Imagine that researchers are conducting a randomized controlled trial of a high-fiber supplement as a preventive measure in persons at increased risk of type 2 diabetes. People enrolled in the study are disease-free at the time they agree to participate in the trial, but they all have a family history of type 2 diabetes and are considered at high-risk (80%) to develop the disease during their lifetime. The 10,000 participants who start the trial are healthy individuals who are randomly allocated to receive either high-fiber supplements or placebo for several years. As you can imagine, this study will be quite expensive and will require a large infrastructure of personnel and materials to carry it out successfully.

Because type 2 diabetes has reached epidemic proportions in the United States, the potential benefits of this research are important at a population level. Unfortunately, high-fiber supplements have also been shown in a few studies to be associated with gastrointestinal blockage (which can be life-threatening) and reduced nutrient absorption, which may lead to anemia, osteoporosis, and other debilitating chronic diseases. The supplements may also reduce absorption of certain medications and cause gastrointestinal distress. The potential side effects of continuous high-fiber supplementation are only partially understood, and long-term effects are unknown.

a. What are the potential risks and benefits to be considered when designing this study?

2. When the side effects and long-term effects of a potential preventive measure are largely unknown, is it ethical to expose participants to these risks? Why or why not?