The human body is designed with both input and output systems. We make use of the input aspect when we consume foods or fluids, while the output system comes into play when the body removes the unwanted waste materials. Urinating is one of the several mechanisms that the body uses to remove unwanted waste materials in the body. It is a complex process that involves the filtration of the substances by the kidney and the storage of the urine in the bladder until the body feels the urge to ease itself of the stored urine.
According to science, a normal individual is expected to typically use the bathroom about four (4) to eight ( times a day. A departure from this 'normal' range could see a person having the urge to urinate more than eight ( times in a day or even waking up while sleeping just to urinate. Unless such a person has had too much fluid to drink or drank close to bedtime, urinating more than eight times or waking to urinate could be indicative of a health problem and frequent urination is the way the person's body has chosen to give warning signals.
Many underlying health conditions could cause a person to urinate frequently more than normal but some of them are diabetes mellitus, kidney disease, prostate problems, interstitial cystitis, hyperglycemia, diabetes insipidus, pelvic organ prolapse (in females), bladder cancer, bladder dysfunction, pregnancy. It is important to visit a doctor to undergo medical tests that would help to ascertain the exact cause of your frequent urination. This would also help to know the right course of treatment to embark upon to help solve the situation.
However, eating a balanced diet is a helpful tool in either preventing frequent urinating or moderating the level of output of urine. Some foods (irritants) are known to irritate the bladder or serve as diuretics, causing you to urinate frequently. Below are such types of food that you should avoid or reduce their intake to reduce the frequency with which you urinate:

1. Alcohol
2. Caffeinated Beverages
3. Chocolate
4. Spicy Foods
5. Raw Onions
6. Carbonated Drinks

On the other side of the divide are some foods that are advisable to consume as they are known to help reduce frequent urination by reducing the additional pressure that is put on the urinary bladder, the urethra or both when you have constipation. Such foods are known as high-fibre foods and some examples of them are given below:

1. Beans
2. Barely
3. Oats
4. Fruits such as bananas, watermelon, coconut, apples, etc.
5. Vegetables such as lettuce, carrots, cucumber, etc.