Upset stomach? How to identify your food intolerances


by Rassa Shahidzadeh, MD

Jul 20, 2021

Bloating, excessive gas, abdominal discomfort and even diarrhea. These are all frequent symptoms that often lead people to seek a physician’s help, unsure of what is going on to trigger their discomfort after eating. Most often, the culprit is this—a food intolerance. You are likely eating a food that you’re actually intolerant to. In fact, more than half of people have a food intolerance they are not aware of. You should plan to consult a medical professional early on if you are experiencing any of these symptoms to make sure there is not something more serious going on.  

Pinning down a food intolerance

Once you’ve discussed your symptoms with a medical expert, you can consider an elimination diet to identify trigger foods. Generally, there are three steps recommended to identify and combat food intolerances:

1. Go dairy free.

The first thing to try if you are experiencing gastrointestinal discomfort is to eliminate lactose (i.e. dairy products) from your diet. Lactose intolerance accounts for most cases of food intolerance.

In fact, humans are the only mammals who continue to drink milk after infancy. This is because most mammals’ (including humans’) ability to break down the sugars that are in milk often deteriorates over time. While you may have easily been able to tolerate dairy in your youth, it’s likely that what once was tolerable will eventually become harder to digest.

Try going two weeks completely dairy-free, including eliminating products such as yogurt, milk and cheese. You might find it helpful to keep a food diary and write down your symptoms during the two weeks you’re avoiding dairy. If you are lactose intolerant, you will usually start to see a decrease in your symptoms after just one week.

2. Stop all artificial sweeteners.

If after two weeks of no dairy, you are still experiencing symptoms, consider eliminating artificial sweeteners from your diet. This includes anything labeled as “zero calorie.” Artificial sugars are designed not to be absorbed so while they may taste sweet, they are not easily digested. It’s common for artificial sugars to disrupt your GI tract. Again, keep track of what you’re eating and any symptoms in a food diary or app.

Related: 6 strategies for managing your family’s food allergies

3. Try the FODMAP diet.

The last step to identify food intolerances takes the most discipline but can also be the most effective. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols, which are short-chain carbohydrates (sugars) that the small intestine absorbs poorly. Some people are intolerant to natural sugars and the FODMAP diet can help identify exactly what your trigger foods are.

The first step is to avoid all FODMAP foods (see this FODMAP food chart) for two full weeks. Similar to eliminating dairy or artificial sweeteners, it is also helpful to track your meals and your symptoms.

After two weeks, you can slowly start introducing one category of food at a time. For example, you would start by introducing fermentable foods such as apples, mangos and corn syrup. If no symptoms persist, then you can move on to oligosaccharides such as asparagus and broccoli. If you start to have symptoms, you can then drill down the specific sugar category and eventually the exact food that is triggering your symptoms.

Sticking to eliminating food groups you’re use to eating can take discipline. The good news is that there are lots of tools that can help, including apps that give you an easy place to track your diet and symptoms.

Next steps

The goal of an elimination diet is to identify and eventually avoid the foods that are triggering any GI discomfort so you can get back to doing—and eating—the things you love! If you’re having troubling nailing down a suspected food intolerance, talk to a doctor today.

About the Author

Rassa Shahidzadeh, MD, is a gastroenterologist on the medical staff at Baylor Scott & White Medical Center – Plano. He is clinically interested in colorectal cancer prevention, gastroesophageal reflux disease, disorders of the pancreas and biliary system, disorders of the intestinal tract, disorders of the liver, gastroparesis and nutrition. In 2006, Dr. Shahidzadeh received the American College of Gastroenterology Fellow Recognition Award and was featured in D Magazine’s Best Doctors list.

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