Simply put, dehydration is caused by consuming too little or losing too much fluid. While foods don't directly cause dehydration, your eating habits can contribute -- either by keeping you from consuming fluid-rich foods or by encouraging you to lose fluids. Improving your eating habits and replenishing fluids lost through sickness or perspiration can help stave off bothersome symptoms, such as headaches and dry mouth. If you experience severe symptoms, such as dizziness, a rapid heartbeat or very dark urine, seek prompt medical guidance.
Eating Few Hydrating Foods
Water isn't only present in liquids. Fruits, vegetables and broth-based soups also supply valuable amounts, fulfilling an estimated 20 percent of your water needs, according to Iowa State University Extension. If you're at risk for or have already developed dehydration due to hot weather, heavy sweat, a lack of hydrating beverages, diarrhea or vomiting, eating mainly nonhydrating foods could worsen your symptoms. To prevent these effects, have fruit or veggies, a smoothie or broth-based vegetable soup with your meals or snacks instead of merely dry foods, like bread and potato chips. Particularly fluid-rich options include melon, citrus fruit, berries, leafy greens and celery.
Caffeine as a Diuretic
Coffee has long been considered dehydrating, but research shows that its potential diuretic, or fluid-flushing, effects are compensated for by the liquid it provides. In a study published in "PLOS ONE" in January 2014, 50 habitually coffee-drinking males drank equal, moderate amounts of water or coffee for three days. At the study's end, both groups were equally hydrated. Researchers concluded that coffee consumed in moderation is as hydrating as water. If you enjoy coffee or tea, aim for no more than moderate intake -- around 300 milligrams or 3 cups of caffeinated coffee -- per day. Caffeinated tea provides 14 to 60 milligrams per cup. A 1.5-ounce chocolate bar or 12 ounces of caffeinated cola provides about 45 milligrams. Take caution with energy drinks, which may contain over 200 milligrams of caffeine per serving plus additional stimulants, such as ginseng; due to the high stimulant content, they're much more likely to be dehydrating.
Alcohol and Dietary Supplements
While not considered foods, alcoholic beverages and many dietary supplements can negatively influence your hydration levels. Alcohol promotes urine production, which leads to fluid loss. The more alcohol you consume, the more fluid you'll lose, increasing your risk of a hangover. Hangovers are headaches caused by dehydration. Supplements geared toward weight loss and energy boosting often contain stimulants, such as ginseng. Ginseng is only considered possibly safe for short-term use, according to MedlinePlus, and could trigger side effects, including diarrhea -- a common cause of dehydration.
Individual fluid needs vary, based on factors such as age, activity level and gender. Most people need 8 to 13 cups of water per day, says Iowa State, along with hydrating foods. You should drink enough so as not to feel thirsty, and until your urine appears clear or pale yellow. Darker urine shows a higher concentration of waste product and less water -- a sign of dehydration. Intense exercise, sweating and hot weather increase your fluid needs. If your symptoms derive from diarrhea or vomiting, drink whatever fluids you can tolerate and seek guidance from your doctor for severe symptoms. To make water more convenient and palatable, keep a water bottle with you throughout the day, adding a splash of juice or fresh fruit, such as apple slices, for flavor.