DEAR DR. BLONZ: There are many companies offering vitamin and mineral deficiency tests, claiming to let you know which supplements you need. They test blood, saliva, urine and hair samples, in addition to asking questions about lifestyle and symptoms. In theory, these tests might take the guesswork out of finding the supplements one needs. But do these services work? -- W.S., Phoenix
DEAR W.S.: I remain skeptical of the deficiency tests you describe. Granted, vitamins and minerals play an integral role in bodily systems. Laboratories can determine if there is enough of a nutrient by observing or measuring specific tissues or chemical reactions. Such tests, however, are only useful in helping to determine if there is a stark deficiency.
A blood test, for example, might measure the activity of a particular enzyme that depended on the presence of a particular nutrient. Another approach might be to check for the occurrence of a particular symptom or abnormal metabolic byproduct that only appears when a particular nutrient is in short supply. In both these cases, you would detect a deficiency, but nutrient deficiencies of this type are uncommon. (Check tinyurl.com/jlz7unv for a report on the prevalence of nutrient deficiencies.) This is not the same as a test that can give you advice on the best vitamin and mineral regimen.
What about hair tests? In this approach, hair clippings are sent to a laboratory for analysis. The idea is that hair provides a running diary of our nutritional status at the time it was created inside the hair follicle. On the surface, this might seem to be a convenient procedure to provide useful clues to our inner workings. Hair analysis has been shown to be of value in uncovering certain toxicities, but it has never proven itself as a useful measure for determining an individual's unique dietary requirements. The same, unfortunately, can be said for saliva and urine tests.
The bottom line is that there isn't a precise way of determining an optimum intake level of any given nutrient for any given person. If anyone tells you otherwise, ask for evidence of their assertions.
DEAR DR. BLONZ: Are there certain B vitamins that stimulate the growth of fat cells? If so, which ones? -- N.K., Newark, New Jersey
DEAR N.K.: Fat cells, also called adipocytes, are distributed throughout the body, and they represent our energy reservoir. They grow in size as more fat, in the form of triglycerides, is dropped off for storage. Once they reach capacity, the body can make more fat cells. Once formed, fat cells are difficult to get rid of, remaining throughout our lives and changing only in the amount of fat they contain.
Fat cells, like all cells, depend on essential nutrients, but there is no evidence that B vitamins will stimulate fat cell growth, unless excess dietary energy continues to fill the existing fat cells. In that case, the issue is the intake of excess calories -- not vitamins.
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