RESEARCH UPDATE:
Study Examines Impact of Almonds and Almond Processing on Gastrointestinal Physiology, Luminal Microbiology, and Gastrointestinal Symptoms
A recent study2, funded by the Almond Board of California, showed almond consumption in adults increased butyrate, a specific microbiota byproduct connected with several health benefits, including improving sleep quality, fighting inflammation, improving stool output, and has been associated with a lower risk of colon cancer. In this trial, 87 healthy adults participated, aged 18 to 45 years, who described themselves as regular snackers enjoying two or more snacks daily. Participants were consuming a typical diet that was lower in fiber than recommended and screened extensively for exclusion criteria.
Each group was comprised of 29 participants. Group One ate 56 grams (about 2 one-ounce servings, or ~340 calories) of whole almonds per day, Group Two ate 56 grams (about 2 one-ounce servings, or ~340 calories) of ground almonds (almond flour) per day, and the control group ate 2 energy-matched snack muffins per day. Participants were required to take their study snacks instead of customary snacks, and they did this twice daily for 4 weeks. They drank at least 100 mL of water with each snack.
Measured outcomes included relative abundance of fecal bifidobacteria, fecal microbiota composition and diversity, fecal SCFAs, whole-gut transit time, gut pH, stool output (both frequency and consistency), and gut symptoms.
Limitations of the study include the sex distribution of volunteers, where more than 86% were female, as well as the age of participants, as the average age was 27.5 years. The researchers recognize their findings are not necessarily generalizable to males or to older populations.
Study at-a-Glance:
The Study
- Researchers explored the prebiotic effect of almonds and the potential impact almond processing had on this effect in a free-living, 4-week, 3-arm, parallel-design randomized controlled trial.
- Eighty-seven healthy adults participated and received either 56 g/d whole almonds, 56 g/d ground almonds, or an isocaloric snack muffin as the control.
- Baseline and endpoint measures included gut microbiota composition and diversity, short-chain fatty acids, volatile organic compounds (VOCs), gut transit time, stool output, and gut symptoms (n=87). A subgroup (n=31) was measured for the impact of almond form, ground or whole, on particle size distribution (PSD) along with predicted lipid release.
Results
- Researchers observed no significant differences in the abundance of fecal bifidobacteria following consumption of either form of almond or the control snack. Almond consumers (both ground and whole almonds), had higher butyrate (24.1 µmol/g; SD 15.0 µmol/g) compared to the control (18.2 µmol/g, SD 9.1 µmol/g; p=0.046).
- There was no effect of almonds on gut microbiota at the phylum level or diversity, gut transit time, stool consistency, or gut symptoms. Three VOCs increased following almond consumption compared to control muffins, but this change was not statistically significant.
- Ground almonds resulted in significantly smaller PSD and higher predicted lipid release (10.4%, SD 1.8%) in comparison to whole almonds (9.3%, SD 2.0%; p=0.017).
- Of the subgroup participating in the mastication study, analysis of PSD demonstrated a significant interaction between whole almonds and the particle size on PSD; however, commercially ground almonds did not differ meaningfully in their nutrient bioaccessibility from whole almonds.
- Post-hoc testing showed whole almond participants had higher intakes of monounsaturated fatty acids, total fiber, potassium, along with other nutrients when compared to the control participants. Similarly, ground almond consumers had higher intakes of monounsaturated fatty acids, total fiber, and other micronutrients.
Conclusion
- Participants who consumed almonds experienced small but significant differences in stool frequency as well as significant increases in butyrate in the colon. Researchers indicate that these findings suggest positive alterations to gut microbiota functionality. The impact of almond consumption on bacterial metabolism has the potential to influence human health.
- These results have inspired thinking regarding how almonds may benefit older adults as well as those with constipation, as these populations are known to have lower levels of bifidobacteria than healthy, young adults as well as those without constipation.
In summary, Professor Whelan and his colleagues found that study participants who consumed almonds experienced significant increases in butyrate as well as increased stool frequency. Almonds were well tolerated and did not lead to gastrointestinal symptoms, which indicates almond consumption may be a way to increase fiber without causing any adverse effects. This is suggestive of positive alterations to microbiota functionality.
