The Importance of True Bioavailability

Bioavailability starts when a nutrient passes from the digestive system into the bloodstream. Absorption into the bloodstream, however, is only a partial measure of the body’s ability to benefit from a nutrient.

True bioavailability is the degree to which a substance (such as a nutrient) becomes available to the target molecular site after administration. For substances like vitamin C and glutathione, the target molecular site is typically inside the cell, and not just inside the bloodstream.

How do Nutrients Enter the Bloodstream?

The process of uptake from the digestive system varies greatly from nutrient to nutrient. Vitamin C is absorbed almost exclusively in the small intestine and requires the presence of transport proteins. For vitamin C, these transport proteins are called sodium-dependent vitamin C co-transporters (SVCTs). A lack of these proteins produces a corresponding lack of vitamin C uptake. Published research confirms that SVCTs (transport proteins) tightly regulate vitamin C absorption.

In one study with non-liposome-encapsulated vitamin C, 19 mg of a 20 mg oral dose entered the bloodstream. As the dose size increased beyond 30 mg, the blood level of vitamin C decreased drastically. They reported that a dose of 12,000 mg produced a maximum absorption of 16% into the bloodstream – That’s less than 2,000 mg!

This chart represents one of the more optimistic views of vitamin C bioavailability. A National Institutes of Health study suggests that only 200 mg of a single dose, regardless of size, actually gets into the bloodstream. Bioavailability, is only half of the picture, however. The nutrient must also be able to pass into individual cells.

Cellular uptake is required to obtain maximum benefit from nutrients. Recent fluorescent microscopy from laboratory tests with LivOn’s “Smart” lyposomal Nano-spheres®, confirms passage of these liposomes across cellular membranes and into cultured liver cells. The bright magenta spots show that uptake of fluorescent-dye-tagged liposomes.

A study by the National Institutes of Health reveals an even more restrictive control of non-liposome-encapsulated vitamin C uptake. It found that a maximum of 200 mg of non-liposome-encapsulated vitamin C is absorbed at any given time. What happens to all of the non-absorbed vitamin C? It moves into the colon where it is excreted. For some individuals, an excess of vitamin C in the colon causes several unpleasant symptoms, including cramps and diarrhea.

What’s the Best Way to Deliver Nutrients Into The Cells?

Once vitamin C enters the bloodstream, an active transport process is needed for the nutrient to move across any cellular membrane. This process can be just as restrictive as the one that initially limited the nutrient’s entrance into the bloodstream. Much of the vitamin C that is not actively transported into the cells will be filtered out by the kidneys and passed in the urine.

Liposome encapsulation overcomes the absorption barriers and cellular uptake restrictions because liposomes do not rely on SVCTs or any other carrier transport system. Instead, due to their size and composition, they are able to passively absorb through the intestinal wall and through cellular membranes. As a result, liposome-encapsulated nutrients (like Lypo-Spheric™ Vitamin C) achieve maximum bioavailability in the cells, where they are needed most.