Nutritional Epidemiology (external validity) Essay

Nutritional Epidemiology (external validity) - Essay Example Some of the research design factors that affect the validity of research results and recommendations include; Hawthorne Effect, situation specifics such as treatment conditions, pre-test effects and post-test effects to the observation. This paper will discuss the external validity of three studies investigating the effect of micronutrients and vitamins on colorectal cancer development. To study the effect of combined folic acid, vitamin B6 and vitamin B12 on colorectal adenoma, Song et al (2012) used a subset of the Women’s Antioxidants and Folic acid Cardiovascular Study (WAFACS) (Song, et al, 2012). The design was a double blind randomized placebo controlled trial involving women professional at risk of developing cardiovascular disease. The inclusion criteria were age of above 40 years, postmenopausal, and a self reported cardiovascular disease of predisposing factors (Song et al, 2012). This study did not find statistically significant effect (protective or predisposing) of combined B vitamins in colorectal cancer contrary to some of the previous studies (Song et al, 2012). While the blinded approach of the study eliminates potential bias thus enhance its external validity, randomization introduces artificial effect that is not, in real life setting. The single sex specification of the study also limits its generalization across people when compared to the wider community, which is comprised of the two sexes. In real life predisposing risk factors affect both sexes in interactions that may be difficult to simulate in an experimental setup. The timing of the study though is one of the longest treatments and post-treatment follow up assessment (approximately nine years) is far from ecological reality. However, cardiovascular disease predisposing factor improves the generalization of the study to situations. Therefore, the findings of