FAT CHAT (PART TWO)
Know your fats: Here’s the skinny on oils and carbs
From saturated to unsaturated to trans fats, Maverick Life talks to top nutrition experts to demystify the world of fats in part two of our FAT CHAT.
Back in 2014, Professor Tim Noakes co-authored The Real Meal Revolution (RMR), a book that promoted Low-Carb, High-Fat (LCHF) eating. It became a bestseller, and arguably, in some culinary corners, revolutionised food preparation and diet. Like proponents of high-fat diets such as the Atkins diet before them, Noakes and co challenged food guidelines that promoted high carbohydrate consumption and vilified dietary fats.
The Real Meal Revolution went further and separated fats from cooking oils, labelling some bad and some good. Even today on their website, the page on cooking oils opens thus: “Vegetable oils and their fats should be avoided completely. There are much healthier alternatives and there is no reason or need to consume these types of fats.” Soybean oil, sunflower oil and canola oil are among those labelled as “culprits” on the website.
The following year, in 2015, a team led by Cape Peninsula University of Technology Associate Professor Maretha Opperman, whose PhD is in nutrition, authored a paper, South African seed oils are safe for human consumption, explicitly challenging the RMR take on oils: “The authors stated that available seed oils on the South African market were high in trans-fatty acid (TFA), as well as being genetically modified, and thus should be avoided.
“We compared three oils, i.e. canola, sunflower and olive oil, against internationally accepted standards, to determine the quality of these oils using gaschromatographic analysis, to determine whether or not there was any foundation to the statement pertaining to the toxicity of South African seed oils.” The team concluded that the trans-fatty acid content of the oils was “below 0.5%,” and “negligible”, and “therefore, the statement that South African seed oils are toxic is inaccurate, unscientific and without merit”.
They were not the only nutrition experts to challenge the RMR view on seed oils; in 2016, another team led by the director of the Centre of Excellence for Nutrition at North-West University, Professor Marius Smuts, whose expertise lies in the field of fatty acids and micronutrients, and his colleague Associate Professor Linda Malan, whose PhD is also on nutrition, compiled an article titled Perspectives on the use of seed oils in the South African diet, in which they reiterated and expanded on the point made by Opperman and her team, adding that while the oils may have low amounts of trans-fatty acids, how oil is used, such as when it is heated for an excessive amount of time or repeatedly, then the trans-fatty acids amount can go up.
Smuts was also part of the working group that put together South Africa’s Food-based Dietary Guidelines (FBDG), which, when it comes to dietary fat, simply recommends: “Use fats sparingly. Choose vegetable oils rather than hard fats,” instead of recommending specific values, oils and types of dietary fat.
As explained in part one of our Fat Chat series, the World Health Organization (WHO) recommends that “total fat should not exceed 30% of total energy intake to avoid unhealthy weight gain. Intake of saturated fats should be less than 10% of total energy intake and trans-fats to less than 1% of total energy intake, with a shift in fat consumption away from saturated fats and trans-fats to unsaturated fats, and towards the elimination of industrial trans fats.”
One of the main reasons for the WHO recommendations is the result of numerous studies over the past century linking saturated fat to cardiovascular heart disease and coronary heart disease. However, recent studies have challenged the link between heart disease and saturated fat, including one in 2010 which concluded that “there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of [coronary heart disease] or [cardiovascular disease]”.
Debatably, the variety of findings, sometimes contradictory, add to the general confusion about diet, especially in the context of dietary guidelines versus high-fat diets such as the popular LCHF ketogenic diet.
Chemistry intermission: Know your fats – trans, saturated, unsaturated, monounsaturated, and polyunsaturated
“If you leave fat or oil at room temperature and it stays or goes solid, that means that it contains more saturated fat than unsaturated fat. And saturated fat simply means that it has more saturated fatty acids,” says Smuts, adding that “saturated” refers to its molecular structure, which is tightly packed together, and if not converted to energy it is likely that it will become additional body weight, offering little nutritional value. As the professor explains it in more accurate chemistry laboratory terminology: “It’s a long carbon chain molecule, with no double bonds, it’s absolutely saturated!”
This includes oils often considered healthy options such as coconut oil. The document that explains South Africa’s Food-based Dietary Guidelines (FBDG) features a chapter on fats, authored by Smuts and his team, and it specifically states: “Do not eat or frequently eat processed foods that contain plant oils and fats which are high in SFAs [saturated fatty acids], e.g. palm kernel and coconut oil.” It is worth noting that coconut oil has become a contentious issue, with some studies pointing out its ability to boost “good” cholesterol. However, Smuts as well as other health experts are cautious of making too much of that.
Walter C. Willett, a Professor of Epidemiology and Nutrition at Harvard T.H. Chan School of Public Health, as well as Professor of Medicine at Harvard Medical School, wrote in a 2018 article on coconut oil, “But plant-based oils are more than just fats. They contain many antioxidants and other substances, so their overall effects on health can’t be predicted just by the changes in LDL and HDL [cholesterol]… But, for now, I’d use coconut oil sparingly. Most of the research so far has consisted of short-term studies to examine its effect on cholesterol levels. We don’t really know how coconut oil affects heart disease. And I don’t think coconut oil is as healthful as vegetable oils like olive oil and soybean oil, which are mainly unsaturated fat and therefore both lower LDL and increase HDL. Coconut oil’s special HDL-boosting effect may make it ‘less bad’ than the high saturated fat content would indicate, but it’s still probably not the best choice among the many available oils to reduce the risk of heart disease.”
Unsaturated on the other hand, “means somewhere in this chain there’s a double bond”, says Smuts. These are far better for the body, as they have additional functions to fulfil in the human body. Unsaturated fats are further broken down into two categories, monounsaturated and polyunsaturated. Simply, monounsaturated has one double bond, while the even healthier polyunsaturated has two or more.
On the healthy end, unsaturated fats can be a source of essential fatty acids, meaning the kind that are important for human health but which the body cannot produce, hence you have to get them from your diet. “You get omega 3 and you get omega 6,” says Smuts, referring to the two essential polyunsaturated fatty acids. The former is linked to reduction in inflammation, supporting mental health, and heart health; the latter is also essential but has sometimes opposite actions when it comes to inflammation.
“Omega 3 you can get these from fish or some green vegetables. One of the most common sources of omega 6 is sunflower oil. Unfortunately it contains a very small amount of omega 3. But you cannot only consume from the one family, you actually have to consume both omega 6 and omega 3, and there should be a balance in intake. And that’s why we say, fish should be an integral part of our diet,” says Smuts, further explaining that these benefits can be obtained in affordable ways such as canned sardines and pilchards, all the way through to more expensive options such as salmon.
Lastly, there are the notoriously unhealthy trans-fats. Typically, these are naturally occurring fatty acids in meat and milk products from ruminant animals like cows, sheep, and goats. However, these occur in amounts small enough as not to be hazardous to human health. The kind that are considered dangerous are typically formed when manufacturers turn liquid oils into solid fats. Think stick margarine, microwave popcorn, cookies, fried foods, and many other processed foods. “The orientation of that fatty acid is no longer the same as the original source. The industrial process transforms it, making it a trans-fatty acid that is sometimes two times more dangerous than saturated fats. And we know that a higher intake of trans-fatty acids is associated with almost double the risk of cardiovascular heart disease compared with saturated fats,” explains Smuts.
According to a 2010 study titled Trans fats: What physicians should know, these “trans fats have deleterious effects on human health. They not only increase low-density lipoprotein cholesterol but also decrease high-density lipoprotein cholesterol, thus increasing the risk of cardiovascular disease. Trans fats provide no benefits to human health and are not essential. Therefore, there is no such thing as a safe level of dietary trans fat.”
What does it actually mean for my plate?
Understandably, for most consumers whose daily occupation does not require them to wear a lab coat, the breaking down of the daily diet into percentages of saturated versus unsaturated fats, while also consuming a constant stream of dietary information can be impractical. Hence, Smuts is cautious of recommendations that are specific at a macronutrient level.
“We have to be careful when we single out macronutrients; for instance, dietary fat, because that’s not what we eat. We eat a full meal that consists of different food groups containing different nutrients that are the building blocks that the body needs to function normally. For example, if I eat a takeaway hamburger, I’m likely eating refined carbohydrate, protein, and a high level of dietary fat. It’s not the best quality of diet; add French fries to that and you’re likely to be exposed to trans-fatty acids. The problem sometimes is with the preparation of food, not in the fat,” says Smuts.
He recommends a dietary approach that focuses on nutrient density, with an emphasis “on adequate intake of fruits, vegetables, whole grains, legumes and nuts, and limits consumption of refined grains, processed foods, added sugar, sodium, as well as saturated and trans fats. In order to be sustainable, a diet should be culturally acceptable, and above all, enjoyable,” he explains. “It’s not that we want to throw saturated fat out the back door. Every single fat and oil that you eat will have a portion of saturated fat.”
Smuts further emphasises not only the importance of eating a variety of foods in moderation, but also the importance of questioning and understanding what moderation means for different lifestyles: “Fat per gram gives you almost double the energy from the same amount of protein or carbohydrate. Alcohol is almost similar. It has more energy per weight unit in comparison to healthy carbohydrates. So it is also about intake versus expenditure. Moderation has to do with maintaining an energy balance. It depends on the individual. A cyclist for example has different energy requirements from someone who does not exercise.”
But what about research that says there is no increased risk in eating saturated fats?
Responding to studies such as the one mentioned above that challenges the correlation between saturated fat and heart disease, Smuts points out that many of them are either observational or prospective studies. Observational meaning that they study and document the prevalence of certain conditions in population groups that follow certain diets.
For example, one might select a city such as Johannesburg and collect information on their dietary intake of saturated fat, and compare that to the prevalence of heart disease to work out whether or not people eating a high level of saturated fats also have a high rate of heart disease.
“The problem with observational studies is that you cannot make causal conclusions. All you can say is, this is associated with a higher risk, but you cannot say this is the cause. Then you get prospective studies. In other words, if we start with the Johannesburg population, we follow the population for five, 10 or 20 years, and over that period we look at the dietary fat intake, and we see what happens in terms of cardiovascular disease occurrence, and work out how does it explain what we see over that period,” Smuts explains.
Some of these kinds of studies have indeed shown no increased risk of heart disease as was the case for randomised controlled studies, the golden standard to prove causality. Smuts points out that while some have not shown an increase in risk, the same kinds of studies when saturated fats are replaced with unsaturated fats, have shown an actual decrease in heart disease risk.
“It’s about prevention and achieving better health outcomes. If you replace saturated fat with polyunsaturated fat, or monounsaturated fat, you lower the risk. Why stick to a diet that might maintain the level of risk rather than a diet that is proven to decrease your risk of developing heart disease?
“It’s important to realise that nutrition is a challenging field. And with more research, it changes quite quickly. However, we have to see our choices in the context of lifestyle changes towards better health. Generally, we’re not good at preventing illness, we tend to want to resolve it when it happens, and sometimes that’s too late. If we can really start to implement dietary choices that work towards prevention, we’ll be in a much better situation when it comes to health,” explains Smuts. DM/ML
Daily Maverick © All rights reserved