Georgina Elizabeth Dawson, student dietian, Glasgow Caledonian Uiniversity.

As one of the world’s widest consumed foods, the world is truly bananas about this highly nutritious, tasty fruit. With evidence showing the first cultivation of bananas in Papua New Guinea almost seven thousand years ago 1, they are now grown in over 130 countries worldwide, with a growth ring spanning every continent sitting on the equator. Bananas do not have a specific growing season and are available throughout the year. They take between nine and twelve months to harvest. There many different types of banana, which all vary in size, shape and colour. By far the most commonly consumed banana however, is the Cavendish variety.

With the suggested 80g portion size for fruit, a medium banana (120g) can be counted as one of your recommended five fruit and vegetables a day. A 120g banana contains just under 100kcal, providing low calorie content for a quick, no fuss snack. Bananas are also known to contain a wide range of Vitamins and minerals. Of particular note is the potassium content of these fruits, providing nearly 400mg per medium banana.2 This is the equivalent of 11% of the 3500mg recommended daily intake (RNI) for teenagers and adults, and 20% of the 2000mg RNI for children.3 Potassium has a vital part in nerve, muscle and enzyme function in the body, and studies have shown that increased potassium intake could reduce the risk of heart disease,4 and has been found to lower the incidence of stroke.5 A survey of the nutritional intake of the UK population however, has shown a high number of people are not currently meeting the advised daily intake.6 The same survey also highlighted magnesium, a mineral involved in healthy metabolism and hormone production, as being too low in many people’s diet. A medium banana can provide around 10% of an adult’s RNI (300mg) and 16% for that of a child (200mg).2,3

Copper is used in the body to form a large number of enzymes. A medium banana contains enough copper to provide 10% of an adult’s RNI (1.2mg),  8% for pregnant women (1.5mg) and 17% for children (0.7mg).2,3 Folate is a B vitamin used by the body for correct DNA and RNA syntheses, the building blocks for the body. A medium banana is considered a moderate source of folate, and contains 11% of a child’s RNI (150µg), and 8% of an adult RNI (200µ g). Although folate supplements are advised in the very early stages of pregnancy, many women do not begin taking them until later in this advised time period. It is important to try and incorporate folate containing foods in to their daily intake. Cooking foods can reduce the folate levels they provide. As bananas are mostly eaten raw, their folate levels are not affected.13

Another B vitamin found in high quantities in bananas is Vitamin B6.2 This has many functions in the body including metabolism and haemoglobin formation. Vitamin B6 is also a potent antioxidant, providing protection for the body from free radicals associated with early aging and cancer.7 A number of studies have found a link between increased B vitamin intake and reduced cognitive decline, suggesting a link between B Vitamins and brain heath.8 Bananas can set you well on your way to achieving your daily requirements, with one medium fruit providing 22% of the 1.2mg RNI for adults, and 36% of the 1mg/day advised for children.2,3  Another powerful antioxidant found in bananas is Vitamin C.2 Both vitamin B6 and vitamin C are water soluble vitamins. This means the body does not store them, so our bodies require a consistent dietary intake. One medium banana can provide 27% of an adult’s RNI (40mg), 36% of a child’s RNI (30mg), 21% of the RNI for the last trimester of pregnancy (50mg) or 15% for woman who are breastfeeding (70mg).2,3

Bananas have a glycaemic index (GI) of around 51, placing them in the low GI category.9 This means they have a lower effect on blood sugar levels, due to their fibre or fat content causing slower release. Lower GI and higher fibre foods have been linked to a reduced incidence of Type 2 Diabetes, a condition which has increased dramatically in recent years.10,11 Intake of higher fibre foods is also linked to lower levels of heart disease. 12 However, it is thought that many people in the UK are not currently reaching the advised daily intake (30g for adults and 20g for children).6 A medium banana contains around 3g of fibre,2 so add to your morning cereal or slice onto some wholegrain toast to help you on your way to achieving the recommended daily intake.

So eat them fresh, slice them onto your cereal, squish them into a sandwich, blend in a milkshake or bake them in a cake. Whatever your preferred way to eat a banana may be, this nutrient packed food is sure to boost your intake of vitamins, minerals and fibre.

 

References

  1. Denham, T.P., et al. (2003) Origins of agriculture at Kuk swamp in the highlands of New Guinea. Science. 301(5630), pp. 189-193.
  2. Department of Health (2013) Nutrient Analysis of fruit and vegetables. Available from: http://www.dh.gov.uk/publications. [Accessed 11th February 2017].
  3. Department of Health (1991) Dietary reference values for Food and Nutrients for the United Kingdom. London: HMSO.
  4. D’Elia, L., et al. (2011) Potassium Intake, Stroke and Cardiovascular Disease: A Meta-Analysis of Prospective Studies. Journal of the American College of Cardiology. 57(10), pp. 1210-1219.
  5. Alburto, N.J., et al. (2013) Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. 346.
  6. Whitton, C., et al. (2012) National Diet and Nutrition Survey: UK food consumption and nutrient intakes from the first year of the rolling programme and comparisons with previous surveys. British Journal of Nutrition. 106(12), pp. 1899-1914.
  7. Stocker, P., et al. ESR study of a biological assay on whole blood: antioxidant efficiency of various vitamins. Biochimica et Biophysica Acta (BBA) – General Subjects. 1621(1), pp. 1-8.
  8. McGarel, C., et al. (2014) Emerging roles for folate and related B-vitamins in brain health across the lifecycle. Proceedings of the Nutrition Society. 74, pp. 46-55.
  9. Atkinson, F.S., et al. (2008) International Tables of Glycemic Index and Glycemic Load Values: 2008. Diabetes Care. 31(12), pp. 2281-2283.
  10. Hodge, A.M., et al. (2004) Glycemic Index and Dietary Fiber and the Risk of Type 2 Diabetes. Diabetes Care. 27(11), pp. 2701-2706.
  11. Weickert, M.O. and Pfeiffer, A.F. (2008) Metabolic Effects of Dietary Fiber Consumption and Prevention of Diabetes. The Journal of Nutrition. 138(3), pp. 439-442.
  12. Threapleton, D.E., et al. (2013) Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis. BMJ. 347.
  13. British Dietetic Association (2016) Folic acid food fact sheet. Available from: https://www.bda.uk.com/foodfacts/FolicAcid.pdf. [Accessed 11th February 2017].