Dietary fats versus blood fats
Nowadays, all dietary fats appear to be associated solely with something detrimental to our health. Perhaps, if you eat too much French fries.
Otherwise, labeling as negative things we don’t really understand will be just erroneous. In fact, some fats are essential for the human body to function properly and, in small amounts, should be part of our everyday diet.
What the (bloody) fats
Fats play an important role in almost every physiological process in our body. Together with proteins, fats are incorporated into the cell membrane. So much for that.
Dietary fats
There are two types of fats (based on the position of a double bond in their chain):
- unsaturated, and
- saturated
Where we get ‘bad’ fats from
Unlike plants, all meats, including fish, are rich in one particular type of lipid, called cholesterol. What we are talking about is dietary cholesterol, not blood cholesterol, made in the liver. These are two different cholesterols that should not be confused.
Another important question is whether the consumption of some types of dietary fats increases our blood cholesterol.
There is a great deal of evidence that animal fats are indeed capable of raising ‘bad’ LDL cholesterol in the blood.
However, this is a complex, so-called dose-response relationship, meaning that eating too much animal proteins and fats can, over time, reach the point when our body simply can not ‘tolerate’ it anymore, and increased blood cholesterol is clear (bio)marker of that.
Epidemiological studies worldwide found lower saturated fat intake to be strongly correlated with reduced risk of some illnesses, such as some forms of cancer (breast, stomach) as well as coronary diseases.
Namely, to never get seriously sick, we should avoid unhealthy saturated fats and animal-based foods, in the first place.
Most Wanted: Unsaturated Fats
Polyunsaturated fatty acids (PUFA), with two or more double bonds in their carbon chain (Ola!), are the most important for our health.
The two major classes of polyunsaturated fatty acids, omega-3, and omega-6, are considered essential. The human body doesn’t have enzymes to synthesize the fats itself, so it is very important to introduce them through a diet, to prevent deficiency.
Omega-3 fatty acids are part of the cell membrane, where they participate in the proper functioning of cellular receptors. These receptors act as “receivers,” which obtain signals from the external environment and induce various cell processes: synthesis of hormones that regulate blood clotting, contracting and relaxation of the arterial walls, and regulate inflammatory processes in the human body. It practically means that Omega-3 fatty acids are responsible for the activation of processes of gene expression, that is, they act protectively when it comes to cardiovascular disease and stroke, or control of chronic disorders.
Many studies have shown their multiple benefits on fetal development, proper growth and development in children, maintaining good vision and cognitive function, and in preventing the occurrence and relapse of chronic diseases, such as cancer.
Omega-3 fatty acids are present in fatty fish (cod, tuna, salmon, herring, sardines), but also in some plants (although in different forms, as alpha-linoleic acid – ALA). Plants that contain these fatty acids include walnuts, chia seeds, algal oil, Brussel sprouts, hemp seeds, and flaxseeds.
Another group of important omega-fatty acids – omega-6 fatty acids – are most commonly found in plants: flaxseed oil, soybean oil, as well as yellow hazelnut oil, borage, and blackcurrant, and so on.
Although foods with a higher amount of omega-6 and omega-3 fats are also high in calories, regular consumption in moderate amounts, will not result in weight gain.
Unsaturated fats should not be used for food frying due to their instability at high temperatures.
Monounsaturated Fatty Acids (MUFA)
These fats have one double bond in their carbon chain and are almost as good for our health as polyunsaturated fatty acids.
Besides many other benefits, they positively affect the plasma lipid profile, which means that they can potentially protect our heart and the blood vessels from hardening.
Avocado for example, rich in dietary fiber, is an excellent source of MUFA. A recent study showed that the regular intake of fresh avocado, coupled with other healthy interventions, might lower LDL, the bad cholesterol, and total cholesterol levels. Other food sources rich in MUFA include vegetable oils such as olive oil, canola, peanut oil, and avocado oil, nuts, and nut kinds of butter, preferably taken in small amounts.
Researchers found many positive results of extra virgin olive oil on human health, such as anti-cancer properties. They claim its active substances have the ability to selectively enter the tumor cell membrane, making it vulnerable to the action of other anti-tumor agents.
Fats to Avoid: Saturated Fats
The excessive consumption of foods rich in saturated fats (e.g. fatty meats, offal, egg yolk, butter, lard), along with processed carbohydrates, alcohol, and a sedentary lifestyle, may increase cholesterol levels and cause obesity, which are the two major risk factors for cardiovascular disorders, and poor quality of life in general.
Many studies suggest that by substituting saturated with unsaturated fats in our diet and being more physically active throughout the day, we could significantly lower LDL (“bad”) and total cholesterol levels, improve “good” HDL, and the overall lipid profile.
According to the American Heart Association, saturated fats should make up less than 5% of our total calorie intake. For example, if you need 1500 calories per day, around 75 calories should be from saturated fats in total. It would be even better if we could further reduce that percentage.
Saturated fats can be found in all kinds of processed meat: sausages, salami, as well as in margarine, and hard cheese. Pork and lamb meat are also high in saturated fatty acids. Additionally, some vegetable oils such as palm and coconut oil, heavily marketed for their various benefits, also have a high content of saturated fatty acids.
Very Bad Fats – Artificial Trans Fats
Artificial trans fats are created through the industrial processing of unsaturated fatty acids, i.e., by adding hydrogen to liquid vegetable oil to obtain fats that are solid at room temperature (e.g. margarine). Additionally, trans fats are created during food processing and can be found in ready-to-use frozen foods, cookies, creamers, snacks, pre-made pizza, and more.
When chemically treated (e.g. frying at a high temperature), unsaturated fatty acids from vegetable oils lose their normal conformation and healthy properties, and our body ‘translate’ them into saturated.
Trans fats reduce the level of “good” (HDL) cholesterol and raise overall triglyceride and LDL (“bad”) levels in our body. As a consequence, long-term intake of these industrial fats can potentially increase the risk of serious medical conditions such as atherosclerosis, cardiovascular disease, retinopathy, stroke, diabetes type 2, and cancer.
Despite their detrimental effects on our health, fast food chains readily use them because they are cheaper than other oils and also long-lasting, which makes them suitable for deep-frying and re-use.
Although some states officially banned trans fats (and many other have considered banning them), from all processed foods (such as biscuits, frozen meals, cookies, margarine, creams, fast-food and many more), these fats, unfortunately, still remain a substantial part of the everyday diet of millions of people across the globe.
How to minimize the detrimental effect of trans fats on humane health?
It is important not to forget to throw away oil after frying food. However, the best thing is to avoid fast and processed food altogether. Baking and broiling food (preferably wrapped in parchment paper) is a healthier option and produces a similar flavor and texture as frying.
Most importantly, it is best to attentively read nutrition labels on foods, looking for ingredients titled “partially hydrogenated oil”, “trans fats”, “cholesterol” and “sodium”, to figure out their amount in products and avoid their excessive consumption.
Fats preparation and stability
Unfortunately, frying is still the most prevalent method of preparing food, because of the tasty flavor and texture produced in this way. Unfortunately, due to numerous physical and chemical reactions that occur during the frying process, hundreds of by-products are created, many of which are toxic.
Some of the most toxic substances include fat oxides and free radicals. They play a substantial role in the causality of vascular occlusion and hardening, liver damage, immunosuppression, with evidence of the potential to initiate carcinogenesis in experimental animals. Additionally, these altered lipids can interact with macromolecules in cells, such as DNA, and accelerate biological aging.
Some experimental trials in animals fed with thermally oxidized fats showed that they have had indigestion or have died.
Unfortunately, it does not end here. Trans fats exhibit even more nasty traits: they behave as antimetabolites of unsaturated fats and interfere with their physiological role in our body. That is, trans fats have the capacity to mimic the role of good ones while in fact, they act very badly.
Fats are also sensitive to light and moisture, which triggers autoxidation and rancidity that, in turn, adversely affects the body’s utilization of vitamins from other sources.
High-temperature frying also causes depletion of essential fatty acids, omega-3, and omega-6, which are the most unstable in such conditions. So, think twice before frying, especially frying on olive oil!
However, Dr. Emma Feeney, from UCD School of Agriculture and Food Science, and Food for Health Ireland, argues that it is not the type of food itself, nor its quantity, that we should be concerned about.
The pattern of our eating habits, that is, how we combine foods, and our lifestyle in general, greatly determine our health status.
Be that as it may, but one thing is certain: fry-ups should not be part of our everyday nutrition!
And to play it one more time – a balanced diet should include all “the good fats” we have discussed before; those derived from olives, sunflowers, flaxseeds, soybean, canola, nuts, seeds, avocado, and other plant sources.