DEAR DR. BLONZ: I'm taking several vitamin and mineral supplements and OPCs in what is referred to as an "isotonic form." This form is supposed to be a more efficient delivery system as it goes through the stomach and right to the small intestine, thereby allowing close to 95 percent absorption due to not being diluted by stomach acids. Also, it's said to speed up entry into the circulatory system, occurring within 15 minutes as opposed to four hours or more for a regular pill or capsule. What are your thoughts on taking vitamins and minerals in this form as opposed to a regular pill or tablet? -- C.G., Sun City, Ariz.
DEAR C.G.: "OPC" refers to the tongue-twisting term "oligomeric proanthocyanidins." It's no wonder they stick with the letters. OPCs are naturally occurring bioflavonoids that are found in grape seeds and skins, pine bark extract and other plants. They function as antioxidants, meaning that they attract and combine with reactive oxygen species before they can cause damage. OPCs are being investigated for a potential role in protecting against chronic disease, but keep in mind that supplements cannot replace whole foods and what they have have to offer. With supplements you may get a few standouts, but using a sports analogy, it would be like having a star player without a coach or the rest of the team.
As far as "isotonic" goes, it is questionable who benefits besides the company making the sale. Isotonic means "the same tone," but in physiological solutions, it usually refers to a concentration of ingredients similar to those inside of a cell. The idea of an isotonic liquid is that it will not pull fluids from inside the cell and this may facilitate bioavailability. When they give IV solutions, for example, they usually give them in isotonic saline because they don't want to affect blood pressure or volume or the health of the cells. With dietary supplements, the question one might ask is: What difference does it make if the substance is absorbed slightly faster?
In terms of your product, a 95 percent absorption rate is bogus as a general claim. The rate of nutrient absorption depends on a number of factors, such as the nature of the nutrient; whether the subject already had a deficiency, sufficiency or excess of the nutrient; and other substances present in the digestive system at the same time.
You say it is described as "a more efficient delivery system," but I would be interested in seeing any evidence to support such a claim. Pills, capsules, powders or liquids work just fine -- isotonic forms of dietary supplements have not been shown to be more effective. As a rule, it's usually best to take vitamin and mineral supplements at mealtime. Digestion and absorption are designed to liberate the nutrients from the foods by keeping the food churning and in contact with the absorptive surfaces for an extended period of time.
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