Nutrition is generally defined by ones diet. You can have good nutrition which means that you eat healthily most of the time, but poor nutrition can leave you with vitamin and mineral deficiencies that make you feel tired, irritable, and weak. You can learn the difference between these, and when you apply the principals of good nutrition to your lifestyle, you will feel stronger and be healthier.
Keeping an eye on your nutrition is not just a matter of looking for foods that adhere to the latest fad diet: low fat, no sugar, low glycemic. These sound healthy, but foods can still be junk and claim to be a part of one of the latest diets. Think about fat free cookies and sugar free candy. Those have no nutritional value, but they fit into some weight loss regimes. Good nutrition does not mean going on a diet, but it does mean getting the right kinds of foods to help your body operate at its prime.
The best way for the human body to absorb and use vitamins and minerals is to get them from foods. When you are looking for the most nutritious foods, look for those with naturally occurring health benefits. One of the easiest ways to find natural foods that are the most nutritious is to find those which are the most colorful. Many vitamins manifest themselves in the coloring of fruits and vegetables. Beta carotene is turned into vitamin A in the body and it makes carrots and squash orange. Red tomatoes have lycopene, which has been linked to a reduction in incidence of cancer. Possibly thousands of beneficial compounds besides just vitamins and minerals have yet to be discovered in whole foods, and the best way to maintain good nutrition is to have as many of these as possible while reducing your intake of foods with less nutritional value, such as cookies and candy. You can still have sweets and still have good nutrition, but foods with few vitamins and minerals in them should be saved for treats and not as your primary source of food.
When you improve your nutrition, you will find that you have more energy and you are less likely to become sick. Other benefits of good nutrition might not be felt until years later when you are enjoying a longer life with less cancer, heart disease, and other chronic illnesses. It is never to early or too late to begin a healthy regime of good nutrition.