Sunday, March 9, 2014

First Reader: Energy Intake and Cancer

In the studies “Lifestyles, Hormones, and the Risk of Cancer” and “Evolutionary foundations for cancer biology,” I found the discussion of the positive correlation between energy intake and cancer development to be interesting mainly because I always assumed the opposite. Before reading the both papers, I thought that by having a higher energy intake (so long as the food is moderately healthy), more resources/ energy could be allocated to the immune system and lower the overall risk of cancer. However both the papers stated that the positive correlation between energy intake and cancer development was due to increased levels of certain hormones rather than anything related to the immune system. The paper “Evolutionary foundations for cancer biology” specifically explained that greater caloric intake allows more energy to be allotted to reproductive pathways. It makes sense in the sources they cited, as the perpetrators for cancer development were testosterone in males and progesterone in females- both of which are sex hormones.
            A quotation from the study “Evolutionary foundations for cancer biology” which I thought was interesting was the fact that “natural selection does not shape organisms directly for health or longevity. An allele hat increases net reproductive success will tend to increase in frequency irrespective of its effect on health.” In simpler words, it states that natural selection is driven by reproductive success even if aspects of that success are detrimental to one’s health.  So long as an organism is able to create offspring to continue into the next generation, it is deemed as being “good enough” regardless of its’ quality of life. This ties into the aforementioned paragraph as even though higher levels of sex hormones might be harmful later in someone’s life, it helps in increasing the possibility for reproduction.


  1. Edward,
    I found your blog post to be interesting because you linked both of the articles in a way that I had not previously thought. I, too, thought that there would not be a positive correlation between energy intake and cancer development. It is very interesting to think that reproductive success can continue despite the possible consequences of reproduction in terms of an individual with cancer.
    However, it does make sense that the body uses the extra caloric intake to propel the species. Which, as we have learned, can create extra oestrogen and progesterone ultimately causing breast cancer.
    I also found the last segment of the "Lifestyle, Hormones, and Risk of Breast Cancer" interesting. Jasienska (2001) stated that the "link between the risk of breast cancer and the nutritional status of a population" can be mediated "by ovarian sensitivity to environmental conditions". This can be taken a step further to make the assumption that, our reproductive system is very sensitive and that a certain lifestyle choice can possibly make the distinction of the growth of cancer cells.
    It is also very interesting to see the different distinction breast cancer makes among various populations. Maybe culture has a larger part to play in developing diseases and in this case, cancer.

  2. I agree with the above comment. You do a good job linking these two articles and making the point that there is a tradeoff between health and reproductive success. I had no assumptions about the relationship between energy intake and cancer incidence before reading the Jasienska article, but it makes a lot of sense that higher energy intake might mean lower cancer incidence because the immune system would be better able to fight off cancer. There is no doubt that some of that energy intake goes to maintaining the immune system. However, thinking about it further, it also makes sense that more of our energy may go to reproduction, since the ultimate goal is to pass on our genes to the next generation. The Jasienska article isn’t all doom and gloom though. It does mention at the end that increased physical activity (and lower caloric intake) could help lower estrogen and progesterone levels in women and lead to decreased risk for developing breast cancer. It would be interesting to see a study similar to this one that looks at incidence of male reproductive cancers in relation to testosterone or other gonadal hormone levels. It would also be interesting to compare the incidence of reproductive cancer among women who have had a lot of children and women who have not. Progesterone is known as one of the main pregnancy hormones, and I would assume that women who have had many children have actually been exposed to more progesterone than women with few or no children.