Gut Instincts September 2021
By Rebecca Guenard
In This Section
- Lipid role in the immune system November/December 2021
- New essential dietary lipids? October 2021
- Gut Instincts September 2021
- Can computers make better plant-based foods? July/August 2021
- Poisson from a petri dish June 2021
- The latest additions to eco-friendly cleaning May 2021
- Preserving emulsions with plant-based antioxidants April 2021
- Developments in green surfactants for enhanced oil recovery March 2021
- Alternative base oils: a perspective March 2021
- The COVID-19 pandemic, one year later March 2021
- The green machine: commercializing microalgae products February 2021
- Bio-based (edible) oils: feedstock for lubricants of the future January 2021
- The latest on liposomes January 2021
- Fatty acids and athletic performance November/December 2020
- Where are lubricants headed November/December 2020
- New developments in vegetable oil materials science October 2020
- Agriculture at risk: preparing the oilseed industry for a warmer world September 2020
- Science highlights from a cancelled 2020 AM&E July/August 2020
- Managing your career in times of change June 2020
- Lipidomics comes of age May 2020
- Minimally processed oils April 2020
- The high-throughput frontier March 2020
- Nurturing innovation: how AOCS industries are fostering progress February 2020
- The trouble with studying omega-3s and the brain January 2020
- Understanding pulse anti-nutrients January 2020
- Digitizing manufacturing: how companies are using data to improve production November/December 2019
- Weaving together genetics, epigenetics, and the microbiome to optimize human nutrition October 2019
- Taking the cream out of ice cream September 2019
- Science highlights from St. Louis July/August 2019
- Biotechnology conquers consumer goods June 2019
- Cool characterization methods and where to find them May 2019
- Fermentation, the new protein supply chain April 2019
- Oleogels for drug delivery March 2019
- The complexity of clean-label cosmetics February 2019
- Rethinking plastic packaging January 2019
- Trends in synthetic and natural antioxidants for shelf life extension of meat and meat products November/December 2018
- The icing on the cake October 2018
- Enhancing oxidative stability and shelf life of frying oils with antioxidants September 2018
- Under arrest: investigating factors that govern partial coalescence July/August 2018
- Unconventional Oils June 2018
- Beauty from within May 2018
- Pulses rising April 2018
- Lessons learned from Hurricane Harvey March 2018
- Clean meat February 2018
- What makes your shortening suitable for fancy croissants, puff and Danish pastry? January 2018
- Strategic role of peanuts in sustainable global food security November/December 2017
- Science beyond borders: international student exchange October 2017
- Clean label: the next generation September 2017
- Science snapshots from Orlando July/August 2017
- Five new AOCS methods June 2017
- The whys and wherefores of life-cycle assessment May 2017
- China’s evolving edible oils industry April 2017
- The mysterious case of the arsenolipids March 2017
- Red palm oil February 2017
- The Highs and Lows of Cannabis Testing October 2016
- Chia: Superfood or superfad? January 2017
- Generational training divide November/December 2016
- Storage stability of roasted nuts and stabilization strategy using natural antioxidants September 2016
- Good vibrations: online and at-line monitoring of edible oils with vibrational spectroscopy July/August 2016
- Benchtop NMR spectroscopy for meat authentication June 2016
- Coconut oil boom May 2016
- Sink or swim: fish oil supplements and human health April 2016
- Pulsed electric field: groundbreaking technology for improving olive oil extraction March 2016
- Prescribing dietary fat: therapeutic uses of ketogenic diets February 2016
- Organogels of vegetable oil with plant wax January 2016
- The power of peptides November/December 2015
- Separation anxiety: membrane cleaning in the 21st century October 2015
- Using direct solid phase extraction to analyze persistent organic pollutants in oily food samples September 2015
- Big fat controversy: changing opinions about saturated fats June 2015
- Use of spent bleaching earth for economic and environmental benefit May 2015
- An introduction to cosmetic technology April 2015
- Food texture and nutrition: the changing roles of hydrocolloids and food fibers March 2015
- Scientists rank thousands of substances according to potential exposure level March 2015
- Clean smell does not always equal clean air February 2015
- Biotechnology: Using living systems to solve problems February 2015
- Flush to fuel January 2015
- 1970s fish oil study criticized January 2015
- Developing a high-performance, low-streak degreaser November/December 2014
- Detection, monitoring, and deleterious health effects of lipid oxidation November/December 2014
- Modified protein mimics taste and texture of fat October 2014
- Development of the first efficient membrane separations of cis fatty acids October 2014
- Regulatory updates on FSMA and combustible dust September 2014
- How enzymes are transforming manufacturing September 2014
- Two advances in biodiesel technology July/August 2014
- 2014 AOCS Annual Meeting & Expo July 2014
- Peanut genome sequenced June 2014
- A customized approach to frying oil June 2014
- Omics reveals subtle changes in carbon flux that lead to increased oil biosynthesis in oil palm May 2014
- Cannabis testing: a review of the current landscape May 2014
- Industrial hemp gaining traction April 2014
- Emulsions: making oil and water mix April 2014
- Lipid co-oxidation of proteins: One size does not fit all March 2014
- FSMA marches on March 2014
- Disruptive technology? Walmart’s “green” product line may signal a big change February 2014
- Pathways to novel chemicals February 2014
- Specialty lipids in pet nutrition January 2014
- EFSA releases preliminary report on occurrence of 3-MCPD in food January 2014
- Seven new biobased surfactant technologies November/December 2013
- Do oil color scales make you see red . . . or yellow? November/December 2013
- Shortage leads to green route to olefins October 2013
- Sesamol: a natural antioxidant for frying oil September 2013
- FSMA update September 2013
- Patent rights and biotech seeds July August 2013
- The other vitamin E July 2013
- Frac fever heats up June 2013
- Fat fight: Catch-22 for Western oleochemicals? June 2013
- Health and Nutrition News April 2013
- FDA asks for fees from industry to fund FSMA June 2013
- What does it take to start a biodiesel industry? April 2013
- What’s in a Claim? Would a Food Not Labeled “Natural” Taste as Sweet? March 2013
- Regulatory overview March 2013
- The preservative wars February 2013
- Plants producing DHA February 2013
- Swift response to paper on feeding GMO corn, glyphosate January 2013
- AOCS: supporting international standards January 2013
- TSCA and the regulation of renewable chemicals July August 2013
- trans Fatty acid content of foods in China January 2013
- A novel green catalytic process for biodiesel production from Jatropha November/December 2012
- The America Invents Act: Groundbreaking US patent law changes are here November/December 2012
- “Super Phos” esters: the key to higher-performance products November/December 2012
- Advances in field-portable mass spectrometers for on-site analytics October 2012
- EFSA sets upper intake level for LC-PUFA October 2012
- Malaysia: economic transformation advances oil palm industry September 2012
- High-oleic canola oils and their food applications September 2012
- Using enzymes to prepare biobased surfactants July/August 2012
- Oilseeds: at the center of food, water, and energy security July/August 2012
- Health & Nutrition News June 2012
- Hydrocolloids get personal June 2012
- The secrets of Belgian chocolate May 2012
- Plants “remember” drought, adapt May 2012
- The power of mass spectrometry in the detection of fraud April 2012
- Oil in biomass: a step-change for bioenergy production? April 2012
- The Future of LAB March 2012
- World supplies of rapeseed and canola likely to remain tight in the 2012/13 season March 2012
- Methods for differentiating recycled cooking oil needed in China February 2012
- Supercritical fluid-based extraction/processing: then and now February 2012
- Singapore: the place to be in 2012 February 2012
- The Food Safety Modernization Act and its relevance to the oilseed industry February 2012
- Oilseeds in Australia January 2012
- Hydrogen peroxide in home-care formulations November 2011
- A new generation of renewable fuels is on the horizon November 2011
- Omega-3 fatty acids: $13 billion global market October 2011
- Soy and breast cancer October 2011
- EU approves food labeling rules September 2011
- IOM panel recommends tripling vitamin D intake: Panel’s conservative approach receives criticism September 2011
- Self-assembly of lyotropic liquid crystals: from fundamentals to applications August 2011
- Sustainability watch July 2011
- Sustainability Watch July 2011
- Are algae really feasible as fuel? June 2011
- The trouble with crystal polymorphism June 2011
- Insect oils: Nutritional and industrial applications May 2011
- Reconstructing formulas April 2011
- US eggs now lower in cholesterol April 2011
- How to control eating behavior--in mice March 2011
- Maybe we don’t know beans March 2011
- Short- and long-term price forecasting for palm and lauric oils February 2011
- New 3-MCPD (glycidol ester) method February 2011
- Regulatory issues associated with the international oils & fats trade January 2011
- Point-counterpoint on UC Davis olive oil report January 2011
- Biomass--The next revolution in surfactants? December 2010
- One person’s response to a high omega-6 diet November 2010
- Crop residues as feedstock for renewable fuels November 2010
- Universal detectors for determination of lipids in biodiesel production October 2010
- New very long chain fatty acid seed oils produced through introduction of strategic genes into Brassica carinata October 2010
- Surfactants based on monounsaturated fatty acids for enhanced oil recovery September 2010
- Questioning the virginity of olive oils September 2010
- Dietary guidelines report released August 2010
- Keeping up with detergent chemistry August 2010
- News from the Expo floor July 2010
- Degumming revisited July 2010
- First high-GLA safflower oil on market June 2010
- AOCS 2.0 debuts June 2010
- Palm fatty acid distillate biodiesel: Next-generation palm biodiesel May 2010
- Palm oil pundit speaks May 2010
- What is unrefined, extra virgin cold-pressed avocado oil? April 2010
- The ultra-low-linolenic soybean market April 2010
- Dealing with the media: A cautionary tale March 2010
- Hempseed oil in a nutshell March 2010
- Carbon management 101: A conversation with Eric Jackson February 2010
- Giants of the Past: Hermann Pardun (1908-2009) February 2010
- Q&A with Bill Christie February 2010
- Update on Jatropha January 2010
- Unique properties of carbon dioxide-expanded lipids January 2010
- The market situation and political framework in Germany for biodiesel and vegetable oil December 2009
- Industrial oil crops-when will they finally deliver on their promise ? December 2009
- Chemically enhanced oil recovery stages a comeback November 2009
- Field-portable mass spectrometers for onsite analytics: What's next? October 2009
- To make biofuels, or not to make biofuels:That is the question. September 2009
- Melamine analysis at the forefront September 2009
- Global oil yields: Have we got it seriously wrong? August 2009
- Omega-3 fatty acid profiling and dietary forensics August 2009
- Oilseeds of the future part 3 July 2009
- The rise and fall of surfactants lore July 2009
- Oilseeds of the future: Part 2 June 2009
- Codex Alimentarius Commission update June 2009
- Raw material sources for the long-chain omega-3 market:Trends and sustainability. Part 3. May 2009
- Oilseeds of the future: Part 1 May 2009
- Chloroesters in foods: An emerging issue April 2009
- Raw material sources for the long-chain omega-3 market: Trends and sustainability. Part 2. April 2009
- Synthetic HDL created March 2009
- Raw material sources for the long-chain omega-3 market:Trends and sustainability. Part 1. March 2009
- A convenient way to increase legume intake February 2009
- Vitamin E’s safety controversy January 2009
- Universal mechanism of aging uncovered? January 2009
- Mucosal membranes act as a network that provides a connection between the gut and vital organs, like the lungs or the brain, but presumably the entire body.
- Short-chain fatty acids are formed in the colon through the fermentation of soluble fiber, and researchers are interested in finding out more about their role as signaling compounds.
- More research is needed to decisively say that one diet is better for the microbiome over another.
Colonies of bacteria flourish deep in the ocean near hydrothermal vents that expel toxic, superheated water from the Earth’s crust. Other bacteria subsist on rivers of sulfuric acid running through subterranean caves. Given the extreme environments where bacteria dwell, it is not surprising that the human digestive system is another popular home for microorganisms.
The gut microbiota is an ecosystem comprised of an estimated 1,000 bacterial species along with archaea, fungi, and viruses that reside in the human intestinal tract. For a century now, researchers have studied this community of microorganisms, but it was not until modern sequencing tools enabled them to genetically distinguish bacterial colonies 20 years ago that the mysteries of the microbiome were revealed. Since then, scientists have come to understand that this ecosystem in our gut, just like any ecosystem, is a complex environment with a delicate balance.
Furthermore, all the latest research has redefined a healthy gut to mean more than just comfortable digestion. Scientists now know that human health overall may rely on what colonies populate the intestines.
Gut bacteria have been shown to influence diseases such as colon cancer, but also neurological disorders like multiple sclerosis and even autism spectrum disorder. The microbes determine the effectiveness of drug treatments like statins, which fail to lower cholesterol sufficiently in certain gut bacteria environments. Fatty acid metabolites from bacteria are emerging as a means of immune system modulation which could be a treatment mechanism in the future. But the biggest question researchers want to answer is, how can dietary habits be adjusted to maintain the healthiest possible gut?
Here is a look at the latest information on what scientists have learned about the gut microbiome.
There is growing evidence that the gut microbiome is a significant factor in maintaining human health and avoiding disease. However, it is becoming clear that the gut does not act alone. There are colonies of microorganisms throughout the body, and researchers are identifying communication links that allow “cross-talk” among them that help the immune system maintain health.
During the recent SARS-CoV-2 outbreak, for example, scientists in Brazil determined that the virus attacks certain gut bacteria with a cascading effect on lung immunity, while at the same time lung inflammation alters the microbiota of the respiratory system, consequently killing bacteria in the gut (https://doi.org/10.3389/fimmu.2021.635471). Immunology researchers are in the process of trying to understand what unites these physiological systems that serve such vastly different functions.
One explanation of how the microbiome interacts with the immune system could come from the mucosal membrane, a layer of epithelial cells that line the respiratory and gastrointestinal tracts. In fact, mucus, antimicrobial agents, and immune cells cover all the surfaces of the body that interact with the outside world. (Although, the colon contains the largest, most diverse population of microbes.) Until now, these membranes have been viewed simply as a physical barrier, but scientists have found that pathogens interact directly with mucosal epithelia, triggering cellular changes (https://doi.org/10.3389/fcimb.2020.602312).
In response to a pathogen, immune cells can migrate from mucus to threatened tissue through the lymphatic system (Fig. 1). When this happens, epithelial cells in the mucosal membrane secrete peptides that inhibit specific microbial growth. At the same time, receptors established by genetics orchestrate the colonization of certain bacterial lines. Lymphoid cells also coordinate a response by releasing compounds that regulate bacterial composition in the gut.
The specifics surrounding these observations of the microbiome’s role in the mucosal immune system are still being worked out; however, researchers believe that the relationship between epithelial cells and gut bacteria is established in infancy. The adult immune system is activated at birth when the body is first exposed to microbes outside the womb. According to the hygiene hypothesis, exposure to a variety of new cell types early in life is crucial for training the system. Put another way, a sterile early life disorganizes the immune system, increasing the viability of inflammatory pathologies that can lead to allergies or, possibly, irritable bowel disease later in life.
Mucosal cells on infant skin and in the mouth are the gateway to a healthy microbiome that leads to a robust adult immune system capable of fending off pathogens. Scientists are not sure how long the window to feed the microbiome stays open, but they are realizing it is crucial in way they had not previously imagined (https://www.nature.com/articles/s41385-020-0257-y).
Central nervous system
“There seems to be something about the social brain, in particular, that makes it sensitive to signals from the microbiome,” John Cryan, a biochemist at University College Cork in Ireland, said in a Nature article published last year. In the past five years, researchers have determined that gut bacteria are involved in producing bioactive compounds that travel the central nervous system (CNS) up to the brain, affecting thinking and behavior.
Cryan has been studying the association between microbiome composition and autism spectrum disorder. Studies show that children with autism consistently have less Veillonellaceae, Coprococcus, and Prevotella bacteria in their gut. In a study with just five participants, the microbiomes of autistic individuals were transplanted into mice to see how gut bacteria is involved with brain function (https://doi.org/10.1016/j.cell.2019.05.004). The microbiomes did not produce as much of two specific amino acid metabolites that increase the activity of a neurotransmitter involved in sensory processing and motor control, key deficits in autism spectrum disorder. The results from this small study, along with other animal experiments, have prompted researchers to consider the microbiome as a possible mechanism for autism treatment.
There is also evidence that interactions between the microbiome and the central nervous system regulate synaptic plasticity and cognition. Certain amino acid receptors interact with the microbiome, and elevated cyanobacteria in the intestines correlate with a build-up of neurotoxins in the brain that hinder their function. Diseases like amyotrophic-lateral sclerosis (ALS), Parkinson’s dementia, and Alzheimer’s are all associated with altered CNS neurochemistry that potentially originates in the gut (https://doi.org/10.3389/fncel.2013.00153).
Evidence suggests that the microbiome’s connection with the immune system might be the link that influences CNS behavior, but this nascent area of research is still developing. Some experiments have indicated such a possibility, while other experiments signal a different communication mechanism. Researchers have also found that the presence or absence of short- chain fatty acids (SCFA) produced as metabolites of gut bacteria, may act as signaling molecules that modulate cell activity.
Short-chain fatty acids
Soluble fiber in the human diet is fermented in the colon by resident microbes and turned into short-chain fatty acids, such as butyrate, propionate, and acetate. The SCFA are absorbed by the intestines into the bloodstream where studies show they perform vital roles, like modifying gene expression and regulating cholesterol synthesis.
The common SCFA have been studied for a long time, although researchers still have a lot to learn about them (https://doi.org/10.1038/d41586-020-00195-1). They are used by the colon’s epithelial cells as a source of energy and act as protein receptors that regulate lipid and glucose metabolism. SCFA are known to activate fatty acid oxidation while inhibiting synthesis and lipolysis to reduce the amount of free fatty acids in the blood (https://doi.org/10.1194/jlr.R036012).
While continuing to look for answers to questions about how SCFA fluctuations affect human health, researchers also want to better understand branched short-chain fatty acids. For molecules that are so prevalent in the body, not much is known about how they interact with human tissue or what receptors they trigger.
Branched-chain fatty acids (BCFA) are produced through a different fermentation mechanism than SCFA that involves the fermentation of proteins and amino acids instead of soluble fiber. The breakdown of proteins releases nitrogen, which is essential for bacterial growth. However, degradation of proteins is also accompanied by potentially toxic metabolites, such as amines, phenolic compounds, and volatile sulfur compounds.
The significance of BCFA remains unclear. Published results by a team at Stanford University in Palo Alto, California, led them to believe BCFA might regulate cells that produce a protein in mucous membranes involved in the immune system (https://doi.org/10.1038/d41586-020-00195-1). A recent study by a group of German scientists comparing SCFA and BCFA in vegans versus omnivores found that the amount of protein individuals ate did not influence the BCFA concentration in their guts. The researchers hypothesized that gut bacteria may drive SCFA synthesis and maintain stable levels regardless of nutrient levels, switching to proteins as a source when needed (https://doi.org/10.3390/nu13061808). Not enough data has been gathered on these SCFA to draw any lasting conclusions. In time, we are more likely to understand the role of these ubiquitous compounds.
Eating for a healthy gut
It is clear that multiple factors, such as your genes, birth, environment, and the medicine you take, influence the composition of bacterial colonies in the gut. Add diet to this complex system, and differentiating between important factors for maintaining a healthy microbiome becomes a significant research challenge. Still, different microbes have different optimal conditions for growth, and dietary choices eventually end up in the gut.
Researchers have conducted experiments on specific food items and found that certain options can impart beneficial effects. As mentioned earlier, microbiota living in the colon possess enzymes that break down dietary fiber through fermentation. Results from studies on fruits, vegetables, beans, and whole grains prove that when we eat these high-fiber foods their fermentation releases short-chain fatty acids into the large intestines. The high concentration of SFCA’s lowers the pH, creating an acidic environment where harmful bacteria do not prefer to live.
However, as researchers pointed out in a paper published in May 2021, studies that focus on one food item are incomplete. Dietary components can have counteracting or synergistic effects, and the diet as a whole should be considered when determining what makes a healthy microbiome (https://doi.org/10.1093/ajcn/nqab077). The research team from the Department of Food and Nutrition at the University of Helsinki in Helsinki, Finland, conducted a study examining the gut microbiomes of nearly 5,000 Finnish people who consumed foods recommended for a healthy diet. Participants reported what they ate each day in their omnivorous diets, and the researchers assigned a score to healthy food items. Some participants also provided stool samples for DNA analysis of the microorganisms.
The study did not produce overwhelming results. There was no dramatic difference in the microbiome of individuals with a higher healthy food score. But the researchers do claim that their results show a modest association between healthy food choices and “compositionally distinct microbiota.”
As in previous studies, the Finnish researchers also found that fiber has the greatest influence on gut health. Individuals with higher healthy food scores contain more fiber-degrading species of bacteria in their gut, along with more bacteria that produce SCFA and the resulting metabolic enzymes. They also found that the guts of individuals who reported eating less red and processed meat contained fewer enzymes associated with negative health effects known to contribute to colorectal cancer.
Many studies indicate the gut microbiome does not stray too far from a base bacteria population when it is in a state of homeostasis (Fig. 2). Exceptions include infancy, old-age, and during antibiotic treatments. These are times when bacterial numbers are low, and scientists believe there could be a benefit from adding a probiotic to the diet. Otherwise, the science is still out on whether adding prebiotics and probiotics to the diet provide any advantage during homeostasis.
In general, confusion about connections between the diet and the microbiome stem from a lack of research on the human body. In such a complex system, scientists have no choice but to build pared-down models to begin to understand how the process works. That means most of the experiments performed to explain the microbiome, including those mentioned here, are conducted on genetically engineered mice or in a petri dish. The few human studies that have been conducted involve very small groups of people, often fewer than 50.
This article barely scratches the surface of all the immunological and bioengineering research that has taken place in the past five years—not to mention the nutritional studies scientists have conducted. It is likely that in the next five years, more consumer products and pharmaceuticals will apply this research knowledge to improve gut health which, as we now know, leads to better overall well-being.
In the coming years, more microbiome experiments will head into the clinic. Research is inching toward treatments aimed at manipulating the mucosal layer as a means of fighting off viruses (https://doi.org/10.1038/s41423-021-00650-7). Scientists are also hopeful that they can eventually treat autoimmune disorders, such as lupus, type 1 diabetes, rheumatoid arthritis, and multiple sclerosis, with a regiment of pre- and probiotics (https://doi.org/10.1038/d41586-020-00197-z).
About the Author
Rebecca Guenard is the associate editor of Inform at AOCS. She can be contacted at email@example.com
Associations of healthy food choices with gut microbiota profiles, Koponen, K., K., et al., Am. J. Clin. Nutr. 00: 1–12, 2021.
Short- and branched-chain fatty acids as fecal markers for microbiota activity in vegans and omnivores, Trefflich, I., et al., Nutrients 13: 1808, 2021.
Microbiota modulation of the gut-lung axis in COVID-19, de Oliveira, G.L.V., et al., Front. Immunol. 12: 214, 2021.
Mucosal immunity–mediated modulation of the gut microbiome by oral delivery of probiotics into Peyer’s patches, Lin, et al., Sci. Adv. 7: eabf0677, 2021.
Mucosal epithelial cells: the initial sentinels and responders controlling and regulating immune responses to viral infections, Yang, J. and H. Yan, Cell Mol. Immunol. 18: 1628–1630, 2021.
Imprinting of the immune system by the microbiota early in life, Al Nabhani, Z. and G. Eberl, Mucosal Immunol. 13: 183–189, 2020.
The gut microbiome in neurological disorders, Cryan, C.F., et al., Lancet Neurol. 19: 179–194, 2020
The gut microbiome, Brody, H., Nature 577: S5, 2020.