Fat has had a bad reputation for several decades. For years, we’ve been advised to cut down on fat, especially saturated fat, in the mistaken belief that it “clogs the arteries” and “causes high cholesterol”, which both “contribute to heart disease”. Thankfully, in more recent years, more and more research1-5 continues to prove these long-standing misconceptions to be nothing more than stubborn dogma that emerged in the middle of the 20th century from bogus research (thank you, Ancel Adams).
The belief that fat is bad is a difficult one to shake off for a number of reasons. One, the current Government dietary guidelines still advise limiting daily fat intake by keeping high-fat foods to an absolute minimum and choosing reduced-fat food options as much as possible7. Two, fat contains more calories per gram than protein or carbohydrate and we’re told eating too many calories causes weight gain8. When we gain weight, our bodies store fat, so it makes sense to eat less fat, right? Sounds nice and simple, but no… Our bodies are so much more complex than the too-simplistic “energy in = energy out” formula (more bullshit dogma that should have been refreshed and updated decades ago). And thirdly, food companies have literally bombarded us with anti-fat marketing on TV, online, in magazines, and on product labelling in supermarkets for years (and for anyone born after about 1960, our whole lives!). When the vast majority of food packaging boasts slogans such as “low fat”, “0% fat” and “proven to lower cholesterol”, people can be forgiven for assuming these companies are just selling products in line with Government guidelines on diet. And, unfortunately, that’s true – even that faded and slightly retro-looking “Diet Pyramid” poster in your doctor’s surgery waiting room advises limiting fat to the odd sliver of polyunsaturated margarine on a generous portion of toast (wholegrain of course). But their real intentions (profits) are far from the apparently honourable and altruistic messages they broadcast in bright letters on their packaging.
It can be hard to lose an ingrained fear of fat, but we are slowly beginning to recognise the health benefits of fat, including maintaining the health of the brain and nervous system, and that fat is essential for the normal function and health of the entire body. But let’s take a closer look at just how incredible fat really is.
1. Fat allows absorption of the fat-soluble vitamins A, D, E and K
Without fat, the body cannot adequately absorb vitamins A, D, E and K, the four fat-soluble vitamins (though strictly speaking, vitamin D is actually a pro-hormone, which the body can also make from exposure to sunlight). These vitamins perform a multitude of incredibly important functions in the body, including supporting cell growth, immune function and healthy vision; maintaining bone health, normal blood pressure and cognitive function; protection from oxidative stress and free radical damage; and formation of new red blood cells and regulating normal blood clotting, just to name a few.
These four micro-nutrients are crucial to just about every function in the body. But even if you are consciously choosing low-fat foods that still contain these nutrients, (e.g. low-fat yoghurt, mushrooms, spinach and broccoli), your body cannot absorb the ADEK vitamins without fat. And the less fat you eat, the more difficulty your body has with absorption and the more likely you are to become deficient. Indeed, deficiency of vitamins A, D, E and K often occurs, not due to a diet deficient in these nutrients, but a diet deficient in fat9. Unlike those third-world countries, e.g. parts of central and east Africa, where hunger and famine result in the more obvious and serious vitamin deficiency conditions, including blindness (A) and rickets (D), deficiencies are still common in first-world countries due to poor diet, not lack of food. The more ambiguous symptoms of vitamin ADEK deficiencies include skin problems, infertility, fatigue, lowered immunity, muscle pain and bruising easily. These are extremely common complaints for much of the population, but how many people consider ADEK- or fat-deficiency as the cause?
Vitamins A, D, E and K exist in both plant and animal forms; for example the plant version of vitamin A, beta carotene, must first be converted to the animal version, retinol, before it can be utilised by the human body. However, as little as 3%10 is converted, so, as an example, to get the same amount of vitamin A that’s contained within just an 85g serving of beef liver, you’d have to munch your way through over 2kg of carrots (and over 18kg if those carrots were raw – no wonder you never see Bugs Bunny without one!).
In nature, the fat-soluble vitamins A, D, E and K are more often found in higher fat foods, such as oily fish, meat and eggs – these foods not only contain the readily useable animal forms we, as animals, need, but they come with the fat needed for their efficient absorption.
2. The brain is 60% fat
Only about 40% of your brain is made up of neural cells, proteins and blood vessels – the rest is fat. The human brain has developed over more than 300,000 years of evolution to become the incredibly complex organ we have in our skulls today – Mother Nature clearly considered fat to be important. However, while the brain has limited capacity for regeneration, brain fat isn’t static – it is constantly being repaired and replaced, especially the fatty myelin sheath that insulates nerve axons11.
While the brain’s main source of fuel is glucose, it is a misunderstanding (and quite frankly a significant underestimation) that we must consume carbohydrate in the diet to fuel the brain. The body can make glucose from both protein and fat via gluconeogenesis. So, many people who actively follow a low-fat/carbohydrate-dominant diet have rather an upside-down understanding of the brain’s macro-nutrient needs, that is, our brains don’t need dietary carbohydrate12 but most definitely do need dietary fat.
Fat not only makes up more than half of the brain by proportion, but fat and cholesterol are also essential for the production of neurotransmitters, chemical messengers involved in neural signalling. The essential fatty acids (EFAs) omega-3 and omega-6 are termed “essential” because they can only be obtained via the diet and the most important to human health are DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). It has been shown that dopamine and serotonin, two important neurotransmitters responsible for movement, emotional responses and mood, are significantly affected by a diet deficient in EFAs13.
3. The brain contains 25% of the body’s total cholesterol
Like fat, cholesterol is vitally important for health. In fact, you simply cannot survive without it. However, it is unfortunate that cholesterol has been subject to the same historic botched “science” as fat, that is, cholesterol has been wrongly accused of being a contributing factor to heart disease14. So, where did cholesterol’s bad reputation come from? In the same way as Ancel Adams falsely (or some may say fraudulently15) blamed fat for causing heart disease, Brown and Goldstein16 mistakenly accused cholesterol of the same crime.
Indeed, cholesterol is known to build up in the arteries of people with coronary heart disease, but the more up-to-date and accurate science has proven that it is in fact inflammation that causes arterial plaques17, not cholesterol (to use an analogy: if a large oil slick [inflammation] caused several cars [cholesterol] to crash in a pile up [heart attack], it’s like blaming the cars for causing the accident, not the oil. Cholesterol just happens to be at the scene of a heart attack, it is not the cause of it).
Even the term “LDL cholesterol” is a misnomer, as LDL is not cholesterol. LDLs are low-density lipoproteins that carry cholesterol from the liver around the body. HDLs are high-density lipoproteins that carry cholesterol back to the liver. So all LDLs and HDLs do is carry cholesterol. And, while historically it has been assumed that raised LDL is an indicator of poor health (and heart disease risk), more modern scientific research has shown that it is not so much the amount of LDL that is important, as the ratio of HDL:LDL18, whether or not cholesterol becomes oxidised (oxLDL)19, and the size of the LDL particles20 (i.e. put a little less scientifically, big fat fluffy ones are better than small shrunken dense ones). What causes high levels of dense, oxidised LDL? Inflammation21 and metabolic syndrome22 usually due to a diet high in refined seed oils (especially trans fats) and carbohydrates, especially sugar (high-fructose corn syrup being the worst offender). Unfortunately, the current belief of the medical establishment is to focus on reducing LDL by continued use of statins, rather than addressing the causes of ill-health, such as diet. The UK NHS are even trialling a new “cholesterol-busting jab”23 (good grief).
So, cholesterol, like fat, is not only beneficial to health, it is essential to life. So essential, in fact, that, if you eat less, your body just makes more! What does cholesterol do in the body? Cholesterol:
- forms the fundamental structure of all cell membranes,
- is a key constituent (~80%) of the myelin sheath that insulates nerve axons (25% of the body’s cholesterol is found in the brain!),
- is essential for foetal development, in particular maturation of the brain,
- is necessary for nerve regeneration24,
- is a precursor to all steroid hormones, including oestrogen, testosterone and cortisol,
- is required for the conversion of vitamin D2 into the useable form D3,
- is required by the liver to make bile, which is necessary for the digestive system to breakdown fats.
So, fat and cholesterol are beneficial. Fat and cholesterol are essential. In fact, fat and cholesterol are bloody fabulous and I couldn’t live without them (literally!).
- Hooper L, Martin N, Abdelhamid A, Davey Smith G. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev. 2015;(6):CD011737. Published 2015 Jun 10. doi:10.1002/14651858.CD011737.
- de Souza RJ, Mente A, Maroleanu A, et al. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ. 2015;351:h3978. Published 2015 Aug 11. doi:10.1136/bmj.h3978.
- Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010;91(3):535-546. doi:10.3945/ajcn.2009.27725.
- Chowdhury R, Warnakula S, Kunutsor S, et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis [published correction appears in Ann Intern Med. 2014 May 6;160(9):658]. Ann Intern Med. 2014;160(6):398-406. doi:10.7326/M13-1788.
- Schwab U, Lauritzen L, Tholstrup T, et al. Effect of the amount and type of dietary fat on cardiometabolic risk factors and risk of developing type 2 diabetes, cardiovascular diseases, and cancer: a systematic review. Food Nutr Res. 2014;58:10.3402/fnr.v58.25145. Published 2014 Jul 10. doi:10.3402/fnr.v58.25145.
- Anorak News, 2014. Domino Pure Cane Sugar advert [online image]. Available from URL: https://www.anorak.co.uk/409622/reviews/sugar-is-a-legal-high-low-fat-makes-you-fat-and-john-yudkin-was-right.html [last accessed 01/02/2021].
- Public Health England. Eat Well Guide [online]. Available from URL: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/528193/Eatwell_guide_colour.pdf. [Last accessed 25/01/2021].
- NHS. Hidden causes of weight gain [online]. Available from URL: https://www.nhs.uk/live-well/healthy-weight/hidden-causes-of-weight-gain/ [last accessed 31/01/2021].
- Jeppesen PB, Høy CE, Mortensen PB. Deficiencies of essential fatty acids, vitamin A and E and changes in plasma lipoproteins in patients with reduced fat absorption or intestinal failure. Eur J Clin Nutr. 2000;54(8):632-642. doi:10.1038/sj.ejcn.1601067.
- Hedrén E, Diaz V, Svanberg U. Estimation of carotenoid accessibility from carrots determined by an in vitro digestion method. Eur J Clin Nutr. 2002;56(5):425-430. doi:10.1038/sj.ejcn.1601329.
- MS Society. Can we reprogram myelin making cells to improve regeneration? [online]. Available from URL: https://www.mssociety.org.uk/research/explore-our-research/research-we-fund/search-our-research-projects/reprogram-myelin-cells [last accessed 31/01/2021].
- Manninen AH. Metabolic effects of the very-low-carbohydrate diets: misunderstood “villains” of human metabolism. J Int Soc Sports Nutr. 2004;1(2):7-11. Published 2004 Dec 31. doi:10.1186/1550-2783-1-2-7.
- Li F., Liu X., Zhang D., (2016). Fish consumption and risk of depression: a meta-analysis, Journal of epidemiology and community health, 70(3): 299-304.
- Ravnskov U, de Lorgeril M, Diamond DM, et al. LDL-C does not cause cardiovascular disease: a comprehensive review of the current literature. Expert Rev Clin Pharmacol. 2018;11(10):959-970. doi:10.1080/17512433.2018.1519391.
- Dr A. Eenfeldt, 2016. The hidden truth behind Ancel Keys’ famous fat graph [online]. Available from URL: https://www.dietdoctor.com/the-hidden-truth-behind-ancel-keys-famous-fat-graph [last accessed 01/02/2021].
- Adams DD. The great cholesterol myth; unfortunate consequences of Brown and Goldstein’s mistake. QJM. 2011;104(10):867-870. doi:10.1093/qjmed/hcr087.
- Tsoupras A, Lordan R, Zabetakis I. Inflammation, not Cholesterol, Is a Cause of Chronic Disease. Nutrients. 2018;10(5):604. Published 2018 May 12. doi:10.3390/nu10050604.
- Millán J, Pintó X, Muñoz A, et al. Lipoprotein ratios: Physiological significance and clinical usefulness in cardiovascular prevention. Vasc Health Risk Manag. 2009;5:757-765.
- Leonarduzzi G, Sottero B, Poli G. Oxidized products of cholesterol: dietary and metabolic origin, and proatherosclerotic effects (review). J Nutr Biochem. 2002;13(12):700-710. doi:10.1016/s0955-2863(02)00222-x.
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- Rhoads JP, Major AS. How Oxidized Low-Density Lipoprotein Activates Inflammatory Responses. Crit Rev Immunol. 2018;38(4):333-342. doi:10.1615/CritRevImmunol.2018026483
- Hurtado-Roca, Y., Bueno, H., Fernandez-Ortiz, A., Ordovas, J.M., Ibañez, B., Fuster, V., Rodriguez-Artalejo, F. and Laclaustra, M. 2017. Oxidized LDL Is Associated With Metabolic Syndrome Traits Independently of Central Obesity and Insulin Resistance. Diabetes Feb 2017, 66 (2) 474-482; DOI: 10.2337/db16-0933.
- BBC News, 2020. NHS to pioneer cholesterol-busting jab [online]. Available from URL: https://www.bbc.co.uk/news/health-51091083 [ last accessed 01/02/2021].
- Hussain, G., Wang, J., Rasul, A. et al. Role of cholesterol and sphingolipids in brain development and neurological diseases. Lipids Health Dis 18, 26 (2019). https://doi.org/10.1186/s12944-019-0965-z.