Vitamins are essential nutrients for good health.  They can regulate body metabolism, act as antioxidants to salvage free radicals, improve immune system and energy level, reduce stress response, enhance mental clarity, and prevent vitamin deficiency diseases. 

In general, vitamins are abundant in fresh foods, such as fresh meat, legumes, whole grains, fruits and vegetables.  People who consume a healthy and balanced diet with a wide variety of fresh foods should have adequate vitamin supply.  However, in reality, many people do not consume a healthy diet.  Their diet may be high in meat and fat, low in whole grains, fruits and vegetables, or they do not prepare the food properly such as eating fast food and deep-fried food or just heating up a frozen diet using the microwave.  Improper food storage, food preparation and cooking practice can destroy some vitamins in food.

Whether you need vitamin supplements or not depends on your own lifestyle. If you live a healthy life, with minimum exposure to radiation, toxic chemicals, pollution and eat a balanced diet of wide variety of fresh food, you may not require vitamin supplements after all.

On the contrary, if you are too busy to cook for yourself or prepare a healthy balanced diet, consume refined foods more often than fresh foods, feel tired all the time, suffer from high stress level and weak immune function, vitamin supplements may be beneficial to you. 

Vitamins A-K work synergistically with each other, so it is better to consume instead of single vitamin supplements.  Most of these daily complete vitamins also comply with the , which means that the vitamin levels are sufficient to ward off vitamin deficiency diseases.  Nevertheless, the recommended daily intake does not represent the amount of vitamins required for optimal health, which may vary among individuals based on their age, health conditions and stress level, etc.

If you decide to take vitamin supplements, do bear in mind that they are not magical pills.  Changing your diet and eating style, staying active and avoiding unhealthy habits such as heavy drinking and cigarette smoking are just as important if not more important than the consumption of dietary supplements.