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Almonds & their skins show prebiotic potential: Human data

By Stephen DANIELLS , 06-Mar-2014
Last updated the 06-Mar-2014 at 14:47 GMT

Almonds & their skins show prebiotic potential: Human data

Fiber-rich almonds and almond skin may selectively boost the populations of bifidobacteria and lactobacilli in the gut, says a new study funded by the Almond Board of California.

In addition to enhancing the populations of Bifidobacterium spp. and Lactobacillus spp., the data indicated that six weeks of ingesting almonds or almond skins also repressed levels of the pathogen Clostridum perfringens.

“[W]e showed that almond skin and almond ingestion may lead to an improvement of the intestinal microbiota profile and modify the intestinal bacterial activities, which induce the promotion of health beneficial factors and inhibition of harmful factors,” wrote researchers from Fuzhou University and the Almond Board of California in the journal Anaerobe .

“Thus, we believe that almond skins and almonds possess potential prebiotic properties.

“The abundance of dietary fiber and polyphenols may be associated with the prebiotic effects observed upon ingestion of almond skins and almonds.”

The number one nut…

According to data from Innova Market Insights, almonds are the number one nut in new food products worldwide, having grown 148% since 2005. Almond product introductions reportedly grew faster in 2012 (9.7%) than all food (5.3%) and nut (7.1%) introductions. Almonds maintain a significant share of global new nut introductions (36%), and have seen double-digit growth in Europe (45%), Asia-Pacific (26%) and North America (15%).

A prebiotic is a selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health. (Gibson et al. 2010.)

Molly Spence, Regional Director of North America at the Almond Board of California, welcomed the new study, telling us: “Almonds are truly multi-functional, both from the consumer’s standpoint, and from the product developer’s. They’re available in more forms than any other tree nut, and depending how they’re used, can provide a variety of sensory attributes from deep roasted crunch to delicate creaminess."

Spence added that, in addition to consumers ranking almonds as the top nut they associate with snacking, almonds are also the top nut they associate with being nutritious, heart healthy and helpful in weight management.   

In terms of prebiotic potential, this isn't the first report of such activity. In 2010, scientists from the Institute of Food Research (IFR) in Norwich, England used the Model Gut Platform to find hat both natural and blanched almond skins produced significant increases in the population of various gut microbes, including bifidobacteria (Microbiology Letters, doi: 10.1111/j.1574-6968.2010.01898.x). The Norwich-based scientists gave almond skins a prebiotic index of about 3.2, which they said “compared well” with a prebiotic index of 4.2 observed for commercial fructooligosaccharides.

The new study involved 48 health human volunteers aged between 18 and 22. Participants were randomly assigned to one of three groups: The first group supplemented their diets with 56 grams per day of roasted almonds; the second group added 10 grams per day of almond skins to their diets; and the final group consumed 8 grams per day of commercial fructooligosaccharides (FOS) as positive control.

After six weeks of intervention, the results indicated that the almonds and the almond skins had different effects on different strains of intestinal bacteria. Both interventions significantly increased Bifidobacterium spp. and Lactobacillus spp. populations, while no changes were observed in E. coli levels.

The data indicated that bifidobacteria and lactobacilli levels increased promptly in both the almond skin and FOS groups, with the greatest bifidogenic effect observed for FOS intake. The enhanced levels were of viable bifidobacteria and lactobacilli were sustained for two weeks after almond skin ingestion, they added.

On the other hand, the roasted almonds did not produce a noticeable stimulation of bifidobacteria or lactobacilli populations until week six, by which time the levels between the almond and almond skin groups were similar.

Fiber and polyphenols

“These results indicated the stimulation effects of almond skin and almond intake were typical prebiotic effects,” wrote the researchers. “Any food or ingredients that reach the colon without being digested are prebiotic candidates; nondigestible carbohydrates, in particular FOS, are authentic prebiotics.

“Almond skins contain approximately 50% dietary fiber and almonds contain about 12% dietary fiber. Dietary fiber is resistant to digestive enzymes and passes undigested to the large intestine where it interacts with the intestinal mucosa and microbiota to enhance gut health.”

The polyphenol content of the almonds and almond skins may also be associated with the potential prebiotic effects observed, they added.

“Further study is necessary to explore the specific prebiotic components in almonds and almond skins,” they concluded.

Source: Anaerobe
April 2014, Volume 26, Pages 1-6, doi: 10.1016/j.anaerobe.2013.11.007
“Prebiotic effects of almonds and almond skins on intestinal microbiota in healthy adult humans”
Authors: Z. Liu, X. Lin, G. Huang, W. Zhang, P. Rao, L. Ni

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