The Hungry Brain gives off a bit of a Malcolm Gladwell vibe, with its cutesy name and pop-neuroscience style. Stephan Guyenet is no Gladwell-style dilettante.
There is growing recognition of the role of diet and other environmental factors in modulating the composition and metabolic activity of the human gut microbiota, which in turn can impact health.
This narrative review explores the relevant contemporary scientific literature to provide a general perspective of this broad area. Molecular technologies have greatly advanced our understanding of the complexity and diversity of the gut microbial communities within and between individuals.
Diet, particularly macronutrients, has a major role in shaping the composition and activity of these complex populations. Despite the body of knowledge that exists on the effects of carbohydrates there are still many unanswered questions. The impacts of dietary fats and protein on the gut microbiota are less well defined.
Both short- and long-term dietary change can influence the microbial profiles, and infant nutrition may have life-long consequences through microbial modulation of the immune system.
The impact of environmental factors, including aspects of lifestyle, on the microbiota is particularly poorly understood but some of these factors are described. We also discuss the use and potential benefits of prebiotics and probiotics to modify microbial populations. A description of some areas that should be addressed in future research is also presented.
Introduction There are approximately 10 times as many microorganisms within the gastro-intestinal GI tract of humans approximately trillion as there are somatic cells within the body. While most of the microbes are bacteria, the gut can also harbor yeasts, single-cell eukaryotes, viruses and small parasitic worms.
Some of the most commonly found or recognized genera of gut bacteria in adults are Bifidobacterium, Lactobacillus, Bacteroides, Clostridium, Escherichia, Streptococcus and Ruminococcus. Although individuals may have up to several hundred species of microbes within their gut, recent findings from The Human Microbiome Project and others [ 34 ] show that thousands of different microbes may inhabit the gut of human populations collectively and confirm a high degree of variation in the composition of these populations between individuals.
AS THE SUN set over Lake Eyasi in Tanzania, nearly thirty minutes had passed since I had inserted a turkey baster into my bum and injected the feces of a Hadza man – a member of one of the last remaining hunter-gatherers tribes in the world – into the nether regions of my distal colon. The Evolution of Diet. By Ann Gibbons. Photographs by Matthieu Paley. Some experts say modern humans should eat from a Stone Age menu. What's on it may surprise you. An Introduction to the Basic Concepts of Food Security Food Security Information for Action Practical G uides 3 low (unless their crops are in the valley!). However, if they .
Despite this variation in taxa the abundance of many of the microbial genes for basic or house-keeping metabolic activities are quite similar between individuals [ 3 ]. There is growing evidence that imbalances in gut microbial populations can be associated with disease, including inflammatory bowel disease IBD [ 5 ], and could be contributing factors.
Consequently, there is increased awareness of the role of the microbiota in maintaining health and significant research and commercial investment in this area. Gut microbes produce a large number of bioactive compounds that can influence health; some like vitamins are beneficial, but some products are toxic.
Host immune defenses along the intestine, including a mucus barrier, help prevent potentially harmful bacteria from causing damage to tissues. The maintenance of a diverse and thriving population of beneficial gut bacteria helps to keep harmful bacteria at bay by competing for nutrients and sites of colonization.
Dietary means, particularly the use of a range of fibers, may be the best way of maintaining a healthy gut microbiota population.
Strategies such as ingestion of live beneficial bacteria probiotics may also assist in maintaining health. In this review, we will expand upon these subjects relating to diet and lifestyle, the gut microbiota and health, and provide some indication of opportunities and knowledge gaps in this area.
Microbial Products that Impact Health—Beneficial and Harmful Microbial mass is a significant contributor to fecal bulk, which in turn is an important determinant of bowel health.
Consumption of dietary fibers reduces the risk of colorectal cancer CRC [ 6 ] at least partly as a consequence of dilution and elimination of toxins through fecal bulk, driven by increases in fermentative bacteria and the presence of water-holding fibers [ 789 ].
Aspects of this will be discussed in more detail later in the review. Gut microbes are capable of producing a vast range of products, the generation of which can be dependent on many factors, including nutrient availability and the luminal environment, particularly pH [ 10 ].
A more in-depth review of gut microbial products can be found elsewhere [ 11 ]. Microbial products can be taken up by GI tissues, potentially reach circulation and other tissues, and be excreted in urine or breath.
Fermentation of fiber and protein by large bowel bacteria results in some of the most abundant and physiologically important products, namely short chain fatty acids SCFA which act as key sources of energy for colorectal tissues and bacteria, and promote cellular mechanisms that maintain tissue integrity [ 121314 ].
SCFA can reach the circulation and impact immune function and inflammation in tissues such as the lung [ 15 ]. However, some protein fermentation products such as ammonia, phenols and hydrogen sulphide can also be toxic.
There are many other products which deserve mention for their influence on health. Bacteria such as Bifidobacterium can generate vitamins e.
Synthesis of secondary bile acids, important components of lipid transport and turnover in humans, is mediated via bacteria, including Lactobacillus, Bifidobacterium and Bacteroides [ 11 ]. Numerous lipids with biological activity are produced by bacteria, including lipopolysaccharide LPSa component of the cell wall of gram negative bacteria that can cause tissue inflammation [ 16 ].Paul Kingsnorth is a writer and poet living in Cumbria, England.
He is the author of several books, including the poetry collection Kidland and his fictional debut The Wake, winner of the Gordon Burn Prize and the Bookseller Book of the Year Award. Kingsnorth is the cofounder and director of the Dark Mountain Project, a network of writers, artists, and .
I originally introduced the term “orthorexia” in the article below, published in the October issue of Yoga Journal. Some of the things I said in the article are no longer true of . Adopting a theory of healthy eating is NOT orthorexia.
A theory may be conventional or unconventional, extreme or lax, sensible or totally wacky, but, regardless of the details, followers of the theory do not necessarily have orthorexia.
Unhappy Meals By Michael Pollan The New York Times Magazine, January 28, Eat food. Not too much.
Mostly plants. That, more or less, is the short answer to the supposedly incredibly complicated and confusing question of what we humans should eat in order to be maximally healthy.
May 23, · American photographer Peter Menzel and writer Faith D’Aluisio have traveled the world documenting that most basic of human behaviors—what we eat.
Witch Hazel May Work Wonders on Your Skin. Witch hazel is a shrub with a long history of medicinal use. Learn how you can grow this plant in the comfort of your own home, and how it may benefit your well-being.