Apple a day may keep doctor away thanks to 100 million bacteria in each fruit, scientists say

Every single apple contains more than 100 million bacteria and it helps us stay healthy, scientists have revealed.

But a study of the fruit's bacterial composition found that, if you leave the core and seeds, the number of microbes you will consume from each fruit drops to 10 million.

Professor Gabriele Berg, of Graz University of Technology, Austria, said: "Putting together the averages for each apple component, we estimate a typical 240g apple contains roughly 100 million bacteria.

"The bacteria, fungi and viruses in our food transiently colonise our gut. Cooking kills most of these, so raw fruit and veg are particularly important sources of gut microbes."

Some of these microbes are important in maintaining a healthy gut environment, or microbiome, Professor Berg, one of the authors of the research, added.

The microbiome contains around 100 trillion bacteria and other microbes and the more varied its composition, the better it is for us.

The study found the majority of the bacteria are in the apple's seeds, with the flesh accounting for most of the remainder.

The research, published in Frontiers in Microbiology, compared the bacteria in conventional shop-bought apples with those in visually matched fresh organic ones, assessing the stem, peel, flesh, seeds and calyx - the straggly bit at the bottom where the flower used to be.

Overall, organic and conventional apples were occupied by similar numbers of bacteria but they discovered organic apples have a more varied and balanced bacterial community.

"Freshly harvested, organically managed apples harbour a significantly more diverse, more even and distinct bacterial community, compared to conventional ones," Professor Berg said.

"This variety and balance would be expected to limit overgrowth of any one species, and previous studies have reported a negative correlation between human pathogen abundance and microbiome diversity of fresh produce."

Specific groups of bacteria known for health-affecting potential also weighed in favour of organic apples.

Escherichia-Shigella, a group of bacteria that includes known pathogens - disease-causing micro-organisms - was found in most of the conventional apple samples, but not in organic apples.

However for Lactobacilli, which is often used in probiotics, the reverse was true.

The researchers also offer some vindication to those who claim they can taste the difference in organic produce.

Methylobacterium, known to enhance the biosynthesis of strawberry flavour compounds, was significantly more abundant in organic apples, the study found.