Almonds: Gut Microbiome and Prebiotic Effects

Table of Contents

1. What Reaches the Colon From an Almond
2. What “Prebiotic” Formally Means
3. How the Studies Measured Gut Bacteria
4. Laboratory Digestion and Fermentation Studies
5. Feeding Trials in Healthy Adults
6. Whole, Chopped, Roasted, Ground, Butter and Skins
7. College Students and Young Children
8. Adults With Raised Blood Sugar, Overweight or Metabolic Syndrome
9. Butyrate and Other Short-Chain Fatty Acids
10. Stool Output, Gut Transit and Bowel Habit
11. What the Pooled Analysis and Reviews Conclude
12. Animal Work: Almond Beverage in Young Rats
13. Who Paid for the Research
14. What Is Not Known
15. Who the Research Raises Concerns For
16. Connections
17. Key Research Papers
18. Featured Videos

What Reaches the Colon From an Almond

Most of a meal is absorbed in the small intestine. What is left — the parts human enzymes cannot digest, or cannot reach — moves on into the large intestine (the colon), where most gut bacteria live. For almonds, three kinds of material make that journey.

• Cell-wall fiber. An almond kernel is built from small plant cells, each wrapped in a wall. Ellis and colleagues analysed those walls in 2004 and found them rich in non-starch polysaccharides (the carbohydrate chains that make up dietary fiber), particularly arabinose-rich polysaccharides. Human digestive enzymes cannot break these down; gut bacteria can.
• Fat locked inside intact cells. Ellis and colleagues found that chewing or mechanical crushing ruptured only the first layer of cells at each broken surface. In stool samples from volunteers who had eaten almonds, they saw intact almond cells with the fat still enclosed by the cell walls. That fat, they reported, “appeared susceptible to colonic fermentation once the cotyledonary cell walls were breached by bacterial degradation” — in other words, bacteria in the colon open the walls and reach the fat.
• Skin polyphenols. The same 2004 analysis detected a high concentration of phenolic compounds in the cell walls of the seed coat, the thin brown skin. Polyphenols are a large family of plant chemicals; many are poorly absorbed higher up and arrive in the colon, where bacteria break them down.

Later studies put numbers on how much fat escapes. In a randomised crossover chewing study, Grundy and colleagues (2015) had 15 healthy adults chew natural or roasted almonds and spit out the result. Only a small share of the fat was released from cells ruptured at the surface of the chewed particles — a predicted 8.5% for natural almonds and 11.3% for roasted — because 35–40% of the chewed material was in large particles over half a millimetre across. Under the microscope, most of the fat stayed inside intact cells. In a 2023 chewing study of 31 healthy adults, Creedon and colleagues found that ground almonds (almond flour) broke into smaller particles than whole almonds, raising predicted fat release only modestly, from 9.3% to 10.4%.

The fat that escapes shows up in stool. Nishi and colleagues (2021) re-analysed a crossover trial in which men and postmenopausal women with high blood lipids ate about 73 g of almonds a day, about 38 g, or a muffin control, for a month each. Fat excretion in stool rose with almonds, and the energy actually absorbed from the almonds was 78.5% of what standard calorie factors predict — an average shortfall of about 21%. That unabsorbed share is what the colon receives. The calorie side of this story is covered on the weight, satiety and calories page.

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What “Prebiotic” Formally Means

“Prebiotic” is a technical term with a formal definition, not a general word for “good for the gut.” In 2017 an expert panel convened by the International Scientific Association for Probiotics and Prebiotics (ISAPP) published a consensus statement defining a prebiotic as a substrate that is selectively utilized by host microorganisms conferring a health benefit (Gibson and colleagues, 2017). The panel kept the requirement that the effect works selectively through gut microbes, and stated that beneficial health effects must be documented for a substance to be considered a prebiotic.

That definition has two halves, and the almond research covers them unevenly:

• Selective use by gut microbes. Laboratory fermentation work and several feeding trials, described below, show that particular groups of bacteria change when almond material is supplied.
• A documented health benefit that follows from that. No trial found for this page has linked an almond-driven shift in gut bacteria to a measured health outcome. Choo and colleagues (2021) wrote that the capacity for such microbiological effects to precipitate host benefit is not known.

The studies themselves use careful wording. Mandalari and colleagues titled their laboratory papers “potential prebiotic properties”; Liu and colleagues (2014) concluded that almonds and almond skins possess potential prebiotic properties; and a 2025 review by Tahiri and Gilbert, titled “Examining the potential prebiotic effect of almonds,” describes almonds as a potential prebiotic food while noting variability in study outcomes. The word “potential” in each case is the authors’ own. The broader topic of prebiotic substances is on the prebiotics page.

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How the Studies Measured Gut Bacteria

Almost all of the human trials below analysed stool samples. Most read a standard stretch of bacterial DNA (16S rRNA gene sequencing), which gives relative abundance: the share of all bacterial reads belonging to each group. A rise in one group’s share can mean that group grew or that others shrank. Alpha-diversity is a summary number for how many different groups are present and how evenly they are spread within one person; beta-diversity compares the overall community between samples. A genus (for example Roseburia or Bifidobacterium) is a narrow level of classification; a phylum is a very broad one, and a change at genus level can be invisible at phylum level.

Bacterial groups are reported on this page as the studies named them. Where an author called a group “potentially beneficial” or “pathogenic,” those are quoted as the authors’ words. A fuller explanation of these methods is on the pistachio gut microbiome page, and the general background is on the microbiome page and in the gut barrier and microbiome animation.

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Laboratory Digestion and Fermentation Studies

The earliest almond gut work was done in laboratory vessels, not in people. These are in-vitro studies: almond material is first passed through a model of stomach and small-intestine digestion, then incubated with bacteria taken from human (or animal) stool. They show what gut bacteria can do with almond material under controlled conditions; they cannot show what happens inside a living gut.

• Ground almonds, 2008 (in vitro). Mandalari and colleagues fermented digested finely ground almonds, and finely ground almonds with the fat removed, with mixed human fecal bacteria. Full-fat ground almonds significantly increased bifidobacteria and Eubacterium rectale, giving a “prebiotic index” (a laboratory score of how strongly selected groups grew) of 4.43, against 4.08 for the commercial prebiotic fructooligosaccharides (FOS). Defatted almonds produced no significant change in the bacterial groups. The rise in E. rectale correlated with increased butyrate production.
• Almond skins, 2010 (in vitro). Mandalari and colleagues ran the same kind of model with natural almond skins and with blanched skins (a by-product of almond processing). Both increased bifidobacteria and the Clostridium coccoides/Eubacterium rectale group, with prebiotic indices of 3.3 and 3.2 against 4.2 for FOS after 24 hours. There was no difference between natural and blanched skins in bacterial groups or short-chain fatty acid production; the authors concluded the skin polyphenols “did not affect bacterial fermentation” and that the effect came from the skin’s dietary fiber.
• Five tree-nut fibers compared, 2023 (in vitro). Şahin and colleagues fermented isolated dietary fiber from almond, cashew, hazelnut, pistachio and walnut with human fecal bacteria. Cashew fiber produced the most butyrate, which the authors attributed to its higher share of soluble fiber and its sugar make-up. Fibers from all the nuts stimulated bacteria in the Lachnospiraceae and Ruminococcaceae families. This study suggests almond fiber is not unusual among tree nuts in this respect.
• Particle size, 2024 (in vitro, pig stool bacteria). Bermudez and colleagues fermented almond and macadamia particles of two sizes with bacteria from pig stool for 48 hours. Short-chain fatty acid output depended on particle size more than on nut type, though each nut stimulated some distinct genera. Under the microscope, bacteria attached to the nut particles over time as the fat inside them decreased — laboratory support for the idea that colon bacteria take part in breaking down the fat that chewing leaves locked in.

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Feeding Trials in Healthy Adults

Four trials in healthy adults sampled stool before and after almonds were added to the diet.

• Liu and colleagues, 2014 (China). 48 healthy adults ate 56 g a day of roasted almonds, 10 g a day of almond skins, or 8 g a day of fructooligosaccharides (a positive control) for 6 weeks. The authors reported significant increases in Bifidobacterium and Lactobacillus with almonds or almond skins; Escherichia coli did not change; and the growth of Clostridium perfringens, which the authors call a pathogen, was significantly reduced. Fecal enzyme activity also shifted: β-galactosidase rose, while β-glucuronidase, nitroreductase and azoreductase fell. The abstract compares each group with its own starting point and does not report a comparison against a no-almond control group.
• Ukhanova and colleagues, 2014 (USA). In a controlled crossover feeding study, 18 adults ate 0, 1.5 or 3 servings of almonds a day, 18 days per diet period (a parallel study did the same with pistachios). Several bacterial groups appeared to respond to almonds, but the authors wrote that the effect of pistachios was much stronger than that of almond consumption. Bifidobacteria were not affected by either nut. The pistachio side is on the pistachio gut microbiome page.
• Holscher and colleagues, 2018 (USA). 18 healthy adults rotated through five controlled diets of three weeks each: no almonds, or 42 g a day of whole, whole roasted, roasted chopped almonds, or almond butter. Almond consumption increased the relative abundance of Lachnospira, Roseburia and Dialister. Results by form are in the next section.
• Creedon and colleagues, 2022 (UK). The largest trial and the only one built around a pre-stated primary microbial outcome. 87 healthy adults were randomised to 56 g a day of whole almonds, 56 g a day of ground almonds, or a snack of equal calories, replacing their usual snacks for 4 weeks; 79 were analysed. The primary outcome, fecal bifidobacteria, did not differ: 8.7% of bacteria after whole almonds, 7.8% after ground almonds, and 13.0% in the control group. There was no effect on bacterial phyla or diversity. Butyrate was higher with almonds (next sections), while gut transit time, stool consistency and gut symptoms did not change.

Two of these trials point in opposite directions on the bacterium most often linked to the word “prebiotic.” Liu and colleagues reported an increase in bifidobacteria; Ukhanova and colleagues and Creedon and colleagues, the latter with bifidobacteria as their primary outcome, did not find one.

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Whole, Chopped, Roasted, Ground, Butter and Skins

Because what reaches the colon depends on how finely the almond is broken up, several studies asked whether the form of the almond matters.

• Chopped versus whole versus butter (Holscher, 2018). Compared with the no-almond diet, roasted chopped almonds increased Lachnospira, Roseburia and Oscillospira; whole almonds increased Dialister; and almond butter showed no differences from control. The authors concluded that the degree of processing — roasting, chopping and grinding into butter — differentially impacted the relative abundances of bacterial genera.
• Whole versus ground (Creedon, 2022). Almond form had no effect on any outcome in this trial, even though ground almonds broke into smaller particles and released slightly more fat when chewed (10.4% against 9.3% predicted).
• Natural versus roasted (Grundy, 2015). Roasted almonds chewed into a different particle-size pattern from natural almonds and released a little more fat (predicted 11.3% against 8.5%). This was a chewing study; it did not measure gut bacteria.
• Almond skins. In laboratory fermentation, natural and blanched almond skins behaved alike and both raised bifidobacteria (Mandalari, 2010). In people, Liu and colleagues (2014) reported that 10 g a day of almond skins for 6 weeks produced changes similar to those from 56 g of roasted almonds. No other human trial found for this page tested skins on their own.

The overall picture is that form changed which genera shifted in one small crossover study and made no measurable difference in the larger parallel trial. The question is open. Soaking, a separate form question, is covered on the soaking and phytic acid page.

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College Students and Young Children

College freshmen

Dhillon and colleagues (2019) randomised 73 first-year college students aged 18–19, without heart or metabolic disorders, to a daily morning snack of 56.7 g of almonds (364 kcal) or 77.5 g of graham crackers (338 kcal) for 8 weeks. Most were breakfast-skippers. After 8 weeks the almond group had 3% higher alpha-diversity by one measure (Shannon index) and 8% higher by another (Chao1) than the cracker group, and a 48% lower abundance of Bacteroides fragilis, which the authors describe as a pathogenic bacterium. The overall community also shifted significantly over the course of the trial, with time explaining no more than about 3% of the variation. The dietary and clinical factors that best matched community structure at week 8 were the share of energy from carbohydrate, fiber intake, and fasting total and HDL cholesterol.

A companion analysis of the same trial (Dhillon and colleagues, 2023) measured blood metabolites and used the stool DNA to predict bacterial metabolic pathways with a computer tool (PICRUSt2), rather than measuring them directly. Predicted microbial amino-acid production and amino-sugar and nucleotide-sugar pathways differed between groups at the end of the trial; the authors describe these as “potential changes in microbial metabolism.”

Parents and their young children

Burns and colleagues (2016) ran a crossover trial in 29 parents (average age 35) and their 29 children (average age 4). Parents ate 1.5 oz (about 42 g) and children 0.5 oz (about 14 g) of almonds and/or almond butter a day, or no almonds, for 3 weeks, with 4-week washouts in between. Diet-quality scores rose in both parents and children. On the gut side:

• Gut symptoms changed minimally and stool frequency did not change.
• The microbiota was stable at phylum and family level, with genus-level changes especially in children.
• No differences were seen in the immune markers measured (salivary secretory IgA, and an antioxidant/inflammatory balance measure in parents). The authors suggested higher intakes or longer interventions might be needed.

This is the only trial found for this page that included children.

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Adults With Raised Blood Sugar, Overweight or Metabolic Syndrome

• Raised fasting glucose (Choo and colleagues, 2021, Australia). 69 adults who were overweight or obese, average age about 61, with fasting glucose in the prediabetes range, ate 56 g of almonds a day or a high-carbohydrate biscuit snack of equal calories for 8 weeks. The almond group, but not the biscuit group, showed significant changes in overall microbiota composition and increases in bacterial richness, evenness and diversity. The main drivers were increases in several groups in the Ruminococcaceae family, which the authors call potentially beneficial ruminococci. There was no change in stool short-chain fatty acids or in a gene used for butyrate production, and no reduction in gut permeability (“leaky gut”). Stool pH and stool moisture fell compared with the biscuit group. More on the blood-sugar side is on the blood sugar and diabetes page.
• Type 2 diabetes, whole-diet change (Ren and colleagues, 2020, China). 45 people with type 2 diabetes completed 3 months of either an almond-based low-carbohydrate diet or a low-fat diet. The almond diet group showed increases in Roseburia, Ruminococcus and Eubacterium, which the authors describe as short-chain-fatty-acid-producing bacteria, along with improved depression scores, HbA1c and GLP-1 (a gut hormone involved in blood-sugar control). Short-chain fatty acids themselves were not reported as measured; the authors speculate about that route and say it should be examined in future studies. Because the whole diet differed between groups, this trial cannot separate the effect of the almonds from the effect of cutting carbohydrate.
• Overweight or obesity, controlled feeding (Park and colleagues, 2025, USA). 15 adults with overweight or obesity ate a typical American diet for 4 weeks and, in random order, the same diet with 42.5 g of almonds a day. The authors report that almonds increased Faecalibacterium prausnitzii and suppressed what they call opportunistic pathogens, along with changes in stool and blood metabolites, inflammation markers and satiety hormones. The trial was small.
• Same trial design, wider sample (Riley and colleagues, 2026, USA). A secondary analysis of a four-period controlled-feeding crossover trial in adults with overweight or obesity compared a typical American diet with versions containing 42.5 g of raw almonds, dark chocolate and cocoa, or both, each replacing butter, cheese and crackers, for 4 weeks each. Stool samples were available from 21 of the 48 people randomised. The almond diet produced an overall stool community different from the pre-study, American-diet and chocolate periods, and lower Lactococcus. No other differences in diversity or composition were seen, and the authors describe the effects as modest.
• Metabolic syndrome, gut inflammation markers (Beaver and colleagues, 2025, USA). 77 adults with metabolic syndrome ate 2 oz (about 56 g) of whole dry-roasted almonds or crackers of equal calories as a daily snack for 12 weeks. In participants who started with raised gut inflammation, almonds improved stool markers of intestinal inflammation and gut barrier function: fecal calprotectin and myeloperoxidase (proteins released by white blood cells in the gut lining). Blood markers of whole-body inflammation (interleukin-6, C-reactive protein, LPS-binding protein, CD14) did not change. The calprotectin test itself is explained on the calprotectin and IBD diagnostic workup page.

See also prediabetes, type 2 diabetes and metabolic syndrome.

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Butyrate and Other Short-Chain Fatty Acids

When gut bacteria ferment fiber, their main products are short-chain fatty acids — small acids, chiefly acetate, propionate and butyrate. Butyrate is the one most discussed, because the cells lining the colon use it as a main fuel. Only some bacterial groups make much of it. In the studies on this page, Mandalari and colleagues linked Eubacterium rectale to butyrate output, and Ren and colleagues describe Roseburia, Ruminococcus and Eubacterium as short-chain-fatty-acid producers.

The almond evidence on butyrate itself, as opposed to the bacteria that can make it, is split:

• Higher butyrate. Creedon and colleagues (2022) found higher stool butyrate after 4 weeks of almonds (whole and ground combined) than after the control snack: 24.1 against 18.2 micromoles per gram of stool (P = 0.046, just inside the usual threshold). The authors described this as suggesting positive alterations to microbiota functionality.
• No change. Choo and colleagues (2021) found no change in stool short-chain fatty acids, and no change in a bacterial gene used to make butyrate, after 8 weeks of 56 g a day in adults with raised blood sugar.
• More of the producing bacteria, butyrate not reported. Holscher (2018) found more Roseburia, and Ren (2020) more Roseburia, Ruminococcus and Eubacterium, without reporting a measured rise in butyrate itself.
• In the laboratory. Mandalari and colleagues (2008) found that the rise in E. rectale during fermentation of ground almonds correlated with more butyrate; the 2023 five-nut comparison found more butyrate from cashew fiber than from almond fiber.

A 2023 review by Mandalari and colleagues summarises the state of play: the effect of nuts on bacterial diversity has been inconsistent, and some scientific evidence suggests an increase in fecal butyrate after almond consumption. How fiber feeds butyrate production in general is covered on the dietary fiber page and, for another fiber source, the resistant starch gut microbiome page.

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Stool Output, Gut Transit and Bowel Habit

Fiber-rich foods are often assumed to speed the gut and ease constipation. For almonds, the trials that measured bowel function largely found no change.

• Gut transit time. Creedon and colleagues (2022) measured transit directly with a swallowed wireless motility capsule, which records how long it takes to pass through each part of the gut. Four weeks of 56 g a day of whole or ground almonds had no effect on transit time, stool consistency or gut symptoms (recorded in a 7-day diary).
• Stool frequency. Burns and colleagues (2016) found no change in stool frequency in parents or young children over 3 weeks.
• Stool moisture and pH. Choo and colleagues (2021) found that stool moisture content and stool pH both decreased with 56 g a day of almonds compared with a biscuit snack. The abstract does not report constipation or bowel-movement outcomes.
• Pooled trials. The 2020 meta-analysis by Creedon and colleagues found no effect of nuts on stool output.
• Irritable bowel syndrome with diarrhoea (Darvishmoghadam and colleagues, 2019, Iran). In a double-blind trial, 50 people with diarrhoea-predominant IBS (IBS-D) took a 40 g sachet of almond or wheat-flour placebo daily for 20 days. None of the primary symptom outcomes improved with almond; bowel movements and pain severity increased compared with placebo and baseline. The authors note that almond is listed among low-FODMAP foods, but contains oligo-fructans that at higher intakes can supply enough fermentable carbohydrate to worsen symptoms, and conclude that the amount of almond intake is a determining factor.

No trial found for this page tested almonds specifically in people with constipation. General background is on the constipation, irritable bowel syndrome and low-FODMAP diet for IBS pages.

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What the Pooled Analysis and Reviews Conclude

The meta-analysis. Creedon and colleagues (2020) pooled randomised controlled trials in healthy adults that gave tree nuts or peanuts and measured stool bacteria, gut function or gut symptoms. Eight studies reporting nine trials qualified: five of almonds, three of walnuts and one of pistachios. Pooled across nuts, they found increases in the genera Clostridium, Dialister, Lachnospira and Roseburia, and a decrease in Parabacteroides. They found no effect on bacterial phyla, diversity or stool output, and called for larger parallel-design trials that include functional and clinical outcomes. The walnut trials in that pool are covered on the walnut gut microbiome and urolithins page.

The reviews. Four narrative reviews discuss almonds and the gut. Narrative reviews are not systematic: the authors choose which studies to discuss.

• Mandalari and colleagues (2023) emphasise that cell-wall integrity, cell size and chewed particle size govern what is released from nuts during digestion, and that the undigested remainder delivered to the colon is expected to affect gut bacteria. They describe the diversity findings as inconsistent and the butyrate evidence as suggestive.
• Dreher (2021), reviewing almond clinical trials, states that eight trials show almonds can promote microbial richness and diversity.
• Singar and colleagues (2024) discuss a “gut–heart axis” and describe almonds as promoting bacterial growth and butyrate production.
• Tahiri and Gilbert (2025) describe almonds as a potential prebiotic food and attribute the variability between studies to differences in participants’ health status, study design and how the almonds were prepared.

The reviews are more confident than the individual trials. The trial with bifidobacteria as its primary outcome found no change, the largest trial found no change in diversity, and the two trials that measured short-chain fatty acids disagreed.

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Animal Work: Almond Beverage in Young Rats

One animal study in the research for this page concerns an almond drink, not whole almonds. Cakebread and colleagues (2022) fed three-week-old male rats a protein-free amino-acid diet with ultra-heat-treated cow’s milk, soy beverage or almond beverage as their only liquid, for four weeks. Almost all bacterial phyla differed between groups. In the almond-beverage group, Bacteroidetes and several Firmicutes families rose. Cow’s milk increased the Bifidobacteriaceae; the soy and almond beverages did not. The authors had previously found poorer bone health in the almond-beverage rats. An almond beverage is a different food from whole almonds, and these findings come from rats, so they say little about people eating almonds.

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Who Paid for the Research

Much of the almond gut research has had support from an almond-industry trade body. Where a paper states this in its abstract record, it is noted here; industry funding does not by itself make a result wrong, but readers often want to know.

• Holscher and colleagues (2018): partial support from an almond-industry trade body and the US Department of Agriculture’s research service.
• Creedon and colleagues (2020 meta-analysis and 2023 chewing study): the lead author’s doctoral fellowship was funded by an almond-industry trade body, as were other authors’ grants.
• Dhillon and colleagues (college-freshmen trial): the 2023 companion paper discloses grants from an almond-industry trade body for conducting the study.
• Beaver and colleagues (2025): financial support from an almond-industry trade body, alongside public agricultural and NIH funding.
• Liu and colleagues (2014) and the 2023 Mandalari review: one author on each lists an almond-industry trade body as their affiliation.
• Dreher (2021): the author was a voluntary member of an almond-industry trade body’s nutrition research committee from 2006 to 2018.

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What Is Not Known

• Whether the bacterial shifts matter for health. No trial found for this page connects an almond-driven change in gut bacteria to a health outcome. Under the ISAPP definition, that link is what would make almonds a prebiotic in the formal sense.
• Which bacteria respond. Different trials found different genera: Bifidobacterium and Lactobacillus (Liu), Lachnospira, Roseburia and Dialister (Holscher), Ruminococcaceae (Choo), Faecalibacterium (Park), lower Bacteroides fragilis (Dhillon), lower Lactococcus (Riley). The overlap is limited.
• Butyrate. One trial found more, one found none, and the rest did not measure it.
• Long-term effects. The trials lasted from 18 days to 12 weeks. Nothing is known from trials about years of regular almond eating and the gut.
• Bowel habit in people with constipation. No trial has tested this; in people without constipation, transit and stool frequency did not change.
• Children. One small 3-week crossover trial exists.
• Skins versus kernel. Only one human trial tested skins alone, and its abstract does not report a comparison against a no-almond control.
• Dose. Ukhanova tested 1.5 and 3 servings; no study found for this page establishes a dose–response curve for any gut outcome.
• Comparators. Most trials compared almonds with crackers, biscuits or a typical American diet. A positive result may partly reflect removing those foods rather than adding almonds.

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Who the Research Raises Concerns For

• People with diarrhoea-predominant IBS. In the 2019 trial, 40 g a day of almond worsened bowel-movement frequency and pain compared with placebo. The authors link this to almond oligo-fructans at higher intakes, and conclude that the amount eaten is a determining factor.
• People with tree-nut allergy. Almonds are tree nuts. None of the gut trials on this page studied people with nut allergy.
• Gut symptoms in healthy adults. In the largest trial, 56 g a day did not change gut symptoms, and the authors wrote that almonds can raise fiber intake without gut symptoms. Burns and colleagues reported minimal symptom changes in parents and children.

Questions about gut symptoms, IBS or food allergy belong with a clinician.

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Connections

• Nuts — all nut pages
• Almonds — the main almond page
• Almonds — Benefits — the hub for every almond deep dive
• Almonds: Nutrient Profile — the full composition table
• Almonds: Weight, Satiety and Calories — the unabsorbed-calorie side of the cell-wall story
• Almonds: Blood Sugar and Diabetes
• Almonds: Heart Health and LDL
• Almonds: Soaking and Phytic Acid
• Pistachios: Gut Microbiome — the companion crossover study
• Walnuts: Gut Microbiome and Urolithins
• Gut Health — the gut-health section
• Microbiome — background on gut bacteria
• Dietary Fiber — how fiber feeds fermentation
• Prebiotics — the wider prebiotic topic
• Gut Barrier and Microbiome (animation)
• Low-FODMAP Diet for IBS
• Constipation
• Prediabetes

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Key Research Papers

1. Ellis PR, Kendall CW, Ren Y, et al. Role of cell walls in the bioaccessibility of lipids in almond seeds. The American journal of clinical nutrition. 2004;80(3):604-13. PubMed PMID: 15321799
2. Grundy MM, Grassby T, Mandalari G, et al. Effect of mastication on lipid bioaccessibility of almonds in a randomized human study and its implications for digestion kinetics, metabolizable energy, and postprandial lipemia. The American journal of clinical nutrition. 2015;101(1):25-33. PubMed PMID: 25527747
3. Creedon AC, Hung ES, Dimidi E, et al. Particle Size Distribution and Predicted Lipid Bioaccessibility of Almonds and the Effect of Almond Processing: A Randomised Mastication Study in Healthy Adults. Nutrients. 2023;15(3):489. PubMed PMID: 36771196
4. Nishi SK, Kendall CWC, Bazinet RP, et al. Almond Bioaccessibility in a Randomized Crossover Trial: Is a Calorie a Calorie? Mayo Clinic proceedings. 2021;96(9):2386-2397. PubMed PMID: 33853731
5. Gibson GR, Hutkins R, Sanders ME, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nature reviews. Gastroenterology & hepatology. 2017;14(8):491-502. PubMed PMID: 28611480
6. Mandalari G, Nueno-Palop C, Bisignano G, et al. Potential prebiotic properties of almond (Amygdalus communis L.) seeds. Applied and environmental microbiology. 2008;74(14):4264-70. PubMed PMID: 18502914
7. Mandalari G, Faulks RM, Bisignano C, et al. In vitro evaluation of the prebiotic properties of almond skins (Amygdalus communis L.). FEMS microbiology letters. 2010;304(2):116-22. PubMed PMID: 20146750
8. Şahin M, Arioglu-Tuncil S, Ünver A, et al. Dietary Fibers of Tree Nuts Differ in Composition and Distinctly Impact the Fecal Microbiota and Metabolic Outcomes In Vitro. Journal of agricultural and food chemistry. 2023;71(25):9762-9771. PubMed PMID: 37334468
9. Bermudez C, Yao H, Widaningrum, et al. Biomass attachment and microbiota shifts during porcine faecal in vitro fermentation of almond and macadamia nuts differing in particle sizes. Food & function. 2024;15(5):2406-2421. PubMed PMID: 38265095
10. Liu Z, Lin X, Huang G, et al. Prebiotic effects of almonds and almond skins on intestinal microbiota in healthy adult humans. Anaerobe. 2014;26:1-6. PubMed PMID: 24315808
11. Ukhanova M, Wang X, Baer DJ, et al. Effects of almond and pistachio consumption on gut microbiota composition in a randomised cross-over human feeding study. The British journal of nutrition. 2014;111(12):2146-52. PubMed PMID: 24642201
12. Holscher HD, Taylor AM, Swanson KS, et al. Almond Consumption and Processing Affects the Composition of the Gastrointestinal Microbiota of Healthy Adult Men and Women: A Randomized Controlled Trial. Nutrients. 2018;10(2):126. PubMed PMID: 29373513
13. Creedon AC, Dimidi E, Hung ES, et al. The impact of almonds and almond processing on gastrointestinal physiology, luminal microbiology, and gastrointestinal symptoms: a randomized controlled trial and mastication study. The American journal of clinical nutrition. 2022;116(6):1790-1804. PubMed PMID: 36130222
14. Dhillon J, Li Z, Ortiz RM. Almond Snacking for 8 wk Increases Alpha-Diversity of the Gastrointestinal Microbiome and Decreases Bacteroides fragilis Abundance Compared with an Isocaloric Snack in College Freshmen. Current developments in nutrition. 2019;3(8):nzz079. PubMed PMID: 31528836
15. Dhillon J, Newman JW, Fiehn O, et al. Almond Consumption for 8 Weeks Altered Host and Microbial Metabolism in Comparison to a Control Snack in Young Adults. Journal of the American Nutrition Association. 2023;42(3):242-254. PubMed PMID: 35512761
16. Burns AM, Zitt MA, Rowe CC, et al. Diet quality improves for parents and children when almonds are incorporated into their daily diet: a randomized, crossover study. Nutrition research (New York, N.Y.). 2016;36(1):80-9. PubMed PMID: 26773784
17. Choo JM, Tran CD, Luscombe-Marsh ND, et al. Almond consumption affects fecal microbiota composition, stool pH, and stool moisture in overweight and obese adults with elevated fasting blood glucose: A randomized controlled trial. Nutrition research (New York, N.Y.). 2021;85:47-59. PubMed PMID: 33444970
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