5 nutrition myths that need busting
1. Don’t fry with olive oil
Extra virgin olive oil, a classic ingredient of Mediterranean diets, can be used for frying because it has a high smoking point (210°C), well above the ideal temperature for frying food at 180°C.
Olive oil will not change its structure at these temperatures so it will keep its nutritional value. Extra virgin olive oil is rich in antioxidants (phenolics and vitamin E) and the monounsaturated fat oleic acid, which helps keep it stable when heated.
Studies have shown that adding olive oil to vegetables helps make compounds such as phenolic antioxidants and carotenoids more available for absorption, and may just make people eat more vegetables because they taste better.
The best tip is to buy good-quality extra virgin olive oil in dark glass to ensure freshness and highest levels of antioxidants.
2. Vitamin C prevents colds
Regular vitamin C supplementation doesn’t prevent the common cold; that was the finding of a 2013 Cochrane review of the available evidence.
Vitamin C may reduce the severity and duration of colds but trials have found no consistent effect. Interestingly though, in those who are heavy exercisers, for example endurance athletes and soldiers, vitamin C supplements reduce the risk of developing colds by 52%.
It appears no research has been done to prove that a diet rich in fruits and vegetables reduces colds.
The top 5 fruits for vitamin C content per 100g are guava, kiwifruit, lychees, oranges and persimmons, and the top 5 vegetables, capsicum, kale, broccoli, brussels sprouts and cauliflower.
Vitamin C dissolves in water, so avoid soaking fruits and vegetables. It's fine to steam and microwave them or, if cooking in water, use the water for stocks, stews and soups.
3. Potatoes are fattening
Not many studies have been found that assess the effect of eating potatoes on body weight. When potatoes are eaten as part of a healthy diet, they do not appear to cause weight gain. High-fat potato chips and crisps are another story.
Potatoes do contain carbohydrate, but in terms of energy potatoes have only 280kJ per 100g (equivalent to about 2 small new potatoes), which is the same energy content as a large banana or a dinner bread roll.
Potatoes generally have a moderate to high glycaemic index (53-93). The GI can be lowered if the skins are kept on, if they are cooked, cooled then eaten, if vinegar dressing is added or if lower GI varieties are consumed.
As a plant food, potatoes are rich in a variety of nutrients including vitamin C, B group vitamins, potassium, antioxidants (if they have coloured skins) and fibre (if skins are left on).
4. Sea salt beats table salt
Both sea salt and table salt are high in sodium, so one is not healthier than the other.
Depending on the source, salts may contain trace quantities of other minerals giving the salt a distinct colour and/or flavour. Table salt may have iodine added which may be important for pregnant women or those with iodine deficiency.
The upper level of intake for sodium for adults is 2300mg a day, with a recommended dietary intake of just 920mg a day. It’s estimated that Australians aged two years and older eat an average of 2150mg of sodium per day.
About 80% comes from processed foods and 20% from salt used at the table or in home cooking. Look for low-sodium food products (less than 120mg sodium per 100g) and only add salt to favourite foods, for example, eggs or tomatoes, rather than routinely adding to all foods.
5. Raw nuts beat roast nuts
There are few significant nutritional differences between dry/oil-roasted nuts and raw nuts (unless they are salted).
Most nutrients become slightly more concentrated during the roasting process as the nuts lose more moisture.
B group vitamins are not heat stable so their levels are reduced after roasting. The natural high fat content of nuts prevents any significant absorption of other fats into nuts even if they are submerged in oil. Only about 2—5% is absorbed, depending on the nut variety.
Eating a 30g serve of nuts (either raw or roasted) 5 to 7 times a week can reduce heart disease risk by 30—50%. Roasted nuts can still lower blood cholesterol and even salted nuts may reduce blood pressure.
Lisa Yates is an Advanced Accredited Practising Dietitian with a Masters in Nutrition and Dietetics, graduating in 1995. Lisa runs her own private practice in Frenchs Forest Sydney and has interests in cardiovascular disease, diabetes, weight management, gastroenterology and sports nutrition.
Disclosure: Lisa Yates works for the Australian Tree Nut Industry.
Last Reviewed: 23/09/2015
Reproduced with kind permission from Medical Observer.
1. International Olive Oil Council http://www.internationaloliveoil.org/estaticos/view/85-frying-with-olive-oil 2. Casal S et al Olive oil stability under deep-frying conditions. Food Chem Toxicol. 2010 Oct;48(10):2972-9. 3. RamÃrez-Anaya Jdel P et al Phenols and the antioxidant capacity of Mediterranean vegetables prepared with extra virgin olive oil using different domestic cooking techniques. Food Chem. 2015 Dec 1;188:430-8. 4. Arranz S et al Influence of olive oil on carotenoid absorption from tomato juice and effects on postprandial lipemia. Food Chem. 2015 Feb 1;168:203-10. 5. Fielding JM, Rowley KG, Cooper P, Oâ€™ Dea K. EIncreases in plasma lycopene concentration after consumption of tomatoes cooked with olive oil. Asia Pac J Clin Nutr. 2005;14(2):131-6. 6. HemilÃ¤ H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013 Jan 31;1:CD000980. doi: 10.1002/14651858.CD000980.pub4. http://www.foodstandards.gov.au/science/monitoringnutrients/nutrientables/nuttab/Pages/default.aspx 7. Glycemic Index Foundation http://www.glycemicindex.com/foodSearch.php Camire ME et al Potatoes and human health. Crit Rev Food Sci Nutr. 2009 Nov;49(10):823-40. 8. Randolph JM et al Potatoes, glycemic index, and weight loss in free-living individuals: practical implications. J Am Coll Nutr. 2014;33(5):375-84. 9. Vinson JA et al High-antioxidant potatoes: acute in vivo antioxidant source and hypotensive agent in humans after supplementation to hypertensive subjects. J Agric Food Chem. 2012 Jul 11;60(27):6749-54. 10. Australian Government NHMRC Nutrient References Values â€“ Sodium paper https://www.nrv.gov.au/nutrients/sodium 11. Food Standards Australia New Zealand â€“ How miuch salt are we eating? http://www.foodstandards.gov.au/consumer/nutrition/salthowmuch/pages/howmuchsaltareweeating/howmuchsaltandsodium4551.aspx 12. Albert CM et al. Nut consumption and decreased risk of sudden cardiac death in the Physicianâ€™s Health Study. Arch Intern Med 2002;162(12):1382-7. 13. Ellsworth JL et al. Frequent nut intake and risk of death from coronary heart disease and all causes in postmenopausal women: the Iowa Womenâ€™s Health Study. Nutrition Metabolism and Cardiovascular Disease 2001;11(6):372-7. 14. 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. 15. Fraser GE et al. A possible protective effect of nut consumption on risk of coronary heart disease. Arch Intern Med 1991; 152: 1416-24. 16. Blomhoff R. et al. Health benefits of nuts: potential role of antioxidants. Brit J Nutr 2007;96(SupplS2):S52-S60. 17. Spiller GA et al. Effects of plant-based diets high in raw or roasted almonds, or roasted almond butter on serum lipoproteins in humans. J Am Coll Nutr 2003;22(3):195-200. 18. Sauder KA et al Pistachio nut consumption modifies systemic hemodynamics, increases heart rate variability, and reduces
Nuts in a healthy diet
Nuts provide protein and are a source of dietary fibre as well as contributing many vitamins and minerals. Many studies show nuts are beneficial to health, especially heart health.
Mediterranean diet plus olive oil lowers risk of breast cancer
Risk of breast cancer was cut by 68% in those who ate a Mediterranean diet supplemented with extra-virgin olive compared with those who stuck to a low-fat diet, large study finds.