‘Good fats’ has become an overused almost meaningless health label.
We advocate a whole food plant-based diet – a diet built mainly on whole grains, legumes, vegetables, and fruits. This is a low-fat diet because most of the energy these foods provide is in the form of carbohydrates and proteins with only a small contribution from fat. It’s the dietary pattern with evidence for reversal of heart disease and insulin resistance and is of low caloric density, assisting weight loss. The macronutrient ratio (typically >70% carbohydrate, 10-15% protein, 10-15% fat) is a consequence of the composition of our core foods rather than the macro ratio determining our food choices.
“But what about good fats?” is a question or objection often raised when we describe our low-fat dietary approach and the amazing health results we see when people eat this way. People love their fat-rich foods, and the dairy, olive oil and nut industries have successfully dismantled the low-fat diet paradigm during the preceding couple of decades. ‘Good fats’ have gained de facto status as a food group and even many plant-based foodies seem to regard ‘good fats’ as an essential component of every meal. In mainstream nutrition Australians are being encouraged to add hundreds of calories of olive oil to their meals every day in the name of ‘good fats’. Has anyone paused to consider what a ‘good fat’ is? It would seem not when we review the composition of many of these so-called good fats.
Criteria for a ‘good fat’
Whole food: Our first criterion for a ‘good fat’ is that the fat is in the context of a whole food. Vegetable oils and margarine are not ‘good fats’ because they have lost all the fibre and most of the nutrients of their plant of origin (see our No Oil page).
Low in saturated fat: ‘Good fats’ are good because bad fats – i.e. saturated and trans fats – are bad for our health. Any ‘less bad’ fat than these are usually labelled a ‘good fat’ by nutritionists. We can sideline trans fats because they have been largely eliminated from ultra-processed foods, leaving ruminant meats and dairy as the primary dietary source. Saturated fats are widespread in both plant and animal-derived foods. The issue is how much saturated fat does it take to lose the ‘good fats’ tick of approval? The commonly accepted upper healthy limit of saturated fat intake is 10% of total dietary calories. The American Heart Association recommends an even lower target of 5% to 6% of calories from saturated fat. Adding in more calories from foods with a greater percentage of saturated fat than this (e.g. olive oil or avocado) is never going to get us to these targets. How do some common ‘good fats’ compare to these criteria?
Saturated fat as a percentage of total calories:
Olive oil, avocado, and many nuts owe their ‘good fats’ label to their high monounsaturated fat content. Monounsaturated fats have a neutral effect on blood cholesterol and metabolic health. We have no requirement for monounsaturated fats other than as a source of calories (energy). Plants with a high monounsaturated content may qualify as ‘good fats’ if they meet our criteria.
Essential fat ratio: The only ‘good fats’ that are essential are two groups of polyunsaturated fats, the omega 6 and omega 3 series. Human requirements for these amounts to only a few percent of daily energy intake and clinical deficiency is extremely rare. What may be more relevant is the ratio (omega-6: omega-3) as the two groups are transformed within the body by the same enzymes, and too much of one may compromise conversion of the other into the long chain form. The modern diet has become skewed towards the omega-6 group, far from the optimal ratio of 4:1 or less. This is thought to contribute to long-term adverse health outcomes. Omega-6 fats are widespread in grains, nuts, seeds, and oils and are more often present in the diet in excess. In contrast, few foods are high in omega-3 fats. The omega-6 to omega-3 ratio of the total dietary pattern is important, rather than that of individual food items. One could eat some high omega-6 meals and counterbalance these with other meals of higher omega-3 content. However, anticipating that something else will compensate for what’s currently on our plate can be a slippery slope in nutrition. Giving the ‘good fats’ tick to foods low in omega 3’s may take people further from an optimal fat ratio. Our final criterion for the ‘good fats’ label is that the item has an omega 6 to omega 3 ratio supporting a total dietary ratio of 4:1 or less. Many foods promoted as ‘good fats’ do not meet this criterion.
Omega 6 to omega 3 ratio in foods of moderate to high fat content:
*Green leafy vegetables are low in fat therefore it takes a lot of them to have a meaningful effect on your omega-3 intake.
The aim of this article was to bring nutrition science into the ‘good fats’ meme to help you make healthier food choices, regardless of where you are on the fats-starches continuum of whole foods, plant-based nutrition. Some individuals and groups may benefit from eating more ‘good fats’ to maintain an adequate calorie (energy) intake. Our personal low-fat, WFPB diet includes ground flaxseed, a few walnuts, a little peanut paste, and tahini as condiments.
Our ‘good fats’ tips:
Source ‘good fats’ from whole foods or minimally processed whole foods.
Limit consumption of ‘good fats’ with a higher saturated fat content, particularly if you have heart disease or type 2 diabetes.
Choose ‘good fats’ with a lower omega 6:3 ratio.
Balance higher intakes of omega 6 predominant ‘good fats’ with increased omega 3 foods.
Be mindful that high-fat foods are calorie-dense and good for weight gain.
In recent years, the long standing recommendation to eat a low fat diet has been questioned. There has been a sustained attack on low fat diets that goes beyond the rational consideration of higher fat alternatives. Language such as “Low fat diets are dead”, “old nutrition” and “the nail in the coffin for low fat diets” are not terms one would expect to hear from nutrition scientists. Neither would one expect to find that research cited to discredit low fat diets did not actually have any subjects eating low fat diets – the PREDIMED Study for example had a “low fat” group who averaged a 37% fat diet. It is interesting to consider which industry groups might have the most to lose were low fat diets to become reality rather than rhetoric – the pharmaceutical industry would be in there along with the meat, egg and dairy industries. These industry groups have become big sponsors of nutrition research.
The ongoing health debate over carbs vs fats is a gross oversimplification of the types of foods that contain these nutrients and positions animal protein beyond reproach. It sometimes seems to us that the fats vs carbs debate is a proxy used to argue for increased consumption of fat-rich animal products over starchy plant-based foods – an idea that would be quickly dismissed if it were not disguised by talking about nutrients rather than foods. It is ironic to hear of people on plant-based diets embracing the calls of the meat-based Atkins-Paleo advocates to eat a more fat-rich, reduced carbohydrate diet.
We are confident to continue to recommend a low fat diet as optimal, not because we are clinging to an outdated paradigm, but because the nutrition research of recent years has not provided good evidence to overturn the cumulative research findings of the last 50 years supporting the health benefits of a low fat plant-based diet. The following are our reasons for recommending a diet based predominantly on the low fat whole plant foods. The list includes points that are well supported by evidence from population studies, clinical trials and intervention studies, as well as other factors that we consider relevant:
All lean healthy populations that were free of heart disease and other Western diseases have had diets based on low-fat starchy staple foods such as rice, wheat, beans, corn and potatoes.
While modest quantities of olive oil were used by some Mediterranean cultures, their overall diet was largely based on grains and legumes, leaving us with no observations of the long term health effects of a diet based on high-fat plant foods.
The randomised controlled trials and intervention programs that have had the most remarkable results in treating heart disease (Pritikin, Ornish, Esselstyn), diabetes (Barnard) and other Western diseases have all used low-fat, high-carbohydrate, plant-based diets.
The plant-based nutrition experts with the most knowledge and clinical experience, with few exceptions, advocate a diet based on whole grains, legumes, vegetables and fruits – i.e. the low-fat plant foods.
A low-fat, whole foods, plant-based diet reduces body fat without food rationing. Starchy plant foods generally have a lower calorie density than high-fat plants and the metabolic process of converting excess carbohydrate to body fat is inefficient.
High intakes of dietary fat, particularly saturated fat, leads to fat accumulation in the muscle cells and liver cells, resulting in insulin resistance and type 2 diabetes.
The health benefits of adding nuts to a Western diet (i.e. one that is extremely low in whole plant foods) may not extrapolate to added health benefits for those already consuming mostly whole plant foods. The quantity of nuts observed to reduce health risks was only a small fraction of the diet, typically 30g per day.
Humans are highly adapted to starch-based diets. We have multiple copies of the starch digesting enzyme, amylase, and we even secrete it in our saliva so that starch digestion begins as we chew. Our over-sized brain uses 20% or more of our resting energy and runs exclusively on carbohydrates except during periods of prolonged fasting. Our muscles can only perform at their peak when they have been adequately ‘charged’ with carbohydrates.
High carbohydrate plant foods provide the resistant starch and dietary fibre that nourish healthy gut microbes. While much remains to be learnt about our gut microbiome, we know that it only takes a few days of high fibre, starchy foods to build a healthy pattern of microbes. Low carb dieters forget that most dietary fibre is composed of carbohydrates.
‘Good fats’ is more an endorsement of high fat foods than a meaningful definition. Foods with moderately high saturated fat content, low omega 3 fat ratios and minimal nutrients and fibre have all been called good fats. Perhaps the term just means that there are worse fats that could have been chosen. ‘Good fats’ are said to be the reason why the Mediterranean diet is not as bad as the standard Western diet, although we suspect it’s because it’s more plant-based.
Most high-fat plant foods (nuts, avocados, olives etc.) have an omega 6:3 fatty acid ratio greatly in excess of the suggested optimal ratio of 4:1 or less. Flaxseed, chia seed and hemp seeds are exceptionally high in omega 3’s and may be beneficial in small quantities (amounts compatible with a low fat diet). High intakes of omega 6’s provide more precursors for the production of inflammatory omega 6 mediators and inhibits the production of anti-inflammatory omega 3 mediators.
Many of the plant foods that are considered to be ‘good fats’ are actually moderately high in saturated fats – 15% of calories in avocados and olive oil for example. Saturated fats are damaging to the intestinal lining, raise cholesterol levels, have adverse effects on blood and endothelial cells and increase insulin resistance. To what degree other components of whole plant foods counter these effects is uncertain.
Women’s health can be adversely affected by high fat intakes due to increased production and recycling of oestrogens. The excess oestrogen levels cause heavy bleeding, uterine fibroids and breast disease. High omega 6 fat intake, particularly arachidonic acid from animal products, promotes inflammation and menstrual pain.
Consumption of high fat foods results in lipaemic blood – centrifuge this blood and the serum layer appears milky. Lipaemic blood impairs the capacity of arteries to dilate and causes red cells to clump and stick as they flow through capillaries. High intakes of high fat plant foods may have the same effect – see this video by ultra-distance runner Randy Kreill whose diet was heavy in high fat plant foods.
A single high-fat meal increases blood clotting through activation of Factor VII
The final point is that a diet based largely on high fat plant foods is unprecedented from a population perspective and has not been adequately assessed by clinical trials. It’s an ‘experimental’ diet in comparison to the ‘evidence-based’ starch-based diet.
How much fat is OK?
After explaining why we advocate a low fat diet, people often ask us what macronutrient ratio they should aim for. We prefer to turn this reasoning around the other way, such that it’s the food group recommendations that come first, and the macronutrient ratio becomes just one of many metrics, including fibre content and calorie density, that describe this dietary pattern, recognising that whole plant foods have a composition and complexity that is not adequately described by a handful of measurements or a full nutrient analysis. We recommend a diet based on whole grains, legumes, starchy and non-starchy vegetables and fruit. Nuts and seeds are optional and are limited to a small proportion of the total diet – with the type and quantity depending on individual energy balance and health status. If you follow this pattern, then your ‘macros’ will be in the vicinity of 70-80% carbohydrate, 10-15% protein and 8-15% fat.
The diet we recommend for weight loss is a high carbohydrate, low fat diet, with modest but adequate amounts of protein. These macronutrient proportions, rather than being targets, are secondary to having a diet based on whole grains, legumes, starchy and non-starchy vegetables and fruits. The typical fat content of meals based on these food groups is around 10% of calories, far below the 30% fat diet that many researchers call a ‘low fat diet’. Typical fibre contents for this diet are in the order of 60g per day which is also far different to the diets typically used in high carb vs high fat diet research (usually 15-20g fibre).
While there is a lot of controversy about the healthy range of fat intakes for humans, the fact remains that a low fat diet, based mainly on starchy plants, keeps people lean. Dr McDougall often makes the point that all large populations of lean healthy people have eaten starch-based diets – rice in Asia, sweet potatoes in PNG, taro in the Pacific, corn and beans in North America, potatoes in South America and in the past, wheat and barley in Europe. If this is not enough to dispel the notion that carbs make you fat then consider some of the best known and well researched plant-based diet programs – Pritikin, McDougall, Ornish, Barnard and Esselstyn – all high carb, low fat diets, and all get spectacular weight loss results, and good long term adherence.
Now for some theory. Protein and carbohydrate both have 4 calories per gram while fat has more than twice the calories, with 9 calories per gram. It’s already not looking good for low carb diets (which are always high in fat), but it gets worse. The fat we eat is readily stored as body fat with an efficiency of 95% (only 5% of calories lost in the process). In contrast, carbohydrates in excess of our immediate needs are not readily stored as fat. They are used as fuel for our metabolic processes and stored in liver and muscles as glycogen – the storage form of glucose, the preferred fuel for our brain and muscles. The conversion of carbohydrates to fat (de novo lipogenesis) does not occur readily in humans and when it does, the efficiency is only 75% (that means that 25 out of 100 calories of excess carbohydrate are lost when those carbs are trying to make you fat).
The gut microbiome and its interaction with gut hormones is an emerging area of research and may influence the development of obesity. A plant-based high carb diet is a winner in this respect too. It provides the resistant starch and other classes of dietary fibre that best support a healthy profile of gut microbes (See: Resistant starch).
While there are experts who argue that eating less carbs and more high fat plant foods – nuts, seeds, avocados, soy, and even olive oil – may be healthy, the evidence is very much in favour of a low fat, whole foods, plant-based diet.
Research purporting to show low fat diets “don’t work”
Several recent studies including systematic reviews and meta-analyses have claimed that a low-fat diet is no better, or is less effective than low-carbohydrate diets for weight loss and also for various chronic diseases. The key point to understand with these studies is that they did not use a low fat diet as defined by plant-based experts (10-15% calories), rather they have used diets which averaged between 29%-37% fat and have claimed them as “low-fat”.
Tobias, D. K., Chen, M., Manson, J. E., Ludwig, D. S., Willett, W., & Hu, F. B. (2015). Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults. Lancet Diabetes Endocrinology, 3(12), 968-979. Low-fat diets in this meta-analysis were “as defined by the investigators of each trial”. This included the large PREDIMED trial where subjects in the “low-fat” group averaged 37% calories from fat.
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)
Good fats?
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 and our FAQ What are ‘good fats’?
Coconut oil 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.
Vitamin E 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
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.
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.
Cholesterol
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.
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.
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
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.
http://www.nejm.org/doi/full/10.1056/NEJMoa1200303
