We get it. For every list of unhealthy foods you find online, your list of health-proclaiming or comfort foods gets shorter. It’s hard to navigate nutrition information when faced with contradictory advice, and we all need to eat. While no food’s effects exist in a vacuum or are isolated from other influences, your health, which can fluctuate with different needs, can also predetermine what is harmful versus beneficial. While research studies significantly differ, this article reviews a few of the currently regarded worst foods for impaired digestive function often found in (or presenting a risk for) autoimmunity, and how you can lessen the blow without going hungry.

Why Is Gut Health Important? 

While the special energy-producing structures called mitochondria are famously considered the powerhouse of the cell, the gastrointestinal (GI) tract could be the powerhouse of the entire body. Although internal to us, the GI tract is the primary place where the outside world (i.e., food, medicines, some bacteria, viruses, and the like) comes into contact with our internal world. The organs of the intestinal tract help food move through, while signaling for digestive juices and enzymes to extract nutrients and materials to nourish our cells and dispose of what is not useful. (Source)

But the digestive tract isn’t only the organs and parts (mouth, esophagus, stomach, small and large intestines, pancreas, liver, anus) we associate with it. Digestive and immune functions are closely related to the functioning of our GI tract barrier, or gut lining, and to the gut microbiome, the GI tract’s massive and diverse microbial population. 

If that sounds a little off-putting, rest assured that human health is closely related to our gut microbiome’s thriving diversity and balance. Actually, beneficial gut bacteria help us by synthesizing some vitamins and amino acids from food, and by creating short-chain fatty acids that support colon health. On the other hand, microbiome imbalance is connected to many conditions and diseases inside and outside the GI tract, showing us that what happens in the gut can influence any body system. (Source)

An impaired gut lining, or increased intestinal permeability known as leaky gut, can promote ongoing immune system activation (inflammation) in the body. Additionally, it can play a role in intestinal dysbiosis, or an imbalanced microbiome, which also promotes chronic immune system activation, and is implicated in many conditions both inside and outside the GI tract. Increased permeability and dysbiosis occur with most autoimmune conditions, indicating that the gut is critical for managing autoimmune health and reducing chronic inflammation. (Source, Source)

What’s Food Got to Do With It?

The food you eat is raw material not only for your direct energy use (and enjoyment) but for your gut microbes, which can’t easily be separated from you. Different foods can affect populations of harmful and beneficial microbiota in your digestive tract as those microbes adapt to your diet, and the food itself can introduce new bacterial, viral, or fungal components to your microbiome. Additionally, especially for those with autoimmunity, the breakdown products of foods can either promote immune activity or be anti-inflammatory, and induce either a leakier or a more intact gut lining. Food has enormous potential and sway within our bodies, so if your health is in disrepair, you may want to consider a few of the worst foods for your gut. (Source, Source)

5 Worst Foods for Gut Health

Supporting both microbiome balance and intestinal lining function is key to improving digestive health and autoimmune conditions. Here are a few foods and ingredients that impair the balance of intestinal bacteria or the function of the lining, as well as some simple ways to rebalance your tract.

1. Processed Red Meats

Regular intake of processed red meats has long been associated with the risk of intestinal and colorectal cancers and inflammatory bowel disease. Meats such as hot dogs, pepperoni, salami, and bacon that are preserved by salting, smoking, or use of other additives creates breakdown products that can influence gut microbiota, cause oxidative damage (inflammation), and are toxic to the gut lining. Consistent intake of processed red meats can create an intestinal environment that promotes inflammatory processes. This may be due not only to the breakdown products but also because a meat-centered diet tends to be lower in fiber and short-chain fatty acids. (Source, Source, Source)

Food for Thought

There is a benefit to balancing your plate. Studies have shown that including vegetables containing magnesium and resistant starches in the same meal with red meat can counter some potential damage to the intestinal tract. Analysis of dietary intake in less industrialized countries, as well as dental studies on ancient humans, suggest that significantly higher fiber intake protects against cancer and inflammatory bowel diseases and supports a thriving and diverse balance of beneficial bacteria. (Source)

2. Gluten

Several studies have found that gliadin, a protein component of gluten, can react with an intestinal lining regulator protein called zonulin, leading to increased intestinal permeability in susceptible individuals. For those with already dysbiotic guts (which are found in many autoimmune conditions), gluten can have a big role in worsening dysbiosis and the symptoms that can go with it, and avoiding or limiting gluten may help reduce symptoms.

However, research also shows that following a gluten free diet if you don’t have celiac disease or non-celiac gluten/wheat sensitivity can upset the balance of your gut microbiome and affect the way you metabolize starch, decrease production of important short-chain fatty acids, and increase your risk of nutrient deficiencies. This means that individuality plays a role in the benefits and effects of removing gluten. (Source)

Food for Thought

Despite the risks in healthy individuals brought on by a gluten free diet, abstaining from gluten if you have GI symptoms or non-celiac gluten sensitivity may help resolve symptoms, improve intestinal permeability, and significantly improve quality of life. Additionally, the quality of a gluten free diet is important — along with avoiding gluten, you need to make sure you’re taking in the nutrients you need. Increasing non-gluten resistant starches and non-processed whole foods can support nutrient intake and gut repair. (Source)

3. Artificial Sweeteners

Having something sweet without the detrimental health effects of sugar was the promise of non-nutritive sweeteners such as aspartame (found in diet soda) and erythritol (a sugar alcohol found in packaged snacks, especially of the low-carb or keto variety). It turns out it was too good to be true, as we now see that blood glucose balance can still be affected by artificial sweeteners, and their effect on the gut microbiota is not so sweet, as they can diminish diverse and healthy populations. What’s more, artificial sweeteners such as aspartame and saccharin promote intestinal cell death and intestinal permeability, and new evidence shows that the erythritol we now consume (via processed foods), though minimally absorbed in our GI tracts, can make blood more prone to clotting and increase the risk for heart attacks and strokes. (Source, Source, Source)

Food for Thought

Current insights about the gut–brain connection relating to sugar and artificial sweetener intake reveal that consumption of sweet things is first detected by cells in our guts, which then deliver messages to our brains within 60–800 ms (milliseconds). This is quite different from an understanding of appetite and satiety that is driven by the process of digestion. While several factors can influence cravings, microbiome populations can actually drive our hands in the foods we reach for, and a consistent need for sweets may mean we have some dwindling beneficial microbes that need our support. (Source, Source, Source)

4. Food Additives

Food additives like emulsifiers (such as carboxymethyl cellulose, polysorbates, and carrageenan) in processed foods have been designated Generally Recognized as Safe (GRAS) by the FDA. They are so common that up to 60% of calories consumed in the United States is ultra-processed foods, where ingredients are components of foods that have been chemically or mechanically altered and contain food additives.

One problem with food additives like emulsifiers is that they have been shown to breach the mucus barrier of the protective gut lining and increase intestinal permeability. They have also been connected to changes in the bacterial balance of the microbiome, which can damage the digestive tract and is associated with risk of inflammatory and chronic diseases. (Source, Source, Source)

Food for Thought

The list of potentially harmful foods (or food-like substances) grows longer, and so does the list of potentially beneficial food substances from plants, called polyphenols, on gut barrier function and microbiome balance. Polyphenols, in contrast to food additives, are unaltered components (except by cooking or supplement forms) of whole foods that offer support for the digestive tract. For example, quercetin (found in onions and apples), curcumin (found in turmeric), kaempferol (found in kale, spinach, broccoli, and beans), and other prebiotic foods have a role in regulating tight junctions of the intestinal lining. While it can seem like processed foods dominate the food landscape, know that healing support can be found in going back to the basics of simple plant foods. (Source)

5. Alcohol

Alcohol consumption is associated with intestinal dysbiosis and impaired gut barrier function. However, the specific type of dysbiosis caused by alcohol use affects short-chain fatty acid production, which may increase the risk of bowel diseases, including cancer.

Additionally, while occasional alcohol use is not likely to have a significant effect on your nutritional status, long-term excessive use is associated with deficiencies of important nutrients such as vitamins A, B1, B2, C, D, E, and K, as well as magnesium, folate, and more. These deficiencies not only rob your body of needed nutrients, they make liver damage more likely. (Source, Source, Source)

Food for Thought

While alcohol has been linked to an increased risk of disease starting with interactions in the gut, there may be at least one exception to the “rule” of alcohol as a worst food for gut health, and that is with wine — specifically resveratrol, the polyphenol found in grapes, blueberries, raspberries, and mulberries. Resveratrol has been found to downregulate inflammatory immune cells, so there may be a particular benefit in occasionally enjoying a glass of wine, alcoholic or non. (Source, Source)

Additional Resources

In addition to the resources listed in this article, we recommend checking out:

The National Institutes for Health: The Healthy Microbiome

Time Magazine: What We Know About Leaky Gut Syndrome

The Bottom Line

Much of your immune system resides in your gut, and if you have an autoimmune condition attending to the health of your gut lining and microbiome plays an important role in quelling inflammation and chronic immune activation. While the list can feel limiting, many powerful components in plant foods can support gut health. Sometimes it’s not only about what you cut out, but also what you add to your diet.

Navigating food’s impact on your health can be challenging, but the team at WellTheory are experts at this very task. Learn more about how we can support your autoimmune health journey.