Fat - Good & Bad
In the nutrition field, nothing is quite so confusing as fat. And we all have views on the subject:
- Polyunsaturated vegetable oils are healthy, whereas saturated animal fats are not
- It is the animal fat in our diet that is responsible for heart disease
- It is the trans fat in animal fat that is really bad for us
- We should avoid butter, and eat margarine instead
- If my blood cholesterol is raised, I should eat a low cholesterol diet
- We should all be taking statins to reduce the amount of heart disease
- The omega oil found in flax seed is as valuable as that from fish oil.
Test yourself - how many of the above are true? It may interest you to know that they are all false, and the 'experts' have been lying to us for years. What is true is that it is wise to reduce the overall amount of fat in our diet.
Ancel Keys (1904-2004) was an American scientist who studied the epidemiology of cardiovascular disease (CVD). He noticed that American business executives, who he assumed were among the best-fed, had high rates of CVD, whereas CVD rates had fallen sharply in post-war Europe, in the wake of reduced food supplies. Keys postulated a correlation between blood cholesterol levels and CVD. He presented this diet-lipid-CVD hypothesis at a 1955 expert meeting of the World Health Organisation in Geneva, where he was roundly criticised.
Undeterred, and after observing that southern Italy boasted the highest percentage of centenarians in the world, Keys argued that a Mediterranean diet, low in animal fat, protected against CVD and that a diet high in animal fats led to CVD.
What later became known as the Seven Countries Study systematically examined the relationships between lifestyle, diet, CVD and stroke in different populations from different regions of the world. The results appear to show that blood cholesterol is strongly related to CVD mortality. As a result, in 1956, representatives of the American Heart Association appeared on television to inform people that a diet which included large amounts of butter, lard, eggs and beef would lead to CVD. This resulted in the American government recommending that people adopt a low-fat diet in order to prevent CVD.
Keys had actually concluded that the saturated fats found in milk and meat had adverse effects, whereas the unsaturated fats found in vegetable oils were beneficial. But this message, though false, was obscured for a 20 year period, starting around 1985, when all dietary fats were considered unhealthy. This was driven largely by another hypothesis that all dietary fats cause obesity and cancer.
Several scientists stepped forward at the time to disagree with Keys's conclusions. Ahrens and Albrink considered that other fats (triglycerides) mattered in CVD risk more than total cholesterol, and came to believe that carbohydrates, not fats, actually cause CVD. Mann studied the mainly meat diet of Eskimos, Pygmies and the Maasai, and argued that other factors, like lack of exercise, were responsible for CVD. Yudkin thought that sugar, not fat, was the root cause of CVD and other human ills.
In his 2009 video, Sugar: The Bitter Truth, Lustig says his purpose is to debunk the prior thirty years of nutrition research, specifically Keys. Despite this, as of mid-2015, WebMD and the Mayo Clinic both still recommend that their readers avoid or minimise saturated fats and replace them with polyunsaturated or monounsaturated fats.
There are two large flies in this dish of ointment - sugar and trans fat. Sugar is covered under Carbs - Good & Bad, but what exactly is trans fat?
Unsaturated fats can be either cis fats or trans fats. Cis fats are common in nature. They are beneficial and can promote good cholesterol (HDL). Their melting point is usually low. Some cis fats are liquid at room temperature. Examples are those vegetable oils that can be obtained by cold pressing - e.g. olive, groundnut, coconut.
While some natural trans fats occur in meat and dairy products, the majority of trans fats come from processed foods (i.e. hydrogenated oils). These trans fats are detrimental to health. They lower good cholesterol (HDL), increase the level of bad cholesterol (LDL), increase blood triglycerides and promote systemic inflammation. As a result, they are a major cause of CVD. Their melting point is usually high; trans fats, like saturated fats, are solid at room temperature.
It is perhaps for this reason that researchers often confuse trans fats with saturated fats. As a result, when patients are advised to stop eating saturated fats, they often end up eating more trans fats instead. The truth is that saturated fat can never be trans fat. Moreover, several clinical and epidemiological studies have shown that the natural trans fats found in dairy fat and meats from grass eating ruminant animals are not associated with any increased risk of CVD.
So trans fat is uncommon in nature, but from the 1950s, has been produced on an industrial scale from vegetable oils for use in margarine, snack food, packaged baked goods and for deep frying. Trans fat has been shown consistently to be associated, in an intake-dependent way, with the risk of CVD, the worldwide leading cause of death. It has been found that for every 2% increase in energy derived from trans fats, there is an associated 23% increase in cardiovascular risk. Other studies have also found links between trans fat and obesity, and trans fat and colorectal cancer.
In 2013, the US Food and Drug Administration (FDA) issued a preliminary determination that partially hydrogenated oils (which contain trans fats) are not ‘generally recognised as safe’, which was expected to lead to a ban on industrially produced trans fats. On 16 June 2015, the FDA finalised its determination that trans fats are not generally recognised as safe, and set a three-year time limit for their removal from all processed foods.
So, Keys was barking up the wrong tree. Wrongly believing that saturated animal fat was the CVD culprit, the real offender was the partially hydrogenated vegetable oil, which he considered to be so healthy. What should really make our blood boil is that this trans fat, which is so dangerous to health, is the margarine that the scientists used to insist was so healthy. Has anyone apologised about this?
So, how are we to avoid trans fat? Trans fats are currently present in a wide range of foods: according to one estimate, 40 percent of products in a typical supermarket contain trans fat. They are to be found, for example, in margarine, vegetable shortening, ice-cream, ready-made pies, cakes and cake mixes, biscuits, pizza, potato chips, fritters, doughnuts, gravy and sauce mixes, artificial creamers, confectionery and other processed foods, including many foods marketed to children, including some sugary breakfast cereals.
Before there is a total ban, what can we do? The best advice is to buy fresh, local and seasonal, and cook at home. Alternatively, look at the list of ingredients. If a product contains hydrogenated vegetable oil, partially hydrogenated vegetable oil, vegetable shortening or margarine, leave the product on the shelf.
What can you do at home?
A hundred years ago, housewives cooked exclusively with lard and butter. Among their many benefits is that, being saturated fats, they do not oxidise when heated. Nor do they form dangerous aldehydes or other toxic oxidation products, and they are solid at room temperature, which is why they make great cooking fats.
Sadly, their demise was brought about by unscrupulous scientists, gullible medics and greedy food industry moguls, who demonised saturated fats.
And what of vegetable oils? Healthy oils are those that you could produce at home by cold pressing. They include avocado, cocoa butter (cacao), coconut, flax seed, olive, macadamia nut, peanut, sesame, walnut and wheat germ.
Despite their overwhelming and ubiquitous presence on the supermarket shelves, you should avoid all industrially produced oils, including canola, corn, cottonseed, grape seed, rice bran, soy, safflower and sunflower. Without going into too much detail, these ‘dead’ oils are produced by cleaning, grinding, pressing, solvent extraction, refining, degumming, bleaching and deodorising. They are odourless, tasteless, colourless, indigestible and void of most nutritional value. Worse, they contains trans fats and other toxic substances. None of these products even existed when your grandmother was a girl. Avoid them all. One possible exception is cold pressed sunflower seed oil, if you can find a reputable source, but there are plenty of other healthy oils to choose from.
The best fats and oils to use safely for cooking are avocado, butter, cocoa butter (cacao), coconut, duck and goose fat, ghee, lard and macadamia nut. Palm oil is also good, but is best avoided because its ubiquitous production is destroying the rain forests.