it could be that you have too much/too little water or salt.
Try a all natural (no processed foods) diet to see if its corn syrup or some other processing additive. These are tough diets to begin but they are worth it. Its easier now because organic food stores have a wide selection (food dosn't have to be organic, but the organic frenzy makes raw food easy to find)
This is a list of what an active, healthy young man should consume in a week. A less active man, or a woman can cut down ingredients(except milk and veggies) by 2/3.
32oz meat
1/4 cup Baking Soda
1 cup Brown Sugar
1/4 cup Bouillon (chicken, beef or vegetable)
2/3 cup margarine or butter
1 ½ cups of not processed cheese
4 cups Cornmeal
3 cups Wheat Flour
1 cup Fruit Drink (Tang) (white sugar)
3 cups Lentils
2 cups Macaroni
4 ½ cups of regular milk
3 cups Oats
2 cups Raisins
3 cups Rice
1/3 cup Salt
2 cups Un-toasted Sunflower Seeds (could be any nut)
tomato paste
Potato
2-3 Carrot
Onion
Apple
Bulb of Garlic
Also useful: peanut butter, hot sauce