Caffeine, alcohol, herbs and other food-related aspects
In this lesson I will discuss other food, nutrient and digestion-related factors that can have an effect on gut symptoms.
COFFEE/CAFFEINE
Whether coffee or caffeine affect the gut seems to be very individual. My advice: moderation – caffeine is not an essential nutrient (though some might disagree with me :D).
Caffeine has been linked to a higher risk of diarrhea. It is a stimulant that can induce GI contractions and stimulate stomach secretions. One study saw that coffee stimulated contractions in the colon in 29% of the study participants in 4-30 minutes after drinking it – however, what is interesting is that decaffeinated coffee had similar effects, so caffeine wasn’t probably what caused the effects. (1)

People with IBS often avoid coffee and caffeinated drinks, but studies are conflicting in that some studies connect caffeine with a higher risk of IBS and others with a lower risk of IBS. Studies also are often not considering the placebo/nocebo effect. (2-5) If you have noticed that you get IBS symptoms from caffeine, or if you drink a lot of other drinks that contain caffeine, there’s no harm in reducing or avoiding it (other than some withdrawal symptoms I know some get when they stop drinking coffee). Also think about whether you are subconsciously expecting caffeine to quicken your gut, as this can have an effect. There’s also no real evidence to confirm that caffeine could be helpful for constipation or IBS-C. (1,5) Moderate caffeine consumption is not dangerous, but FDA recommends getting a maximum 400 mg of caffeine per day, or 4-5 cups of coffee to avoid side effects (6).
Coffee, apart from caffeine can also have effects on gut functions (7). It can be irritating to the stomach and cause heartburn, but it also contains polyphenolic antioxidants, that are linked with numerous health benefits. There is some evidence showing coffee drinking increases the beneficial Bifidobacteria in the gut, but if there is true significance, it is not known yet. It is also not clear whether it is the polyphenols in coffee that are beneficial to gut microbes, or both caffeine and polyphenols. (8)
The effects of coffee and the compounds it contains on the gut-brain connection have also been studied. Coffee and caffeine are stimulating to the nervous system by activating the sympathetic nervous system (fight-or-flight) and increasing blood pressure. However, salivary cortisol (one of the stress hormones) was not increased. (8)
Interestingly, dark roast coffee might be more gentle to the gut than light roast coffee. This is because it is suggested that lower acidity coffee, which includes dark roast coffee, might reduce the risk of heartburn (not so much the risk of diarrhea). Cold brew and espresso are other lower acidity options. (10) I was unable to find studies discussing this, but if you are a coffee lover, feel free to try lower acidity coffee and see if it makes a difference for your gut, and don’t drink coffee on an empty stomach.
ALCOHOL

While alcohol, if consumed chronically, affects gastrointestinal motility, is harmful for the gut lining, decreases nutrient absorption, and causes inflammation (11), there is no evidence that shows that alcohol causes IBS symptoms, or that avoiding alcohol would improve symptoms.
Alcohol is certainly not something we need, so avoiding it is not bad for us. Of course, on the other hand, moderate consumption is not dangerous, and sometimes perhaps it improves our quality of life. The most common recommendation is to not exceed 1 drink per day for women and 1-2 drinks per day for men (1 drink = 1 small beer or equivalent). One thing to know is that alcohol can decrease the quality of sleep even in small amounts, so since sleep is definitely connected to gut health, this is something to be mindful about. (12)
CAPSAICIN

This is the substance in hot peppers that causes burning in the mouth. It seems to increase blood flow in the gut, and it has antioxidant properties. (11) When it comes to IBS, occasional use seems to cause IBS symptoms in some, but when used regularly it actually could decrease pain and bloating in IBS patients. This is probably why in Asian patients with IBS, reports of pain and changes in bowel habits are less than in Western IBS patients. Capsaicin also influences the gut microbiota, which has been suggested to be protective of obesity, but whether this would affect IBS is not known.
POLYPHENOLS

Polyphenols are important health promoting compounds found in fruits, vegetables, grains, tea, coffee, and wine. They provide antioxidant effects and other beneficial health effects, e.g. by lowering chronic disease risk. The body absorbs some of the smaller polyphenols, but they mostly end up in the colon where our microbiota ferments them. This is good for the gut microbes, which in turn is good for us, as you well know. Polyphenols are being recognized as a highly important factor in the health of the microbiota, along with fiber. A list of the top 20 highest polyphenol containing foods can be found here. (13) Make sure you eat fruits and vegetables every day!
HISTAMINE
Histamine intolerance can have very similar symptoms to IBS, which is why I wanted to give a bit of information what it is. Read more below in the accordion (30, 36-39).
FOOD EMULSIFIERS
These are food additives that are used to help water based and fat based components mix, and to improve food texture and stability. Western diet, which is rich in processed foods, is also rich in emulsifiers. For example, foods like ice cream, desserts, margarine, bread etc. often contain emulsifiers. (14)

Our body makes such molecules also (bile salts), but as food additives they may have a negative effect on the intestinal mucus layer, microbiota and inflammation, which are linked to the development of leaky gut, which in turn is connected to IBS. Especially polysorbate 80 and CMC (carboxymethylcellulose) have been identified to be problematic. But, these studies were done on mice, and much further research is needed. (14)
FDA considers all emulsifiers used in food “generally recognized as safe”. If you’d like to avoid emulsifiers, check food labels for polysorbate 80 and CMC, but also lecithin, mono- and diglycerides of fatty acids, carrageenan and guar gum are emulsifiers, though perhaps not worth avoiding (15). As with other restrictions, being rational is important as too many restrictions make life more difficult and can make your diet too restrictive and stressful for good health. That said, cooking and baking yourself is an easy way to limit emulsifiers as well as other food additives.
NON-NUTRITIVE SWEETENERS (NOT SUGAR ALCOHOLS)

These are food additives that provide a sweet taste to food or drink without adding any calories. They have been very popular as you can enjoy your favorite soft drink with the same calorie profile as water. FDA considers them safe at the moment (the safety of food additives are assessed periodically), although there is much controversy surrounding sweeteners. When it comes to the gut, unfavorable changes in the microbiota composition have been observed with many of the sweeteners. There may be concern for intestinal inflammation, as well. (16) Studies have also shown a connection between non-nutritive sweeteners and obesity, which is highly interesting (17).
As with other food additives, we don’t need non-nutritive sweeteners for our health, and avoiding foods with sweeteners is often easier than avoiding many other additives. That said, occasional use is unlikely to cause issues in the average person. Read on about two of the most common sweeteners.
HERBS AND SUPPLEMENTS
It is common to look at herbal remedies to ease gut issues, as they seem more natural than medications. Here I’ve gathered information about the ones I’ve heard have been used for gut health purposes and whether there is any scientific evidence on their efficacy. Since the FDA and EFSA don’t control herbal products, the quality and purity of supplemental products are more difficult to verify. Look for products that are produced in CGMP-compliant facilities and tested for purity and potency, ideally by a third-party organization such as NSF International, U.S. Pharmacopeia, or Underwriters Laboratories.
Also, while we tend to think that natural, food derived supplements and herbal remedies are safe because they come from nature, it is a fact that this is not always the case. Furthermore, many herbs can have drug-herb interactions, which could mean a higher or lower potency of the drugs you are taking, which is undesirable. ALWAYS check with your health care provider if you are interested in herbs to make sure it is appropriate for you.
Below I discuss a few of the more well known herbs and supplements used for IBS.

You’ve reached the end of the lesson, I hope you learned something new and useful! This lesson is meant to be expanded with time, so stay tuned for additions. You can also request for something to be added here and I will gladly look into it – use the contact form in the left sidebar.
You have now completed the “Diet” section of IBSwise. Amazing job! The next chapter is filled with information about perhaps the most important factor behind the evolution of IBS – stress.