An apple, and a few bacteria, a day

If you eat your apples, core and all, you’re consuming 100 million bacteria each time, new research has found.

That’s because about 90% of them are in the seeds.

Eating them is likely to be a good rather than a bad thing, but how good comes down to how and where the apple is grown.

Austrian researchers have found that organic apples have a more balanced bacterial community, making them healthier – as well as tastier – than store-bought alternatives.

“Freshly harvested, organically managed apples harbour a significantly more diverse, more even and distinct bacterial community, compared to conventional ones,” says senior author Gabriele Berg, from Graz University of Technology.  

Berg and colleagues Birgit Wassermann and Henry Müller also found that some bacteria strains that are potentially harmful to our health are found in common apples, but not in organic. 

“Escherichia-Shigella – a group of bacteria that includes known pathogens – was found in most of the conventional apple samples, but none from organic apples,” says Berg. “For beneficial Lactobacilli – of probiotic fame – the reverse was true.”

The addition of apples to our diet is known to induce changes in the composition of microbiota and metabolic activity, which is beneficial for our health.

Then there’s the all-important matter of taste.

“Methylobacterium, known to enhance the biosynthesis of strawberry flavour compounds, was significantly more abundant in organic apples; here especially on peel and flesh samples, which in general had a more diverse microbiota than seeds, stem or calyx,” says Berg.

Wasserman says their findings, which are published in the journal Frontiers in Microbiology, “agree remarkably” with a recent study on apple fungal communities, which revealed “specificity of fungal varieties to different tissues and management practices”.

Together, she says, the studies show that across both bacteria and fungi, the apple microbiome is more diverse in organically grown fruits. Since another study has shown that the apple fungal community is also variety-specific, the bacterial analyses too should be repeated in other cultivars.

“The microbiome and antioxidant profiles of fresh produce may one day become standard nutritional information, displayed alongside macronutrients, vitamins and minerals to guide consumers,” she adds.

“Here, a key step will be to confirm to what extent diversity in the food microbiome translates to gut microbial diversity and improved health outcomes.”