Healthy individuals who eat a balanced diet rarely need supplements. In fact supplements can be dangerous. Too much vitamin A, for example, can be toxic and excessive consumption of vitamin C, niacin, vitamin B6, folic acid, and vitamin B12 may lead to liver damage, nausea, inflammation of the oral cavity, dermatitis, muscle weakness, and fatigue. Excessive use of iron may lead to inhibition of electrolyte and trace elements absorption and zinc supplements exceeding the RDA (recommended daily allowance) may lower HDL (the good cholesterol) and copper and iron levels in the blood.
For about forty percent of the daily requirements needed by adults and children over four years of age a serving would roughly be half a cup of vegetables or half a medium sized fruit, like a mango, or about 85 grams of meat.
A good rule of thumb is to eat a variety of foods. Two to three servings of milk, yoghurt or cheese, two to three servings of meat, poultry, beans, eggs or nuts, two to three servings of fruit, three to five servings of vegetables and six to eleven servings of bread, cereal, rice, or pasta each day will provide all the necessary nutrients for good health according to the recommended dietary allowance (RDA). Fruits and vegetables are the main source of essential vitamins and your body prefers to absorb them from food. Avoiding fruit and vegetables may cause a deficiency in vitamins B1, B6, C, calcium, magnesium and potassium that protect your body from cancer and heart disease.
The amount of energy we need varies with age, sex, activity level, and environmental temperature. If we eat more energy food (protein, carbohydrates) than we need it is simply stored and could lead to obesity, Type II diabetes, arteriosclerosis, cancer and hypertension. Although physical activity increases the need for some vitamins and minerals, ideally, such requirements should be met by maintaining a balanced, high carbohydrate diet with moderate protein and low fat. We should all make an effort to shift from fatty foods to carbohydrates and from saturated to unsaturated fats.
Fad diets based exclusively on one particular food or food component can have unhealthy and potentially dangerous consequences. Always consult your doctor before starting a diet program that strays from a balanced approach to nutrition