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The Devil's Advocate on Antioxidants: Scientific Studies

 Part 1C: In vivo & Ex vivo Laboratory Trials

ex vivo studiesIn order to evaluate the studies about pharmaceuticals and nutritional supplements, including antioxidants, it is useful to understand “scientific” studies and the games that can be played with statistics, variables and factors involved. In Part 1B of “The Devil’s Advocate on Antioxidants,” I laid out a simplified version of the progression of scientific studies, along with the pros and cons of each stage:

1) Research-- thousands of lead compounds are narrowed down to hundreds for a targeted issue
2) Pre-Clinical Trials-- laboratory and animal testing
    • Laboratory Studies
      • In vitro-- test tube experiments that may or may not correspond to human testing
Now we will look at the other types of laboratory studies:
      • Ex vivo studies: “conducted on functional organs that have been removed from the intact organism.” (1)
        • Pros: specific reactions can be observed in targeted organs, more broad than in vitro studies
        • Cons: like in vitro studies, the effects on a part of the body may not accurately represent what would happen with the organ in the context of the body
      • In vivo(Latin: in life) studies: “conducted with living organisms in their normal intact state” (2). This type of testing can be conducted in a lab, which could include Animal Testing.
        • Pros: The whole organism is being tested, so real-life results can be studied, including the effects upon the untargeted body systems.
        • Cons:   An approach that works well in the lab or animals doesn't always work well in people. Thus, research in humans is needed. (3) A case in point is how ascorbic acid (one component of Vitamin C, often the synthetic form)d) is effective in treating scurvy in guinea pigs, however, in humans it is ineffective; the entire Vitamin C complex is needed to treat scurvy in humans. Ethically there may be disadvantages to animal studies as well.

Outside of a lab, Human Studies are another form of in vivo studies. This is typically the final phase which incorporates several stages, including three primary phases, that typically span a period of 6-7 years in total. The difference between phases within Human Studies has to do with the size of the group sampled as well as the pre-existing health of study participants. Each phase also has a specific goal in mind such as determining general or statistical data related to the safety, effectiveness, optimal dosage and benefit-risk ratio of the compound or pharmaceutical being studied. In the case of pharmaceuticals, each new product must complete all of the phases before being submitted to the FDA for review.

The cons of studies on humans may include factors such as the volunteers not being consistent with lifestyle choices, for instance consumption of fats may change based on education and perception of what is healthy to the participant. (4) Ethics is definitely involved in human studies as well, such as the tested compound having an unanticipated negative or dangerous effect upon the health of the participants-- antioxidant clinical trials fall into this category. Ethically they could not continue with several studies because of the increased incidence of cancers with the use of antioxidants. (5, 6, 7)

Next time, we will discuss the two main types of Human Studies along with the pros and cons of the different types. As you can see there are many factors that need to be considered when evaluating these studies in order to make healthy choices for you and your family. Hopefully this blog series has helped to remove some of the confusion!

L'chaim-- To Life!

Sources:

2 Ibid.
3 Ibid.
4 In Defense of Food, Michael Pollan
5 JAMA, February 28, 2007—Vol 297, No. 8, www.jama.com at University of Wisconsin -Madison.
6 The Journal of American Society of Nutrition, 2007, “Antioxidant Supplementation Increases the Risk of Skin Cancers in Women but Not in Men.”
7 Arch Intern Med. 2004; 164: 2335-2342.

 

The Devil's Advocate on Antioxidants: Scientific S...
The Devil's Advocate on Antioxidants: Scientific S...
 

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