Vitamins are indispensable to human metabolism. Vitamins are present in small quantities in food and sometimes, the human body produces them. Vitamins can also be artificially created. We all need vitamins; if we don't have enough vitamins in our diet, we run the risk of developing vitamin deficiencies that can ultimately lead to serious ailments. If you are looking for the best diet for life it should include the food sources for each of the vitamins mentioned below.

Vitamin A: The Vitamin for the Eyes

A fat-soluble vitamin, vitamin A plays an important part in eyesight, helping us to distinguish things around us when there isn't enough light. Vitamin A also contributes to the creation of skin, hair and mucous membranes and keeps them in good condition. Vitamin A strengthens the immune system and it is also connected with the development of bones, teeth, and epithelial cells, the cells situated on the inside and outside of body cavities such as the nose, mouth, throat, lungs, stomach, intestines, urinary tract.

Sources: Foods that contain high levels of vitamin A include orange and yellow vegetables and fruits (e.g., nectarines, cantaloupe, carrots), spinach, broccoli, butter, eggs, milk, fish oil and liver (beef, pork, chicken, turkey, lamb).

Vitamin B: The Vitamin for Metabolic Activities

Vitamin B consists of several vitamins: B1, B2, B6, B12, biotin, folic acid, niacin and pantothenic acid. The B vitamins have an essential role in the human metabolism. They are responsible for transporting red blood cells, which contain oxygen, throughout the body. The B vitamins also have a major role in the process of protein synthesis and creation of energy.

Sources: Vitamin B is present in whole grains (e.g., oats and wheats), peas, beans, leafy green vegetables, citrus fruits, seafood, eggs and dairy products such as milk and yogurt, and meat. A type of bacteria residing in the large intestine is also capable of producing some types of B vitamins.

Vitamin B deficiency is responsible for the occurrence of the so-called "Beri Beri" disease. Symptoms of vitamin B deficiency include weak muscles, cracked lips and malformed red blood cells. Vitamin B deficiency can affect a person's normal growth and can create problems in the nervous system.

Vitamin C: The Antioxidant Vitamin

Vitamin C is also called ascorbic acid. It is a water-soluble vitamin with antioxidant properties. Vitamin C plays a key role in collagen production. Collagen is a type of protein that provides strength in the case of bones, cartilages, ligaments, tendons, muscle, teeth and blood vessels. Vitamin C helps keep the gums and muscles in good shape. Vitamin C is also responsible for accelerating the healing of various wounds. Vitamin C also prevents fat-soluble vitamins like vitamin A and vitamin E, and other fatty acids from oxidizing.

Sources: High levels of vitamin C are present in citrus fruits (e.g., orange, lemon) and in other fruits (e.g., cantaloupe, strawberries) and vegetables (e.g., broccoli, tomatoes, cabbage).

To keep your skin healthy, have enough vitamin C in your diet. Deficiency in vitamin C can lead to poor wound healing and, in extreme cases, a disease known as scurvy.

Vitamin D: The Bone Vitamin

A fat-soluble vitamin, vitamin D aids in the process of calcium and phosphorous absorption from the intestine and in bone formation. Vitamin D regulates calcium movement from bone to blood and the other way around. Vitamin D also contributes to the development of strong teeth and bones as it helps the body absorb calcium.

Sources: Egg yolk, milk and fish liver oil are rich sources of vitamin D. In the presence of sunlight and ultraviolet light, the body can synthesize vitamin D.

Vitamin D deficiency causes weak bones. However, too much vitamin D in the body can also be toxic, causing appetite loss, nausea, weight loss, headaches and calcium deposits in the kidneys.

Vitamin E: The Vitamin for Oxidation

Vitamin E is a valuable anti-oxidant that prevents oxidation in body tissues, contributes to red blood cell formation and protects the lungs from polluted air.

Sources: Whole grains, wheat germ, cereals, bread, nuts, seeds, leafy green vegetables, egg yolks and sardines.

Vitamin E deficiency can lead to diseases like diabetes, cancer, heart disease and Alzheimer's disease.