During the past two decades, there has been a rapid increase in studies that report associations with gene polymorphisms, nutrition and disease risk (Burdge, Hoile, & Lillycrop, 2012). This is a paradigm shift from traditional nutritional recommendations that have been based on age, sex, and pregnancy. The advances in the association with epigenetics and nutritional requirements have been the driver of the advancement in the field of nutrigenomics, which has been wildly exploding.
What is epigenetics? We learned in middle school that our genetic code is the sequence of nucleotides in our DNA, which can certainly influence health status. However, I was amazed when I learned for the first time that there is another set of instructions that affects our gene expression, and this set of instructions can actually influenced by our environment such as our diet! This is referred to as epigenetics. I remember learning in my Biology Masters that Epigenetics meant “above the genome”. Epigenetics is the “study of heritable changes in gene function that occurs independent of a change in DNA sequence” (Kauwell, 2008) which involves a group of modifications that do not alter the actual DNA structure, but rather chromatin structure that can regulate transcription. “The major epigenetic processes are DNA methylation, histone modification, and noncoding RNA’s” (Burdge et al., 2012).
As we learned once in college, through the process of meiosis, there are multiple ways that diversity occurs among our genotypes to ensure no two genotypes are alike (well, except in the case of identical twins). These include crossing over, independent assortment, and random fertilization. This creates genetic uniqueness that is a result of variations in our DNA in which one nucleotide is substituted for another at specific locations on our genome, often called SNP’s (single nucleotide polymorphism) (Kauwell, 2008). We are finding out that SNP’s can alter certain nutrient requirements and metabolism, and although they do not affect regions that code for proteins, they do affect events that occur at the molecular levels such as transcription factor binding to the promoter region of the gene, which can thus alter the expression of that gene. Studies with identical twins have demonstrated some interesting results in the role environment indeed can play a role as seen in insights from identical twins (Learn Genetics, n.d.).
One common nutritionally relevant SNP that is a hot topic in functional medicine occurs on the MTHFR gene which provides instructions for making an enzyme called methylenetetrahydrofolate reductase. This enzyme plays a role in processing amino acids such as homocysteine to methionine (NIH, n.d.). This SNP involves the substitution of cytosine with thymine (C->T) at the base pair 677 of the gene, that results in a coding change where alanine is replaced with valine at position 222 in the gene product (Kauwell, 2008). Inheriting one or two copies of this gene variant can down-regulate the enzyme function, which has some health implications. For example, someone with two copies of the gene (homozygous) may experience elevated plasma homocysteine, especially when paired with low folate status (Kauwell, 2008). This can put the person at risk for coronary artery disease. “Fortunately, reduced MTHFR activity associated 677C->T polymorphism is attenuated when folate status is adequate” (Kauwell, 2008).
What is fascinating about our epigenome is that it provides an extra layer of instructions besides our genetic sequence that codes for proteins synthesized by our bodies. This “extra layer of instructions” can affect whether certain genes are turned on or off, which can thus affect cellular function and metabolism. In fact, the environment has a strong influence on these instructions, such as nutrient status from food and supplements, which can alter the epigenetic state of the genome and subsequent gene expression. What this means is that the same exact DNA sequence for a particular gene may give rise to different outcomes based on things like diet-induced epigenetic modifications that can influence gene silencing and activation.
This is an exciting time for the field of nutrition and nutrigenomics, as we are finding increasing evidence that nutrition throughout the life course can modify the epigenome in such a way that can influence risk of a number of important diseases. “Therefore, if nutritional recommendations are to be targeted at individuals then epigenetic effects must be included in any attempt at personalized nutrition” (Burdge et al., 2012).
Burdge, G. C., Hoile, S. P., & Lillycrop, K. A. (2012). Epigenetics: are there implications for personalised nutrition? Curr Opin Clin Nutr Metab Care, 15(5), 442-447. doi:10.1097/MCO.0b013e3283567dd2
Kauwell, G. P. (2008). Epigenetics: what it is and how it can affect dietetics practice. J Am Diet Assoc, 108(6), 1056-1059. doi:10.1016/j.jada.2008.03.003
Learn Genetics. Insights from Identical Twins. Retrieved (2019, April 25) from https://learn.genetics.utah.edu/content/epigenetics/twins/
NIH (n.d.) MTHFR gene. Retrieved (2019, April 25) from https://ghr.nlm.nih.gov/gene/MTHFR
The rapidly expanding discoveries in the fields of nutrigenomics and nutrigenetics are transforming the field of nutrition and health education. As a health educator, I plan to use this information to empower and enlighten clients to make informed decisions on their lifestyle choices. It also will help me become a proficient “translator” in the language most people are unfamiliar with. Genetics can be confusing and for many people, unknown territory. As a result, I see my role as a “genetics literate” health educator that can regurgitate the complex terminology into something the average person can understand. I believe it is a skill that every clinician should adopt.
What is the impact of genomics on the practice of nutrition?
By using genetics and molecular biology to predict individual risks, based on genotype, nutrigenomics may have the potential to prevent and treat diet-related chronic disease and conditions. The push for personalized nutrition began in 2003 after the Human Genome Project published the first sequence of the human genome, as it began to uncover that the “one-size-fits-all” nutritional strategies are not as effective as we once thought (Dennett, 2017). Since then, gene-diet interactions that affect various metabolic pathways related to disease risk and health are continuously being uncovered, shaping personalized nutrition, which targets dietary recommendations to an individual’s genetic profile (Nielsen & El-Sohemy, 2012). To date, both nutrigenetics (influence of gene variants and the interaction with the environment) and nutrigenomics (the influence of the environment to our gene expression) both have opportunities as well as challenges. A greater understanding on how gene-nutrient interactions influence key metabolic pathways that influence gene expression and changes in the metabolome can aid in treatment and prevention of disease (Kohlmeier et al., 2016). Genetic data can be integrated with phenotypical, social, cultural and personal preferences to provide a more individual nutritional approach (Kohlmeier et al., 2016).
If we have a greater understanding of potential gene-nutrient interactions, then it may be possible to manipulate diet in such a way to minimize the metabolic risk certain diseases, such as obesity(Phillips, 2013). It may be possible to diagnose disease risk early and target interventions such as lifestyle modifications or changes in nutritional behavior or exercise therapy to reduce the risk of disease development (Phillips, 2013). Knowledge gained from current research in the field could lead to the development of personalized nutritional guidelines for individuals and specific subpopulations, (Nielsen & El-Sohemy, 2012), while also providing the ability to categorize individuals into subgroups (Kohlmeier et al., 2016). And finally since nutrients can regulate gene expression patterns, by influencing gene transcription and translation, the information obtained can provide important insights about the influence of specific food components on important biological processes in risk of certain diseases (Fenech et al., 2011).
As promising as this may sound, there are some challenges. Genomics can make it difficult to make simple, general recommendations (Kohlmeier et al., 2016). As a result, as our understand of genomics expands, nutrition therapy may be perceived as more complex, and that could be a deterrent for individuals who want to make simple lifestyle changes. For example, a subset of the participants who had lower educational status and were members of ethnic minority groups reported a more deterministic interpretation of the results and were more confused by the information (Nielsen & El-Sohemy, 2012). Another issue is that the genetic testing industry is largely unregulated and there are some concerns over the consumer’s ability to accurately interpret the meaning of the test results, given that no healthcare professional involvement is required (Nielsen & El-Sohemy, 2012.
Some questions that still are unanswered include (Fenech et al., 2011):
- Will public health really be improved with individualized tailored recommendations?
- How costly will personalized nutrition be? Will this approach only be available for those with money and education?
- Will people be motivated to adhere to a tailored diet?
- How will this affect those who really need a simplistic view on the role of food on our health? Will this new information dilute general healthy eating messages?
And finally, there are also some legal and social issues that need to be addressed (Kohlmeier et al., 2016).
I believe there is still quite some room for growth in the genomics world to address some of the challenges that arise. However, the opportunities are evident and continuously expanding, and only time will tell what the future holds.
Dennett, C. (2017). The Future of Nutrigenomics. Retrieved (2019, May 5) from https://www.todaysdietitian.com/newarchives/1017p30.shtml (Links to an external site.)Links to an external site.
Fenech, M., El-Sohemy, A., Cahill, L., Ferguson, L. R., French, T. A., Tai, E. S., . . . Head, R. (2011). Nutrigenetics and nutrigenomics: viewpoints on the current status and applications in nutrition research and practice. J Nutrigenet Nutrigenomics, 4(2), 69-89. doi:10.1159/000327772
Kohlmeier, M., De Caterina, R., Ferguson, L. R., Gorman, U., Allayee, H., Prasad, C., . . . Martinez, J. A. (2016). Guide and Position of the International Society of Nutrigenetics/Nutrigenomics on Personalized Nutrition: Part 2 – Ethics, Challenges and Endeavors of Precision Nutrition. J Nutrigenet Nutrigenomics, 9(1), 28-46. doi:10.1159/000446347
Nielsen, D. E., & El-Sohemy, A. (2012). Applying genomics to nutrition and lifestyle modification. Per Med, 9(7), 739-749. doi:10.2217/pme.12.79
Phillips, C. M. (2013). Nutrigenetics and metabolic disease: current status and implications for personalised nutrition. Nutrients, 5(1), 32-57. doi:10.3390/nu5010032