By Rick Henriksen, MD
Personalized medicine is a new buzzword in healthcare. The FDA defines this as “an innovative approach to disease prevention and treatment that takes into account differences in people’s genes, environments and lifestyles.” This sounds too good to be true, however with the advances in genetics we are now closer to understanding how our genes affect our outcomes.
Through sky-rocketing computing power our understanding has improved of how environments and lifestyles affect gene expression—a field called epigenetics. Imagine a day when you could look up your patient’s genome and determine their risk of prostate cancer. Or think of a Framingham 3.0, which includes lab testing, Apo genetic markers, and air quality.
The desire for personalized medicine has also led to an increase in genetic sequencing through companies such as ancestry.com and 23andme.com. We can now sequence parts of the genome to find a few hundred specific SNPs and mutations. However, the basic sequence of our genes does NOT give the whole picture. As providers we need to understand that our patients are not simply a projected pictures of their genes. My genes suggest that I have a low likelihood of going bald—the few hair strands left find this comical!
To fully understand how to use epigenetics and personalized medicine, providers should also understand the basic principles of Evolutionary Medicine, which is the application of modern evolutionary theory to understanding health and disease. Evolutionary medicine gives a foundation and framework on the why and not just the how.
If personalized medicine is about our individual differences, then evolutionary medicine answers why those differences exist.
If epigenetics shows how environmental and lifestyle factors influence gene expression, then evolutionary medicine provides the foundation of why that process works.
Here are the top 5 things that all clinicians need to know about Evolutionary Medicine.
- Natural Selection
Natural Selection is the backbone of modern evolutionary theory. Selection states that for specific traits or adaptations there is a non-random benefit for one trait over another trait. And this trait will also be passed on to the organism’s progeny. This is the classic “survival of the fittest.” In practical terms, over the course of time our specific traits have become the way they are in order to give the best advantage to our children.
Mismatch occurs when our previously helpful genes are not match to new environment. For example, a bright green bird is adapted to survive in a jungle, but then is disadvantage when it migrates to a gray volcanic island. Similarly, the fact that humans love the taste of sugar is a mismatch to our current environment. The sweet taste was once an important adaptation for our survival. If your distant ancestor had not liked honey or fruit, then that ancestor would have been at a disadvantage. However, now in our modern environment this desire for sweet foods leads to obesity and diabetes. Patients do not need to feel guilty for liking ice cream—we are built that way! Understanding this however, can provide clues to why we should structure our day to avoid such foods.
- Natural Selection Endures through Retirement
One false thought about evolutionary selection is it only applies until an organism has found a mate and had offspring. However, natural selection works throughout the lifespan as parents and grandparents provide advantages to the likelihood that their children live long enough to pass on genes. This theory is called the grandmother theory, and adaptations such as menopause are evidence.
Modern diseases such cancer and diabetes are not because natural selection no longer applied to our older ancestors, but these diseases more likely explained through mismatch.
- Sickle Cell and Malaria
If selection weeds out the dangerous traits then it would not make sense why diseases such as sickle cell persist. Evolutionary medicine provides the answer—the sickle cell trait persists because it does provide an advantage to the population. It turns out that being heterozygous for the sickle cell trait provides a 6% benefit against malaria.
- Lactose Intolerance is Continuing Evolution
Lactose tolerance is an example of ongoing evolutionary processes. Until the domestication of dairy animals, humans lost the ability to digest lactose around the age of 2. Dairy consumption has been tracked to genome changes in the lactase gene at several locations including northern Europe, Asia, and Africa. It has been estimated that lactase persistence was associated with a 3% advantage of survival in dairy drinking locations, which has led to high tolerance in Scandinavia for example. In areas without a history of dairy like in East Asia there is only a 0-10% persistence of lactase. Natural selection in different environments created this difference.
This is a great example of why personalized medicine is important! Without understanding the evolutionary nature of the lactase gene you may be causing a lot of undue gastric disease by recommending milk and dairy in your patients.
Want more information on Evolutionary Medicine?
- The Story of the Human Body by Daniel Lieberman: Start here!
- Evolutionary Medicine in Primary Care by C. Rick Henriksen: This is video of a Grand Rounds presentation I gave a few years ago.
- Evolutionary Medicine by Stephen C. Stearns and Ruslan Medzhitov: New textbook on evolutionary medicine
- Physicians for Ancestral Health: Physician group dedicated to bringing evolutionary medicine to patients
- International Society for Evolutionary Medicine and Public Health: International organization for research in evolutionary medicine
- Food and Western Disease by Staffan Lindberg: Textbook on nutrition through an evolutionary perspective.
Rick Henriksen, MD is n assistant professor in the Department of Family & Preventive Medicine at the University of Utah School of Medicine.