When you’re fighting off an illness, certain foods can slow your recovery by suppressing immune function, worsening dehydration, or irritating an already-sensitive digestive system. The short list: sugary foods, greasy meals, alcohol, and rough or acidic foods are the main ones to skip until you’re feeling better. Here’s why each one matters and what to reach for instead.
Sugary Foods and Drinks
Sugar does more than offer empty calories when you’re sick. It actively weakens your body’s ability to fight infection. A classic study in The American Journal of Clinical Nutrition found that consuming 100 grams of simple sugar (from glucose, fructose, table sugar, honey, or even orange juice) significantly reduced the ability of white blood cells to engulf and destroy bacteria. The effect kicked in within one to two hours and lasted at least five hours. Importantly, the sugar didn’t reduce the number of immune cells in the blood. It just made them worse at their job.
That means a couple of glasses of soda, a bowl of sugary cereal, or a big serving of juice could leave your immune system functioning below normal for most of the day. Starch, interestingly, did not produce this effect, so plain toast, rice, or oatmeal are fine. If you’re craving something sweet, a small amount of whole fruit is a better choice than juice or candy, since the fiber slows sugar absorption.
High-Fat and Greasy Foods
Fat naturally slows stomach emptying. When you’re healthy, that’s not a big deal. When you’re nauseated, running a fever, or dealing with a stomach bug, a greasy burger or plate of fried food can sit in your stomach for hours and make you feel significantly worse. The longer food lingers in your stomach, the more likely you are to experience bloating, cramping, and nausea.
This applies to obvious culprits like fast food and fried snacks, but also to rich, creamy soups and heavy cheese dishes. Stick with brothy soups, boiled potatoes, or skinless poultry until your appetite and digestion are back to normal.
Alcohol
Alcohol is one of the worst things you can consume while sick, for several reasons at once. It’s a diuretic, meaning it increases fluid loss and accelerates dehydration at exactly the time your body needs more fluids. Fever, sweating, vomiting, and diarrhea already push you toward dehydration, and alcohol compounds every one of those losses.
Beyond hydration, alcohol disrupts sleep quality. You may fall asleep faster, but alcohol fragments the deeper stages of sleep your body relies on for immune repair. Even a single drink can interfere with recovery. Skip it entirely until you’re well.
Caffeine in Large Amounts
A small cup of tea or coffee is unlikely to cause problems for most people, and the warmth can actually soothe a sore throat. But heavy caffeine intake promotes fluid loss, which works against you when you’re already losing fluids to fever or a stomach illness. Energy drinks are a particularly bad choice because they combine high caffeine with large amounts of sugar.
If you normally drink coffee and stopping entirely gives you a withdrawal headache, one small cup is reasonable. Just make sure you’re drinking plenty of water or an electrolyte drink alongside it.
Acidic and Spicy Foods
If you have a sore throat, acidic foods like oranges, lemons, tomatoes, grapefruit, and their juices can sting inflamed tissue and make swallowing more painful. This is one reason orange juice, despite its vitamin C reputation, is often a poor choice when you’re actively sick. The acid content can outweigh any nutritional benefit when your throat is raw.
Spicy foods present a different problem, especially during stomach illness. Capsaicin, the compound that makes peppers hot, speeds up digestion in the intestines and can trigger or worsen diarrhea. It also isn’t fully broken down during digestion, so it continues to activate pain receptors as it moves through your gut. If you’re dealing with any kind of gastrointestinal symptoms, spicy food will likely make them worse.
Sugar-Free Candies and Gum
This one catches people off guard. Many sugar-free products contain sugar alcohols like sorbitol or xylitol as sweeteners. These compounds act as osmotic laxatives, meaning they pull water into the intestines. In one documented outbreak tracked by the CDC, dietetic candies containing just 3 grams of sorbitol per piece caused widespread diarrhea among consumers. Studies on volunteers found that as little as 10 grams of sorbitol caused bloating and gas, while 20 grams triggered cramping and diarrhea.
When your gut is already irritated from illness, the threshold for symptoms drops even lower. If you’re sucking on lozenges or chewing gum to soothe a sore throat, check the label. Choose options sweetened with real sugar in small amounts, or skip them in favor of warm liquids.
Raw Vegetables and Rough-Textured Foods
Raw vegetables, whole nuts, seeds, and crunchy granola are nutritious when you’re healthy, but they’re hard on a sensitive stomach. Raw produce contains a lot of insoluble fiber, which adds bulk and speeds transit through the intestines. During a stomach illness, that extra roughage can worsen cramping and diarrhea.
Cooking vegetables softens their fiber and makes them far easier to digest. Steamed carrots, mashed sweet potatoes, or well-cooked zucchini give you nutrients without the mechanical irritation. Save the salads and raw snacks for when your digestion has stabilized.
Dairy: Less Harmful Than You Think
You may have heard that milk increases mucus production and should be avoided during a cold. Research doesn’t support this. The Mayo Clinic notes that drinking milk does not cause the body to produce more phlegm. What actually happens is that milk and saliva mix in the mouth to create a slightly thick coating that can briefly linger on the throat. People mistake that sensation for extra mucus, but it clears quickly and has no effect on congestion.
That said, dairy can still be worth avoiding in one specific situation: if you have a stomach bug with active diarrhea. Some people temporarily lose the ability to fully digest lactose during a gastrointestinal infection, which can make dairy products cause gas, bloating, and looser stools. Plain yogurt is usually the exception, since its bacterial cultures have already broken down much of the lactose.
What to Eat Instead
The old standby advice was the BRAT diet: bananas, rice, applesauce, and toast. It’s gentle on the stomach, but the Cleveland Clinic and the American Academy of Pediatrics no longer recommend following it strictly because it’s too low in protein, fat, and overall nutrition to support recovery. It’s fine as a starting point when you can barely keep anything down, but you should expand beyond it as soon as you’re able.
Better options include brothy soups (which deliver both fluids and electrolytes), oatmeal, boiled potatoes, saltine crackers, and dry cereal. As your appetite returns, add scrambled eggs, skinless chicken or turkey, and cooked vegetables. These provide the protein and micronutrients your immune system needs to finish the job, without overwhelming your stomach.
Above all, prioritize fluids. Water, diluted broth, herbal tea, and oral rehydration solutions do more for your recovery than any single food. Small, frequent sips are easier to keep down than large gulps, especially if nausea is still a factor.