There are three different types of fats in food, each having different health effects. These are classified into saturated fats and unsaturated fats (monounsaturated and polyunsaturated fats). Each type of fat is made up of fatty acid building blocks and where ever there is fat in food you will find all three present but in different proportions.
- Saturated fatsare found mostly in animal foods such as fatty meats, butter and full fat milk, but also in palm and coconut oil (often used in processed foods such as biscuits, chips, pastries and fast foods). Saturated fats are generally considered unhealthy as they can increase blood cholesterol particularly LDL cholesterol a risk factor for heart disease.,2
- Unsaturated fats,found in fish and plant foods (such as nuts, seeds, avocado, their oils and spreads made from these oils) are healthy fats, which can improve blood cholesterol levels and reduce heart disease risk.2 Polyunsaturated fats are found predominantly in sunflower, safflower and soybean oils, margarine spreads made from these oils, as well as seeds and nuts (see below). Monounsaturated fats are found predominantly in olives, olive oil, canola oil and margarine spreads from these oils, avocado, and many nuts, nut spreads and oils (see below).
- You may have heard of Trans fats – these are a type of unsaturated fat, but due to their unusual structure behave more like a saturated fat. These are found in small amounts naturally in meat and dairy products but are mainly found as hydrogenated vegetable oils in foods like chips, biscuits, pastries and snack foods. Margarine spreads in Australia are virtually trans fat free. Surprisingly nuts do contain trace amounts of trans fats naturally but less than 0.3g per 100g. Trans fats increase the level of LDL cholesterol and reduce HDL cholesterol, increasing heart disease risk.2 On average Australians eat less trans fat than the World Health Organisation recommends so we need to watch out for foods high in saturated fat instead.3
Essential fats and our health
Diets high in monounsaturated fat (such as a Mediterranean diet with plenty of olive oil, nuts and fish) have a number of health benefits, particularly for heart health and metabolic syndrome.4, 5 Polyunsaturated fats can be further divided into omega-6 and omega-3 fatty acids, and omega-3 fats can be further divided into short chain omega-3 fats (from plants) and long chain omega-3 fats (from fish, seafood, Australian pasture fed meat, eggs and other fortified foods). Some polyunsaturated fats are essential fatty acids that must be eaten as they are required for normal growth and development but cannot be made by our body. These include the omega-6 fat linoleic acid (LA), the short chain omega-3 fat alpha-linolenic acid (ALA), and the long chain omega-3 fats eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA). Essential fats play important roles in maintaining cell membranes, regulating many body processes including inflammation and blood clotting, and improving the absorption of fatsoluble vitamins A, D, E and K from food. Essential fatty acids are also needed for brain and eye development, so vital during pregnancy, breastfeeding and in newborn babies.6
Fat in nuts
Most nuts (apart from chestnuts) are high in fat. Yet they contain more polyunsaturated and monounsaturated fats, have a lower proportion of saturated fats and and naturally contain trace amounts of trans fats. The fat profile of nuts varies from one type to another (see table 1) so including a variety of nuts in your diet ensures you have a good balance of healthy fats.
Almonds, cashews, hazelnuts, macadamias, peanuts, pecans and pistachios are higher in monounsaturated fats while Brazil nuts, pine nuts and walnuts have more polyunsaturated fats. Walnuts are one of the few plant foods that contain the essential omega-3 fat, ALA, with a handful (30g) of walnuts providing the recommended amounts of ALA. Smaller amounts are found in pecans, hazelnuts and macadamias. This is particularly important for vegetarians or anyone who doesn’t eat fish or seafood as a small proportion of ALA can be converted into EPA in the body.8
Fats and weight management
Despite the type of fat all fats are high in kilojoules or energy. Eating too many kilojoules overall can lead to weight gain. This is why many people think nuts are off the menu if they are watching their waist. Interestingly most studies looking at regular nut consumption have not found this to be the case. Epidemiological studies (which have followed large groups of people over time) have found that regular nut eaters are less likely to be overweight than those who don’t eat nuts.9–14 The Australian Dietary Guidelines state that consumption of nuts 65–110g is not associated with weight gain in the short term.15 So a daily 30g serve of nuts can be included in weight management diets.
Why is this the case?
- Nuts are satisfying as they contain protein and fibre so help control appetite.16, 17 Plus nuts increase the release of satiety hormones in the intestine making you feel full.18–20
- Not all the fat in nuts is absorbed by the body – some studies have found that nut eaters excrete more fat – between 5 and 15% of the energy.21 Studies have also shown the more you chew or process nuts,the less fat is excreted.20, 22
- The body appears to burn more energy when digesting nuts boosting metabolism.21
- And of course people enjoy eating nuts so they stick to weight loss diets for longer.21
So get cracking and enjoy a handful of nuts everyday to get your healthy smart fats.
Fat content of individual nut varieties7
|Total Fat(g)||Saturated Fat(g)||Monounsaturated Fat (g)||Polyunsaturated Fat (g)||Omega-3 fat as ALA (mg)|
|n/a = data not available|
- Australian Government NHMRC Nutrient Reference Values (NRVs) Fats and Total Fatty Acids paper 2006 Commonwealth of Australia (www.nrv.org.au)
- Denke MA. Dietary fats, fatty acids, and their effects on lipoproteins. Curr Atheroscler Rep. 2006;8(6):466-471.
- Food Standards Australia New Zealand Trans fatty acids consumer fact sheet May 2010 www.foodstandards.gov.au/consumerinformation/transfattyacids.cfm
- Mente A, et al. A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease. Arch Intern Med. 2009;169(7):659-669.
- Martínez-González MA, et al. Benefits of the Mediterranean Diet: Insights From the PREDIMED Study. Prog Cardiovasc Dis. 2015;58(1):50-60.
- Uauy R, et al. Essential fatty acids in visual and brain development. Lipids. 2001;36(9):885-895.
- Nuts for Life 2016 Nutrient Composition of Tree Nuts. 2016, Nuts for Life www.nutsforlife.com.au
- Welch AA, et al. Dietary intake and status of n-3 polyunsaturated fatty acids in a population of fish-eating and non-fish-eating meat-eaters, vegetarians, and vegans and the product-precursor ratio [corrected] of α-linolenic acid to long-chain n-3 polyunsaturated fatty acids: results from the EPIC-Norfolk cohort. Am J Clin Nutr. 2010 Nov;92(5):1040-51.
- Bes-Rastrollo M, et al. Prospective study of nut consumption, long-term weight change, and obesity risk in women. Am J Clin Nutr 2009;89 1913-1919.
- Albert CM, et al. Nut consumption and decreased risk of sudden cardiac death in the Physicians Health Study. Arch Intern Med 2002;162(12):1382-7.
- Jiang R, et al. Nut and peanut butter consumption and risk of type 2 diabetes in women. Journal of the American Medical Association 2002;288(20):2554-60.
- Ellsworth JL, et al. Frequent nut intake and risk of death from coronary heart disease and all causes in postmenopausal women: the Iowa Women’s Health Study. Nutrition Metabolism and Cardiovascular Disease 2001;11(6):372-7.
- Hu FB, et al. Frequent nut consumption and risk of coronary heart disease in women: prospective cohort study. British Medical Journal 1998;317(7169):1341-5.
- Noakes M. The role of protein in weight management. Asia Pac J Clin Nutr 2008;17(S1):169-71.
- National Health and Medical Research Council (2013) Australian Dietary Guidelines. Canberra: National Health and Medical Research Council. www.eatforhealth.gov.au
- Fraser GE, et al. A possible protective effect of nut consumption on risk of coronary heart disease. Arch Intern Med 1991;152:1416-24.
- Pereira MA, et al. Dietary fiber and body-weight regulation. Observations and mechanisms. Pediatr Clin North Am. 2001;48(4):969-80.
- Pasman WJ, et al. The effect of Korean pine nut oil on in vitro CCK release, on appetite sensations and on gut hormones in post-menopausal overweight women. Lipids Health Dis. 2008:20;7:10
- Hughes GM, et al. The effect of Korean pine nut oil (PinnoThin) on food intake, feeding behaviour and appetite: a double-blind placebo-controlled trial. Lipids Health Dis. 2008;7:6.
- Cassady BA, et al. Mastication of almonds: effects of lipid bioaccessibility, appetite, and hormone response. Am J Clin Nutr. 2009;89(3):794-800
- Mattes R. The energetics of nut consumption. Asia Pac J Clin Nutr. 2008;17(Suppl 1):337-339.
- Traoret CJ, et al. Peanut digestion and energy balance. Int J Obes. 2007;32(2):322-328.