Don’t tolerate food intolerance

Matthew Solan

Executive Editor, Harvard Men's Health Watch

Who hasn’t eaten something that did not agree with them? But when your stomach issues become more frequent and severe, you might have a bigger digestion problem called food intolerance. Food intolerances occur more often as you age since your digestion naturally becomes slower and your body produces fewer enzymes needed to break down food. “This allows more time for bacteria to ferment in the GI tract and lead to digestive distress,” says Evagelia Georgakilas, a registered dietitian and nutritionist with Harvard-affiliated Beth Israel Deaconess Medical Center.

Over time, you also may become more sensitive to particular foods, chemicals, or additives.  Some examples include sulfites found in wine, dried fruits, and canned goods, or foods flavored with monosodium glutamate (MSG). However, the most common food sensitivities are lactose and gluten. With lactose intolerance, your body can’t break down the sugar lactose in dairy products because your gut contains reduced levels of the intestinal enzyme lactase.

People with gluten sensitivity have trouble digesting gluten, a protein found in wheat, rye, and barley. (This is different than Celiac disease, an immune disease in which consuming gluten damages the lining of the small intestine.)

Track possible food intolerance with a food diary

Common symptoms of food intolerance include nausea, diarrhea, cramps, and stomach pain, but also may involve other issues like vomiting, heartburn, headaches, and irritability or nervousness.

Food intolerance is often tricky to pinpoint because you may be able to eat small amounts of a problem food without having any reaction. Instead, symptoms may only appear after you eat a large portion of the food, or eat it frequently.

The best way to identify problem foods is with a food diary. Write down what you eat for every meal, including individual foods and portions. Then list any symptoms that occur afterwards and rate their level of intensity on a scale of one to 10, with one being no reaction to 10 being the most severe.

Maintain your diary for two weeks to a month, and then review. “You should be able to find a connection between foods and common symptoms,” says Georgakilas.

How to ease the discomfort of food intolerance

Once you pinpoint one, or several, potential problem foods, eliminate them from your diet. After a few days, add only one food back into your diet and monitor your reaction. “If your symptoms return, you’ve found the offending food,” says Georgakilas.

Eliminating the problem food from your diet is the easiest move, but here are some other strategies to consider:

Reduce serving sizes. Sometimes you can still enjoy your favorite foods by reducing the amount, says Georgakilas. “For instance, if you have an intolerance of excessive fructose, you may discover that a half-cup of fruit may not cause any problems,” she says.

Make adjustments. Your food intolerance may be a cumulative effect. For instance, pizza might cause you problems, but it may be the result of certain ingredients, or combinations. “You may be able to tolerate the cheese and tomatoes on their own, but together they create the perfect storm,” says Georgakilas. Try to eliminate specific ingredients one at a time, and then experiment with eliminating certain combinations until you find the right balance.

Also, if the problem food is a source of vital nutrients, make sure you find an adequate replacement. “Cutting out gluten foods like wheat can rob your diet of fiber and B vitamins,” says Georgakilas. Switch to gluten-free bread, or increase your intake of gluten-free grains like quinoa, sorghum, teff, millet, and buckwheat. For lactose intolerance, drink almond or coconut milk to ensure you get enough calcium and protein.


  1. Norm G

    Easy? My path as I aged was anything but! (trying to figure out what was going on). I saw specialist after specialist over a period of months and finally I was blown away when I was told I had a gluten intolerance. I thought the whole gluten thing was stupid, and I never had it before….

    Turns out I have developed a dairy intolerance, too….and I consumed a lot of diary; milk, cheeses, yogurt. So, yes, as you age these things seem to develop unexpectedly!

    Now I read all the warnings about LECTIN, including all grains, beans, and nightshade (peppers, tomatoes, eggplant…) I am going to starve!

    My question is, after reading your food plate article in 2011 with 1/4 of the chart in grains, have you amended the chart in light of the many sources and studies linking lectin to digestive problems, diseases, and related issues?

    What should a person do about lectin? (One former Harvard expert suggests removing all lectin sources from diets, including grains and beans). I would like to hear from you.

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