Nutrition plays a key role in maintaining good human health. A balanced diet can prevent many diseases, including obesity and other metabolic diseases. Hence, food is sometime referred to as medicine. It is a known fact that each individual respond to diet differently, and therefore it is difficult to recommend on an individual’s diet for a healthy life and to prevent diseases. For instance, intake of high quantities of fatty foods may result in gaining body weight in some individuals, but in others it could lead to higher risks of diseases. In many cases, it is linked to the family. The progress in the field of nutrition science has correlated this response to a differential behavior of genes due to an individual's diet pattern. The modifications in our daily actions specifically, the foods we eat can influence on the behavior of our genes leading to several diseases. Indeed, the study of how an individual’s genes respond to foods/nutrients is called as the “nutritional genomics” or “nutrigenomics”. This gene-diet interaction study significantly identifies the specific causes of an individual’s susceptibility to diseases.
Nutrigenomics involves molecular tools for identifying in what way nutrients and other food chemicals may alter both DNA transcription and translation processes to upset the expression of certain genes that are involved in the regulation of many metabolic pathways linked to health problems. Nutrigenomics has the potential to control/prevent and cure diet-associated chronic diseases and conditions by recommending a specific nutritional diet on the basis of individual’s risks identified through genomics analysis. Thus, the application of nutrigenomics to daily life would be the prospect of the nutrition science, allowing nutritionists, doctors and dietitians employ personalized nutrition therapy against diseases.
The availability of the complete sequence of the human genome due to the efforts of the Human Genome Project has enforced studies towards the precision/personalized medicine or nutrition. Each individual’s response to diet is not equal, and nutrigenomics studies focus on how a single-nucleotide polymorphism (SNP) interrelate either alone or in combination with nutrition/diet, and diseases. At the molecular level, signals are transmitted by nutrients causing changes in the gene expression, protein, and metabolite synthesis. In total, nutrigenomics help to find out the functioning of our body cells in response to what we eat. In future, this could function as a new tool to understand our genome/genetic variations which can assist in designing or advocating a precise diet to promote good health. The role of diet in disease progression and management can be explained by identifying the genetic variations. This means that genomic evidences will help to decide on the diet one should eat so as to have a healthy life.
Some of the major diseases such as cardiovascular diseases, obesity and type-2 diabetes are investigated in detail using nutrigenomics approach. Several cellular activities linked to energy balance are controlled by gene expressions and gene-surroundings interactions. A variation in the genetic makeup may affect appetite, nutrient preference, quantity of food, insulin signaling, adipogenesis, and lipid metabolism. A recent study has reported two variants of the APOA5, namely 1131 C>T and S19W which are associated with hypertriglyceridemia. These variants were discovered in type-2 diabetic patients consumed with whole grains, refined rice and legumes. Likewise, other polymorphisms (rs662799, rs2075291, rs3135506, rs2266788) of the APOA5 gene have significantly increased the levels of triglyceride in patients. Moreover, triglycerides and the APOA5-1131T>C polymorphism have an age-related association for those with the TT allele, but not with the CT or the CC alleles. Likewise, it is a known fact that a number of people exhibit lactose intolerance, while others can digest cow’s milk. In children, the intolerance to milk is due to a mutation in the LCT gene. However, adults also can become intolerant to lactose later in their life. This is to be blamed for the continued reducing activity of the LCT gene. Similarly, the cause of inflammatory bowel disease is due to various factors, including environmental factors, nutrients and gut microbiota. On the basis of the genome wide association studies, more than 160 SNPs has been identified to relate to this disease susceptibility. In patients with the Crohn's disease, SNPs in the SEPHS1 and SEPSECS genes significantly interact with the serum selenium levels. A low zinc level is correlated to inflammatory bowel diseases. So far, four ZNF365 isoforms have been recognized. Remarkably, supplementing zinc sulfate orally has considerably improved intestinal barrier function in many patients.
Nutrigenomics is an emerging field in which genetic analysis will decide in treating and preventing diseases through supplementing nutrition. It allows us to understand on the activity of genes, proteins to be produced according to our DNA makeup. Importantly, the conventional prescription of a diet is based on large-scale studies that may work for many people, but not all. In this regard, nutrigenomics offer a great advantage in deciding how and what an individual should consume foods on the basis of their genomic data, genes and their variants. Nutrigenomics offer an option to a nutritional expert in forming a nutrition plan suitable for our body’s health. Moreover, a medication can be made personalized avoiding the adverse drug reactions in the body. With nutrigenomics approach, the possibility of preventing and treating several diseases is very high. Some of the ethical issues of nutrigenomics include; monitoring or protecting the personal genomic data, controlling the assay cost, accessibility of the data, etc.
Figure 1. Nutrigenomics and challenges
(Source: Adopted from Pavlidis et al. (2015); https://doi.org/10.1016/j.atg.2015.02.003)
The importance and interest on nutrigenomics studies is constantly growing. A recent survey shows that nearly 80.5 % of health care specialists and nutritionists recommend to use nutrigenomics analysis, while about 23.5 % of the patients have frequently asked for nutrigenomics tests. In general, more than 76 % of the common people believe that a personalized diet designed as per their genetic profile would be advantageous in dealing with health problems. Future research should focus on evaluating the genes, networks between the genes and proteins, developing new computational approaches, epigenetics, and identifying the impact of the nutrients and food compounds on the gene or protein expression (Figure 1). Nutrigenomics is a new hope with the potential for modifications of diet or food to maintain good health and reduce the risk of food or diet-associated diseases.