Describe some of the common limitations students in our class have discussed as they critiqued their studies.

Describe some of the common limitations students in our class have discussed as they critiqued their studies.  What are some of the difficulties researchers encounter as they design experiments/studies to try to understand the link between nutrition and health?  List and describe briefly at least four common problems we have discussed/heard about in the presentations or readings.

 (20 points, approx. 300-400 words) Your sister is taking iron supplements because she has been diagnosed with iron-deficiency anemia.  She hears on the news that a new study has found that excess iron ingestion increases risk of heart disease.  She also tells you she has read about an amazing new iron supplement that is all natural, and thus, much safer than her prescription iron supplements.  She asks your opinion.  How would you prepare to respond to her and what is your advice to her?