From the archives: Keto diets, in which followers are urged to ditch carbs in favour of fats or proteins, look to be more than a passing fad. As recently as January, the results of studies into their benefit – or otherwise – were being reported. In 2021, Jennifer Bowden answered a question about bananas and the keto diet which remains useful information, especially if you’re snacking on the run.
Question:
I love bananas and eat a lot of them. So, I was interested in the recent article comparing the keto diet with a plant-based diet, as I know keto dieters typically don’t eat much fruit and many avoid bananas. Are bananas good for us?
Answer:
Bananas are packed with nutrients and also come in biodegradable packaging. Australian cricketer Peter Siddle found bananas extremely convenient when he became a vegan. He famously ate between 15 and 20 a day to fuel his fast bowling in the back-to-back Ashes test cricket series. So, what’s the keto weight-loss dieters’ beef?
Bananas are a rich source of carbohydrate, which mainly occurs as starch in unripe bananas. However, as it ripens, the banana’s natural enzyme action converts its high starch content into sugar. Keto dieters aim to avoid high-carbohydrate foods because they are trying to force their body into a state of ketosis. This is a metabolic state in which a high concentration of ketones is circulating in the blood. This happens when the body has limited access to glucose – a carbohydrate and the preferred energy source of many of our body cells – and instead fuels itself with fats. Maintaining a ketosis state is the reason keto dieters typically avoid bananas.
The high content of easily digestible carbohydrates in bananas means they have a high glycaemic index; this rating denotes how quickly each food affects your blood-sugar levels. However, a large observational study published in 2013 reported that bananas were not associated with a greater risk of type 2 diabetes. Nor were blueberries, grapes or apples, fruits that also have a high glycaemic index. But researchers did find an association between fruit juice consumption and an increased type 2 diabetes risk.
One medium banana contains about 2g of dietary fibre, a useful addition to our daily requirements of 25g and 30g, respectively, for men and women. Diets high in fibre may decrease our risk of heart disease, certain cancers and also diabetes.
Think banana, think potassium; it’s an association many of us make, and for good reason. They are a rich potassium source, and this is an essential mineral needed by all our body cells. In recent years, potassium has garnered more attention, thanks to its possible role in reducing the risk of high blood pressure and strokes.
Some people have suggested that eating too many bananas may cause dangerously high potassium intake, but that’s unlikely to happen. In reality, issues with potassium levels are typically the result of kidney failure or consuming too much potassium in the form of supplements (something we should take only under medical supervision). Excessive potassium intake is associated with gastrointestinal discomfort and arrhythmia.
Bananas are also a good source of other essential nutrients such as vitamins C and B6, folate and fibre, which have a critical role in maintaining our wellbeing and reducing the risk of disease. For example, vitamin C is an essential part of the antioxidant defence systems that protect our bodies from damage by free radicals, which can ultimately lead to disease. They also contain a host of other bioactive compounds, such as phenolics, carotenoids, biogenic amines and phytosterols, which have health benefits, including antioxidant activities.
But before you load up on bananas, there is one important thing worth considering. Variety is the spice of life. And that’s no truer than in terms of our eating habits. By eating various coloured fruits and vegetables, we’re ensuring we get a wide range of the different vitamins and minerals we need. When we eat a lot of one food, we must consider all the other foods we’re not eating. So, yes, bananas are tasty and nutritious, but selecting a wide variety of fruit and vegetables is a better option than Siddle’s 15-plus bananas a day.
This story is from the New Zealand Listener’s archives and was first published in the March 20-26, 2021, edition.
