Genetic Testing for Personalized Nutrition and Its Impact on Behaviour Change

Knowledge and perception of Registered Dietitians: Genetic testing for personalized nutrition and its impact on behaviour change

In 2003, when the Human Genome Project published the full sequence of the human genome, the drive for personalized or more precise medicine and nutrition began (Plavlidis et al, 2015). This started the evolution of nutritional genomics which is a broad term for a study which involves the interaction between nutrients, genes and health outcomes. Each cell in humans contains 46 chromosomes made up of 23 pairs.  Chromosomes are made up of DNA which contains genetic information or the blueprint for life.  Nucleotides are the building blocks of DNA.  These nucleotides are Adenine (A), Guanine (G), Cytosine (C) and Thymine (T).  DNA is made up of double strands of these nucleotides, for example AG pair together and CT pair together. Different kinds of genetic variations exist such as a single-nucleotide polymorphins (SNP) which is a variation or alteration in one nucleotide where one nucleotide is replaced with another. For example, C will pair with G instead of T.  These SNPs can often be referred to as modifier genes.  Nutritional genomics looks at how single-nucleotide polymorphins (SNPs) interact with disease, diet and other health conditions (Plavlidis et al, 2015). An individual’s genotype might benefit from specific nutritional interventions while other strategies may have no benefit or even cause harm. For example, someone following a low sodium diet might see an increase in blood pressure or someone following a low saturated diet where it is expected to see blood fats improve but instead it has no effect or the opposite effect.  This difference in response was observed in some early research done in 2002 that looked at what happens to triglycerides (TG) four hours after eating a meal high in saturated fat (Shaefer et al, 2002).  TG were expected to increase and for most people this is what happened but for some TG went down (Shaefer et al, 2002).  Another study done in 2001 looked at a group of 420 randomly selected men and women who were divided into two groups; low saturated fat intake (mean of < 8.6% of energy from saturated fat) and high saturated fat intake (mean > 13.5% of energy from saturated fat).  For most participants following a high saturated fat diet LDL (bad cholesterol) increased and HDL (good cholesterol) decreased as expected. However, some participants in the high saturated fat group showed improved blood fats with a decrease in LDL and an increase in HDL (Campos et al, 2001).  In both studies, all participants under went genotyping, specifically for the APOE genotype which modulates saturated fat intake. Variations in this gene (APOE2, APOE3, APOE4) were observed.  It was discovered that individuals with the APOE4 genotype experienced a reduction in TG and very low density lipoproteins (VLDL) and an increase in high density lipoproteins (HDL) which is the opposite of what was expected when consuming a high saturated fat diet (Campos et al, 2001).   Genetic variations appear to explain why there are discrepancies in research exploring the role of diet in disease, and why some people do not have typical responses to standard nutrition interventions. The science of nutritional genomics can shed light on these different responses and help identify who might benefit from a specific dietary intervention and who might see no effects, but most importantly that the advice offered does not cause harm. 

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  Genetic variations may affect calorie intake, appetite, body fat distribution, weight, caffeine metabolism and food preferences. This research paper will investigate the scientific evidence behind nutritional genomics and its potential to be used as a tool for nutritional professionals to prescribe personalized nutrition therapy. As well, most health professionals and people are aware that motivation is a crucial factor in behaviour change.  Generally, telling someone that they are at an increased risk for developing a medical condition or disease isn’t helpful and results in minimal to no change in behaviours.  This paper will also explore the impact to behaviour change when individuals are given the evidence of genetic variations along with detailed explanations and personalized guidance from a health professional such as a Registered Dietitian. Dietitians have the expertise and training in the science of nutrition and therefore a reliable and trusted source of nutrition information and most qualified to give personalized nutrition advice.  As the science of nutritional genomics evolves, are Dietitians equipped with the knowledge and understanding of genetics and the relationship between genes and an individual’s diet, as clearly all people do not respond to food the same way and one size fits all nutritional interventions often fail?

Works Cited

Campos H, D’Agostino M, Ordovas JM (2001). Gene-diet interactions and plasma lipoproteins: role of apolipoprotein E and habitual saturated fat intake. Genet Epidemiol. Jan;20(1):117-28. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/11119301

Pavlidis, C., Patrinos, G., & Katsila, T. (2015). Nutrigenomics: A controversy. Applied & Translational Genomics, 4, 50-53. doi: 10.1016/j.atg.2015.02.003

Schaefer EJ. Lipoproteins, nutrition, and heart disease (2002). Am J Clin Nutr. Feb;75(2):191-212. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/11815309

Genetics and Nutrition

Knowledge and Perception of Registered Dietitians: Genetic testing for personalized nutrition and its impact on behaviour change

Interpreting the science into practice

3 examples that explore SNP variations

And their potential impact on diet and/or health

 

 

#1 research review and evidence to support – Caffeine CYP1A2 genetic variation and risk for disease (Hypertension and Heart Attack)

#3 research review and evidence to support – Genetic variation in TAS1R2 and its association with taste and desire for certain foods ie sugar

#2 research review and evidence to support – Weight management FTO genotype looking at response to weight loss and disease risk (Fat)

 

 

–Awareness of genetic test results and detailed explanation motivates

Behaviour change (research to support this)

-Who best to translate, explain and offer personalized dietary advice

Based on genotype – consumers report Registered Dietitians.

-Knowledge and attitudes of Registered Dietitians re: genetic testing – research available > a decade ago

– is there still a need for continuing education

– To explore/study if knowledge or perception has changed via survey for Registered Dietitians that looks at basic demographics, knowledge and perception of genetic testing in the past 10 years

-If Dietitians are the experts in nutrition their role is important in translating the science of nutritional genomics into sound nutritional advice and perhaps even the advancement of the science, are they prepared?