Worst Foods For Gut Health
Improve your gut in 2025 by limiting these foods.
The start of the new year has many of us setting goals and thinking about how we can improve our health and feel our best.
Whether you want to lose weight, improve blood sugar levels, reduce inflammation, lower your cholesterol or blood pressure, or simply reduce your risk of disease in general, optimizing your gut health is a great goal to focus on since it impacts all of these aspects of our health (and more).
For example, last week I shared that the bacteria in the gut produce short-chain fatty acids (SCFAs) that regulate cholesterol, improve glucose tolerance, reduce visceral and liver fat accumulation, reduce satiety, and have anti-obesity effects.
Research shows that these SCFAs are abundant in healthy microbiomes, but reduced in those with gut dysbiosis “thereby contributing to various diseases” including obesity and type 2 diabetes.
This means that improving your gut health will lead to increased levels of these SCFAs that are associated with better health outcomes.
Recently I shared the #1 way to achieve microbial diversity through your diet (leading to increased levels of these SCFAs), and today we’re going to look at the opposite end of the spectrum: the worst foods for gut health that contribute to gut dysbiosis, aging, and disease.
Limiting your intake of these foods will result in a healthier gut, lower levels of inflammation, and can ultimately help you live a longer, disease-free life.
Let’s take a look at what they are.
1. Soda & Sweetened Beverages
According to microbiome expert Dr. Tim Spector, soda and sugar-sweetened beverages “are absolutely terrible” for the microbiome. He shares that drinking soda “consistently comes up as the worst thing to be eating or drinking in all the epidemiological studies.”
This includes both regular and diet soda, since high levels of sugar in regular soda and the artificial sweeteners in diet soda both alter the microbiome by increasing levels of pro-inflammatory bacteria and decreasing levels of the “good” bacteria. This leads to gut dysbiosis, leaky gut, and increased levels of inflammation throughout the body.
Try swapping out soda and sweetened beverages for herbal tea, lemon water, or sparkling waters instead.
2. Ultra-Processed Foods
According to recent research, ultra-processed foods make up 60% of the average American’s diet, and 70% of the average child’s diet.
This means that majority of calories in the average Americna’s diet are coming from fake food which has a major impact on the microbiome.
These ultra-processed foods promote inflammation, which contributes to gut dysbiosis, disease, and even cancer. This is because chronic inflammation causes cell mutations and rapid growth—the ideal environment for cancer development.
According to Dr. Timothy Yeatman, associate director at the TGH Cancer Institute“If your body is living daily off of ultra-processed foods, its ability to heal…decreases due to the inflammation and suppression of the immune system that ultimately allows the cancer to grow.”
Ultra-processed foods include:
Frozen pizza
Frozen meals
Fast food
Processed meats like ham, deli meats, sausage, brats, pepperoni, etc.
Packaged sweets, baked goods, cookies, poptarts, and candy
Refrigerated/frozen doughs and biscuits
Salty snacks like chips,
Boxed and canned meals like mac & cheese, ravioli, spaghettiOs, etc.
Most breakfast cereals
3. Hydrogenated Vegetable Oil
Research shows that hydrogenated vegetable oil disrupts the microbiome and promotes inflammation.
One study found that consuming hydrogenated vegetable oil resulted in increased levels of harmful bacteria in the gut, and decreased levels of beneficial bacteria (contributing to gut dysbiosis and leaky gut).
They also found that inflammatory makers increased, and the short-chain fatty acid (SCFA) butyrate decreased. Butyrate is known for its role in reducing inflammation and keeping the lining of the gut strong (protecting against leaky gut). Butyrate also has anti-obesity effects by reducing appetite, inhibiting fat synthesis and storage in the liver and adipose tissues, and increasing fat burning (fat oxidation).
The authors concluded that consumption of hydrogenated vegetable oil “resulted in a significant dysbiosis of gut microbiota, which may contribute to the development of chronic diseases.”
Hydrogenated vegetable oil is banned in most countries since it’s caused an estimated 500,000 coronary heart disease deaths globally per year, but is still being used in the United States and is found in many processed foods including:
Most processed baked goods like cakes, cookies, muffins, pastries, and donuts
Coffee creamers including Coffee Mate and single-serve coffee creamers found at restaurants and hotels
Majority of peanut butters
Margarine
Store-bought frosting
Many granola bars and protein bars
Flavored instant oatmeal
Microwave popcorn
Fast food
Check the ingredients list on the foods in your home this week and before puchasing foods from the grocery store to make sure you're not consuming hidden sources of hydrogenated vegetable oil (start with your jar of peanut butter).
Refer to this post for more info on hydrogenated vegetable oil.
4. Refined Vegetable Oils (aka, seed oils)
Most standard vegetable oils are processed using high heat, which destroys the beneficial fats and causes them to oxidize and become extremely inflammatory.
Research shows that consuming these oxidized oils leads to a loss in the number and diversity of good bacteria in the gut.
In addition, these inflammatory oils damage our cells and promote inflammation throughout the body, accelerating the aging process and increasing the risk of disease.
Refined vegetable oils to avoid include:
Vegetable oil
Canola oil
Palm oil
Sunflower oil
Safflower oil
Corn oil
Soybean oil
Switching from these refined vegetable oils to extra-virgin olive oil or avocado oil is a great first step to take. It’s also important to check for these oils on the ingredients list of foods you buy since they’re also found in the majority of processed foods including chips, crackers, snack foods, and even “healthy foods” like almond milk, nuts, and hummus.
As a recap, the 4 worst foods for gut health include:
Sugar and sweetened-beverages
Ultra-processed foods
Hydrogenated vegetable oil
Refined vegetable oils (seed oils)
Reducing your intake of these foods will allow your microbiome to heal and start improving, leading to improvements in all other areas of your health as a result.
Research shows that the microbiome can start to improve within days of changing your diet (by cutting out the foods that disrupt it, and adding in the foods that optimize it).
If you’re looking for some guidance to optimize your gut health, check out my cookbook Recipes For Longevity! It’s filled with over 70 recipes and a 4-week meal plan to reduce inflammation, improve gut health, and slow aging at the cellular level.
Wishing you all the health and happiness in 2025!
-xo Kate