Artificial sweeteners

Artificial Sweeteners:

Consider this yet another reason to ditch diet soda for good. One study found that when people consumed artificial sweeteners—aspartame, sucralose, and saccharin (a.k.a. Equal, Splenda, and Sweet'N Low)— they altered the gut bacteria that controls metabolism. That can lead to all sorts of gastrointestinal (GI) problems, only one of which includes an increased conversion of food into fat, says Lieberman. Meaning not only does it become more difficult to lose weight, but it's actually easier to gain.

Coffee

Coffee:

Your daily pick-me-up could do more than just wake you up. "Not only is coffee acidic, but it also contains caffeine, which speeds up the digestive tract and may cause diarrhea," explains Katie Cavuto, M.S., R.D., a nutritionist and chef in Philadelphia. That caffeine is also a diuretic, she explains, meaning it can lead to dehydration and even nausea. What's more: Coffee causes the stomach to produce hydrochloric acid (HCL), which can cause heartburn and indigestion. So if you find yourself regularly experiencing GI issues after your cup of joe, limit it to one cup a day and don't drink it on an empty stomach, as that can help ease those unpleasant symptoms.

Carrageenan

Carrageenan:

Not every ingredient in a natural food product may be good for you. Case in point: Carrageenan, a gum derived from seaweed and used as a stabilizer in organic and natural foods like soy milk, low fat yogurt, salad dressing, or ice cream, can cause a host of gut issues, says Lieberman. Research even suggests that the additive may cause inflammation, which can lead to ulcerations and inflammatory bowel disease (IBS).

This isn't to say you should skip dairy completely, though. "In fact, organic low-fat yogurt has beneficial effects on your gut by improving the natural flora (good bacteria) in your GI tract," says Lieberman. She recommends sticking to one cup per day, but if you're experiencing GI issues after eating dairy, try one cup of lactose-free, low-fat milk instead. And be sure to check that carrageenan doesn't appear on the ingredient list—you should only see "low-fat milk" and cultures—and avoid the fruit-flavored kinds with added sugars.

Broccoli

Broccoli:

"Cruciferous veggies, such as broccoli and cauliflower, contain complex sugars that you can't digest," says Cavuto. "They're called raffinose, and they can produce gas. They're also rich in soluble fiber, which doesn't break down until reaching the small intestine, so that can cause gas, too." This, in turn, causes all those familiar symptoms of indigestion—bloating, upset stomach, and gas. But, we're not saying you shouldn't munch on broccoli for dinner (there are way too many health benefits for that).

Instead, do your best not to overcook them, as that destroys the health bennies you're after, and consider taking a digestive supplement (Cavuto recommends Digest Gold), which contains enzymes that help break down those hard-to-digest plant fibers. If you're still in need of a healthy-gut-bacteria boost, dig into some Greek yogurt for breakfast, which is full of probiotics that can help.

Sugar-free foods

Sugar-Free Foods:

Steer clear of those "sugar-free" sweets and gum. Sorbitol, maltitol, xylitol, and other sugar alcohols are frequently added to these products, which can cause bloating, gas, or a laxative effect when eaten in excessive amounts, says Lieberman. Her rule of thumb is that if a sugar alcohol appears in the first three ingredients of a food, avoid it. Oh, and another reason to cut back on that chewing gum habit? It can stimulate the stomach to secrete acids that your body doesn't need, which may contribute to the development of stomach ulcers.

Milk, coft cheese, and ice cream

Milk, Soft Cheese, and Ice Cream:

While only 4% of adults have true food allergies, according to the National Institutes of Health, lactose intolerance is more common and found in around 70% of adults, explains Cavuto. It happens when you lack the digestive enzyme (lactase) to process lactose, a sugar found in milk, and results in GI distress with symptoms like bloating and diarrhea.

But even if you're not lactose intolerant, eating too much dairy leads to digestion in the large intestine instead of the stomach, which can cause an upset stomach, diarrhea, and gas, she says. A better choice: Hard (aged) cheeses have lower amounts of lactose, and yogurt is typically well tolerated because the live cultures digest lactose better, says Lieberman.

Fried foods

Fried Foods:

Obviously, a plate of french fries and chicken fingers isn't exactly the picture of health. But it's worse than we thought as fried, fatty foods can cause major distress on your GI tract in more than one way: "Fried foods can move undigested through the body too quickly, leading to diarrhea," says Lieberman. Or it can do the exact opposite. Since these foods are usually low in fiber, they could stay in your digestive tract too long, making you feel full, bloated, and potentially causing constipation. Either way, it's a lose-lose.

Citrus fruit

Citrus Fruit:

If you're having digestive trouble, it can be tempting to load up on healthy foods like fruits and veggies. But watch out: "Acidic foods, like tomato sauce, and citrus fruits, like lemons, limes, oranges, and grapefruits, may cause you more trouble," says Lieberman. They can further irritate the lining of your stomach, leading to heartburn or acid reflux. Cut back on these until you're feeling better, and instead load up on applesauce or bananas to help ease discomfort, she suggests.

Onions and garlic

Onions and Garlic:

Ever heard of FODMAPs? They're a group of sugars and fibers found in foods—think onions, garlic, and wheat products—that aren't absorbed well in the small intestine, causing a host of gut issues like gas, bloating, stomach pain, diarrhea, or constipation, says Cavuto.

Other FODMAP-containing foods include healthy bites like pears, apples, beans, cabbage, and cauliflower, so unfortunately, it can be hard to pinpoint what's causing your distress. If you're having serious GI problems, talk to a doctor to see if FODMAPs could be to blame, as the process to determine whether you have a sensitivity to them can be tricky.

Corn

Corn:

Lieberman says "if you don't chew [corn] long enough, it can pass through your system undigested and cause an upset stomach." Blame the cellulose inside, which is an insoluble plant fiber, and the fact that humans lack the enzyme properly needed to break it down in our bodies. When you do nibble a cob, remember to chew thoroughly before you swallow.

Raw foods

Raw foods:

Bacteria in raw meats can cause food poisoning (talk about stomach issues), so take appropriate precautions when handling perishable foods like raw meat, poultry, eggs, and seafood, warns Lieberman. Make sure to cook foods to proper temperatures to destroy bacteria, and don't leave these foods unrefrigerated for more than two hours to prevent bacterial growth.

And, if spending the entire night next to the toilet due to food poisoning isn't enough of a warning, keep in mind that contracting harmful bacteria like E. coli and salmonella through these foods can potentially be life threatening. In other words, play it safe and fire up the heat.