Irritable Bowel Syndrome, also known as IBS, is a common but uncomfortable gastrointestinal disease or condition that affects the intestines. Individuals with IBS experience a group of symptoms that affect their digestive system. These symptoms include abdominal pain and cramps. Additionally, you may also have frequent diarrhea, constipation, or both.

IBS is categorized by researchers based on the way your stools (poop) look on the days you are experiencing symptom flare-ups. Most individuals with IBS have normal bowl movements on some days and abnormal bowl movements on others. The abnormal days define the kind of IBS you have, which includes:
IBS with constipation (IBS-C): with this kind, your stools are hard and lumpy.
IBS with diarrhea (IBS-D): with this kind, your stools are loose and watery.
IBS with mixed bowel movements (IBS-M): with this kind, you can experience both hard and lumpy bowl movements as well as loose and watery movements.
The differences between these types of IBS are important since certain treatments only work for specific types of IBS.

As stated above, you don’t always experience symptoms with IBS and therefore will also have normal bowl movements, but symptoms of IBS can return at other times. Symptoms of IBS may appear frequently, or they may occur during flare-ups. Additionally, a person with IBS may notice that certain things trigger symptoms. A trigger does not cause the condition itself. However, it can cause or worsen a symptom flare-up. Common triggers include:
Periods: women may notice their symptoms constantly worsen according to their menstrual cycle.
Certain foods: Food triggers vary from person to person. Common culprits include dairy, foods that contain gluten (such as wheat), and foods and drinks known to make you gassy.
Stress: Some researchers suggest that IBS is your gut’s response to stress.

Meal changes
A dietitian can help modify eating and drinking habits to avoid symptom flare-ups. Recommendations that dietitians might give you are:
To increase fiber in your diet, which can help if you are struggling with constipation. Fiber-rich foods include fruits, vegetables, grains, prunes, and nuts. However, it is recommended to introduce fiber slowly into your diet to give your gut time to adjust.
To limit dairy products, such as milk and cheese. Lactose intolerance is more common in individuals with IBS. However, when cutting back on dairy, it is important to make sure to consume nondairy foods rich in calcium, including broccoli and spinach.
To limit foods that can make you gassy, including beans, Brussels sprouts, and cabbage. In addition, carbonated sodas and chewing gum can make you gassy as well.
To avoid gluten: People with IBS, even those without celiac disease, tend to be more sensitive to gluten. If you opt for a gluten-free diet, work with a dietitian to ensure you are getting enough of the key vitamins and minerals (such as fiber, iron, and calcium) often found in foods with gluten.
To try the low-FODMAP diet, which reduces the amount of hard-to-digest carbohydrates. It recommends alternatives that allow you to get the nutrients you need while going easier on your GI tract.
To drink at least 2 liters of water a day. Water keeps your GI tract lubricated and may help treat or prevent constipation.
To keep a food diary. Your provider may recommend that you write down the foods you eat to determine which foods trigger IBS flare-ups.
Your physician may also recommend that you exercise regularly, try relaxation techniques, and get enough sleep. Additionally, many people with IBS benefit from seeing a therapist since therapy can help you get a handle on stress and conditions such as anxiety and depression that contribute to IBS.

Sources:
https://my.clevelandclinic.org/health/diseases/4342-irritable-bowel-syndrome-ibs