An apple a day keeps the doctor away, or so the old proverb goes, but can a single apple help with our health? New research out this week shows that in addition to the vitamins and minerals apples provide, the bacteria that they host may also be a big part of why they are so good for us.

Apples are among the most consumed fruits around the world, with 7500 different varieties and a global apple market growing to more than 83 million tonnes last year.

Filled with vitamins including vitamins B and C as well as minerals such as calcium, potassium and phosphorus, apples are known to be good for our health when incorporated into a balanced diet. In addition to great nutritional benefits, apples also contain pectin - a great source of fibre to keep our bowels moving as well as procyanidins which are powerful antioxidants.

Different apple varieties have different levels of bacteria. Photo / 123RF
Different apple varieties have different levels of bacteria. Photo / 123RF

When it comes to buying apples, most of us select them by making some simple choices: red or green, organic or non-organic.

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What we don't usually select our apple for is bacterial content, but new research published this week in the journal Frontiers in Microbiology made some interesting findings when it comes to microbes and our favourite fruit.

Firstly, when we think of bacteria, we usually assume that they are on the outside of the fruit and that they are bad. Multiple hands touching our apples from the pickers to the packers to the supermarket stackers must lead to large amounts of tummy-ache inducing bacteria sitting on the apple skin. Surely this is why our parents always told us to wash our apples before eating. Interestingly, the study found that the majority of the bacteria in an apple are actually found in the seeds, with the apple flesh accounting for most of the remainder - the skin it seems isn't as microbe hosting as you might have thought.

Organic apples were found to have much higher diversity in their bacterial community. Photo / 123RF
Organic apples were found to have much higher diversity in their bacterial community. Photo / 123RF

Also, not all bacteria are bad, and eating raw fruit could be an important source of good microbes for your gut. Although still in its infancy, research around gut microbiome is showing that the richer and more diverse the community of microbes you have in your gut, the lower your risk of disease and allergies may be.

The apple study compared the bacteria found in both supermarket bought standard apples and organic apples that were of a similar variety and had roughly the same appearance.

The researchers tested all of the parts of the apple including the skin, stem, flesh, peel, seeds and calyx which is the fluffy bit at the bottom where the flower used to be. They found that if you ate a whole 240g apple, seeds and all you'd be ingesting around 100 million bacteria. Most of us don't actually eat the core, so our intake would fall to a mere 10 million bacteria.

Researchers tested all of the parts of the apple including the skin, stem, flesh, peel, seeds and calyx. Photo / 123RF
Researchers tested all of the parts of the apple including the skin, stem, flesh, peel, seeds and calyx. Photo / 123RF

The study also found that the amount of bacteria in both organic and non-organic apples was the same, however the variety was vastly different. The organic apples were found to have much higher diversity in their bacterial community and a significantly higher level of a specific microbe called methylobacterium. This microbe is known to enhance strawberry-flavoured compounds and could be part of the reason why die-hard organic apple eaters claim they taste better than the standard supermarket variety.

The extent that apple microbiome diversity translates to gut microbial diversity is still unknown and more research is needed to see if it results in improved health outcomes. However, the old wives' tale of an apple a day keeps the doctor away might be true after all, thanks to the apple being such a great home to millions of delicious bacteria.