Genetic Susceptibility to Disease

In the early days of DNA research, it was believed that your DNA sequence determined everything about you, from your eye color, to your personality, to your susceptibility to disease, etc.  From one angle, this is true.  You cannot change an adenine nucleotide to a guanine in an adult's entire genome (at least not yet), but genetic science has led us to the realization that how genes are expressed can be altered throughout a person's life and have effects on subsequent generations (1).

Now, I do not claim to be an expert on this at all.  I only know the basics - your DNA has specific nucleotide sequence sections called genes, which, when activated or "expressed" result in protein products that direct other cellular activities. (Disclaimer: This is a gross simplification. I am just learning this all myself.)    What I have been quite interested in lately and wanted to bring up in this post, however, is epigenetics: the study of how gene expression can be altered in ways that do not involve changes in the DNA sequence.

There are some interesting examples of this phenomenon.

Decreased birthweights in infants after maternal in utero exposure to the Dutch famine of 1944-1945 (2).  This study looked at females who were in utero during the Dutch famine from Nov 1944 to May 1945.  The babies who were exposed to famine during 1st and 2nd trimesters had lower birthweights than their non-famine controls.  This is not too surprising.  What is more interesting is that the children of these females who were exposed to famine in utero also had decreased birthweight, compared to the children of the controls.

Maternal and grandmaternal smoking patterns are associated with early childhood asthma (3). This study shows that children whose mothers smoked while pregnant were 1.6 times more likely to develop asthma than those who had non-smoking mothers.  Again, not too surprising.  But, this effect is magnified - grandchildren of the smoking, pregnant moms were 2.1 times more likely to develop asthma.  Clearly, something else is going on.

Today, it seems that every disease has some sort of genetic component: heart disease, obesity, cancer, you name it.  And the occurrences of these diseases are only on the rise.  Some statistics..... If they do indeed have such a strong genetic disposition, and gene expression can be changed by diet and lifestyle, then I would have to conclude that we are all screwing up our genes and it is only going to get worse with our children and grandchildren.

This is why I urge everyone to really think about his/her daily life, the acts that we do that may be influencing our gene expression.  Lifestyle, stress, exercise, and food all play an important role on how we feel, and probably how our bodies respond.  I would argue that food is of the utmost importance.  After all (I'll say it again!), you are what you eat.  A species can withstand famine or a crappy diet for quite some time, as human bodies are adept, efficient, and resourceful.  However, subsequent generations will suffer if the diet isn't fixed.

Take care of your genes.  I know that my food and health endeavors can seem crazy, but all I think is that people should make an effort to learn about what they are actually ingesting, and then make their own decisions.  I welcome debate - together maybe we can dig deeper and really discover the secret to a health that we can proudly pass down to our children and grandchildren.

References:
1. Cummings JA, Clemens LG, Nunez AA. Mother counts: how effects of environmental contaminants on maternal care could affect the offspring and future generations. Front Neuroendocrinol. 2010 Oct;31(4):440-51.
2. Lumey LH. Decreased birthweights in infants after maternal in utero exposure to the Dutch famine of 1944-1945. Paediatr Perinat Epidemiol. 1992 Apr;6(2):240-53.
3. Li YF, Langholz B, Salam MT, Gilliland FD. Maternal and grandmaternal smoking patterns are associated with early childhood asthma. Chest. 2005 Apr;127(4):1232-41.