© istock/getty images Tea and milk

Some foods play really well together. Take these 13 health boosting combos, for example. Their chemical compounds merge to create a turbo-charged nutritional symbiosis. It's a beautiful and tasty thing. Other foods, however, don't play so nice together—we're talking combos that leave you bloated, send blood sugar levels soaring, and dampen the absorption of important nutrients. Here, six pairings to avoid if you want to feel your best:

1. Tea + milk

"Black tea is rich in antioxidants that work to decrease inflammation that's linked to many chronic diseases, including heart disease and diabetes," says Rumsey. However, splashing even a little milk (cow or soy) into your cup short-circuits those benefits: "Milk proteins bind to antioxidants in tea and prevent them from being absorbed," she explains.

What's more, milk doesn't even offer a calcium boost in this situation. "The caffeine in tea can decrease calcium absorption," says Rachel Meltzer Warren, RDN, author of The Smart Girl's Guide to Going Vegetarian. "If you really want to add something good to your tea, squeeze some lemon in there instead. It'll actually increase the amount of antioxidants that your body can absorb."

2. White bread + jam

© istock/getty images Bread and jam

"Simple carbohydrates spike blood sugar the most," says Liz Weinandy, RD, MPH, a dietitian at Ohio State University Wexner Medical Center. Put two or more together—think white bread and jam or soda and French fries—and you've got a recipe for disaster. "Your blood sugar goes up fast, and your body has to work very hard to bring it down by releasing insulin from the pancreas," explains Weinandy. Once that inevitable drop happens, your energy and mood can bottom out, leaving you tired and irritated.

"In the long term, this process can eventually wear the pancreas down and create insulin resistance and diabetes," adds Weinandy. A smarter idea: Swap out those refined carbs for fiber-rich whole grains, which help to slow down digestion and keep you off the blood sugar roller coaster. 

3. Salad + nonfat dressing 

© istock/getty images Pouring dressing on salad

"When you avoid fat on your salad, you put up a roadblock to your absorption of nutrients," says Meltzer Warren. In fact, a study in the American Journal of Clinical Nutrition found that carotenoids—plant pigments linked to a reduced risk of cancer, cardiovascular disease, and macular degeneration—are more readily absorbed when paired with full-fat dressing as opposed to low-fat or fat-free varieties. But you don't need a heavy pour of ranch to reap the benefits—splash greens with olive oil and vinegar and you're good to go.

4. Alcohol + caffeine

© Los Angeles Times/Getty Images Bartender mixing Red Bull and vodka

You know the drill: You're drinking wine at dinner, start to yarn after a few glasses, and perk yourself up with a post-meal cappuccino. Bad idea. Why? The energy boost you get from caffeine can mask intoxication, so you underestimate how drunk you are. The same goes for directly mixing caffeine + booze (think vodka and Red Bull or coffee and Kahlua). Research out of Wake Forest University School of Medicine found that people who combine caffeine and alcohol are at a greater risk of being in an accident than those who steer clear of the combo. 

5. Lentils + red wine

© istock/Getty Images Red lentils

Red wines contain compounds called tannins. When tannins intermingle with plant-based sources of iron, like those found in lentils and soybeans, it seriously hinders your body's ability to absorb the mineral. This issue is particularly relevant to vegans and vegetarians, notes Rumsey: "Plant-based iron is already more difficult to absorb than meat-based iron," she says. "Add tannins to the mix and it's that much harder to get the iron you need."

6. Burgers + beer

"Both are processed by the liver, and your body naturally prioritizes breaking down the alcohol first, since it recognizes alcohol as a toxin," says Rumsey. This leaves fat floating in your blood stream, where it can then be stored in fat tissue. Moreover, you'll feel especially gross afterward. "Fat causes food to digest more slowly, which is why a high-fat meal can leave you feeling stuffed and bloated long after you eat it," says Rumsey.