HOW TO PREVENT CANCERS

Balanced diet means getting the right amount and composition of foods and beverages according to your condition. Different people might need different amount and composition of foods. For a standard, a healthy adult usually need 2000 calorie per day. If you work harder than average person, you need more calorie.
Basically, our need of food can be represented as the following pyramid:

1. Rice and alternatives (starchy foods): rice, potatoes, breads, noodles, corn flakes, etc. These kinds of food must be consumed in higher quantity comparing to other groups (see the pyramid). Our body needs 5-7 servings of this starchy foods per day (one servings of rice equals to 1/2 cup). 
2. Fruit and vegetables: spinach, broccoli, apples, etc. These kinds of foods supplies vitamins and minerals to our body, since most of vitamins and minerals cannot be self-produced. 2 servings of fruit and vegetables are important for our body each day. Specific kind of fruits may not be consumed too much, such as banana, papaya, and mango, since they'll make you have stomach ache if eaten to much.
3. Meat and alternatives: fish, meats, milk and other dairy products. These kinds of foods only need to be consumed a little. About 2-3 servings is enough. Too many meats can increase blood pressure and other disease.
4. Fats, oil, sugar, and salt: Apparently, sugar sometimes consumed in high amount through chocolates, candies, and sweet desserts. Too much sugar can increase sugar level in blood which cause diabetes. Too much fats also not good. Fats can clog our veins and also make us fat. Salt also can increase blood pressure. Fat, sugar, and salt should be consumed only in small amounts per day.

If you have certain disease, the composition of foods might be changed. For patient with diabetes, starchy foods must be reduced to only 3 servings per day, since carbohydrate on starchy foods will turn into sugar in our body. For patient with high blood pressure, meats and other dairy product must be avoided. In contrary, person who have low blood pressure must eat a lot of meats.
Supplements can also be taken if you cannot fulfill the necessary amount and or composition of balanced diet, or you need certain nutrition in higher amount than average people. But it must be noted that supplements can never really substitute the necessary of foods to our body. You cannot only ear supplements but not eat foods, since natural vitamins/minerals/other nutrition are in the best form that can easily digested and absorbed by our body.
Eating supplements is a tricky things to, since supplements sometimes depend on another. Vitamin A, D, E, and K cannot be digested if there is no fat. They're known as fat soluble vitamins. Vitamin B and C is water soluble, and more effective if you also eat enough foods with bioflavonoids along with those vitamins. Zinc and iron also work as a team in our body. If you really not sure about supplements you're taking, drinking milk might be easier since milk contains more balanced nutrition.