Good Fats and Bad Fats

It’s difficult to simply categorise fats as either good fats or bad fats. ‘Fat’ is a word that is often viewed negatively or associated with poor nutrition. Some people believe that eating fat means getting fat, others that all saturated fats are bad, and polyunsaturated fats are good. 

In reality of course, things are more complex than that. Here, we’ve spelt out in plain English some of the differences between fats, why some have been labelled as ‘good fats’ or ‘bad fats’ and what the real story is.

Differences between good and bad fats

Our bodies need good sources of healthy fats in order to function properly. Without some measures of fats, put simply, we’d die. Additionally, some of the fatty acids we need can’t be produced by our body from other nutrients, so we have to get them directly from what we eat. These are found in so-called ‘good fats’ or, occasionally ‘heart-healthy fats’ – monounsaturated fats and polyunsaturated fats, sometimes simply referred to together as unsaturated fats. Polyunsaturated fats come in two main types, Omega-3 and Omega-6. 

There are some types of fats which may do us harm, and that are linked to issues such as heart disease, diabetes and obesity. These are the so-called ‘bad fats’ – saturated fats and trans fatty acids, often shortened to trans fats. That’s not to say they have to be avoided at all costs, but you should eat them very sparingly, as an occasional treat. Trans fats are worse for our bodies than saturated fats, so should be generally avoided. [1]

There are also Medium-Chain Triglycerides, or MCTs. These are partially man-made fats, usually made by processing coconut or palm-kernel fats.

The main types of fats

These then are the six main groups of fats. Below you can find more information on each group, along with some of the foods in which they might be found.

‘Good’ fats:

  • Monounsaturated fats 
  • Omega-3 Polyunsaturated fats
  • Omega-6 Polyunsaturated fats 

‘Bad’ fats: 

  • Saturated fats 
  • Trans fatty acids or ‘trans fats’ 

‘Other’ fats:

  • Medium-Chain Triglycerides or MCTs

‘Good fats’ or fats to build into your diet

Monounsaturated Fats

Monounsaturated fatty acids (MUFAs), have one double bond of carbon atoms in their molecular structure, with other carbon atoms bonded singly. 

Having more of these fats as a proportion of our total fat intake may help to reduce blood LDL levels (bad cholesterol), whilst keeping our HDL levels (good cholesterol) high[5, 6], reducing the risk of heart disease[7, 8]. Because of this double benefit MUFAs are the opposite of trans fats and are some of the healthiest on the spectrum of fats. You should therefore incorporate recommended amounts of MUFAs into your diet. 

Foods which are high in MUFAs include:

  • Olive, rapeseed and flax oils
  • Avocado oil 
  • Peanuts
  • Cashews 
  • Pumpkin seeds 
  • Some oily fish, such as salmon, mackerel, sardines and anchovies

Polyunsaturated Fats

Polyunsaturated fatty acids (PUFAs) have more than one double bond of carbon atoms in their structure. There are two main types; omega-6 and omega-3 PUFAs. As a general rule, increasing levels of PUFAs in our diet has been shown to help reduce total blood cholesterol[9, 10]

Eating a good intake of omega-3s can improve cardiovascular health[11-13], reduce some cancer risk[12], improve brain function[14], and possibly enhance athletic performance[15]. These fats are used by the body as building blocks to construct brain cells and nerves, and they are also important for the cardiovascular system.

Omega-3 fatty acids are found in:

  • Oily fish such as salmon, mackerel, sardines, pilchards, and trout. 
  • Flaxseed and flaxseed oil 
  • Walnuts
  • Canola oil
  • Chia seeds
  • Spinach

Read our Guide to EPA and DHA for more information. 

Omega-6s

Omega-6s are important for proper cell function, including cell repair. They can also lower negative LDL cholesterol levels and may help the body reduce inflammation.[20] 

Omega-6 fatty acids can be found in:

  • Vegetable oils (including sunflower oil, rapeseed oil and soybean oil)
  • Pine nuts and sunflower seeds
  • Walnuts
  • Almonds and cashews
  • Tofu

Due to their cheap cost of production, many heavily processed junk foods which contain vegetable oil are also high in omega-6s.

‘Bad Fats’ or fats to avoid or moderate 

Saturated Fats

Saturated fatty acids (SFAs) are fats that have a molecular structure which contains no double-bonds. They are most commonly found in meat and dairy products, but can also be found in some plant fats such as coconut oil. 

Although SFAs are not essential you can have them in moderation as part of a balanced diet, although not at the expense of monounsaturated or polyunsaturated fats. SFAs have had a bad reputation in the past due to some studies that linked a high intake of SFAs with an increase in blood cholesterol levels and therefore an increased risk of cardiovascular disease (CVD) [1]

However, this may have been caused by other dietary factors with some evidence suggesting there isn’t necessarily a link between SFAs and increased blood cholesterol[2-4]. Foods which are high in SFAs include:

  • Fatty cuts of meat, especially pork, beef and lamb
  • Poultry skin and dark poultry meat
  • High-fat dairy such as butter or cheese 
  • Coconut oil
  • Palm oil
  • Lard

Trans Fats

Trans fatty acids, or trans fats have a different molecular structure to SFAs. Specifically, trans fats are unsaturated fats whose chemical structure has a double bond with hydrogen atoms on opposite sides.Trans fats are formed when liquid oils are converted into a semi-solid fat, a process known as hydrogenation. 

They’re frequently found in foods such as confectionery, margarines, and some heavily processed foods. On the spectrum of fats, trans fats are the most harmful and should be consumed very rarely or avoided altogether. This is because they increase the levels of LDL cholesterol in the blood. This form of cholesterol creates ‘plaque’ in your arteries, partially blocking them and making them less flexible. This puts a greater strain on your heart. 

At the same time, trans fats lower the levels of HDL cholesterol. This form of cholesterol, ‘good’ cholesterol. 

Foods with high levels of trans fats include:

  • Confectionary
  • Fried or deep-fried foods such as French fries or donuts
  • Margarines
  • Baked goods such as cookies, cakes or pastries
  • Processed snack foods such as microwavable popcorn or crackers

Other fats

Medium Chain Triglycerides (MCTs)

The fats listed above are known as long chain triglycerides (LCTs), this means that their molecular structure is in the form of a long chain. as the name suggests, these have a molecular structure in the form of a shorter chain. [23]

MCT’s are rare in nature but traces are present in a small number of natural fats. The majority of MCTs consumed by humans are man-made,, often from coconut or palm oil. MCTs are absorbed and metabolised differently to LCTs and are treated by the body more like an energy-dense carbohydrate source rather than a fat. It is this property that enables them to be processed by people who cannot process LCT fats. [23]

MCTs are a type of saturated fat and you’ll find them under saturated on food labels where they are present. 

Sources of MCTs include:

  • Coconut oil
  • Palm oil
  • Dairy fats
  • Supplements
  • Medical treatments prescribed and taken either by mouth or by injection 

Essential fats

There are two essential fatty acids (EFAs) that we need to include in our diet, which are both types of polyunsaturated fats. These are linoleic acid (LA), an omega-6, and alpha-linolenic acid (ALA), an omega-3. There are also four conditionally EFAs, that are fatty acids which become essential if we do not consume enough LA or ALA. These are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both are omega-3s, and arachidonic acid (AA) and gamma-linolenic acid (GLA), omega-6s. Again these are all forms of polyunsaturated fat.

Fatty Acid Type of PUFA Rich dietary source
Linoleic acid (LA) Omega-6 Corn, safflower, sunflower, soyabean, peanut oils
α-linolenic acid (ALA) Omega-3 Flaxseed, soya, rapeseed oils
Arachidonic acid (AA) Omega-6 Small amounts in animal fats
γ-linolenic acid (GLA) Omega-6 Hemp seed, borage seed, evening primrose oils
Eicosapentaenoic acid (EPA) Omega-3 Oily fish
Docosahexaenoic acid (DHA) Omega-3 Oily fish


Oxidation and free radicals

In order to understand how fats work in the body, we need to understand oxidation. Oxidation is a naturally occurring process where a molecule reacts with oxygen and forms ‘free radicals’.  

A free radical is a molecule with an unpaired electron, which means they are highly reactive to other molecules around them. It is this reactivity which is potentially damaging to human tissues as it can be involved in the process of some diseases, including cancer and cardiovascular disease. It also plays a role in the ageing process.

Although free radical formation is natural and inevitable, we can help minimise their formation and slow the damage they do. [24]

Antioxidants are substances which help stop this oxidation. They include vitamins C and E, some types of vitamin A, selenium, and phytonutrients like carotenoids and flavonoids. Eating a healthy diet rich in these substances will go a long way to help slow down oxidation.

Foods which contain relatively high levels of antioxidants include:

  • Blueberries
  • Beetroot 
  • Red cabbage
  • Matcha and green tea
  • Sweet potato
  • Mushrooms
  • Coffee beans

Cardiovascular disease

Cardiovascular disease, or CVD, is a term which covers heart disease, stroke, and peripheral vascular disease. A common cause of CVD is a build-up of ‘plaque’, which are fatty deposits on artery walls. This makes them narrower and harder, both meaning the heart has to pump harder to force blood through the smaller opening – increasing the strain on the heart muscle itself - and increasing the risk of a blood clot which could get stuck and cut off the blood supply to a region of the body. A stroke is this happening in the brain, if it happens in the heart this is a heart attack. 

Diets which are high in saturated fat have been shown to be linked to a high blood cholesterol level, in particular LDL cholesterol[1, 10]. These high levels have been linked to an increased risk of CVD[1]. When cholesterol oxidises, it becomes sticky and becomes attached to artery walls, forming a plaque. This process is known as atherosclerosis. This is the link between fatty diets and CVD. 

However, there is a very important codicil to this. Saturated fats cannot be oxidised, whereas unsaturated fats can.

Processed foods

The modern Western diet is high in overly processed junk foods that are full of saturated fats and contain large amounts of cheap vegetable oils. Some of these vegetable oils have also been hydrogenated and are high in trans fats that can cause a build-up of plaque on artery walls. These vegetable oils are also high in processed omega-6s which may have been damaged by oxidation and therefore by consuming these, you’re consuming oxidised fats with a higher risk of causing plaque formation. However, not all processed foods are bad, read our article to find out more.

How much fat should I consume?

Healthy eating guidelines suggest that less than 35% of our energy intake should come from fats[16]. From this, no more than 11% should be from saturated fats[16]. None of the saturated fatty acids are essential, so we don't need them, but they’re an excellent source of energy and shouldn’t be shunned.

The optimal ratio of omega-6 to omega-3 is thought to be around 1 or 2 to 1[17]. However, Western diets have been shown to be as high as between 6 and 20 to 1[17]. In areas of the world where their diet has a high omega-6 to omega-3 ratio, there are also high CVD rates. In regions where the ratio is nearer to 1 or 2 to 1 the incidences of CVD are significantly lower[17]. An omega-6 to omega-3 ratio of 1 or 2 to 1 is suggested with total polyunsaturated fats being 10-12% of the total energy input[17]. Monounsaturated fats should make up the remainder of the energy input.

Omega-3 supplements

It’s quite rare to be consuming insufficient omega-6s, but it’s not uncommon in the modern world for people to have a low intake of omega-3s. If you don’t eat oily fish or flaxseed, then supplementing your diet with flaxseed oil or a specifically formulated oil blend might be a good idea. Cod liver oil supplements have been available for decades but offer little benefit in respect of fatty acid supplementation, as the doses of EFA are low. However, if you do prefer to take a capsule fish oil supplement, check that it’s from a reputable brand first, as some cheaper, low quality brands come from fish which have been raised in poor conditions and they may contain oxidised fats. Oils are very prone to oxidation and must be stored in cool, dark conditions. 

Marine algae supplements also provide EPA and DHA, and ALA supplements are available, but don’t overdo these. Exceptionally high intakes of supplementary ALA have been linked to a higher incidence of prostate cancer in men[18].

Fats in Huel

Huel Powder v3.0 and Hot & Savoury provides 30% of total energy from good sources of fat. The fats are from the natural ingredients; ground flaxseed, sunflower oil, MCTs from coconut, and even from the oats. Huel has been formulated to provide the optimum amounts of all the fats.

Huel Powder

The level of polyunsaturated fats in Huel Powder provides an ideal ratio of omega-3s:omega-6s (just under 1:1). The total polyunsaturates level is higher than some sources recommend, for example, the Nordic Nutrition Recommendations suggest polyunsaturates should be below 10% of total energy intake[19]. These recommendations are based on data collected from people who consume high-fat junk foods where the polyunsaturates have been exposed to oxidative damage. The polyunsaturates in Huel Powder are from natural ingredients that have been protected from oxidation. The higher level of polyunsaturates in Huel Powder is necessary to provide sufficient ALA conversion to EPA and DHA, as well as ample LA. At 10% of the total energy intake, there wouldn’t be sufficient amounts at 2,000kcal for the optimal intakes of the fatty acids discussed above.

Saturated fats in Huel Powder provide 5.2-5.5% (varies between flavour) of total energy intake. MCTs make up a large amount of this as they provide an efficient source of energy.

Huel Ready-to-drink

Similar to Huel Powder, Huel Ready-to-drink provides an ideal omega-3:omega-6 ratio of 1:2. Again, polyunsaturates make up over 10% of the total energy intake to ensure adequate ALA conversion MCTs make up a significant proportion of the saturated fats.

Huel Hot & Savoury

Polyunsaturated fats provide approximately 16% of the calories of Huel Hot & Savoury. The omega-3:omega-6 ratio is around 2:1 which is the highest ratio of all Huel products.

Good fats and bad fats summary

  • It’s fine to consume moderate amounts of saturated fat
  • Avoid trans fats
  • Include foods rich in monounsaturated fats
  • Include omega-6 polyunsaturates from natural sources; avoid them in junk foods
  • Increase your intake of omega-3 fats by eating oily fish, flaxseed oil or ground flaxseed
  • MCTs are an efficient source of energy
  • Huel has the optimum proportions of the various fats

References

  1. Kromhout D, et al. Dietary saturated and trans fatty acids and cholesterol and 25-year mortality from coronary heart disease: the Seven Countries Study. Prev Med. 1995; 24(3):308-15.
  2. Lawrence GD. Dietary fats and health: dietary recommendations in the context of scientific evidence. Adv Nutr. 2013; 4(3):294-302.
  3. O'Sullivan TA, et al. Food sources of saturated fat and the association with mortality: a meta-analysis. Am J Public Health. 2013; 103(9):e31-e42.
  4. Heileson JL. Dietary saturated fat and heart disease: a narrative review. Nutrition Reviews. 2019; 78(6):474-85.
  5. Grundy SM. Comparison of monounsaturated fatty acids and carbohydrates for lowering plasma cholesterol. N Engl J Med. 1986; 314(12):745-8.
  6. Ginsberg HN, et al. Reduction of plasma cholesterol levels in normal men on an American Heart Association Step 1 diet or a Step 1 diet with added monounsaturated fat. N Engl J Med. 1990; 322(9):574-9.
  7. Kris-Etherton PM, et al. High-monounsaturated fatty acid diets lower both plasma cholesterol and triacylglycerol concentrations. Am J Clin Nutr. 1999; 70(6):1009-15.
  8. Katan MB, et al. Should a low-fat, high-carbohydrate diet be recommended for everyone? Beyond low-fat diets. N Engl J Med. 1997; 337(8):563-6; discussion 6-7.
  9. Simopoulos AP. Omega-3 fatty acids in health and disease and in growth and development. Am J Clin Nutr. 1991; 54(3):438-63.
  10. Clarke R, et al. Dietary lipids and blood cholesterol: quantitative meta-analysis of metabolic ward studies. BMJ. 1997; 314(7074):112-7.
  11. Ruxton CHS, et al. The health benefits of omega-3 polyunsaturated fatty acids: a review of the evidence. 2004; 17(5):449-59.
  12. Connor WE. Importance of n−3 fatty acids in health and disease. The American Journal of Clinical Nutrition. 2000; 71(1):171S-5S.
  13. Lavie CJ, et al. Omega-3 polyunsaturated fatty acids and cardiovascular diseases. J Am Coll Cardiol. 2009; 54(7):585-94.
  14. Swanson D, et al. Omega-3 Fatty Acids EPA and DHA: Health Benefits Throughout Life. Advances in Nutrition. 2012; 3(1):1-7.
  15. Mickleborough TD. Omega-3 Polyunsaturated Fatty Acids in Physical Performance Optimization. 2013; 23(1):83-96.
  16. Food Standards Agency. FSA nutrient and food based guidelines for UK institutions. London2007.
  17. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002; 56(8):365-79.
  18. Brasky TM, et al. Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial. JNCI: Journal of the National Cancer Institute. 2013; 105(15):1132-41.
  19. Nordic Council of Ministers. Nordic Nutrition Recommendations 2002: Integrating nutrition and physical activity. 5 ed. Copenhagen. 2002.
  20. Innes JK and Calder PC. Omega-6 fatty acids and inflammation. Prostaglandins, Leukotrienes and Essential Fatty Acids. 2018; 132: 41-48. 
  21. Wang L. Omega-3 and Omega-6 Fatty Acids: Role in Body Fat Gain and Development of Obesity. The North American Journal of Medicine and Science. 2015; 8 (4): 163-171. 
  22. Tortosa-Caparrós E, Navas-Carrillo D, Marín F and Orenes-Piñero E. Anti-inflammatory effects of omega 3 and omega 6 polyunsaturated fatty acids in cardiovascular disease and metabolic syndrome. Critical Reviews in Food Science and Nutrition. 2017; 57(16): 3421-3429. 
  23. Jiang, Z., Zhang, S., Wang, X., Yang, N., Zhu, Y. and Wilmore, D., 1993. A Comparison of Medium-Chain and Long-Chain Triglycerides in Surgical Patients.
  24. Lobo, V., Patil, A., Phatak, A. and Chandra, N., 2010. Free radicals, antioxidants and functional foods: Impact on human health.

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