Ph.d. thesis: "Plasma enterolactone and physical activity in relation to colon and prostate cancer" by Nina Føns Johnsen

The ph.d. thesis "Plasma enterolactone and physical activity in relation to colon and prostate cancer" by Nina Føns Johnsen was successfully defended on November 25^th, 2009 at the Danish Cancer Society in Copenhagen. The thesis was based on the following three studies:

A study of the plasma concentration of the wholegrain-derived phytoestrogen, enterolactone, in relation to colon and rectal cancer revealed a lower risk of colon cancer among women with higher enterolactone concentration, and a higher risk of rectal cancer among men with higher enterolactone concentration.

A study of the association between physical activity and colon cancer in the Danish Diet, Cancer & Health cohort revealed no association between colon cancer risk and physical activity in terms of occupational activity, participation in or time spent on the six types of leisure time activity, sports, walking, cycling, gardening, housework, or do-it-yourself activity. However, participation in a higher number of different activities may be associated with lower colon cancer risk.

A study of the association between physical activity and prostate cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) study revealed no association between prostate cancer risk and physical activity in terms of participation in or time or energy (METs) spent on the four types of leisure time activity, sports, walking, cycling, and gardening, or participation in more leisure time activities. However, a higher level of occupational activity was associated with lower risk of advanced prostate cancer risk.

Furthermore, some results from a study on enterolactone and prostate cancer were also presented, but no association was found.

Besides the controversy of some of the above findings, the thesis includes a discussion of the use of confounders in epidemiological studies, the use of time scale in survival analysis with an age-dependent outcome, and the inclusion of data on antibiotics in studies on the microflora-produced phytoestrogen, enterolactone.