The Big Fat Myth

Cholesterol molecule (black: Carbon; white: Hydrogen; red: Oxygen – picture by Jynto, CC Zero, Public Domain Dedication

Good Fat, Bad Fat

Fat is not the enemy. It is the quality and nature of the fat that we eat that is a problem. Health professionals, the food industry and government public health messaging have been telling us to avoid fat for decades. But the reality is significantly different.  

Example of a Nutrition label from USA. Image in Public Domain

Some fats, particularly the omega-3 and omega-6 fats are not only good for us, they are absolutely essential. Some fats, particularly trans fats which are in hydrogenated and partially hydrogenated processed fats, are highly toxic and we really shouldn’t be eating them. And some fats, like saturated fats, fall somewhere in the middle, we need some, but too much is not necessarily a great idea.  

How the Myth Started

Back in the 1950s, heart disease was on the increase. Scientists thought it might have a dietary cause and so some researchers fed animal fats and cholesterol to rabbits. This didn’t turn out so well for the rabbits who do not naturally eat animal products or foods containing cholesterol. The diet created build up in arteries similar to those found in humans with heart disease. Despite human biochemistry being completely different from that of rabbits, the researchers decided that heart disease was caused by saturated fat.

For decades, research based on this idea continued. In the 1980s, the outcome of a big study was published that showed that eating unsaturated vegetable oils instead of saturated animal fats significantly reduced cholesterol and heart disease. Public health policy around fat consumption in most of the world has been based on this study ever since.  

Laboratory Rabbit – photo by Andrew Skowron; Creative Commons Attribution 2.0 Generic

The Myth Exploded

And then, in 2011, a researcher found the original data that had been gathered for the study. He re-analysed it and found that the data in the original study had been cherry-picked. Only the results that fitted their theory were included, which skewed the results of the study to match their viewpoint.

So now the questions are, does saturated fat really increase cholesterol and cause heart disease? And, if saturated fats are replaced with unsaturated vegetable oils do cholesterol levels fall and does heart disease decrease?

Probably not. 

Cholesterol Good

Cholestrol molecule: see above

First off, we need cholesterol to stay healthy. Most of it doesn’t come from our diet; we make it in our own bodies. It forms part of our cell membranes and is used to make a lot of the chemicals our bodies need to function, like hormones and neurotransmitters. Nor does saturated fat appear to cause heart disease, clog our arteries, or increase the risk of having a stroke.

Along with cholesterol (and the essential fatty acids omega-3 and omega-6), saturated fats form part of our cell membranes where they hold proteins in place and provide structure. Our bodies can also use them to make energy.

This does not mean that everyone can start eating huge quantities of saturated fat. But it would be nice if governments took notice of current developments in scientific evidence and amended their dietary advice accordingly.

It would also be nice if foods like eggs and full fat dairy products which have been demonised over the years for being high in saturated fat and cholesterol could be rehabilitated. Because, it turns out, they are very healthy.

Eggs and Full Fat Dairy are Good for You

“White ceramic mug with white eggs” – photo by Mae Mu Free to use under the Unsplash License

Eggs are packed with great nutrition. They contain vitamins A, D, a load of B vitamins, the minerals phosphorus, iodine and selenium, and around 13 grams of protein. They also contain lutein and zeaxanthin, powerful antioxidant substances which support eye health, and biotin and choline, which support the health of the nervous system and brain.

Eating an egg or two a day does not increase cholesterol levels, or the risk of heart disease. Eggs are affordable, widely available, easy to cook and fantastically versatile. What’s not to love?

Full fat dairy products are great sources of the fat-soluble vitamins A, D, and E – vitamins that have a worryingly low intake in much of the UK population. Low fat versions of dairy products contain almost none of these vitamins. Both full and low-fat milk contain potassium, calcium, magnesium, and phosphorus but, without the vitamin D contained in the full fat variety, those minerals cannot be absorbed or used. And full fat dairy seems to be good for us. It does not increase cholesterol: instead, it actually lowers the risk of cardiovascular disease, stroke, high blood pressure, and diabetes. Plus it tastes way better than the low-fat stuff.

Seed Oils – Not Always Great

So are those unsaturated seed oils good for you?  

Not all of them.  

There is evidence that swapping saturated fats for processed vegetable seed oils may actually increase the risk of heart disease and stroke: possibly because of what happens to those seed oils when they get processed.  

When you squish a seed to get the oil out, a lot of other stuff comes out too. The oil industry generally views that “stuff” as impurities that need to be removed because they shorten the shelf life of the oil.  Nutritionists view that “stuff” as nutrients – things like vitamins, minerals and phospholipids like lecithin and choline. The only seed oils that do not go through a load of processing, and which keep their nutrients, are those which are labelled “extra virgin” or “cold pressed”.

Heat, Light and Oxygen

Those ranks of pale seed oils, glowing gently on the supermarket shelves – sunflower, corn, rapeseed, groundnut, vegetable (a mixture of lots of oils), and even olive oil, (if it doesn’t say “extra virgin”), all go through a series of processes which can create toxic by-products.

Seed oils are sensitive to damage from heat, light and oxygen, and the processing involved in oil extraction exposes the oil to all of them. Crushing the seeds generates a lot of heat and when oil is hot it reacts to oxygen and light much faster than it does at room temperature. Combining heat with oxygen and or light can create rancidity in the oil.  But it is expensive to exclude oxygen and light from the processing and not all manufacturers do so.  

Oil Processing Uses Toxic Chemicals

Once the oil is extracted, it goes through a series of processes to remove “impurities”.  Phosphoric acid is used to get rid of phospholipids and other sticky stuff. Then sodium hydroxide (caustic soda) is used to neutralise the acid and remove free fatty acids. The oil is then treated with aluminium silicate which absorbs the phosphoric acid and caustic soda and takes out things like chlorophyl. The oil is filtered to remove the aluminium silicate, cooled to room temperature, and then filtered again.  

All these processes mean that the oil now smells and tastes a lot less then lovely. And so the final step in processing is deodorisation. High temperature steam is pushed through the oil, once again exposing it to heat, and removing the taste and smell, as well as things like beta-carotene and vitamin E.  

Although the majority of the toxic substances used will be removed during processing, there is no guarantee that the oils sold in supermarkets have had all traces eliminated.  

Which Oils Should We Use?

The best type of oil to use depends on what you want to do with it.  All oils have different “smoke points” which is the point at which an oil starts to burn. Burnt oil not only tastes awful, it also creates chemicals which can harm our health.  

Frying chopped onions in a frying pan – photo by Dnor; public domain dedication

Extra virgin and cold pressed oils have quite low smoke points because they contain those “impurities”. Butter has a very low smoke point, it is fine to scramble some eggs in, but not a lot more than that. Extra virgin olive oil is ok for sautéing onions but not for doing any serious frying.

Coconut oil has a higher smoke point and is OK for wok frying, but it has a strong taste which not everyone will like. The best thing you can use for any intensive frying, or roasting vegetables is good old-fashioned animal fat, chicken, duck or goose fat, lard, or beef dripping.  

Keep It Natural

When it comes to fat, probably the most important thing you can do is eat the least processed types of fat possible. Because the more processed the fat, the greater the likelihood that it could be damaging to your health. And don’t stress about saturated fat. It’s really not so bad after all.