Q. I'm a man and 55 years old. Please suggest a blood-test that would help me determine which herbs and supplements to take. I came across a web site that says if I send them a blood sample they can analyze it and tell me what vitamins and minerals and other products I need to take.

    A. Medical research has not reached a level of sophistication where a comprehensive blood testing for levels of vitamins, minerals, nutrients and other substances in the body would lead to an accurate determination of which vitamins, minerals, amino acids, hormones, fatty acids, herbs or other dietary supplements one should take over the long term that will prove to increase longevity. There are many websites that claim through an extensive blood test they can accurately advise a specific multivitamin and multimineral regimen. Some of these sites may not actually do a comprehensive test but rather make up some numbers since it is too expensive to test for tons of nutrient, mineral and vitamin levels. The human body is much, much more complicated than many people realize. An important point that many people do not consider is that blood levels sometimes do not reflect the levels of a substance within tissues or cells. For instance, one can have a low level of DHEA hormone shown on a blood test but the levels could be high in hair or prostate tissue. Hence, by taking a DHEA pill, one could cause more harm than good, for instance hair loss or prostate gland growth. Other factors to consider: Changes in daily food intake make a significant impact on levels of nutrients at any one time in the bloodstream; There are variations throughout the day depending on what time the blood sample is taken; There are changes throughout the seasons; Different labs may provide results that can vary up to 20 to 30 percent or more from other labs; Changes in sleep and activity level could influence blood results; Use of medications and resulting interactions with supplements could have an influence; There could be racial differences in optimal levels. There are hundreds of potential vitamins, minerals, amino acids, fatty acids, hormones, etc that could be supplemented and how do we know the proper ratios? Could taking a few dozen and missing out on several other crucial ones throw things out of balance and make health matters worse? As you can see, with all of these uncertainties, I do not suggest you fall for the scams that some websites are promoting. For general overall diet and longevity advice, see http://www.raysahelian.com/diet.html and www.raysahelian.com/longevity.html