High-fiber foods improve gut microbiome in type-2 diabetes mellitus and healthy individuals
By Ifeanyi O. Oshim
Table-farm foods such as onions, garlic, ginger, watermelon, cucumber, avocado, and carrots have long been in existence in our locality (South East Nigeria). So, they are not grown in some far away place – they’re on our doorstep. It can be said that some of them have a particularly delicious flavor without even considering their nutritional and medicinal properties.
Some of these foods may have made up an important part of the diet of pyramid-builders from more than 3,500 years ago: it says in the fourth book of Moses, Numbers, that while the Israelites wandered in the Sinai desert, they yearned for the foods they had eaten in Egypt. Specifically, they mentioned onions, garlic, and leek (Numbers 11:5).
“We remember the fish, which we did eat in Egypt freely; the cucumbers, and the melons, and the leeks, and the onions, and the garlick” [Numbers 11:5]
But the fiber in these foods has important benefits for health, and may even help prevent chronic disease such as diabetes, colon cancer, and hypertension.
Several lines of evidence suggest that a high-fat and low-fiber diet could lead to gut microbiome imbalance, characterized by an increase in the ratio of Gram-negative bacteria (Bacteroidetes) to Gram-positive (Firmicutes). This in turn is linked to chronic inflammation and insulin resistance and ultimately, obesity, diabetes, and other metabolic disorders (Oshim et al.,2020). This evidence supports Jean Anthelme Brillat-Savarins’ statement that says, “Tell me what you eat, and I will tell you what you are”.
Indeed, the prevalence of metabolic disease, especially Type-2 diabetes mellitus, in Nigeria is increasing in alarming rate.
The novel research on human microbiomes in relation to diabetes mellitus prompted me to conduct this project: ‘Role of gut microbiome in Type-2 diabetes and healthy individuals in Nigeria’ (Oshim et al.,2020) [http://doi.org/10.5281/zenodo.4050381]. Using the 16S rRNA amplicon metagenomics approach, one can now begin to appreciate these bacterial communities in the gut that may exist as ‘good’ gut bacteria and ‘bad’ gut bacteria associated with health and diseases respectively (Anukam and Agbakoba, 2017).
What bacteria in your gut support health?
In this present study, we discovered many ‘good’ beneficial gut bacteria in apparently healthy individuals compared to those with Type-2 diabetes. These bacteria that are present in the gut of healthy individuals were Butyrate-producing bacteria, propionate-producing bacteria and mucin-degrading bacteria, respectively (Oshim et al., 2020). They play a major role in our health, as follows: First, the specific good bacteria in the gut break down foods enriched in fibers, producing smaller molecules called short-chain fatty acids (SCFA) such as butyrate, propionate and acetate which normalize intestinal permeability. Second, the bacteria are not only involved in the alteration of a metabolic pathway that produces fatty acids from excess carbohydrates via de novo lipogenesis, but also, they are associated with a metabolic pathway that synthesizes glucose from non-carbohydrate carbon substrates through gluconeogenesis. Third, they also cause the reduction of by-products of the metabolism of fat in adipose tissues as free fatty acid production by all body fat tissues or organs – muscles, liver, etc. (Whang et al., 2019). These effects contribute to reduced food intake and to improved glucose metabolism. Propionate is primarily used in the liver for gluconeogenesis and butyrate is a major source of respiration for the ceco-colonic epithelium. Propionate can also bind to receptors called G protein coupled receptors (GPR)-43 expressed on lymphocytes in order to maintain appropriate immune defenses against any form of foreign bodies or pathogenic bacteria in our system (Topping and Clifton, 2001). Butyrate activates another receptor called peroxisome proliferator-activated receptor-γ (PPAR-γ) found in colonocytes, leading to oxygen consumption, a phenomenon contributing to maintenance of anaerobic conditions in the gut lumen and providing a conducive environment for good gut bacteria to thrive in our body. Acetate can be taken up by the liver or delivered to our peripheral tissues and metabolized by muscle cells for energy. In addition, acetate functions as a substrate for cholesterol synthesis.
Furthermore, we found that the Akkermansia muciniphila proportion in healthy individuals in this study was higher than in those with Type 2 diabetes mellitus. Akkermansia muciniphila is a Gram-negative, mucin-degrading bacterium that lives in the gastrointestinal tract of humans, which protects the integrity of the intestinal epithelium against foreign invaders and toxins. Specifically, A. muciniphilia has been shown to reduce high-fat-induced endotoxaemia, which develops as a result of the impaired gut barrier (Everard et al., 2013).
What bacteria in your gut do not support health?
Similar 16S rRNA metagenomic studies on gut microbiome in type-2-diabetes mellitus have been conducted which show the higher proportion of ‘bad’ bacteria in the gut of people with T2 diabetes compared to healthy individuals. These bacteria include Prevotella copri, Bacteroides vulgatus and Escherichia coli and are mainly Gram-negative bacteria that produce toxins that cause chronic inflammation in immunocompromised individuals such as those with Type-2-diabetes mellitus (Oshim etal.,2020). These bacteria are associated with diabetes and obesity etiology in the following ways:
They cause an increase in bacterial release of toxic components called lipopolysaccharide (LPS) inside our body.
They trigger our body to produce an immune system reaction to fight against the toxin in our circulatory system.
They cause an increase in the number of ‘bad’ gut bacteria and their toxins to deliver them to our body fat tissue, resulting in a robust immune system response to fight against them.
Our specific body cells that store fat cause the release of more by-products of fat metabolism within our system.
They cause a drastic reduction of our immune system
There will be increased LPS, free fatty acids, and cytokines in our circulatory system via portal circulation and also a decrease in the activities of liver cell and insulin production respectively.
They cause a continuous increase in the movement of LPS, FFA, and cytokines into our circulatory system through systemic circulation that negatively affect the activities of B-cell and systemic insulin sensitivity in our body (Conrad and Weest, 2014). These effects contribute to lower mucus thickness in the gut, decrease butyrate and propionate producing bacteria, and make L-cells secrete fewer gut peptides. A lack of PPAR-γ activation leads to higher oxygen availability for the microbiome at the proximity of the mucosa and increases the proliferation of Enterobacteriaceae with greater numbers of opportunistic pathogens (Oshim et al.,2020).
Fructan-containing foods:
Tomato and Onion salad. You can chop onions with tomatoes and extract juice from the mixture. Contains ~9 grams of fructans per cup.
A baked sweet potato with canned beans and chopped avocado. Try mixing these together and topping with melted cheese. Contains ~6 grams of fructans per cup.
3. Grind watermelon with cucumber and extract juice from the mixture. Contains ~1 gram of fructans per cup.
4. Grind garlic and ginger with carrots and extract juice from the mixture. Contains ~1 gram of fructans per cup
The study also revealed that xylan alpha-glucuronosyltransferase gene involved in the metabolism of non-digestible fiber was switched off in T2DM patients (Oshim et al.,2020). This could be attributed to the high abundance of ‘bad’ gut bacteria and low abundance of beneficial gut bacteria in obesity related-T2 diabetes (Oshim et al.,2020).
However, the high prevalence of Type 2 diabetes mellitus may be drastically reduced in Nigeria, once we improve on table-farm foods like fresh vegetable and fruit, some of which are highly enriched in fibers (prebiotics). For instance, studies have demonstrated that consuming vegetables and fruit help to keep your gut healthy by feeding a diverse collection of bacteria. Gut bacteria love to feed on food that constitute fructans and cellulose in abundance.
How can you boost fiber intake?
Fructans are high-fiber natural carbs found in onions, garlic, wheat and other plant foods. You should know that fructan fibers are more likely to survive longer in your gastrointestinal tract, and that’s good for a healthy gut. You should be careful whenever you are preparing any food enriched in fibers because heat breaks down certain fibers, so cook fructan-rich foods as little as possible to get the most benefit.
Cellulose is the insoluble fiber your body can’t digest. It’s found in foods such as carrot peels and asparagus stalks, especially the tough part is highly enriched in cellulose. You should avoid peeling the carrot before you eat it. You should try to incorporate more whole fruits and vegetables into your meals--peels, stems and all--to help keep your gut healthy.
Sadly, most of us get only about half the total daily fiber we need, and even less of the super-beneficial fructans. But many studies have suggested that upping your fiber intake can improve your gut bacteria fast--sometimes in as little as five days.
Right now, you won’t find live cultures of Akkermansia muciniphila in food sources but you can enhance the abundance in your gut by eating polyphenol rich foods like fruit and vegetables. Polyphenols are also thought to have a key role in the anti-obesity and anti-diabetic effects of Akkermansia muciniphila too.
The fiber-rich foods listed below-all good-to-excellent sources of fructans and polyphenols-can get you off to a great start to modulate your gut bacteria. Just remember to take it slow. Adding more fiber gradually will help you avoid gas and bloating as well as maintaining the glucose level in your body. Some people have fructan intolerance, so check with your doctor first if you have concerns.
Generally, it is a very exciting moment to participate in this kind of research. Some table-farm foods should now not only be considered appetizing but as prebiotics to our body.
Ifeanyi O. Oshim is a PhD student in the Department of Medical Laboratory Sciences, Faculty of Health Sciences and Technology, College of Health Sciences, Nnamdi Azikiwe University, Nnewi Campus, Nnewi, Anambra State, Nigeria.
Ifeanyi is being supervised by Dr. Kingsley C Anukam and Prof. Nneka R Agbakoba.
References
Agbakoba,N.R (2018).Pondering the wonders of bacteria.44th inaugural lecture of Nnamdi Azikiwe University,Awka.
Anukam,K.C and Agbakoba, N.R (2017). A comparative study of the oral microbiome composition of healthy postmenopausal, premenopausal, and prepuberal Nigeria females, using 16s rRNAmetagenomics methods. Nigerian Journal of Clinical practice. 20(10):1250-1258.
Conrad, D and Weest, S(2014).Bacterial products, changes in adipose tissue lead to insulinresistance and decrease insulin release.Physiology.29:304.
Everard, A., Belzer,C., Geurts, L.,Ouwerkerk,J.P., Druart,C., Bindels,L.B., Guiot,Y.,Derrien,M., Muccioli,G.G and Delzenne,N.M (2013). Cross-talk between Akkermansia muciniphila and intestinal epithelium controls diet-induced obesity. Proceedings of National of Academy of Science USA.110:9066–9071.
King James Bible (Numbers 11:5).
Oshim,I.O., Agbakoba, N.R., Oguejiofor, O.C and Anukam, K.C (2020).Gut microbiota compositions and Modulation of Bacterial metabolic Functional genes in Type2 Diabetes Mellitus individuals,Anambra State, Nigeria. Journal of Medical laboratory Science;30(3):136-150.
Topping, D.L and Clifton, P.M(2001). Short-chain fatty acids and human colonic function: roles of resistant starch and non-starch polysaccharides. Physiology Review. 81(3):1031–1064.
Whang, A., Nagpal,R and Yadav, H(2019). Bidirectional drug-microbiome interactions of Anti-
diabetes. Ebiomedicine.39:591-602.
Wu,G.D., Chen,J., Hoffmann,C., Bittinger, K., Chen,Y.Y., Keilbaugh,S.A., Bewtra,M., Knights,D., Walters,W.A and Knight,R(2011).Linking long-term dietary patterns with gut microbial enterotypes.Science.334:105–108.