​
By Melissa Blake, ND

The evidence is overwhelming: diet matters. Much of the benefit of diet is related to the impact on the gastrointestinal system.

A few signs that your digestive system may not be working at its best include:

• Gas
• Bloating
• Discomfort
• Belching
• Cramps
• Changes in bowel movements (more frequent, less frequent, painful, urgent, loose, hard, changes in color, etc.)
• A bad taste in your mouth
• Changes in appetite

When it comes to optimal digestion, many foods and supplements support a strong digestive tract, while others do not and may even cause harm. This article is a discussion on the top five foods, or food-like substances, you may want to avoid or reduce for a happy and healthy gut.
“There is no medicine you can take that will replace what you can do for your own health.”―Aarti Patel

1. Refined sugar

Sugar is everywhere, and we are doing a terrible job when it comes to consuming it in moderation. The average American is eating sugar at a rate that far exceeds the daily recommended intake.1

The gut connection:
​
Helpful bacteria in the gut rely on fiber as an energy source. Whole fruit, for example, provides natural sugars along with fiber, vitamins, and minerals. Refined sugar is just sugar, with all the good stuff removed. Essentially, a diet high in refined sugar provides little to no fiber and changes the food available to the gut microbiome. As a result, the good bacteria starve which leaves an opening for harmful bacteria to flourish.1

​2. Artificial sweeteners

Noncaloric artificial sweeteners arrived on the scene partly in an attempt to reduce the trend in weight gain attributed to sugar consumption.2 They unfortunately did not live up to their expectations.
Current evidence suggests these now common food additives contribute to changes in blood sugar that can result in an increase in appetite, a higher intake of calories, and unwanted weight gain.3 Wait! Is that not the opposite of the desired effect?

The gut connection:
​
Much of this unwanted impact may be the relationship between artificial sweeteners and the microbiome. We are still not clear exactly how these sugar alternatives work against the gut bacteria. It might be that they harm the helpful bacteria or directly promote the growth of harmful ones.4
Either way, the results are not exactly the sweet story we were hoping for.

​​Artificial sweeteners are also known as: nonnutritive sweeteners, noncaloric sweeteners, and sugar substitutes.

​3. Alcohol
​
Alcohol affects human health by influencing the function of many organs and systems, but perhaps most importantly the gastrointestinal system.5

The gut connection:

Specifically, chronic alcohol intake disrupts the microbial balance, contributing to a remarkable shift in the gut community and an increase in intestinal permeability.5,6
​
The resulting dysbiosis (imbalance in your digestive bacteria) has a negative impact on the production of important metabolites, including short-chain fatty acids and precursors to neurotransmitters and hormones.7   

In addition to the impact on the gut and associated dysbiosis, acute alcohol consumption promotes unsafe behaviors, is a stress on the liver, contributes to sleep disturbances, and is a source of sugar and empty calories.8 Not exactly news worth making a toast to.

​​4. Conventionally raised animal products
​
Animal products can provide a wide variety of important nutrients, including amino acids, B12, and iron. Problems can arise when a high intake of animal products leads to a lower intake of vegetables and other plant foods.

The gut connection:

Long-term adherence to high-protein diets, especially in the absence of plant fiber, contributes to an imbalance in gut bacteria.10,11 It makes sense, then, that a higher intake of meat, red and processed meats in particular, contributes to lower levels of protective metabolites and an increase in harmful metabolites produced by gut bacteria.12

It is not just quantity, but also quality that matters.

Conventional farming and the associated exposure to pesticides has implications for both the farmers and the environment,while organic farming promotes better animal welfare and a slightly better nutritional profile.13,14
​
A major concern related to conventionally raised animals is the extensive use of antibiotics that is contributing to resistant strains of harmful bacteria.15 Although research has not yet extensively studied the specific implications of prophylactic antibiotic use in animals to the gastrointestinal tract in humans, we can only assume this global health and environmental issue is also a gut one.15

​
​5. Conventionally grown coffee

Now, let us talk coffee.

Conventionally grown coffee is one of the most heavily chemically treated foods in the world. Think synthetic fertilizers, pesticides, herbicides, fungicides, and insecticides that have short and long-term implications for farmers and local environments.16 Reason number one to choose an organic, fair-trade option.

Here are a few more reasons to keep coffee intake to a moderate level and always choose a quality option.

The gut connection:

Drinking coffee causes an increase in stomach acid. This might be okay for the average Joe, but too much acid can irritate the stomach lining and contribute to sensation of burning and digestive distress. This irritation does not stop at the stomach but can move along the entire digestive tract, contributing to its laxative effect and promoting cramps, spasms, and diarrhea.17

When it becomes a habit, coffee can contribute to dependency and symptoms of withdrawal when trying to reduce intake. Coffee is also a diuretic and can contribute to dehydration, especially as consumption increases and it starts to replace water intake.18
​
In moderation, coffee can be a delightful morning ritual, but if you already suffer from stomach or digestive complaints, coffee is likely to make things worse.

​
​Summary:
​
Food choices play a huge role in gut health. Certain foods can wreak havoc on the digestive system by contributing to an imbalance in the microbiome, irritating the gut lining, and influencing the amount of digestive enzymes present.

An optimal diet goes beyond looking at food as simply a source of calories. Diet composition and quality are important factors to consider when it comes to optimizing function and promoting health.

Three takeaways to help improve your digestive health:

• Choose local, organic options when possible, especially animal products and coffee.
• Eat more vegetables. Aim for the ideal plate that includes 50% vegetables, 25% whole grains/starchy vegetables, and 25% protein as often as possible.
• Keep track of how you feel physically, emotionally, and mentally when you eat/drink certain foods or food-like substances. This knowledge will empower you to make decisions that best reflect your health and wellness goals.

References:

1. Di Rienzi SC et al. Adv Nutr. 2020;11(3):616-629.
2. Mooradian AD et al. Clin Nutr ESPEN. 2017;18:1-8.
3. Pearlman M et al. Curr Gastroenterol Rep. 2017;19(12):64.
4. Bokulich NA et al. Cell Metab. 2014;20(5):701-703.
5. Dubinkina VB et al. Microbiome. 2017;5(1):141.
6. Bishehsari F et al. Alcohol Res. 2017;38(2):163-171.
7. Qamar N et al. Behav Brain Res. 2019;376:112196.
8. Delker E et al. Alcohol Res. 2016;38(1):7-15.
9. U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015–2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at http://health.gov/dietaryguidelines/2015/guidelines/.
10. Russell WR et al. Am J Clin Nutr. 2011;93(5):1062-1072.
11. Singh RK et al. J Transl Med. 2017;15(1):73.
12. Zeneng W et al. Eur Heart J. 2019;40(7):583-594.
13. Nankongnab N et al. J Agromedicine. 2020;25(2):158-165.
14. Mie A et al. Environ Health. 2017;16(1):111.
15. Seal BS et al. Anim Health Res Rev. 2013;14(1):78-87.
16. Hutter HP et al. Int J Environ Res Public Health. 2018;15(8):1641.
17. Boekema PJ et al. Scand J Gastroenterol Suppl. 1999;230:35-39.
18. Seal AD et al. Front Nutr. 2017;4:40.

Melissa Blake, ND

Melissa Blake, ND is the Manager of Curriculum Development at Metagenics. Dr. Blake completed her pre-medical studies at Dalhousie University in Halifax, Nova Scotia, and obtained her naturopathic medical training from the Canadian College of Naturopathic Medicine. Dr. Blake has over 10 years of clinical experience, specializing in the integrative and functional management of chronic health issues.

Conversations surrounding the microbiome and how it impacts our health have gained significant attention. But what exactly does it mean when we talk about the human “microbiome”? The microbiome is a community of microorganisms, such as bacteria, viruses, and fungi that reside in our skin, gut, and vaginal tract.1 The microbiome aids in digestion, supports vaginal health, improves cognition, and promotes general wellbeing.1
Not all microbiomes in our body’s system are exactly the same. The gut and vaginal microbiomes differ, and understanding this difference helps us find the right solutions to avoid unwanted women’s health issues.2 The gut microbiome is more diverse, while the vaginal microbiome is more selective in bacteria strains that keep the vagina balanced and healthy. In other words, what may be good for the gut may be harmful to the vagina.2
Bacteria that help keep our gut healthy, or any bacteria that are harmful in general, can cause problems if they find their way to the vagina.3 This can occur when certain bacteria travel through the gut-vagina axis— a collection of intricate pathways connecting the vaginal tract to our gut.3  This can upset the balance in the vaginal and/or urinary tract and lead to women's health problems.3

Effects of imbalance within the vaginal microbiome

Any imbalance in the vaginal microbiome can impact a woman’s gynecological health, including:

• Overall vaginal health and wellbeing: The vagina is home to specific types of bacteria. When these bacteria are lost, it can upset the balance and lead to physical discomfort.4
• Fertility: A decline in beneficial bacteria that leads to imbalance may affect fertility and reproduction.5
• Sexual health: Vaginal imbalance may also affect intimacy and sexual health. Sexual activity may be uncomfortable.6,7

Factors affecting the vaginal microbiome

Throughout a woman’s lifecycle, different factors can upset the balance of bacteria in the vagina, including:
​

• Menstrual cycle and hormones: Estrogen helps maintain a healthy environment in the vagina, including keeping a low pH level, which is important for vaginal health. If you have high estrogen levels, you're more likely to experience an imbalance.8 This can happen to women who are in their reproductive years, those who take strong birth control pills, or those receiving hormone therapies.9
• Contraceptives: Some birth control methods have shown to alter the healthy vaginal microbiome. It’s a good idea to discuss contraceptive methods that are right for you with your physician.10
• Menopause and aging: When estrogen levels drop during menopause, it can impact the vaginal microbiome by decreasing vaginal flora, leading to imbalance.5,11
• Lifestyle: Everything from the soap you use, choice of undergarments, and the choice to practice safe sex can impact your vaginal health.7 Also, the stress in our daily lives can affect our body's balance as well. Stress can increase levels of a hormone called cortisol, which in turn can affect our estrogen levels.5,7
• Diet: Eating processed foods loaded with fats and carbs can compromise your vaginal health. It’s important to eat a balanced diet with plenty of fiber, vitamins, and minerals.12,13 And don't forget about the potential benefits of high-quality probiotics!

Visit Metagenics.com for more product education.

References:


1. Ogunrinola GA et al. Int J Microbial. 2020; 2020:8045646.
2. Amabebe E et al. Front Immunol. 2020;11:2184.
3. Brannon JR et al. Nat Commun. 2020;11:2803.
4. Han Y et al. Front Micriobiol. 2021;12:643422.
5. Lehtoranta L et al. Front Micriobiol. 2022;13:819958.
6. Gholiof M et al. Front Reprod Health. 2022;4:963752.
7. Lewis FMT et al. Obstet Gynecol. 2017;129(4):643–654.
8. Cheng G et al. Eukaryot Cell. 2006;5(1):180–191.
9. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/yeast-infection/symptoms-causes/syc-20378999. Accessed December 5, 2022.
10. Gupta K et al. J Infect Dis. 2000;181(2):595-601.
11. Szymański JK et al. Int J Environ Res Public Health. 2021;18(9):4935.
12. Neggers YH et al. J Nutr. 2007;137(9):2128-2133.
13.  Tohill BC et al. Am J Clin Nutr. 2007;85(5):1327-1334.

By Molly Knudsen, MS, RDN

According to the Centers for Disease Control and Prevention, adults need seven or more hours of sleep each night to support overall health.1 Unfortunately, a staggering 35.2% of adults fall short of this goal, experiencing what is known as short sleep duration.1 This lack of sleep can have a significant impact on both our mental and physical wellbeing.1

Getting a restful night's sleep can be a challenge for many reasons. Exposure to light, electronic media usage, and caffeine consumption late at night are all habits that have been shown to contribute to poor sleep quality.2 Mounting evidence suggests that a lack of sleep might be linked to an unexpected source: our gut health.


What is the gut-brain axis?

It’s common knowledge that sleep plays a crucial role in brain health and function. But what does gut health have to do with your sleep?
Surprisingly, your gut and brain are in constant communication. They are connected through what is called the gut-brain axis. Studies suggest a strong link between the gut-brain axis and our sleep quality, where microbiome diversity plays a pivotal role.3 The “gut” in gut-brain axis refers to the microbiome, or the collection of all microorganisms like bacteria, yeasts, and fungi that live in the intestines. The gut-brain axis is a two-way communication system. This means that the microorganisms in the gut can influence health, while a person's mental and emotional state can also impact the microbiome.4

What is known about gut health and sleep patterns?

The science of gut health and sleep is still emerging, but one recent study was able to dig a little deeper into the relationship between microbiome diversity and sleep quality.4 In this study, 40 healthy men wore an Actiwatch®, a sophisticated smartwatch, for 30 days. This device tracked their sleep patterns, from bedtime to waking up; sleep efficiency; and the frequency of nighttime awakenings. Stool samples were also collected to assess the richness and diversity of their microbiome, including the number of bacterial species and individual bacteria.
The study revealed an interesting correlation: enhanced microbiome diversity and richness were linked to improved sleep efficiency and longer sleep duration. Furthermore, a more diverse and richer microbiome was associated with fewer interruptions and disturbances during the night.
So, the key takeaway here? Our microbiome diversity likely influences our sleep patterns. In addition, other studies have found that short-term sleep deprivation can affect the balance of gut bacteria, further emphasizing the connection between the gut and brain.5 This means that not only can gut health impact sleep and the brain, but poor sleep can also have a negative effect on the gut bacteria.

What are ways to promote gut health for better sleep? 

Eat a varied diet: The more diverse the diet, the more diverse the microbiome!6 Load up on a variety of different-colored fruits and vegetables, whole grains, and lean protein sources like fish and legumes.

Eat a diet rich in fibrous foods: Adding fiber-rich foods to your diet can be a game changer for your gut health. Incorporating a diverse range of plant-based foods, such as fruits, vegetables, grains, beans, peas, and lentils, is a proactive step towards improving your overall gut health and quality of sleep.7

Eat fermented foods: Fermented foods like yogurt, kefir, kimchi, and kombucha often contain live beneficial microorganisms, which may contribute to intestinal health.8


Metagenics offers a variety of products to support gut health and restful sleep:

1. Formulas for nighttime restlessness: MyoCalm Plus
2. Formulas to support a healthy gut microbiome: UltraFlora® Balance.

References
​

1. Sleep and sleep disorders. CDC.gov. https://www.cdc.gov/sleep/data_statistics.html. Accessed January 2020.
2. Shochat T. Impact of lifestyle and technology developments on sleep. Nat Sci Sleep. 2012;4:19–31.
3. Carabotti M et al. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Ann Gastroenterol. 2015:28(2):203-209.
4. Smith RP et al. Gut microbiome diversity is associated with sleep physiology in humans. PLoS ONE. 2019; 14(10): e0222394.
5. Thaiss CA et al. Transkingdom control of microbiota diurnal oscillations promotes metabolic homeostasis. Cell. 2014;159(3):514-529.
6. Heiman ML et al. A healthy gastrointestinal microbiome is dependent on dietary diversity. Mol Metab. 2016:5(5):317-320.
7. Makki K et al. The impact of dietary fiber on gut microbiota in host health and disease: Cell Host Microbe. 2018;23(6):705-715.
8. Bell V et al. One health, fermented foods, and gut microbiota. Foods. 2018;7(12):195.

Actiwatch® is a registered trademark of Respironics, Inc.

Submitted by the Metagenics Marketing Team
​
Did you know that the majority of your immune system is in your gut?1 Think of it as a thriving rainforest, home to over 1,000 microbial species, most of which are beneficial bacteria. Your gut’s microbiome is an essential part of your immune system, helping to defend against harmful pathogens and keeping bad bacteria in check.2

Want to support your gut health? Here are 10 of the best ways to boost your beneficial gut bacteria:

1. Eat Whole Foods to Nourish Your Gut Microbiome

Your gut thrives on healthy food, so diet matters! Highly processed foods and refined sugars can starve good bacteria, allowing harmful ones to take over—a condition called dysbiosis.3,4 Instead, eat the rainbow—a variety of colorful, high-fiber whole foods that nourish your gut microbiome. Choosing organic produce can also introduce beneficial bacteria into your system.5 When you feed your good bacteria, they help keep you healthy in return.

2. Incorporate Fermented Foods for Gut Health

Fermented foods have been around for thousands of years—yogurt dates back to 10,000 BCE!6  They’re a delicious way to boost your gut health by adding beneficial bacteria to your microbiome, which contains around 100 trillion microbes. Here are some delicious ways to add fermented foods to your daily diet:

• Aged cheese
• Fermented vegetables
• Kefir
• Kimchi
• Kombucha
• Miso
• Natto (fermented soybeans)
• Olives
• Pickles (fermented)
• Sauerkraut
• Tempeh
• Umeboshi (Japanese fermented plums)
• Yogurt

​3. Select the Right Probiotics to Enhance Gut Health

Probiotics are live microorganisms that support your health when consumed in the right amounts.7 Think of them as friendly reinforcements for your gut. Choosing a high-quality, clinically backed probiotic can help introduce beneficial bacteria to your microbiome. However, not all probiotics are created equal. Different strains of probiotics offer different health benefits. Here are six things to look for when choosing a probiotic.

4. Consume Prebiotics to Support Beneficial Gut Bacteria

Now that you’ve loaded up on good bacteria from probiotic foods, it’s time to feed your new friends. Probiotics and prebiotics work together like a perfect pair. Prebiotics are fibers that resist digestion and make their way to the colon, where they become food for beneficial gut bacteria.8,9 Here are some prebiotic-rich whole foods to nourish your microscopic friends:10

• Apples
• Apple cider vinegar
• Asparagus
• Bananas (with a bit of green)
• Barley
• Buttermilk
• Celery
• Chicory root
• Dandelion greens
• Flaxseeds
• Garlic
• Honey (raw)
• Human milk oligosaccharides (HMOs)
• Jerusalem artichoke
• Jicama
• Leaks
• Legumes
• Oats
• Onions
• Rye
• Seaweed
• Scallions
• Watermelon
• Wheat bran

5. Prioritize Quality Sleep for a Healthy Gut

Your gut health and sleep are closely connected. Research shows that getting 7–9 hours of uninterrupted sleep supports a diverse and healthy gut microbiome.11 In fact, better sleep is linked to bacterial strains associated with overall good health.12,13

6. Engage in Regular Exercise to Boost Gut Health

Physical activity isn’t just great for your body—its great for your gut too. A six-week study found that exercise increases beneficial gut bacteria. But here’s the catch: when participants stopped exercising for six weeks, their microbiome returned to baseline.14 So stay active to keep your gut thriving.

7. Manage Stress Levels to Improve Gut Health

Stress has been shown to have a negative impact on gut health. Heightened stress levels can trigger an increase in bad/pathogenic bacteria, crowding out good bacteria.15,16 Try these six simple ways to reduce stress.

8. Increase Vitamin D Intake for Gut Microbiome Support

Sunlight does more than boost your mood, it also benefits your gut. A 2019 study found that UVB light exposure helps improve microbiome diversity.17 Plus, vitamin D supplements have been shown to increase the richness and variety of gut bacteria.18,19

9. How Alcohol Affects Gut Bacteria

While red wine has been known for its health benefits, too much alcohol can negatively impact your gut bacteria.20,21 The CDC’s 2020-2025 guidelines recommend no more than one drink per day for women and two for men—but also note that drinking less is always better for your health.22,23 The benefits of red wine likely come from polyphenols—powerful plant compounds found in grape skins during winemaking.24-27  These antioxidants act as prebiotics, supporting both gut health and overall wellness.28,29

Plenty of foods are packed with polyphenols, such as:30

• Apples
• Blueberries
• Coffee
• Cranberries
• Dark chocolate
• Dried oregano
• Dried parsley
• Flaxseed
• Kiwis
• Pecans
• Tahini
• Tea

10. Quit Smoking to Promote Gut Health

Smoking doesn’t just harm your lungs—it also reduces the diversity of your gut microbiome. Quitting smoking has been shown to increase gut microbial diversity, helping to restore a healthier balance.31

All of these are great ways to support the beneficial bacteria in your gut. To further enhance your gut health journey, Metagenics™ offers expertly formulated probiotic supplements.

References

1. Vighi G et al. Allergy and the gastrointestinal system. Clin Exp Immunol. 2008;153 Suppl 1(Suppl 1):3-6.
2.  Wang W et al. Gut microbiota and allogeneic transplantation. J Transl Med. 2015;13:275.
3. Gagliardi A et al. Rebuilding the gut microbiota ecosystem. Int J Environ Res Public Health. 2018;15(8):1679.
4. Di Rienzi SC et al. Adaptation of the gut microbiota to modern dietary sugars and sweeteners. Adv Nutr. 2020;11(3):616-629.
5.  Blum WEH et al. Does soil contribute to the human gut microbiome? Microorganisms. 2019;7(9):287.
6. Fisberg M et al. History of yogurt and current patterns of consumption. Nutr Rev. 2015;73 Suppl 1:4-7.
7. Hill C et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-514.
8. Charalampopoulos D et al. Prebiotics in foods. Curr Opin Biotechnol. 2012;23(2):187-191.
9. Gibson GR et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nat Rev Gastroenterol Hepatol. 2017;14(8):491-502.
10. Jovanovic-Malinovska R et al. Oligosaccharide profile in fruits and vegetables as sources of prebiotics and functional foods. Int J Food Prop. 2014;17(5):949-965.
11. Smith RP et al. Gut microbiome diversity is associated with sleep physiology in humans. PLoS One. 2019;14(10):e0222394.
12. Fei N et al. Gut microbiota alterations in response to sleep length among African-origin adults. PLoS One. 2021;16(9):e0255323.
13.  Bowers SJ et al. Repeated sleep disruption in mice leads to persistent shifts in the fecal microbiome and metabolome. PLoS One. 2020;15(2):e0229001.
14. Mailing LJ et al. Exercise and the gut microbiome: a review of the evidence, potential mechanisms, and implications for human health. Exerc Sport Sci Rev. 2019;47(2):75
15. Zeng MY et al. Mechanisms of inflammation-driven bacterial dysbiosis in the gut. Mucosal Immunol. 2017;10(1):18-26.
16. Kiecolt-Glaser JK et al. Modulation of cellular immunity in medical students. J Behav Med. 1986;9:5–21.
17. Bosman ES et al. Skin exposure to narrow band ultraviolet (UVB) light modulates the human intestinal microbiome. Front Microbiol. 2019;10:2410.
18. Bashir M et al. Effects of high doses of vitamin D3 on mucosa-associated gut microbiome vary between regions of the human gastrointestinal tract. Eur J Nutr. 2016;55(4):1479-1489.
19. Waterhouse M et al. Vitamin D and the gut microbiome: a systematic review of in vivo studies. Eur J Nutr. 2019;58(7):2895-2910.
20. Zhang X et al. Alcohol-induced changes in the gut microbiome and metabolome of rhesus macaques. Psychopharmacology. 2019;236(5):1531-1544.
21. Dubinkina VB et al. Links of gut microbiota composition with alcohol dependence syndrome and alcoholic liver disease. Microbiome. 2017;5(1):141.
22.  https://www.cdc.gov/alcohol/fact-sheets/moderate-drinking.htm. Accessed September 21, 2021.
23. https://www.dietaryguidelines.gov/sites/default/files/202012/Dietary_Guidelines_for_Americans_2020-2025.pdf. Accessed September 21, 2021.
24. https://journalsblog.gastro.org/is-red-wine-consumption-good-for-your-intestinal-microbiome/. Accessed September 21, 2021.
25. https://www.winespectator.com/articles/understanding-wine-polyphenols-health-benefits. Accessed September 21, 2021.
26. Wiciński M et al. The influence of polyphenol compounds on human gastrointestinal tract microbiota. Nutrients. 2020;12(2):350.
27. Cavallini G et al. Resveratrol requires red wine polyphenols for optimum antioxidant activity. J Nutr Health Aging. 2016;20(5):540-545.
28. Pandey KB et al. Plant polyphenols as dietary antioxidants in human health and disease. Oxid Med Cell Longev. 2009;2(5):270-278.
29. Nazzaro F et al. Polyphenols, the new frontiers of prebiotics. Adv Food Nutr Res. 2020;94:35-89.
30. Yang J et al. Polyphenols in foods. Nutri Today. 2016;51(6):290-300.  
31. Capurso G et al. The interaction between smoking, alcohol and the gut microbiome. Best Pract Res Clin Gastroenterol. 2017;31(5):579-588.