The Varying Applications of Nutrigenomics
Nutrigenomics is an emerging research area capable of revolutionizing healthcare and nutrition. While there is no exact definition of the science, put simply, nutrigenomics describes the relationship between diet, nutrients, and gene expression (Nutrigenomics. The Basics. | The Nutrition Society, n.d.).
This new field of genomics utilizes common tools and techniques such as omics technologies, bioinformatics, genome sequencing, microarrays, and genome-wide association studies (GWAS), among others, to observe how certain food bioactives (i.e., nutrients) affect the genes of an individual. In other cases, nutrigenomics can also describe how a person’s genetic makeup determine how their body responds to nutrients, which could also have an effect on a particular phenotype (e.g., disease risk, etc.).
With numerous combinations of tools and experimental approaches already available, as well as having the entire human genome sequenced (Human Genome Project Fact Sheet, n.d.), nutrigenomics is currently being applied to many different areas of healthcare and nutrition. Below are some examples of how nutrigenomics is applied in various areas, along with specific case studies that highlight these applications.
Prevention of chronic diseases
The presence of chronic diseases around the world continues to increase at an alarming rate. These non-communicable diseases, or NCDs (e.g., cardiovascular diseases, cancers, diabetes, etc.), have been responsible for around 35 million deaths (around 60% of the global population) in 2005 alone (Neeha & Kinth, 2013).
According to the World Health Organization (WHO), NCDs or chronic diseases account for 71% of the total deaths around the world each year (Budreviciute et al., 2020). In the United States alone, for a population of individuals 50 years and older, the number of people having at least one chronic disease is projected to increase by 99.5% from 2020 to 2050 (i.e., 71.522 million to 146.66 million, respectively) (Ansah & Chiu, 2022). Fortunately, nutrigenomics has been making strides in helping to curb these statistics as an additional research tool.
In one example, a gene-diet interaction experiment performed in 2007 revealed that the adiponectin gene polymorphism had an influence on a person’s diabetes and insulin resistance. It was found that this influence appeared to be heightened for those whose diets have a higher glycemic load, thus informing patients with this particular polymorphism to be more cautious of their carbohydrate intake (Neeha & Kinth, 2013).
Another study highlighted the use of nutrigenomics in correlating coffee consumption to heart disease risk. Cornelis et al. report that individuals with a genetic polymorphism in the CYP1A2 gene – which is the gene responsible for caffeine metabolism – are more likely to metabolize caffeine at a slower rate; this inefficient metabolism also increases the risk of myocardial infarction. In relation, firm evidence that caffeine influences the risk of coronary heart disease was also found in the study, noting that CYP1A2 does not detoxify any other major compound in coffee other than caffeine (Cornelis & El-Sohemy, 2007; Fenech et al., 2011).
Cancer is also found to be partially influenced by chronic exposure to certain food components (Afman & Müller, 2006). In relation, Sharma et al. (2017) also report that diet has an effect on around 30-40% of all cases of cancer, with multiple studies suggesting that breast, liver, lung, prostate, and colon cancers are correlated to intakes of dietary bioactives (Sharma & Dwivedi, 2017). One study by Omer et al. (2001) linked the consumption of aflatoxin-contaminated peanut butter with developing hepatocellular carcinoma in Sudanese populations. Results indicate that Sudanese individuals with the glutathione S-transferase M1 null genotype are more likely to develop this cancer from consuming peanut butter versus those without the genotype (Omer et al., 2001).
With all this knowledge obtained from nutrigenomics, experts can provide more reliable dietary advice so as to prevent further exacerbation of their patients’ condition.
Diet supplementation and weight management
Nutrigenomics is also found to be a viable tool in addressing obesity as well as diet-related disorders. Some studies suggest that dietary nutrient intake coupled with specific genetic variations contribute to an individual’s likelihood of developing obesity. Therefore, this also implies that due to each person’s unique genetic variations, different people may respond to certain diets differently (Doo & Kim, 2015).
Genome-wide association studies (GWAS) have become a common tool used to detect genetic variations, especially those correlated with obesity risks (Doo & Kim, 2015). Essentially, GWAS analyze entire genomes of large groups of people within a population to find small, genetic variations or SNPs. Multiple researchers resort to GWAS to look for obesity- and weight-related traits in specific populations.
One study conducted by Hunt et al. (2008) aimed to confirm the reliability of variations on the FTO gene or the fat mass and obesity associated gene as an indicator of obesity risk. This particular variant is an SNP of the name “rs9939609, T/A”, of which Hunt genotyped in 5,607 participants from Utah studies (i.e., a random population sample, families of severe thinness and obesity, unrelated obesity subjects, and families participating in a longitudinal study of cardiovascular disease and aging). Results reveal that a greater frequency of the rs9939609 A allele is observed with increasing BMI. It was concluded that the BMI increase associated with FTO genotypes begins as early as the person’s youth and is carried throughout their adulthood (Hunt et al., 2008). The research findings by Hunt et al. (2008), in combination with that of others’ supporting literature, confirm that the FTO gene is a primary gene to screen for when assessing an individual’s risk for obesity.
Certain micronutrients were also found to have a role in obesity management. Jeyakumar et al. (2005) studied the effect of vitamin A on lean and obese mice, as this nutrient is known to regulate adipose tissue (body fat) growth. Both lean and obese mice of the WNIN/Ob strain were given diets supplemented with high doses of vitamin A. Results show lower adiposity index (amount of body fat) and retroperitoneal white adipose tissue (RPWAT) in obese rats; in contrast, the reduction is minimal in lean rat. Results from the study by Jeyakumar’s group thereby confirm that the high dosage supplementation of vitamin A in diets regulate the growth of adipose tissue in both obese and lean mice (Jeyakumar et al., 2005).
Today, the emergence of nutritional science studies being linked with genomic approaches allows researchers to curb obesity risks through “tailor-made” nutritional advice as well as consulting based on the patient’s genetic variations or genetic make-up (Doo & Kim, 2015).
Nutrigenomics also makes use of the links between genetic variations and nutritional requirements in the context of athletes improving their sports performance in an area called “sports nutrigenomics” which includes personalized sports nutrition (N. S. Guest et al., 2019). One of the main objectives of personalized sports nutrition is to generate tailor-made dietary recommendations to athletes in order to optimize both direct and indirect factors that affect athletic performance (N. S. Guest et al., 2019).
One of the most commonly studied compounds in nutrigenomics – with regards to sports performance – is caffeine. Going back to the CYP1A2 gene for caffeine, research by Guest et al. (2018) aimed to assess whether a genetic variation in this said gene would affect or influence the ergogenic (performance-enhancing) effects of caffeine in a timed 10-km cycling trial (N. Guest et al., 2018). Per the results, a 4 milligram per kilogram body mass of the athlete overall decreased cycling time by about 3%, with observable caffeine-gene interactions. In addition, only those with the AA (“fast metabolizer”) CYP1A2 genotype had an improved 10-km cycling time with low to moderate doses of caffeine; those with slow metabolizer genotypes (i.e., AC and CC) showed diminished to no effects (N. Guest et al., 2018). Thus, it was surmised – for this study, at least – that a moderate caffeine dose affects AA CYP1A2 genotype athletes’ endurance performance positively and that genetic variations are to be taken into account when considering a supplemental caffeine dose into an endurance athlete’s diet (N. Guest et al., 2018).
Another application in sports nutrigenomics is the identification of nutrients or dietary compounds that have promise in the prevention of injuries. One such compound is vitamin C given its association with collagen synthesis and collagen is known as a key component of connective tissue (e.g., tendons, ligaments, etc.) (N. S. Guest et al., 2019). To confirm this, one study by Shaw et al. (2016) investigated the collagen synthesis potential of vitamin C in the form of gelatin supplements which are then given to athletes (Shaw et al., 2017). As the study reports, the addition of vitamin C-enriched gelatin to athletes’ intermittent exercise programs improves the synthesis of collagen, thereby facilitating tissue repair and aiding in the prevention of injuries (Shaw et al., 2017).
Based on these cases, nutrigenomics goes beyond alleviating diseases and minimizing disease risks, targeting human performance improvement as well. It is also worth noting the other possible gene variations that could influence an athlete's performance or a reaction towards a particular nutritional supplement, for example. This, along with numerous other studies, is a viable research area in nutritional medicine, especially for athletes that aim to optimize their performance, recovery, and overall health.
Aside from utilizing nutrigenomics for targeting diseases, commercially, it is also widely used to improve one’s well-being. Aging is an inevitable process that is also associated with an increased risk of developing certain diseases or ailments, one of which is neurodegeneration (Virmani et al., 2013). Multiple studies link aging to dysfunctional cell modulation, likely stemming from signaling networks that end in certain pathways (e.g., reactive oxygen and nitrogen species detoxification, apoptosis or programmed cell death, etc.). One of the ways in which these signaling networks can be acted upon is through dietary or caloric restriction which can also be regulated by specific gene families (e.g., sir, foxA, and NrFs) (Virmani et al., 2013).
In Alzheimer’s disease (AD), for example, one study by Norwitz et al. (2021) aimed to explore the impact of precision nutrition in the prevention of (AD) among APOE4 allele carriers (Norwitz et al., 2021). The APOE gene codes for the APOE protein, which is responsible for carrying cholesterol – among other types of fat – in the bloodstream. In addition, the APOE protein also has a role in the metabolism of lipids in the body, especially in the brain (Norwitz et al., 2021). The apolipoprotein E epsilon 4 or the APOE4 gene codes for a mutated form of apolipoprotein E and is widely known as the strongest genetic risk factor for late-onset Alzheimer’s disease; it is important to note that being a carrier of APOE4 does not mean that the person will develop Alzheimer’s.
While the exact mechanism of how APOE4 contributes to the increased risk of developing AD is unknown, it is understood that gene-environment interactions (i.e., environment and lifestyle impact) can play a role in mediating the effect of APOE4 in the development of late-onset AD. In the study by Norwitz et al., the researchers were able to devise a precision nutrition strategy (e.g., ketogenic and low-carb diets, increased fatty fish intake, limiting alcohol consumption, etc.) that aids in the prevention of AD for APOE4 carriers; this strategy was based on biological principles surrounding the way APOE4 changes or affects glial cells as well as insulin resistance (Norwitz et al., 2021).
By recognizing this single gene and its impact on multiple, different proteins and biological pathways that affect the progression of AD, APOE4 carriers are offered more targeted options in preventing the disease. With current nutrigenomic testing procedures already including APOE4 as one of the genes to scan for, mitigating the risk for developing Alzheimer’s disease has become all the more possible.
The future of nutrigenomics
From the numerous cases highlighted in the article, nutrigenomics is currently being utilized to detect and identify genotypes associated with disease risk; this application further emphasized the use of biomarkers – as well as biomarker research – that are known to be valuable targets in disease diagnosis, prognosis, or altered metabolic function.
Nutrigenomics promises an era of revolutionized healthcare, promoting early detection of disease risk – and ultimately, prevention of that disease – rather than cure. With each individual responding uniquely to certain foods, ongoing nutrigenomics research should gear towards combining nutrigenetic or nutrigenomic knowledge with biomarker information from omics experiments to validate whether precision nutrition strategies (e.g., personalized dietary and lifestyle recommendations) are truly effective and produce the desired health benefits for the affected individual. Given the current success of the use of omics approaches – particularly metabolomics – in the development of biomarkers related to food or nutrient intake, more work via these approaches can also be expected.
In addition, further studies on nutrient-gene interactions with regard to their effect on certain phenotypes are also key to developing more appropriate personalized dietary strategies. This, along with utilizing nutrigenomic testing kits that only have well-researched genes included, will likely influence the progression of nutrigenomics research as well as public health recommendations moving forward.
Finally, it is important to recognize that nutrigenomic testing is only one piece of the puzzle in terms of bettering public health. Coordinated efforts between medical and healthcare professionals, researchers, and public health authorities are also integral to achieving this goal. Nevertheless, the field of nutrigenomics has great promise, with precision nutrition gradually being established as a facet of modern healthcare. This emerging science will not only improve individual health outcomes but will also aid in redefining the relationship between diet and health in the future.
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