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The Healf Source
Are These The Worst Foods For Your Gut Health - How To Fix Your Digestion
Written by: Pippa Thackeray
Written on: February 3, 2025
Some foods work with your gut while others have a less friendly relationship. A diet heavy in processed ingredients, sugar, and artificial additives can throw important digestive processes off, leading to gut flora imbalance and a plethora of uncomfortable symptoms. Therefore, knowing the foods to avoid for gut health, is the first step in keeping your microbiome on your side.
The term “gut health” has earned itself a reputation for being enigmatic, to say the least. It seems the more people are researching it and discussing it, the easier it is for one to fall down the rabbit hole. But the path to good gut health doesn’t need to be a minefield of indecision. That’s why we have devised some very simple and science-backed steps for you to try in order to be in tune with your digestive system and the amazing health benefits that a great gut microbiome has to offer on a systemic level.
Defining the “microbiome”: What does it mean for our health?
“Gut Microbiome” as a phrase simply refers to the trillions of bacteria and other microbes, such as fungi, viruses, and archaea living in your gut. While the small intestine does harbour some bacteria, the large intestine (a.k.a the colon) contains the highest microbial density in the human body, making it a primary focus of microbiome research.
We are only just uncovering the tip of the iceberg in terms of understanding health implications and the worst foods for digestion, specifically those effects attributed to the gut microbiome. The health of your gut microbiome spans more than your gut, studies show that it affects nearly every organ system in the body. For example, the gut microbiome may even affect heart health and cholesterol. When balanced, this microbiome works wonders: digesting food, producing essential nutrients, regulating the immune system, and even influencing our mood.
But disrupt this delicate harmony, and the trouble begins. Poor diet, stress, and antibiotics can all throw gut flora off balance, leading to digestive issues, inflammation, and more serious long-term health concerns.
The top offenders: Foods that sabotage proper digestion
Ready for the “no list”? While the research can often be conflicting, leading to arguments, many experts can agree on these top culprits for poor gut health all-round. These foods are famous for encouraging harmful bacteria and inflammation while starving beneficial microbes.
Highly or “Ultra” processed, versus processed foods:
Processed foods, like a really good-quality artisan sourdough with minimal ingredients, undergo minimal alterations to enrich flavour or aid in preservation, while ultra-processed foods are industrial creations packed with additives, preservatives, and artificial ingredients that strip them of their natural integrity, their shelf life is often increased far beyond what is natural as a result.
Such added (and often unnecessary) ingredients are known through consistent research to lead to a lot of inflammation, discomfort and disruption to the gut lining and gut microbiome.
Too much sugar, we are repeatedly told, is never a good idea. Why? It fuels harmful bacteria and yeast in the gut, promoting an imbalance that can lead to digestive distress. Artificial sweeteners like aspartame and sucralose are often not a better option. Studies show they can alter bacterial gene expression and slow glucose metabolism.
Cooking oils used in fried foods (often chemically processed seed oils) contain high levels of omega-6 fatty acids. It is hypothesised that, in excess, these fats can contribute to inflammation and disrupt the gut’s natural balance.
It is important not to condemn all seed oils, however. Most seed oils in highly processed foods and in bottles on the supermarket shelves are refined. This process of refining involves using solvents and heat to extract the oil from the seeds. It is also recommended to look for cold-pressed oils in dark coloured glass packaging to minimise the risk of poor health from seed oil consumption. You can read more about the nuances of seed oils in our dedicated article .
The effect of poor quality fats can further be linked to oxidised fats from high heat exposure. These are commonly low quality oils that break down under high heat, creating harmful compounds that irritate the gut lining and fuel inflammation. This effect is further compounded by the reheating of fats. Oxidised fats disrupt gut bacteria, encouraging the growth of harmful strains while weakening beneficial ones. Oils more tolerant to heat include ghee, coconut oil and avocado oil.
Fibre feeds beneficial gut bacteria, keeping digestion smooth and non-beneficial microbes at healthy levels. Diets low in fibre, often heavy in white bread, refined grains, and ultra-processed snacks, can starve these helpful bacteria, leading to imbalances that impede our health.
Soluble and insoluble fibres explained:
As mentioned previously, the gut is an environment home to around 100 trillion bacteria, some beneficial and others harmful. Therefore, providing both types of fibre nourishes the good bacteria, strengthening their dominance. Meanwhile, neglecting your gut bacteria through poor levels of fibre consumption can lead to them irritating the protective mucin layer of your intestinal lining, resulting in microscopic leaks and the entry of unwanted chemicals into your bloodstream, ultimately resulting in inflammation. This condition is referred to as increased intestinal permeability.
Soluble fibre in food items such as Brussels sprouts, bananas, oats and avocados forms a gel-like substance in the gut, slowing digestion and stabilising blood sugar levels. Insoluble fibre offers a different advantage by acting as a gentle brush within your colon, sweeping away all dead cells and lowering your risk of colon cancer.
Antibiotics are life-saving when necessary, but their overuse, particularly in animal farming, can severely harm gut health, particularly that concerning our microbiome. Their job is to kill off the harmful, disease-causing bacteria, but in doing so they will wipe out beneficial strains too, leaving the gut vulnerable to microbial overgrowth, imbalance and the manifestation of uncomfortable symptoms including gastro-oesophageal reflux disease (GORD), bloating and constipation and diarrhoea.
The best foods for gut health
Foods that nourish and replenish your microbiome can make a huge difference. These microbes handle the tough job of breaking down complex carbohydrates and fibres that our bodies can’t digest alone, producing important nutrients as byproducts.
These contain beneficial bacteria that help repopulate the gut. The best sources include:
- Yogurt (opt for unsweetened, live-culture varieties)
- Kimchi and sauerkraut
- Kefir
- Kombucha
Prebiotics are the fuel for good bacteria. You can find these in:
- Garlic, onions, and leeks
- Asparagus and artichokes
- Bananas (particularly under-ripe ones)
- Oats
A whole food diet is about eating foods in their most natural state, minimally processed, free from additives, and as close to their original form as possible. Think fresh vegetables, whole grains, legumes, nuts, and high-quality proteins, without the long ingredient lists or artificial tweaks. It's food as it was meant to be eaten.
Therefore, a gut-friendly diet isn’t just about probiotics and prebiotics, it’s about a variety of whole foods, including:
- Fermented dairy (like cottage cheese and traditional buttermilk)
- Cooked and cooled potatoes or rice (which contain resistant starch, great for gut bacteria)
- Offal (organ meats), as a source of gut-supporting Vitamin A
Ten simple ways to maintain gut balance through diet and lifestyle
Restoring gut health is also about maintaining good habits.
Both soluble and insoluble fibre feed beneficial gut bacteria, support digestion, and help maintain a healthy intestinal lining.
Excess sugar feeds harmful bacteria, while some artificial sweeteners may disrupt gut microbiota and metabolic processes.
Allowing time between meals gives your digestive system a break, while erratic eating patterns can disturb gut bacteria. Your liver also prefers a predictable rhythm of eating, so try to eat around the same time everyday (on both weekdays and weekends).
Exposure to soil, fresh air, and natural environments can diversify the microbiome and support immune function.
Pay attention to how foods make you feel, bloating, discomfort, or sluggish digestion can be signs that your microbiome needs a helping hand.
The more variety, the better. Different bacteria thrive on different nutrients.
Choosing whole, unprocessed foods ensures you get all the nutrients and fibre your gut needs without harmful additives or preservatives.
Chronic stress negatively impacts gut bacteria, so regular exercise, meditation, or even a simple ritual like a daily walk can help for some.
Water helps fibre do its job, keeping digestion running smoothly.
Poor sleep is linked to imbalances in gut bacteria.
Probiotic supplements can support gut health, especially after antibiotics or periods of poor diet. Not all probiotics are created equal, so look for well-researched brands like Optibac , Symprove , and Wild Nutrition. You can also explore a broader selection of gut health products and probiotics at Healf.
Final thoughts
There is perhaps a lot of truth to the phrase, “Trust your gut.” If you want to support your digestion and overall wellbeing, the choices don’t need to be overly complicated and intuition counts for a lot.
Your gut health depends largely on what you put into it. Good gut health is not simply about identifying the worst foods for gut health, it is also a reflection of a healthy liver and a system able to overcome the burdens our environmental toxins can place on us. Therefore, reducing toxins, via the air we breathe and the products we apply to our skin, also impact our gut health.
Coming back to gut flora imbalance, as we have covered — processed foods, excess sugar, fried foods, and antibiotics can wreak havoc, but a diet rich in probiotics, prebiotics, and whole foods can restore some harmony to the gut.
This article is for informational purposes only, even if and regardless of whether it features the advice of physicians and medical practitioners. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. The views expressed in this article are the views of the expert and do not necessarily represent the views of Healf
Pippa is a content writer and qualified Nutritional Therapist (DipNT) creating research-based content with a passion for many areas of wellbeing, including hormonal health, mental health and digestive health.
As a contributor to The Healf Source, she regularly attends seminars and programmes on a plethora of contemporary health issues and modern research insights with a drive to never stop learning. In addition, interviewing experts and specialists across The Four Pillars: EAT, MOVE, MIND, SLEEP.
In her spare time, she is an avid swimmer, mindfulness and yoga lover, occasionally bringing a raw, honest approach to the topics she faces. You may also discover some personal accounts of eye-opening wellbeing experiences amidst the reality of a disorientating, and often conflicting, modern wellbeing space.
