Your digestive tract plays an important role in processing and absorbing nutrients. The B complex vitamins and vitamin C are water-soluble vitamins that are essential for your good health. These vitamins dissolve completely in water, so they are easily absorbed in small quantities; excessive amounts are excreted in your urine. Water-soluble vitamins do not stay in your body for very long, so it is important that you get proper amounts of them in your diet every day.
Small Intestine
Foods you consume contain large organic molecules that are mostly insoluble. Your digestive system breaks down the food you eat and then disassembles the large molecules from that food into smaller particles and makes it suitable for absorption. A combination of proteins, carbohydrates, fats, minerals, vitamins and water are all essential for your body to function properly. Your digestive system processes each of these elements differently. Carbohydrates, fats and proteins must be broken down through digestion before your small intestine can absorb them. Water, minerals and vitamins can be absorbed by special transport mechanisms without being broken down. The lining of the small intestine has small fingerlike villi that grab onto the nutrients and carry them across the membrane, releasing them into your bloodstream.
Absorbing Water
Your cells cannot absorb or secrete water. The movement of water across the lining of the digestive tract involves passive water flow that follows an osmotic gradient. The epithelial cells in your digestive tract are constantly absorbing nutrients from your intestinal contents. Each day your digestive tract receives water from the food or beverages you consume and also gets fluids from your saliva, gastric secretions, liver bile, intestinal secretions, pancreatic juice and colon mucous secretions. You can think of it this way--starting from your mouth all the way down to the colon, absorption of water and secretions is constant along your digestive tract. Only a small amount of water is lost in your feces.
Vitamin C and Vitamin B Complex
Water-soluble vitamins are components of coenzymes that are important for your body's metabolism. B vitamins and vitamin C from foods and beverages you consume are absorbed by the small intestine, then the water-soluble vitamins enter an internal passageway of your digestive tract and move across your digestive epithelium, to be absorbed finally by your intestinal mucosa. Your small intestine mucosa has villi, which are fingerlike projections that create a surface area to absorb the nutrients. Once they are absorbed, the nutrients are released into your bloodstream and then your tissues. The mechanism used to transport water-soluble vitamins into your system is by diffusion that follows a concentration gradient.
Vitamin B12
Vitamin B12 is a special case. Vitamin B12 is the only B vitamin that cannot be absorbed by your intestinal mucosa. Vitamin B12 is a large molecule and it must be bound to a protein called the intrinsic factor that before absorption can occur. The intrinsic factor is produced by your gastric mucous membrane. Your body can store significant amounts of vitamin B12 similar to fat-soluble vitamins. But if your body is lacking in the other B vitamins, it can cause an imbalance that can interfere with the storing ability of vitamin B12.
Large Intestine
In 2006, researchers from the University of California at Irvine School of Medicine published an update about the "intestinal absorption of water soluble vitamins" in the journal of "Gastroenterology." Researchers have discovered that the large intestine has a specialized system that can absorb several of the water-soluble vitamins that are produced by the good bacterium Lactobacillus and Bifidobacteria. "These new source of vitamins may play a role in regulating and maintaining a relatively constant internal environment of these water-soluble vitamins," the researchers wrote.
Malabsorption
Digestive disorders or illnesses can cause malabsorption of water-soluble vitamins. If your intestine does not have the abiliy to absorb vitamins or your system cannot adequately store vitamins or your body creates an excessive demand of vitamins, you are at risk for malabsorption. Maintaining a healthy digestive system is important for processing and absorbing nutrients. Talk to your doctor about malabsorption of water-soluble vitamins.
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