Part 1D: Human Studies
This blog series began as a discussion about the potentially harmful effects of high doses of antioxidants, synthetic antioxidants in particular, and because most scientific studies and supplement ads promote the benefits of antioxidants to human health, I thought it would be beneficial to investigate the various types of scientific studies and explore how to discern the veracity of claims made by these studies. This has been a rather long discussion, one that is not as interesting as some other topics that we could be cover, but it is in fact very pertinent! Because in order to determine the benefits or risks of any product we put into our bodies, we must first understand how conclusions are reached through scientific studies as well as some of the games that are played with statistics!
There are at least a dozen types of Human Studies, but we will only cover two main types in this blog: Observational Studies and Clinical/ Experimental/ Treatment Studies (3 names for the same thing). In this installment of “The Devil’s Advocate on Antioxidants,” we will only have enough time to discuss the first type:
1) Observational Studies-- are divided into two main sub-types of studies that both follow a group of people over time:
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- Case-Control Study-- uses existing data to identify and follow a group with a certain health problem as well a group without that health problem
- Pros: long-term study, factors can be studied retroactively that would be unethical to study prospectively, such as deliberately subjecting people to harmful situations
- Cons: when people get sick the lifestyle they report currently following may not be responsible for their illness because people adjust lifestyle factors based on their own research (1), recall bias (those who have health problem may be more aware of exposure to toxins than those who are healthy), it is difficult to accurately link the health of an individual to one factor being studied since various uncontrolled factors likely figure into an outcome
- Cohort Study-- such as the Nurses’ Health Study-- a cohort is any group of people who are linked in some way and followed over time. The goal is to break down the cohort into a group of exposed and a group of non-exposed individuals and follow their outcomes over time. Data is collected on the eating habits and health outcomes of more than 100,000 women over several decades costing over $100M before an illness is contracted.
- Pros: a step up in reliability from the case study because it is prospective (what will happen if…?) vs. retrospective (what happened because…?), more awareness of potential health factors
- Cons: relies on food frequency questionnaires (people can misrepresent information based on what they believe to be healthy), pretty much everyone in the group eats a Western diet, which is a high-risk diet, so that when they are divided into five segments for study, there is no significant difference between each part, making a connection between known health factors and health problems is not without error. And, as you can see, this is a VERY expensive type of study!
- Case-Control Study-- uses existing data to identify and follow a group with a certain health problem as well a group without that health problem
So, as you can see, these types of studies have their advantages, but there are equal disadvantages as well. In fact, no study is without its disadvantages! Next time, we will discuss the final type of Human Studies: Clinical Trials-- and this is where it will get interesting because we will analyze the question that precipitated this blog series: “Are antioxidants bad for your health?” Stay tuned for the final verdict! Meanwhile, check out this article for more information about How to Make Sense of Clinical Research, including a Glossary of Terms that is helpful to refer to when learning how to analyze studies.
L'chaim-- To Life!
Sources:
1 In Defense of Food, Michael Pollan