A recent study points to apples' ability to mediate significant gut microbial metabolic activity. All it takes: two apples a day. In light of the increasing link between gut microbiota and human wellness, this new association is worth exploring and further vouches for this fruit's superfood and super healer status
The old saying that eating an apple a day will keep the doctor away may have some scientific basis after all, as scientific literature is packed with findings that vouch for this fruit's healthful benefits.
Showing that the saying above goes beyond folk medicine fantasy, a study found that eating one apple a day for four weeks translated to lower blood levels of oxidized low-density lipoprotein//beta2-glycoprotein I complex, which may contribute to atherosclerosis, by 40% among healthy, middle-aged individuals.[i]
Apple consumption has also been the subject of a few studies on reducing cancer risk, including liver cancer, breast cancer and esophageal cancer.[ii] A study published in February 2020 points to apples' ability to mediate significant gut microbial metabolic activity. All it takes: two apples a day.
Apples are a frequently consumed fruit and a reliable source of polyphenols and fiber, an important mediator for their health-protective effects.[iii]
Validated biomarkers of food intake (BFIs) have recently been suggested as a good tool for assessing adherence to dietary guidelines. New biomarkers have[iv] surfaced in recent decades from metabolic profiling studies for different foods, yet the number of comprehensively validated BFIs remains limited.
BFIs offer an accurate measure of intake, independent of the memory and sincerity of the subjects as well as of their knowledge about the consumed foods.[v] They overcome food intake measurement with inherent limitations, such as self-reported dietary intake questionnaires, as they objectively assess food intake without biased self-reported assessment.
The researchers sought to identify biomarkers of long-term apple consumption, exploring how the fruit affects human plasma and urine metabolite profiles. In their randomized, controlled, crossover intervention study, they recruited 40 mildly hypercholesterolemia patients and had them consume two whole apples or a sugar and energy-matched beverage daily for eight weeks.
At the end of the trial, they found 61 urine and nine plasma metabolites that were statistically significant after the whole apple intake compared to the control beverage. The metabolites included several polyphenols that could serve as BFIs.
Interestingly, the study allowed the group to explore correlations between metabolites significantly modulated by the dietary intervention and fecal microbiota species at genus level -- specifically interactions shared by Granulicatella genus and phenyl-acetic acid metabolites.
"[T]he identification of polyphenol microbial metabolites suggests that apple consumption mediates significant gut microbial metabolic activity which should be further explored," they wrote.[vi]
Gut Health Affects Your Whole Body
The link between the gut microbiota and human wellness is being increasingly recognized, where it is now well-established that healthy gut flora is a key part of your overall health.[vii]
Previous studies corroborate that the richness of the human gut microbiome correlates with metabolic markers. In a study on 123 non-obese and 169 obese Danish individuals, a group of scientists found two distinct groups displaying a difference in the number of gut microbial genes and thus the richness of gut bacteria in the two groups.[viii]
Individuals with a low bacterial richness had more marked overall adiposity and insulin resistance, for instance, compared with high bacterial richness subjects. The obese subjects among the lower bacterial richness group also tended to gain more weight over time.
A series of largely pre-clinical observations showed, too, that changes in brain-gut-microbiome communication may be involved in the pathogenesis and pathophysiology of irritable bowel syndrome, obesity and several psychiatric and neurologic disorders.[ix]
Additional Apple Benefits
More benefits of apple intake are coming out of the medical literature, confirming its superfood and super healer status that shouldn't be missed out on.
These benefits include addressing common issues such as aging (reduced rate), allergies, alopecia or hair loss, diarrhea, insulin resistance, radiation-induced illness, and Staphylococcal infection. In the area of cancer treatment, apples have been found to both prevent and suppress mammary cancers in the animal model, while carotenoids extracted from the fruit have been found to inhibit drug-resistant cancer cell line proliferation.[x]
The GreenMedInfo.com database contains 156 abstracts with apple research, scrutinizing the health benefits of apples and their related compounds.
References [i] Shi Zhao et al "Intakes of apples or apple polyphenols decease plasma values for oxidized low-density lipoprotein/beta2-glycoprotein I complex" J Funct Foods. 2013 Jan;5(1):493-97. [ii] Pierini R et al "Procyanidin effects on oesophageal adenocarcinoma cells strongly depend on flavan-3-ol degree of polymerization" Mol Nutr Food Res. 2008 Dec;52(12):1399-407. PMID: 18683822 [iii] Ulaszewska M et al "Two apples a day modulate human:microbiome co-metabolic processing of polyphenols, tyrosine and tryptophan" Eur J Nutr. 2020 Feb 26. Epub 2020 Feb 26. PMID: 32103319 [iv] Picó C et al "Biomarkers of Nutrition and Health: New Tools for New Approaches" Nutrients. 2019 May; 11(5): 1092. Published online 2019 May 16. [v] Münger L et al "Biomarker of food intake for assessing the consumption of dairy and egg products" Genes Nutr. 2018; 13: 26. Epub 2018 Sep 29. [vi] Ulaszewska M et al "Two apples a day modulate human:microbiome co-metabolic processing of polyphenols, tyrosine and tryptophan" Eur J Nutr. 2020 Feb 26. Epub 2020 Feb 26. PMID: 32103319 [vii] Jandhyala S et al "Role of the normal gut microbiota" World J Gastroenterol. 2015 Aug 7; 21(29): 8787-8803. Epub 2015 Aug 7. [viii] Le Chatelier E et al "Richness of human gut microbiome correlates with metabolic markers" Nature. 2013 Aug 29;500(7464):541-6. [ix] Martin C et al "The Brain-Gut-Microbiome Axis" Cell Mol Gastroenterol Hepatol. 2018 ;6(2):133-148. Epub 2018 Apr 12. [x] Molnár P et al "Biological activity of carotenoids in red paprika, Valencia orange and Golden delicious apple" Phytother Res. 2005 Aug;19(8):700-7.