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  1. Fish is rich in beneficial omega-3 fatty acids, though while cooking under high temperatures we may destroy any benefit of fish. But different cooking methods affect fish differently. Surprisingly, I read that frying reduces amount of heavy metals better than any other cooking method. Is it true? If so, should we opt for fried fish or still it is better to avoid it as any other fried food? 
  2. Recently I came across strange article claiming that some unsaturated fatty acids are not beneficial and even dangerous to human, especially it relates to omega-3 fatty acids. I firstly thought that article was written just to attract attention, and there is not a word of truth, just stupid fabrication. But then I found another similar article in a science journal by chance, though I am no scientist and just having browsed the net. So I wonder if this is a myth or a true fact?
  3.   The two main omega-3 fatty acids are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). It has been generally accepted that fish and sea foods are the best sources of omega-3 fatty acids and should be consumed 2-3 times a week, as these compounds have been suggested to reduce the risk of cardiovascular disease.[1] The main source of these omega-3 fatty acids is oily fish such as salmon, mackerel and sardines. Olive oil and some seeds and nuts such as flax seeds, chia seeds, walnuts and pumpkin seeds are also rich in alpha-linolenic acid (ALA), another omega-3 fatty acid, which the body can then convert to DHA or EPA however to a limited extent of 2-10%.[2] The perceived benefits of omega-3 fatty acids originated from the observation of Japanese and Mediterranean populations. Japanese and Mediterranean consumption of fish is high while Mediterranean diet also encourages the use of olive oil. These populations have a lower incidence of cardiovascular disease and consequently a tendency to live longer.[3]  In addition to being associated with healthier cardiac function, studies have shown omega-3 fatty acids also play a role in healthy ageing and foetal development.[2] In fact studies have demonstrated that the many beneficial attributes of omega-3 fatty acids include reduced incidence of atherosclerosis and reduced inflammation in both overweight sedentary adults and healthy older adults.[4] [5] Furthermore animal studies have also demonstrated that an increase in omega-3 fatty acid intake can reduce the risks of Alzheimer’s disease.[6] Omega-3 supplements have also been linked to a reduction of the risk of prostate cancer. [7] Despite these potentially obvious positive effects, recent evidence has emerged that questions the benefits of omega-3 fatty acids obtained from either consumption of fish or supplements.[1] Recent studies have highlighted that increased omega-3 fatty acid consumption in people already at risk of heart disease does not reduce the incidence of stroke, heart attack or death.[8] Another study also demonstrated that omega-3 fatty acids have no discernible impact on overall mortality or the incidence of cardiovascular disease or cancer.[9]  Furthermore, contrary to some studies, high levels of omega-3 fatty acids in the blood have actually been correlated with an increased risk of prostate cancer.[10] These recent findings have led some to believe that omega-3 fatty acid supplementation may actually be harmful to the body during several medical conditions. This theory comes from the fact that, like all fatty acids, omega-3 fatty acids are prone to lipid peroxidation. Lipid peroxidation is oxidative degradation of lipids, mostly of unsaturated fatty acids making up triglycerides and phospholipids. Consumption of oxidised lipids can result in increased oxidative stress, which is associated with many adverse health effects. Indeed prolonged high levels of oxidised lipids in the blood can lead to atherosclerosis.[11] [12]  Oily fish may also contain persistent organic pollutants or metals, the latter of which may facilitate the lipid peroxidation described above.[1] Furthermore, it has also been suggested that, as omega-3 supplements lack the range of nutrients such as proteins, vitamins and minerals present in whole fish, their efficacy and function may be compromised.[13] When speaking about omega-3 fatty acids consumption the issue of omega-3 to omega-6 fatty acids ratio has to be also taken into account. With the evolution and development of agriculture this ratio has shifted from 1:1 to about 1:15 which is thought to be one of the reasons for increased incidence of heart diseases and obesity. However the optimal ratio is not yet defined according to the UK Food Standards Agency and it is advised to increase the intake of omega-3 rather than focuse on decreasing the amount of omega-6 fatty acids in your diet.[14]   Omega-3 fatty acids are essential fatty acids that play a crucial role in maintaining good health. As our bodies cannot produce them, we need to obtain them from dietary sources such as oily fish and plant oils. Given the potential for reduced efficacy when eaten in its pure form, omega-3 consumption through the diet is preferable to taking omega-3 nutritional supplements. Remember to use mild temperature ways of cooking for omega-3 rich foods to avoid lipid oxidation and preserve the benefit of omega-3. Whilst some of the health benefits previously attributed to omega fatty acids may now be under scrutiny, it is apparent it may be more to do with omega-3 to omega-6 ratios than doubting omega-3 benefits and so it is still a key part of a healthy diet and potential benefits appear to outweigh the potential risks.    [1] Maehre H, et al. (2016). ω-3 Fattyω-3 Fatty Acids and Cardiovascular Diseases: Effects, Mechanisms and Dietary Relevance Acids and Cardiovascular Diseases: Effects, Mechanisms and Dietary Relevance. International Journal of Molecular Sciences, 16(9), 22636- 22661. https://dx.doi.org/10.3390%2Fijms160922636 [2]  Swanson, D. (2012). Omega-3 fatty acids EPA and DHA: health benefits throughout life. Advances in Nutrition, 3(1), 1-7. https://doi.org/10.3945/an.111.000893 [3] Tokudome, S., et al (2004). The Mediterranean vs the Japanese diet. European Journal Of Clinical Nutrition, 58, 1323. http://dx.doi.org/10.1038/sj.ejcn.1601970 [4] Sekikawa A, et al. (2008). Marine-derived n-3 fatty acids and atherosclerosis in Japanese, Japanese Americans, and Whites: a cross-sectional study. Journal of the American College of Cardiology, 52(6), 417-424. https://doi.org/10.1016/j.jacc.2008.03.047 [5] Kiecolt-glaser, J.K. (2012). Omega-3 Supplementation Lowers Inflammation in Healthy Middle-Aged and Older Adults: A Randomized Controlled Trial. Brain, Behavior, and Immunity, 26(6), 998-995. https://doi.org/10.1016/j.bbi.2012.05.011 [6] Lim G.P, et al. (2005). A diet enriched with the omega-3 fatty acid docosahexaenoic acid reduces amyloid burden in an aged Alzheimer mouse model. The Journal of Neuroscience, 25(12), 3032-3040. https://doi.org/10.1523/JNEUROSCI.4225-04.2005 [7] Augustsson K, et al.(2003). A Prospective Study of Intake of Fish and Marine Fatty Acids and Prostate Cancer. American Association for Cancer Research, 12(1), 64-67. http://cebp.aacrjournals.org/content/12/1/64 [8]  The risk and prevention study collaborative group. (2013). N–3 Fatty Acids in Patients with Multiple Cardiovascular Risk Factors. The New England Journal of Medicine, 368(1), 1800-1808. https://doi.org/10.1056/NEJMoa1205409 [9] Hooper, L. et al. (2006). Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review. BMJ, 332(752) https://doi.org/10.1136/bmj.38755.366331.2F [10] Brasky, TM. et al. (2013). Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial. Journal of the National Cancer Institute, 105(15), 1132-1141. https://doi.org/10.1093/jnci/djt174 [11]  Awada M, et al. (2012). Dietary oxidized n-3 PUFA induce oxidative stress and inflammation: role of intestinal absorption of 4-HHE and reactivity in intestinal cells. Journal of Lipid Research, 53(10), 2069-2080. https://doi.org/10.1194/jlr.M026179 [12] Lobo V, et al. (2010). Free radicals, antioxidants and functional foods: Impact on human health. Pharmacognosy Review, 4(8), 118-126. https://doi.org/10.4103/0973-7847.70902 [13]  He, K. (2009). Fish, Long-Chain Omega-3 Polyunsaturated Fatty Acids and Prevention of Cardiovascular Disease—Eat Fish or Take Fish Oil Supplement? Progress in Cardiovascular Diseases, 52(2), 95-114. https://doi.org/10.1016/j.pcad.2009.06.003 [14] Stanley, J., Elsom, R., Calder, P., Griffin, B., Harris, W., & Jebb, S. et al. (2007). UK Food Standards Agency Workshop Report: the effects of the dietary n-6:n-3 fatty acid ratio on cardiovascular health. British Journal Of Nutrition, 98(06). http://dx.doi.org/10.1017/s000711450784284x
  4. What is cholesterol?

    Cholesterols are types of fat found in the blood. The liver produces sufficient cholesterol for the body’s requirements, but it can also be acquired from foods, particularly animal products, such as meat, egg yolks, butter, cheese and milk. Cholesterol is necessary for the body to function properly, as it is involved in the production of hormones and vitamin D, and in the digestive process.[1]  Cholesterol is not soluble in the blood and has to be transported through the bloodstream by carriers called lipoproteins (complexes of fatty acids and proteins).[1] There are two types of proteins that transport cholesterol to and from cells, high-density lipoproteins (HDL), and low-density lipoproteins (LDL). The levels of cholesterol bound to these lipoproteins in the bloodstream can be an important indicator of the risk of heart disease. A blood test commonly used by doctors to determine your ‘cholesterol level’ calculates the overall cholesterol level by adding HDL and LDL to 20% of the amount of triglyceride (another fat present in the blood). [2] LDL is commonly known as ‘bad’ cholesterol. This is because it contributes to the formation of plaques within blood vessels, which are thick hard deposits that can clog arteries and decrease their flexibility, resulting in atherosclerosis. [3] If a blood clot forms in one of these narrowed arteries, it can result in a heart attack or a stroke.[1] Excess LDL can also contribute to peripheral artery disease, which is the result of plaque narrowing an artery that supplies blood to the extremities, such as the legs.[1] HDL is known as ‘good’ cholesterol as it assists in the removal of LDL by acting as a scavenger, carrying LDL back to the liver where it is broken down and excreted.[4] 20% to 30% of cholesterol is carried by HDL.[4], [5]  However, despite its beneficial actions, studies have shown that the level of HDL in the plasma may not reliably indicate the degree of reduction of LDL and so research into this area is continuing.[6] A satisfactory level of HDL can, however, decrease the risk of heart attack and stroke and, conversely, a level that is too low increases the risk.[7]  Triglycerides are another type of fat also present in the blood. They are also produced by the liver and are additionally found in oils, meat and dairy products. Their purpose is to provide energy to the body’s cells and tissues. When excess calories are ingested they are converted to triglycerides and stored as body fat and as fatty deposits within organs and tissues.[8] Like LDL, high levels of triglycerides are also associated with atherosclerosis,[9] and many people with diabetes or heart disease have high triglyceride levels within their blood. It is also common for people with high triglyceride levels to have a high ‘overall’ cholesterol level (i.e. a high LDL level and a low HDL level). One study has shown that a healthy lipid profile (i.e. low LDL, high HDL and low triglycerides), can reduce the risk of chronic heart disease by 71%.[10] Some common causes of elevated triglyceride levels include obesity, high alcohol consumption, cigarette smoking and a diet high in saturated fats.[11] Underlying diseases, e.g. poorly controlled diabetes, an underactive thyroid (hypothyroidism), kidney disease, and alcoholism,[11] and genetic disorders such as familial hypertriglyceridemia[12] can also cause increased levels of triglycerides. The best way to maintain healthy cholesterol levels is by leading a healthy lifestyle: a varied and balanced diet, low in saturated fat and plenty of pesticide-free fruit and vegetables, in addition to sustaining a healthy weight. Exercise is another key factor in reducing or maintaining healthy cholesterol levels, although the exact mechanism for this is not yet clear.[13] Exercise is also beneficial in controlling weight. Smoking should be avoided and alcohol consumed in moderation; as well as increasing cholesterol levels, the adverse effects on health of both smoking and excess alcohol are well documented. [1] NIH (2016) What is cholesterol? Retrieved May 2016 from, http://www.nhlbi.nih.gov/health/health-topics/topics/hbc  [2] Barter, P. et al. (2007) HDL Cholesterol, Very Low Levels of LDL Cholesterol, and Cardiovascular Events. The New England Journal of Medicine. 57. 1301-1310. [3] Kyle, D. (2004) Understanding lipoproteins as transporters of cholesterol and other lipids. Advances in Physiology Education. 28(3). 105-106. [4] Lee-Rueckert, M. et al. (2016) HDL functionality in reverse cholesterol transport - Challenges in translating data emerging from mouse models to human disease. Biochim Biophys Acta. 1861(7). 566-83. [5] Schwartz, CC. et al. (2004) Lipoprotein cholesteryl ester production, transfer, and output in vivo in humans. J Lipid Res. 45(9). 1594-1607. [6] Rothblat, G.H. et al. (2010) High-density lipoprotein heterogeneity and function in reverse cholesterol transport. Current Opinion in Lipidology, 21(3), 229-238. [7] University of Pennsylvania. (2016) Fat and ketoacids, cholesterol, repair. Retrieved June, 2016, from https://www.med.upenn.edu/biocbiop/faculty/vanderkooi/chap7-9.pdf  [8] Toth, P. (2005) The “Good Cholesterol”. Circulation. 111(5). 89-91. [9] Borge, G. et al. (2007) Nonfasting Triglycerides and Risk of Myocardial Infarction, Ischemic Heart Disease, and Death in Men and Women. Journal of the American Medical Association. 298(3). 299-308. [10] Manninen, V. (1992) Joint effects of serum triglyceride and LDL cholesterol and HDL cholesterol concentrations on coronary heart disease risk in the Helsinki Heart Study Implications for treatment. Circulation. 85(1). 37-45. [11] University of Colorado, Denver (2016) Cholesterol and Triglycerides Retrieved August, 2016, from http://www.ucdenver.edu/academics/colleges/medicalschool/departments/medicine/EndocrinologyMetabolismDiabetes/clinical/Documents/Lipid_Brochure.pdf  [12] NIH (2016) Familial hypertriglyceridemia.  Retrieved June, 2016, from https://www.nlm.nih.gov/medlineplus/ency/article/000397.htm [13] Meissner, M. et al. (2010) Exercise enhances whole-body cholesterol turnover in mice. Med Sci in Sports Exercise. 42.1460-1468.
  5. Fat or oil is an important part of a diet. It is primarily made up of building blocks called fatty acids (FAs). Depending on the presence of double bonds between carbon atoms in its molecule FAs can be either saturated or unsaturated. In turn unsaturated FAs may be categorised into monounsaturated (MUFAs) having one double bond available and polyunsaturated fatty acids (PUFAs) with more than one double bond.[1] Unsaturated fatty acids are often referred to as omega fatty acids due to their chemical classification into omega-3, omega-6 and omega-9 FAs. The number stands for the position of first double bond in FA molecule which in turn determines its biochemical properties. While most of the FAs are present in the human body or may be produced in it, there are two fatty acids that can not be derived from other FAs and must be consumed from dietary sources to maintain good health condition. These FAs are called Essential Fatty acids (EFA) and include alpha-linolenic (omega-3) and linoleic (omega-6) FAs.[1][2] Docosahexaenoic acid may also become essential in some conditions but normally it can be synthesized from alpha-linoleic acid.[1]  Omega FAs have many crucial roles within the body. They reduce inflammation and possess protective properties against cardiovascular disease, are essential for pregnant woman for foetal growth and brain development.[3] They are also important for these processes in infants, who obtain them from breast milk.[4] Omega-3 FAs are also involved in the formation of cell walls and help to improve circulation and oxygen uptake.[5][6]   Other benefits include the improvement of mental health and brain function.[5][7] Scientists continue to argue on the role and potency of omega FAs to fight cancer but there is no consensus yet.[6][8][9] Omega-3 FAs have been part of the human diet throughout evolution. In early times, it is thought that the ratio of omega-3 to omega-6 FAs in our diets was approximately 1:1.[10] In Western diets the ratio of omega-3 to omega-6 FAs has dramatically shifted and is now thought to be from 1:15 to 1:20, thus there is a large disparity between modern diet and our inbuilt genetic patterns.[11][12] The reason for this change over time is thought to come from the industrial revolution and development of modern agricultural and aquacultural methods including changes in animal and fish feeds. The good example is the lower omega-3 to omega-6 ratio in cultured fish species than in wild ones. Generally omega-3 content decreased in multiples in regularly consumed food products, including eggs, fish and animal meat.[2][13] It is thought that this large shift in the ratio of omega-3 to omega-6 consumed in the Western diet is a contributory factor in the increasing incidence of atherosclerosis, coronary heart disease, hypertension, obesity, collagen vascular diseases and cancer. Scientists explain this by different biochemical properties of omega-3 and -6 FAs. While the first ones contribute to anti-inflammatory and suppressive effects for many diseases, the latter have proinflammatory and prothrombotic properties. And thus omega-3 to omega-6 ratio in the diet is crucial.[2][10][11]  According to EFSA “250 mg daily intake of long chain omega-3 FAs for adults may reduce the risk of heart disease” and this amount of eicosapentaenoic acid plus docosahexaenoic acid is stated as an adequate intake level.[14] However there is no any recommendations on the omega-3/6 ratio which is surprising if to take into account the recent scientific evidence noted above.[3]   The primary sources of omega-3 FAs are vegetable oils (ALA) and marine fish oils (DHA and EPA), although minor quantities of omega-3 FAs are also found in meat, egg yolk, nuts, seeds, green leafy vegetables and some fruits.[2][15] Flaxseed oil contains 53-62% omega-3 FAs, while canola oil, walnut oil, wheat germ oil and soybean contain 7-11%.[15][16] The richest fish sources of omega-3 FAs are salmon, mackerel, herring and halibut. Raw salmon and mackerel contain 1.2% and 2.5% of omega-3 FAs, respectively.[15] Fresh fish is thought to be higher in omega-3 FAs than processed varieties as processing (especially with heating) may denature omega-3 FAs and convert them to harmful substances.[2] The changes in agriculture and food processing techniques over the last fifty years have resulted in an imbalance in the ratio of omega-3 to omega-6 FA intake. This may have a negative impact on our health, but could still be redressed by increasing consumption of foods high in omega-3 FAs. Unfortunately farmed fish and animals are not that beneficial as wild ones due to a lower omega-3 FAs content. It is also worth noting that processing decreases the contents of PUFAs in food and should preferably be reduced.   [1] Tvrzicka, E., Kremmyda, L., Stankova, B., & Zak, A. (2011). Fatty acids as biocompounds: their role in human metabolism, health and disease – a review. part 1: classification, dietary sources and biological functions. Biomedical Papers, 155(2), 117-130. http://dx.doi.org/10.5507/bp.2011.038  [2] Das, U. (2006). Essential Fatty Acids - A Review. Current Pharmaceutical Biotechnology, 7(6), 467-482. http://dx.doi.org/10.2174/138920106779116856 [3] Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids,transfatty acids, and cholesterol. (2010). EFSA Journal, 8(3), 1461. http://dx.doi.org/10.2903/j.efsa.2010.1461 [4] Muhlhausler, B., Gibson, R., & Makrides, M. (2010). Effect of long-chain polyunsaturated fatty acid supplementation during pregnancy or lactation on infant and child body composition: a systematic review. American Journal Of Clinical Nutrition, 92(4), 857-863. http://dx.doi.org/10.3945/ajcn.2010.29495 [5] Wysoczański, T., Sokoła-Wysoczańska, E., Pękala, J., Lochyński, S., Czyż, K., & Bodkowski, R. et al. (2016). Omega-3 Fatty Acids and their Role in Central Nervous System - A Review. Current Medicinal Chemistry, 23(8), 816-831. http://dx.doi.org/10.2174/0929867323666160122114439 [6] Kremmyda, L., Tvrzicka, E., Stankova, B., & Zak, A. (2011). Fatty acids as biocompounds: their role in human metabolism, health and disease – a review. part 2: fatty acid physiological roles and applications in human health and disease. Biomedical Papers, 155(3), 195-218. http://dx.doi.org/10.5507/bp.2011.052 [7] Lin, P., Chiu, C., Huang, S., & Su, K. (2012). A Meta-Analytic Review of Polyunsaturated Fatty Acid Compositions in Dementia. The Journal Of Clinical Psychiatry, 73(09), 1245-1254. http://dx.doi.org/10.4088/jcp.11r07546 [8] Jing, K., Wu, T., & Lim, K. (2013). Omega-3 Polyunsaturated Fatty Acids and Cancer. Anti-Cancer Agents In Medicinal Chemistry, 13(8), 1162-1177. http://dx.doi.org/10.2174/18715206113139990319 [9] Fabian, C., Kimler, B., & Hursting, S. (2015). Omega-3 fatty acids for breast cancer prevention and survivorship. Breast Cancer Research, 17(1). http://dx.doi.org/10.1186/s13058-015-0571-6 [10] Simopoulos, A. (2008). The Importance of the Omega-6/Omega-3 Fatty Acid Ratio in Cardiovascular Disease and Other Chronic Diseases. Experimental Biology And Medicine, 233(6), 674-688. http://dx.doi.org/10.3181/0711-mr-311 [11] Simopoulos, A. (2016). An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity. Nutrients, 8(3), 128. http://dx.doi.org/10.3390/nu8030128 [12] Simopoulos, A. (2006). Evolutionary aspects of diet, the omega-6/omega-3 ratio and genetic variation: nutritional implications for chronic diseases. Biomedicine & Pharmacotherapy, 60(9), 502-507. http://dx.doi.org/10.1016/j.biopha.2006.07.080 [13] van Vliet, T., & Katan, M. (1990). Lower ratio of n-3 to n-6 fatty acids in cultured than in wild fish. Trends In Food Science & Technology, 1, 51. http://dx.doi.org/10.1016/0924-2244(90)90038-z [14] EFSA. (2010). EFSA sets European dietary reference values for nutrient intakes | European Food Safety Authority. Efsa.europa.eu. Retrieved 10 October 2017, from https://www.efsa.europa.eu/en/press/news/nda100326 [15] Kris-Etherton, P., Taylor, D., Yu-Poth, S., Huth, P., Moriarty, K., & Fishell, V. et al. (2000). Polyunsaturated fatty acids in the food chain in the United States. Am J Clin Nutr, 71(1), 179S-88S. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/10617969 [16] Hunter, J. (1990). n-3 fatty acids from vegetable oils. Am J Clin Nutr, 51(5), 809-14. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/1970702
  6.   In the 20th century, the vegetable oil industry had a great impact on human nutrition. Vegetable oil is a good and accessible source of unsaturated fatty acids, having up to 80% of oleic and linoleic acids combined,[1] which are vital for health. Through the development of a chemical process called ‘hydrogenation of fatty acids’ in the early 20th century, the food industry found a way to expand the application of vegetable oils. The process allowed to obtain cheap margarine products that could be used in several different foods to provide attractive qualities, such as distinctive flavour, crispness, plasticity, creaminess etc.[2] In nature, unsaturated fatty acids are normally found in cis-fat form (see the steric arrangement of hydrogen bonds in the picture below), and only up to 2-8% of them occur naturally in trans-fat form due to bacterial fermentation in dairy products and ruminants’ meat.[3] The unsaturated fatty acids that contain double bonds in trans-fat form are called trans-fatty acids.[2] Hydrogenation is the chemical process that allows to convert unsaturated fatty acids into saturated ones by means of heating, nickel catalyst and hydrogen. Unfortunately, it is almost impossible to achieve 100% hydrogenation, and in this case, trans-fatty acids are formed as a by-product along with saturated fatty acids.[2] Although the causative link between trans fats and coronary artery disease was first published in the 1950s, it took several decades of research to understand and subsequently tackle the problem.[4] It was later found that trans fats cause an increase in LDL cholesterol (the ‘bad’ cholesterol) and a decrease in HDL cholesterol (the ‘good’ cholesterol),[5] leading to an increased risk of heart attacks.[6] The consumption of margarine, one of the most common sources of industrially produced hydrogenated fats, was found to increase the body’s natural cholesterol levels in the blood.[7] Trans fats also increase other blood lipid profiles (such as lipoprotein(a) and triglycerides), which can lead to increased cardiovascular risks.[8]  In previous researches comparing the health effects of various fatty acids – namely saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA) and trans-fatty acids (TFA) – both SFA and TFA have been found to increase cardiovascular risks, resulting in the proposal of specific policies to reduce their consumption by 1 and 7 percent of daily energy intake, respectively.[9] However, more recent studies have shown that only TFA intake is associated with all-cause mortality, while, with methodological limitations, there was mixed evidence to prove that SFA have similar negative health effects.[10]  Many studies have proved the dangers of TFA produced from hydrogenation of vegetable oils, but what about TFA intake from consuming ruminants and dairy products?[11] Researchers have shown that these naturally occurring TFA can hardly pose health risks as their levels are generally low,[3][11][12] but further research is needed.[13] For this reason, we can safely assert that the biggest health risk lies with TFA found in processed, hydrogenated-fat food, rather than the naturally occurring TFA.  The risks associated with TFA are a significant problem acknowledged by many countries. The US Food and Drug Administration has recently announced that a ban on hydrogenated fat use for processed food production will enter into force in June 2018.[14] While possible actions are still under discussion in the European Union, the European Food Safety Authority encourages consumers to opt instead for less processed food products containing less TFA. “TFA” is currently labelled on a voluntary basis only in the European Union, while it is mandatory in the USA.[15] It is anticipated that the European Food Safety Authority will soon provide the updated tolerable limits of TFA to label processed foods accordingly. Heart disease is one of the major causes of death in Europe and worldwide, and TFA are recognised as one of the factors leading to it. Other suggested negative health outcomes of excessive TFA intake include Alzheimer’s disease, diabetes, obesity and even cancer.[16][17] The general biochemical mechanism of these health effects is not yet properly understood; however, it is thought that the human body lacks lipase enzymes that are able to metabolise this artificial fatty acid, and that trans fats also impair the metabolism of essential polyunsaturated fatty acids.[18] Even though trans-fats intake declined in recent years, governments do not do their best to protect the public from TFA exposure. For this reason, food industry manufacturers are not motivated to replace harmful ingredients that provide appealing food qualities (like creaminess and crispness) at low prices with more expensive alternatives. Until TFA are banned, it is strongly recommended to avoid processed foods and consume high-fat dairy products in moderation.    [1] Orsavova, J., Misurcova, L., Ambrozova, J., Vicha, R., & Mlcek, J. (2015). Fatty Acids Composition of Vegetable Oils and Its Contribution to Dietary Energy Intake and Dependence of Cardiovascular Mortality on Dietary Intake of Fatty Acids. International Journal Of Molecular Sciences, 16(6), 12871-12890. http://dx.doi.org/10.3390/ijms160612871  [2] Jang, E., Jung, M., & Min, D. (2005). Hydrogenation for Low Trans and High Conjugated Fatty Acids. Comprehensive Reviews In Food Science And Food Safety, 4(1), 22-30. http://dx.doi.org/10.1111/j.1541-4337.2005.tb00069.x [3] Lindmark Månsson, H. (2008). Fatty acids in bovine milk fat. Food & Nutrition Research, 52(1), 1821. http://dx.doi.org/10.3402/fnr.v52i0.1821 [4] Lichtenstein, A. (2014). Dietary Trans Fatty Acids and Cardiovascular Disease Risk: Past and Present. Current Atherosclerosis Reports, 16(8). http://dx.doi.org/10.1007/s11883-014-0433-1 [5] Brouwer, I., Wanders, A., & Katan, M. (2010). Effect of Animal and Industrial Trans Fatty Acids on HDL and LDL Cholesterol Levels in Humans – A Quantitative Review. Plos ONE, 5(3), e9434. http://dx.doi.org/10.1371/journal.pone.0009434 [6] Nestel, P. (2014). Trans Fatty Acids: Are Its Cardiovascular Risks Fully Appreciated?. Clinical Therapeutics, 36(3), 315-321. http://dx.doi.org/10.1016/j.clinthera.2014.01.020 [7] Liska, D., Cook, C., Wang, D., Gaine, P., & Baer, D. (2016). Trans fatty acids and cholesterol levels: An evidence map of the available science. Food And Chemical Toxicology, 98, 269-281. http://dx.doi.org/10.1016/j.fct.2016.07.002 [8] Ooi, E., Watts, G., Ng, T., & Barrett, P. (2015). Effect of Dietary Fatty Acids on Human Lipoprotein Metabolism: A Comprehensive Update. Nutrients, 7(6), 4416-4425. http://dx.doi.org/10.3390/nu7064416 [9] Hammad, S., Pu, S., & Jones, P. (2015). Current Evidence Supporting the Link Between Dietary Fatty Acids and Cardiovascular Disease. Lipids, 51(5), 507-517. http://dx.doi.org/10.1007/s11745-015-4113-x [10] de Souza, R., Mente, A., Maroleanu, A., Cozma, A., Ha, V., & Kishibe, T. et al. (2015). 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, h3978. http://dx.doi.org/10.1136/bmj.h3978 [11] Da Silva, M., Julien, P., Pérusse, L., Vohl, M., & Rudkowska, I. (2015). Natural Rumen-Derived trans Fatty Acids Are Associated with Metabolic Markers of Cardiac Health. Lipids, 50(9), 873-882. http://dx.doi.org/10.1007/s11745-015-4055-3 [12] Mozaffarian, D., Aro, A., & Willett, W. (2009). Health effects of trans-fatty acids: experimental and observational evidence. European Journal Of Clinical Nutrition, 63, S5-S21. http://dx.doi.org/10.1038/sj.ejcn.1602973 [13] Gebauer, S., Chardigny, J., Jakobsen, M., Lamarche, B., Lock, A., Proctor, S., & Baer, D. (2011). Effects of Ruminant trans Fatty Acids on Cardiovascular Disease and Cancer: A Comprehensive Review of Epidemiological, Clinical, and Mechanistic Studies. Advances In Nutrition: An International Review Journal, 2(4), 332-354. http://dx.doi.org/10.3945/an.111.000521 [14] FDA Cuts Trans Fat in Processed Foods. (2017). Fda.gov. Retrieved 23 July 2017, from https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm372915.htm [15] Trans fats (TFA) - Food Safety - European Commission. (2017). Food Safety. Retrieved 23 July 2017, from https://ec.europa.eu/food/safety/labelling_nutrition/labelling_legislation/trans-fats_en [16] Morris, M., Evans, D., Bienias, J., Tangney, C., Bennett, D., & Aggarwal, N. et al. (2003). Dietary Fats and the Risk of Incident Alzheimer Disease. Archives Of Neurology, 60(2), 194. http://dx.doi.org/10.1001/archneur.60.2.194 [17] Dhaka, V., Gulia, N., Ahlawat, K., & Khatkar, B. (2011). Trans fats—sources, health risks and alternative approach - A review. Journal Of Food Science And Technology, 48(5), 534-541. http://dx.doi.org/10.1007/s13197-010-0225-8 [18] Calder, P. (2015). Functional Roles of Fatty Acids and Their Effects on Human Health. Journal Of Parenteral And Enteral Nutrition, 39(1_suppl), 18S-32S. http://dx.doi.org/10.1177/0148607115595980
  7. Good fats vs bad fats

    Fats in our diet are a valuable source of energy (1 g is equivalent to 9 kcal), and they are essential in a healthy balanced diet. While some fats are beneficial, others, if consumed in excessive amounts, have detrimental effects on health. Fats are classified by their chemical structure, falling into several groups including saturated fats, mono-/polyunsaturated fats and trans fats. The fatty acid chains in saturated fats consist of only single bonds, indicating that there are no bonds available for further binding.[1] Foods that contain high levels of saturated fat include whole milk, butter, cheese, lard, palm oil, coconut oil, “fatty” meat and meat products, fried food, and some cakes, biscuits and pastries. All of the above should be eaten in small amounts as saturated fats have a proven association with increased cholesterol levels, which can progress to clogged arteries and increased risk of heart disease and stroke.[2] There have been numerous studies confirming the benefits of reducing saturated fats in our diets. For example, replacing saturated fats with unsaturated fats reduces cholesterol levels, thus decreasing the risks of heart disease and stroke.[2], [3] Both epidemiological and randomised clinical trials have consistently evidenced that replacing saturated fat with unsaturated fat, is beneficial in coronary heart disease.[4]    The fatty acid chains in unsaturated fats contain either one double bond (monounsaturated fat) or more than one double bond (polyunsaturated fat).[1] Foods rich in these types of fats include vegetable oils such as olive, rapeseed or sunflower oils, avocados, nuts and seeds. It has been demonstrated these fats help decrease the risk of heart disease.[5], [6] Omega-3 fatty acids are a group of polyunsaturated fats found mainly in oily fish such as mackerel, salmon or sardines. Omega-3 fatty acids have many health benefits, and are associated with good heart health as they reduce the risk of blood clots and assist in the regulation of heart rhythm.[7], [8] They are also important during pregnancy and breastfeeding, supporting infant development.[7], [8] Trans-fats are the most harmful to our bodies. This group of fats are manufactured by partially hydrogenating vegetable oils, resulting in a firmer, better tasting fat with an increased shelf life. They are found in most processed and ‘fast’ foods, that are already very high in saturated fats.[9] Manufactured trans-fats have been shown to have an even more adverse impact on cholesterol levels than saturated fats, which in turn is associated with diabetes and cardiovascular disease.[10], [11]   Whilst knowing which fats are more healthy than others can certainly help in reducing the risks associated with fat consumption, some fats can actually become more harmful during cooking, depending on the processes involved. Vegetable oil, for example can accumulate by-products known to pose a significant risk of cardiovascular disease when heated repeatedly.[12] Cooking can also change the ratio of healthier unsaturated fatty acids to unhealthy saturated fats and trans fats.[13] Reducing fat in the diet is advisable to prevent obesity and its related complications, such as type 2 diabetes. Even beneficial mono-/polyunsaturated fats should be consumed in moderation, as they still have a high calorific value. In fact studies on mice have shown that a high fat diet induces greater weight gain than a low fat diet, even if their calorific intake is the same.[14]   A reduction of saturated and trans-fats in the diet can be achieved by avoiding processed and ‘fast’ foods as much as possible and choosing food prepared at home from fresh, low fat ingredients. Lean sources of protein, low fat dairy foods, legumes, fresh fruit and vegetables are a healthier choice than foods high in fat, although beneficial oils such as olive, canola and sunflower oil can be used for cooking and salad dressings. [1] Nelson, D & Cox, M. (2008). Lehninger principles of biochemistry. (5 ed.) [2] Jakopsen, M.U. (2009). Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies. The American Journal of Clinical Nutrition. 85(5). 1425-1432 [3] Mozaffarian, D. et al. (2010). Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials. PLos Med. 7(3). e1000252 [4] Siri-tarino, P.W. et al. (2010). Saturated fatty acids and risk of coronary heart disease: modulation by replacement nutrients. Current atherosclerosis reports. 12(6). 384-390 [5] Covas, M.I. (2007). Olive oil and the cardiovascular system. Nutritional Pharmacology. 55(3). 175-186 [6] Gillingham, L.G. et al. (2011). Dietary monounsaturated fatty acids are protective against metabolic syndrome and cardiovascular disease risk factors. Lipids. 46(3). 209-228 [7] Swanson, D. et al. (2012). Omega-3 fatty acids EPA and DHA: health benefits throughout life. Advances in Nutrition. 3(1). 1-7 [8] Calder, P.C. et al. (2009). Omega-3 polyunsaturated fatty acids and human health outcomes. BioFactors. 35(3). 266-272 [9] Stender, S. et al. (2006). A trans world journey. Atherosclerosis Supplements, 7(2), 47-52. [10] Micha, R. et al. (2009). Trans fatty acids: effects on metabolic syndrome, heart disease and diabetes. Nature Reviews: Endocrinology. 5(6). 335-344 [11] Bhardwaj, S. et al. (2011). Overview of trans fatty acids: Biochemistry and health effects. Diabetes & Metabolic Syndrome: Clinical Research & Reviews. 5(3). 161-164 [12] Ng, CY. et al. (2014) Heated vegetable oils and cardiovascular disease risk factors. Vascul Pharmacol. 61(1). 1-9 [13] Bhardwaj, S. et al. (2016) Effect of heating/reheating of fats/oils, as used by Asian Indians, on trans fatty acid formation. Food Chem. 212. 663-70 [14] Petro, A.E. et al. (2004). Fat, carbohydrate, and calories in the development of diabetes and obesity in the C57BL/6J mouse. Metabolism: clinical and experimental. 53(4). 454-457