD. A humorous look at the nutritional qualities of olive oil.
- FAQ: Dr Esselstyn’s Prevent and Reverse Heart Disease Program – scroll down to ‘More Commonly Asked Questions’
- Dr. David Jenkins Finds Monounsaturated Fats – Like Olive and Canola Oils or Nuts – Raise HDLs and Boost Heart Health. There’s More to the Story – The ‘Healthy Librarian’ gives the full story behind the research into monounsaturated fats
- Why Olive Oil Is Not Healthy for Your Heart – Rosane Oliveira, PhD
- Coconut Oil – (14 min. video) Pam Popper looks at the evidence behind the claims of those advocating coconut oil consumption and finds the evidence supports avoiding it
- The Real Coconut Oil Miracle: How a High-Fat, High-Calorie Condiment Became a “Superfood” – Jeff Novick, RD
- Coconut Oil Increases Cardiovascular Disease Risk and Possible Death Due to Heart Attacks and Stroke – Dustin Rudolph, April 2015
- The Newest Food-Cure: Coconut Oil for Health and Vitality – Dr John McDougall exposes the myths about coconut oil
- Is Coconut Oil Bad For You? – Dr Michael Greger, NutritionFacts.org blog post
- Is Coconut Oil Healthy or Hazardous? – Alona Pulde, MD and Matthew Lederman, MD
- Coconut oil: beyond the hype – Robyn Chuter
The Mediterranean diet:
- Olive Oil is NOT Health Food but Sick Food – (10 min. video) Jeff Novick, RD discusses the myths behind the Mediterranean diet and olive oil
- The Mediterranean Diet: A Closer Look (The PREDIMED Study) – Jeff Novick, RD
- NEJM Study Promotes Olive Oil and Dismisses Low-fat Diet – John McDougall, MD
- Does a Mediterranean Diet Really Beat Low-Fat for Heart Health? – Dean Ornish, MD reviews the key publication of the PREDIMED study.
- The Mediterranean Diet Study: Bad Science, Worse Journalism – (5 min. video) Howard Jacobson, PhD
- The Mediterranean Diet Myth – Vegetables, Fruit, Naturally Low Caloric Density, Hard Physical Work, Yes! Olive Oil, Nuts, Seeds, & Chocolate? I Don’t Think So! – Healthy Librarian
- The Mediterranean Diet – It’s Better Than the Western Diet – But, It’s Definitely Not the Best! Why Settle for Less? – Healthy Librarian
- Esselstyn, C. B. (2019). Is oil healthy? International Journal of Disease Reversal and Prevention, 1(1), 34-36.
- Lithander, F. E. et al. (2013). Postprandial effect of dietary fat quantity and quality on arterial stiffness and wave reflection: a randomised controlled trial. Nutrition Journal, 12(1), 93.
- Perez-Jimenez, J., Neveu, V., Vos, F., & Scalbert, A. (2010). Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database. European Journal of Clinical Nutrition, 64 Suppl 3, S112-120.
- Reboul, E. (2017). Vitamin E Bioavailability: Mechanisms of Intestinal Absorption in the Spotlight. Antioxidants (Basel), 6(4).
- Reboul, E. (2019). The gut: a regulatory hall governing fat-soluble micronutrient absorption. American Journal of Clinical Nutrition, 110(5), 1045-1046.
- Ribaya-Mercado, J. D., Maramag, C. C., Tengco, L. W., Dolnikowski, G. G., Blumberg, J. B., & Solon, F. S. (2007). Carotene-rich plant foods ingested with minimal dietary fat enhance the total-body vitamin A pool size in Filipino schoolchildren as assessed by stable-isotope-dilution methodology. American Journal of Clinical Nutrition, 85(4), 1041-1049.
- Rudel, L. L., Parks, J. S., & Sawyer, J. K. (1995). Compared with dietary monounsaturated and saturated fat, polyunsaturated fat protects African green monkeys from coronary artery atherosclerosis. Arteriosclerosis, Thrombosis, and Vascular Biology, 15(12), 2101-2110.
- Rueda-Clausen, C. F., et al. (2007). Olive, soybean and palm oils intake have a similar acute detrimental effect over the endothelial function in healthy young subjects. Nutrition, Metabolism & Cardiovascular Diseases, 17(1), 50-57.
- Traber, M. G., Leonard, S. W., Ebenuwa, I., Violet, P. C., Wang, Y., Niyyati, M., . . . Levine, M. (2019). Vitamin E absorption and kinetics in healthy women, as modulated by food and by fat, studied using 2 deuterium-labeled alpha-tocopherols in a 3-phase crossover design. American Journal of Clinical Nutrition, 110(5), 1148-1167.
- Vogel, R. A., Corretti, M. C., & Plotnick, G. D. (2000). The postprandial effect of components of the mediterranean diet on endothelial function. Journal of the American College of Cardiology, 36(5), 1455-1460.
- Vrentzos, G. E., Papadakis, J. A., et al. (2007). Diet, serum homocysteine levels and ischaemic heart disease in a Mediterranean population. British Journal of Nutrition, 91(06), 1013.
- Zhang, J., Chen, X., Yang, R., Ma, Q., Qi, W., Sanidad, K. Z., . . . Zhang, G. (2019). Thermally Processed Oil Exaggerates Colonic Inflammation and Colitis-Associated Colon Tumorigenesis in Mice. Cancer Prevention Research (Philadelphia, Pa.), 12(11), 741-750.
Peer reviewed studies funded by olive oil and other industry groups
- Brown, M. J., Ferruzzi, M. G., Nguyen, M. L., Cooper, D. A., Eldridge, A. L., Schwartz, S. J., & White, W. S. (2004). Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. American Journal of Clinical Nutrition, 80(2), 396-403. Two of the authors “were employed by The Procter & Gamble Co, which funded the research.”
- Estruch, R., Ros, E., Salas-Salvado, J., Covas, M. I., Corella, D., Aros, F., . . . Martinez-Gonzalez, M. A. (2013). Primary prevention of cardiovascular disease with a mediterranean diet. New England Journal of Medicine, 368(14), 1279-1290. This is the key publication from the PREDIMED study. Lead authors have a long association with the food, alcohol and pharmaceutical industries.
- Sarapis, K., Thomas, C. J., Hoskin, J., George, E. S., Marx, W., Mayr, H. L., . . . Moschonis, G. (2020). The Effect of High Polyphenol Extra Virgin Olive Oil on Blood Pressure and Arterial Stiffness in Healthy Australian Adults: A Randomized, Controlled, Cross-Over Study. Nutrients, 12(8). “Cobram Estate Pty. Ltd. has provided partial financial support and intervention EVOO for this trial.”
- Tsolaki, M., Lazarou, E., Kozori, M., Petridou, N., Tabakis, I., Lazarou, I., . . . Magiatis, P. (2020). A Randomized Clinical Trial of Greek High Phenolic Early Harvest Extra Virgin Olive Oil in Mild Cognitive Impairment: The MICOIL Pilot Study. Journal of Alzheimer’s Disease, 78(2), 801-817. Supported by “the World Olive Centre for Health (WOCH) and Yanni’s Olive Grove company”.
Page created 26 May 2013
Last updated 6 March 2022