Is a Vegan Diet Good for Gut Health?

Is a vegan diet microbiome-friendly?

As Veganuary sweeps in, it’s not merely about a trendy vegan diet change – it’s a microbiome-friendly opportunity! Wondering if going vegan can boost your gut health, microbiome and overall well-being? Let’s delve into the nuances of a vegan diet, and what you need to do to ensure it has a positive impact on your gut health.

What Is a Vegan Diet?

The vegan diet is based on the principle of eliminating any animal-based food products such as meat, fish, dairy and eggs. Aside from that, there other dietary variations that limit or fully eliminate animal products, including:

  1. Plant-based diet: A vegan diet that often prioritises the health benefits of a plant-based diet. Individuals often avoid any processed foods, and may also avoid sugar and oil. The focus here is on eating whole foods.
  2. Vegetarian diet: This diet focuses on including a wide range of natural plant-based foods such as vegetables, whole-grains, nuts and seeds. Unlike a vegan diet, a vegetarian diet still includes eggs, dairy and honey.
  3. Pescatarian diet: Pescatarian diets involve restricting meat consumption to fish and seafood only. While technically not vegetarian, pescatarians don’t consume red or white meat.
  4. Raw food vegan diet: Individuals following a raw food diet only consume food cooked at temperatures below 48°C. This diet focuses on raw fruits and vegetables, salads, nuts, seeds and avocados.

Additionally, there are countless other iterations – often adopted as part of trends – such as those who follow a keto vegan or paleo vegan diet. The key is finding what plant-based meals suit your palate and goals, and going from there.

Vegan Diet and Its Popularity

The vegan diet has steadily been rising in popularity, with many making simple plant-based tweaks. Moreover, its mainstream appeal is evident in the countless vegan products that can now be found on most supermarket shelves.

Individuals adopt a vegan diet for a collection of reasons: in protest against the animal cruelty associated with the industry, to live in a more environmentally-friendly manner, and for their health and longevity.

Although our modern society is advancing rapidly, we’re still facing the same issues of obesity, cancer and cardiovascular diseases (CVD). In fact, over the last 30 years, prevalence of all these issues are on the rise. In 2019 alone, 9.6 million men and 8.9 million women died of CVD, with more than 6 million of them between the ages of 30-70 years1.

This is where veganism comes in. According to the American Heart Association, a study found that 34% more patients on the plant-based diet had reduction of atherosclerosis than those on a standard omnivorous diet2.

Another study3 found that following a vegan diet can reduce fasting blood glucose by an average of 35%, and around five participants experienced major improvements that they no longer required glucose-lowering medications. Due to this, the number of Americans who follow a vegan diet increased 600% from 2014 to 20184.

What’s more, a recent twin study found that a healthy vegan diet led to improved cardiometabolic outcomes compared with a healthy omnivorous diet5.

Based on all this, it seems only natural that veganism has become more mainstream in the last few years. Still, how does a vegan diet affect the microbiome? Let’s find out.

Is a Vegan Diet Healthy For Your Microbiome?

It is well known that diet is one of the most important factors in shaping our gut microbiome. Veganism is known to have many health benefits such as reduced risk of cancer, cardiovascular diseases and diabetes, as the diet is generally high in antioxidants, minerals and has the potential to lower blood glucose and LDL-cholesterol levels. Yet, how does the vegan diet affect gut health?

Research has found that vegans have a significantly greater microbe diversity compared to omnivores, specifically for certain Bacteroidetes-related operational taxonomic units (OTUs). The OTUs are considered to be protective from epigenetic effects on various risk factors for chronic inflammation and chronic degenerative diseases6.

Additionally, a vegan diet has shown great effects on the Bacteroidetes to Firmicutes Ratio. This ratio is important to note as it is a potential indicator of gut dysbiosis. Bacteroidetes are a dominant beneficial bacteria species, which provide nutrients to the host and other intestinal microbes. While Firmicutes are Gram-positive bacteria that have a negative influence on glucose and fat metabolism, hence a decreased ratio is an indicator for gut dysbiosis7.

A study8 compared the bacterial composition between Indian and Chinese adults. While both populations ate diets centred around carbohydrates and vegetables, the Indian diet mainly comprised of plant-based foods. The percentage of Bacteroidetes within the microbiomes of Indian participants (16.4%) was nearly four times greater than in the Chinese (4.3%). The higher abundance of Bacteroidetes in Indians was hypothesized to be due to their lower consumption of animal products; indicating a diet lower in animal products to be associated with greater Bacteroidetes counts.

Hence, it is evident that a vegan diet does nourish the beneficial microbes in our gut microbiome.

Furthermore, another study investigated the presence of different species of Lactobacillus in people with different dietary habits. They found that Ligilactobacillus ruminis and Lactiplantibacillus plantarum were more prevalent in people following vegetarian and vegan samples, compared to omnivores9.

Nevertheless, existing research that directly compares the microbiomes of those following vegan or omnivorous diets is limited. Future studies would need to account for inter-individual differences.

Vegan Diet Advantages and Disadvantages

Prioritises an abundance of fresh fruit and vegetablesDining out can be more challenging / more need for preparation
Naturally high-fiber diet, which supports smooth digestion and reduced likelihood of constipationRisk of B12 deficiency
without proper supplementation
Increased satiety (high volume, low calorie,) meaning you can eat more food and still lose weightIncreased likelihood to experience social exclusion
Can lead to improved cardiometabolic outcomes compared with a healthy omnivorous dietSome may struggle to eat bigger portions
Positive environmental impact
Supports weight management
Lower disease risk
More affordable (if avoiding processed products)
Ethical and humane

Benefits of a Vegan Diet

Simplifying your diet to focus on vegan foods makes it easier to opt for whole foods, fruits and vegetables. Having to be more creative in the kitchen also often inspires people to experiment with gut-friendly spices (such as turmeric, paprika and fennel seeds!)

Overall, this can have a positive impact, as the default can often be to eat a SAD (Standard American Diet.) According to the U.S. Department of Agriculture, only 11% of a typical SAD consists of whole grains, beans, fruits, vegetables and nuts. The rest animal foods (32% of calories) and processed plant foods (57%).

Of course, the abundance of processed vegan products is increasingly on the rise, too. Vegan or not, it’s important to go for whole foods first.

What To Look Out For On a Vegan Diet

Overall, a vegan diet can have significant favourable effects on the microbiome, thanks to the increased intake of fiber-rich foods that are also filled with numerous phytonutrients and minerals.

Still, it is important to note that swapping from a conventional omnivorous diet to a vegan diet may initially result in some minor gastrointestinal side effects from increased fiber intake such as bloating and excess gas – luckily there are simple strategies to help you beat bloating.

The transition between omnivorous to vegan diet may also cause a temporary microbial “stress.”

A study10 found that a short-term plant-based dietary intervention advising increased fiber consumption resulted in a slight, but significant decrease in microbe diversity. The researchers suggested that this reduction in diversity might have been the result of a rapid dietary change that resulted in a temporary disruption to the microbial composition. This hypothesis of microbial “stress” also explains the slight albeit significant increase in Enterobacteriaceae (pathogenic bacteria) as a result of the intervention. This was surprising as Enterobacteriaceae abundance is typically lower on a vegan diet compared to an omnivore diet.

Despite this, the vegan diet still provides beneficial effects in the long-run. The increased fiber intake act as prebiotics that nourish the gut microbes and lead to the increased production of short-chain fatty acids (SCFAs,) such as butyrate, which can lower colonic pH, preventing the growth of pathogenic bacteria like Enterobacteriaceae11.

Probiotics in Vegan Diet

Interest in gut-friendly diets has led to a greater focus on food products containing probiotics. However, the majority of these are often made from dairy, such as probiotic yoghurts and kefir. Thus, the question remains: how can you get probiotics in a vegan diet?

Fermented beverages are often the main vegan probiotic products, such as kombucha.12 The drawback to the popularity of kombucha is that they often contain a lot of sugar. Beverages can be seen as more optimal sources of probiotics, because the digestion of liquid foods is faster, thereby reducing the contact time with bile acids and low stomach pH – supporting the survival of the probiotic bacteria.13

Still, there are a number of vegan foods that are full of probiotics. They often contain lactic acid bacteria, which can carry various gut health benefits, such as protection against infectious agents, supporting more effective immune responses, antioxidant effects as well as offering protective effects against allergies, obesity and anxiety, among others14.

Vegan Sources of Probiotics Include:

  • Sauerkraut:

    One of the best natural sources of probiotics, that can easily be made at home! Sauerkraut contains lactic acid bacteria, and can also feature three other species in different concentrations: Leuconostoc mesenteroidesLactobacillus brevis, and Lactobacillus pantarum. If you’re getting store-bought sauerkraut, make sure that its unpasteurised – otherwise the good gut bugs will have been killed off.

  • Miso:

    Available as both white and red miso, it is derived from soybeans and grains as a result of the activities of Koji enzymes and beneficial microbes. Generally, miso is known to contain Bacillus amyloliquefaciensBacillus subtilisStaphylococcus kloosiiStaphylococcus gallinarum, and Lactococcus sp. GM00515. Quick tip: turning the heat off before adding miso to your dish can help preserve even more of the gut-friendly bacteria.

  • Kimchi:

    A traditional Korean fermented food, Kimchi is one of the most popular foods in Korea and is often eaten daily. The vegetables most often used to make kimchi include baechu cabbages (Brassica rapa) and radishes (Raphanus raphanistrum), although cucumbers, spring onions and other plants are also used. Kimchi is wonderful for getting a strong dose of lactic acid bacteria, such as species of genera LactobacillusLeuconostoc, and Weissella16.

  • Tempeh:

    This fermented soy product is rich in lactic acid bacteria, and is a great addition to any salad or stew! Bear in mind that heat does cause the probiotics in tempeh to become inactive (paraprobiotics). Still, paraprobiotics also carry many health benefits and are worth including in your meals.

  • Sourdough:

    Known as the oldest form of leavened bread, sourdough is thought to have been used as early as 2000 BC by the ancient Egyptians. Opting for sourdough can give you a wonderful source of lactic acid bacteria!

  • Dairy-free yogurts:

    Certain oat, soy or coconut yoghurts can contain probiotic cultures – check the label to be sure!

  • Pickles:

    Naturally fermented pickles can be rich in Lactobacillus.

How To Adopt a Microbiome-Friendly Vegan Diet?

A vegan diet can provide tremendous benefits to the microbiome. In particular, certain gut-friendly components can help optimise this diet and ensure your gut is healthy and happy.

In particular, look for foods that contain these notable microbiome-friendly food components:

  1. Polyphenols: These naturally occurring plant metabolites can increase the abundance of probiotic Bifidobacterium and Lactobacillus17, these bacteria can provide anti-pathogenic and anti-inflammatory effects. Common polyphenol-rich foods include berries, apples and seeds.
  2. Non-digestible carbohydrates: Non-digestible carbohydrates such as oats, barley, and some fruits, can increase lactic acid bacteria and reduce Clostridium and Enterococcus species17 – otherwise known to be more pathogenic bacteria.
  3. Plant-based protein: As compared to animal protein, plant-based protein does not heighten the abundance of less favourable bacteria Clostridium and Bacteroides. It has also been shown that individuals consuming pea protein exhibit enhanced levels of beneficial Bifidobacterium and Lactobacillus, which subsequently increases their intestinal SCFA levels17.

Take Home Message

Vegan diets can have powerful properties that support your microbiome and overall health. Eating an abundance of whole fruits and vegetables can help reduce gut inflammation, while boosting beneficial bacteria and supporting your digestion and cardiovascular health. Remember, transitioning to a significantly higher fiber diet can lead to temporary side effects, such as feeling a bit more gassy and bloated as your new community of microbes build up. Take it easy and find the microbiome-friendly foods that work for you: it’s worth it!


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