Although the U.S. has the most plentiful food supply in the world, it's sometimes difficult to get all of the nutrition our bodies need. Our hectic lifestyles cause us to eat out more and buy more prepared foods to eat at home. We eat fewer fresh fruits and vegetables and a greater quantity of nutritionally deficient snack and fast foods than did our parents' generation.

To ensure that we're consuming all of the nutrition our bodies need, it's often wise to take a vitamin supplement. Vitamins can fill in the nutritional gaps and shore up our immune systems and stamina. Some vitamins and minerals even act as weight loss pills, by stimulating the body's fat-burning mechanism.

Although it's ideal to consume vitamins through the foods you eat, vitamin supplements can serve to bridge the gap and provide a safety net for those times when you have to grab a bite on the run.

According to the National Institutes of Health, thirteen vitamins are essential for our bodies to function: A, C, D, E, K and the eight B vitamins. Here's the lowdown on eleven of the essentials:

Vitamin A is important for vision, reproductive function, and normal cell reproduction. Beta-carotene, a precursor to Vitamin A, helps to fight disease-causing free radicals. Vitamin A is found in milk products, organ meats, and fish oils. Beta-carotene is found in colorful vegetables, such as carrots, broccoli, spinach, and sweet potatoes.

Vitamin B-1 (thiamin) processes carbohydrates into energy and is necessary for nerve cell function. Breads and cereals are often fortified with thiamin, though it is also found in whole grains, fish, lean meats, and dried beans.

Vitamin B-2 (riboflavin) helps the production of red blood cells and is important for growth.

Vitamin B-3 (niacin) helps control cholesterol, processes alcohol, maintains healthy skin, and converts carbohydrates to energy.

Vitamin B-5 (pantothenic acid) serves several bodily functions, such as converting fats to energy and synthesizing cholesterol.

Vitamin B-6 (pyridoxine) is important in the production of hormones such as serotonin, dopamine, and melatonin, as well as for processing amino acids.

Vitamin B-12 is a crucial component of DNA replication and nerve cell regulation. It is found in milk products, poultry, meat, and shellfish.

Vitamin C is important in wound healing and acts as an antioxidant. It also helps the body absorb iron. It's found in citrus fruits, potatoes, and greens.

Vitamin D helps the body absorb calcium, which creates healthy bones and teeth. The body can synthesize Vitamin D after exposure to sunshine, but it can also be found in fortified milk products and cereals, as well as in fish.

Vitamin E helps to combat free radicals, which can damage our cells. It's found in nuts and seeds, green leafy vegetables, corn, asparagus, and wheat germ.

Vitamin K is what makes the blot clot. While our bodies produce some Vitamin K, it can also be found in vegetables like cauliflower and cabbage.