The complexity and health of the gut is increasingly becoming known as a fundamental part of human health.
There are now clear signs demonstrating the links between gut health and the immune system, mood, mental health, autoimmune diseases, endocrine disorders, skin conditions, and cancer.
Firstly, What Defines “Gut Health”?
Admittedly, phrase “gut health” is a little bit ambiguous; gut health can be categorized into two main categories:
The strength of the gut wall
This determines what substances can enter the bloodstream from the digestive tract, and stops harmful substances from entering circulation. If the permeability of the intestinal wall is increased, this may result in a “leaky gut” and cause inflammation and autoimmune conditions. Tight junctions are the protein structures on intestinal walls, and they seal the space between epithelial cells and regulate the movement of fluid, immune cells, and harmful substances between the bloodstream and the intestines .
The composition of gut bacteria
Over 100 trillion microorganisms live in the gut, mainly different forms of bacteria, and comprise what is known as the “gut microbiome”. This microbiome is responsible for encoding over 3 million genes and producing 1000’s of metabolites that influence human health, phenotype, and fitness. More importantly, the composition of the gut flora is highly sensitive to diet, and studies show that an unbalanced gut flora is linked to numerous diseases, including obesity, diabetes, heart disease, cancer, depression, and alzheimer’s .
Zinc is a necessary element of many metabolic processes and is well-known for its ability to boost the immune system.
The first signs of the importance of dietary zinc for improving intestinal permeability was in malnourished guinea pig models .
Since then, studies have found that zinc supplementation can help to strengthen the gut lining in patients with crohn’s disease (an inflammatory bowel disease) , and does so by modifying the tight junctions of the intestinal lining to limit gut permeability .
This has help crohn’s patients in remission and contributes to a reduced risk of relapse .
Dietary fiber is an indigestible component of plant foods. Due to this, it is not digested in the small intestine, passing through to the large intestine where it actually feeds some forms of “healthy” bacteria that rely on fiber to survive and function properly.
Yes, you eat the fiber first, then your gut bacteria eats the fiber (you are basically a superorganism!).
The type of bacteria which survive off fiber produce beneficial nutrients for the body (via fermentation), including short-chain fatty acids like acetate, propionate, and butyrate .
Importantly, these short-chain fatty acids can feed cells in the colon and effectively reduce gut inflammation, preventing the onset of digestive disorders like irritable bowel syndrome, crohn’s disease, and ulcerative colitis.
In addition, research has suggested that butyrate may stimulate mucus production and improve tight junctions in the lining of the intestinal tract .
Even when studies have purposely used substances to disrupt the structure and function of the intestinal wall, such as acrylamide, fiber has been found to abolish the detrimental effects and prevent damage from occurring .
As side benefits, the short-chain fatty acids produced from gut bacteria can improve satiety signalling, reduce hunger levels, lower cholesterol metabolism, and decrease fat storage.
Probiotics are living microorganisms that, when ingested, provide numerous health benefits.
Most probiotics tend to be some type of healthy bacteria, but they can also possibly be a form of yeast.
Supplementing with probiotics is becoming increasingly popular to try and rid gastrointestinal issues, avoid infectious illnesses, and improve overall health.
The problem is that because there are many different types of bacteria that can be included in a probiotic supplement, it is hard to categorize them into one group. Clearly different probiotic bacteria will offer different health benefits.
This being said, the most common types of bacteria include lactobacillus and bifidobacterium – these bacteria have different species, and each species has many strains.
In simple terms, by consuming these types of bacteria it may be a therapeutic strategy to improve the microbiome diversity and bacterial composition of the gut.
So far, the research has provided evidence for the efficacy of probiotic supplementation. For example:
- 3 months of probiotic supplementation after intense exercise reduced zonulin levels – a key marker of gut leakage .
- Probiotic supplementation has shown to modulate the amount of tight junction proteins at the cell boundaries, increase intestinal barrier function, and prevent or reverse adverse effects of pathogens   .
- Probiotic administration for 4 weeks was associated with increased brain activation patterns in response to emotional memory and decision-making tasks, and improved behavioral measures and memory performance .
- Probiotic supplementation has shown to induce an anti-inflammatory immune response characterized by decreased frequency of pro-inflammatory molecules 
- A meta-analysis analysis provided evidence for beneficial effects of probiotic supplementation in preventing diarrhoea, respiratory tract infections, cystic fibrosis, and eczema .
Improving gut health is mainly a case of eating from a diverse range of food groups, and avoiding processed foods with high amounts of sugar, oil, and additives.
However, supplementation may be able to aid the improvements to gut health once a suitable diet is already in place.
The best supplements to achieve this are zinc, fiber, and probiotics. They all work by independent mechanisms, but will all help to either strengthen the gut wall or improve the composition of gut bacteria.