In Pursuit of Personalized Nutrition for Disease Prevention

Using nutrigenetics and nutrigenomics in your practice

Genetics and diet
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The importance of good nutrition for health has been widely recognized. Hippocrates proclaimed, “Let the food be thy medicine and the medicine be thy food.” What early doctors knew on an intuitive level is now being studied rigorously, using state-of-the-art scientific methods and “omic” technologies. It appears that it might not just be about eating “good” food, but also about eating food that is “right” for you.

Nutrient-gene connections are a hot topic in medical science. Personalized nutrition is emerging as a possible therapeutic modality. Several clinical and preclinical studies have shown the potential of this novel approach, and patients are increasingly interested in commercial nutrigenomics.

How should you as a clinician respond to these new trends in healthcare? And what are some of the factors you might want to consider when talking with your patients about personalized diets?

This article offers a balanced overview of nutrigenomics and explores some of the latest scientific findings in the field with the aim to assist you when assessing the practical value of nutrigenomics.

Nutrigenomics—A Cutting-Edge Science

We know food nutrients, gut bacteria, and intestinal genomics and physiology represent a complex community that importantly influences human health. What we eat not only affects our immediate health and metabolism, but it also contributes to the composition of the gut microbiota and gene expression.

Nutrigenomics is a young science—the term was first used in 2001—that is concerned with the interactions between our diet and genome. It is now feasible to study natural compounds in different metabolic pathways in relation to a person’s genotype. Nutrigenomics marks a shift from epidemiology toward molecular biology and genetics.

Specifically, it looks at the genomic alterations caused by dietary nutrients. As a result, it aims to personalize and update treatments that used to be, and still are, intended for whole populations.

There are a lot of unanswered questions within nutrigenomics. However, solving the nutrition-genomics puzzle will likely bring us closer to developing personalized nutrition that can be used alongside conventional approaches to treat and prevent diseases and chronic conditions. The findings of nutrigenomics are already used to some degree to treat diseases with a diet component, such as inflammatory bowel disease (IBD), diabetes, obesity, and cancer. By taking into consideration an individual’s genetic characteristics (as well as age and lifestyle preferences), we can improve the efficacy of future nutritional interventions.

Knowledge about the benefits of certain nutrients is far from new. For thousands of years, traditional medicine used a variety of plants and natural compounds that have the potential to act as genomic modulators. For instance, anti-cancerogenic effects of phytochemicals, which are found in various vegetables and fruits, have now been scientifically recognized. Researchers are unveiling their active mechanisms—for example, the antioxidant effect.

Initial studies in oncology also show that, when used as an adjunct to conventional therapies, natural phytochemicals can reduce toxicity caused by radiotherapy or chemotherapy. Similarly, the Mediterranean Diet has received a lot of scientific support as a preventative measure against cardiovascular disease due to its anti-inflammatory properties.

The use of specific nutrients in medical therapy is, therefore, becoming an evidence-based practice. Patients are generally encouraged to favor diets rich in plant-based foods because it seems these nutrients can target genes that contribute to chronic disease development and suppress them.

Nutrigenomics is now going a step further, integrating general dietary recommendations with a person’s genotype.

Nutrigenomics has some similarities with pharmacogenomics. The difference, however, is that the latter uses synthetic chemicals to cause gene alterations whereas nutrigenomics relies on natural substances found in the food we eat. A comprehensive review of the subject published this July in Seminars in Cancer Biology predicts that soon, nutrigenomics will be able to assist in the development of new drugs based on natural substances. Therefore, the potential of this discipline probably expands beyond dietary advice and personalized diet. A potential futuristic scenario might include a kitchen fitted with a 3-D printer producing bespoke drugs and nutrients a patient will take each morning with coffee.

Nutrigenetics vs. Nutrigenomics

The difference between nutrigenetics and nutrigenomics is often blurred. Yael Joffe and Christine Houghton, members of the Manuka Science team that teaches nutrigenomics and nutrigenetics to health professionals, note that the two terms can be distinguished by looking at gene actions.

In nutrigenetics, the genes act on environmental elements (e.g. enzymes). In contrast, in nutrigenomics, the environment influences gene expression. In other words, nutrigenomics’ main interest is the influence of biomolecules on gene expression. These bioactive molecules can turn the gene up or down, activate or silence it, which is often described as switching the gene on or off.

When referring to both, nutrigenetics and nutrigenomics, Joffe and Houghton suggest using the term nutritional genomics. Nutritional genomics goes beyond the superficial direct-to-consumer genetic tests, such as DNAfit and 23andme, and encompasses the knowledge of nutritional biochemistry that can help understand health and the occurrence of a disease in a specific person.

Arguably, nutrigenetics and nutrigenomics combined can help you as a practitioner develop more effective management interventions for your patients. However, this might not be a straightforward process, and you should probably also consider some of the limitations and controversies of the field.

Pros and Cons of Using Nutrigenomics in Your Practice

Although many experts believe in nutrigenomics, it is not widely in practice yet. More solid proof of the concept is required before it can be routinely implemented into clinical practice. Research is ongoing; however, it appears that at present, the unknown factors outnumber the known.

It has sometimes been argued that this health technology might have been released prematurely, without hard evidence to support some of the statements made by the companies that offer commercial nutrigenomics tests.

Christiana Pavlidis, a dietitian at the University of Patras in Greece, argues that currently, the 38 genes that are commonly tested in commercial nutrigenomics tests do not show a definite association with diet-related diseases. Pavlidis agrees that it is important to continue with research about the influence of nutrients on gene and protein expression. However, she also warns against making definite claims. Pavlidis suggests that before new tests become available to the public, there should be a thorough evaluation and synthesis of evidence.

A model of health care that aims to prevent diseases based on an individual’s genetic makeup has many advantages. It is concerned with disease prevention rather than symptom treatment. Some leading experts consider personalized nutrition to be the “holy grail” of future medicine. It is important, though, to keep up-to-date with the latest research in the field.

Research, for example, indicates that people metabolize omega-3 fatty acids differently depending on their genotype, meaning some people might not benefit from taking them. A Canadian study led by Melanié Plourde from the Research Centre on Aging in Sherbrooke showed that carriers of the most important genetic risk factor for Alzheimer’s disease (E4) appear to be more vulnerable to omega-3 deficiency and might require supplementation more urgently.

The latest findings need to be consistently integrated into commercial nutrigenomics tests and inform nutritional advice given to patients. As a health-care professional, you might be required to act as a gate-keeper who assesses the validity of new tests and balances innovative “omic” technologies against medical facts.

How to Approach Patients About Nutrigenomics

Studies show that an increasing number of patients are seeking nutrigenomic testing and advice. Conversations about nutrigenomics between you and your patients will, therefore, likely become more common in the future.

Web-based companies make genetic information more available to your patients. However, consumers often lack the training to accurately interpret their test results. Therefore, practitioners with knowledge of nutrigenomics might soon become a very valuable resource.

For example, a direct-to-consumer nutrigenomics test could show that a patient doesn’t produce the enzyme that digests lactose. This does not mean, however, that they are necessarily lactose intolerant as their gut bacteria could still be able to ferment milk. If you can effectively translate your patients’ nutrigenomics testing results into real life “food solutions,” this might add to the positive impact this type of testing provides your patients.

Gaining some additional knowledge in this area is likely to be helpful in your practice. Post-graduate courses in nutrigenomics for health-care professionals are already available; for instance, one is offered by the educational company Manuka Science.

Your role as a clinician might also involve advising patients on the shortcomings of commercial nutrigenomics tests. It has previously been recorded that at-home DNA tests still suffer from inaccuracies. For instance, significant differences between companies have been noted. These same criticisms apply to commercial nutrigenetics and nutrigenomics tests as well.

Your patients need to be aware that some of the commercial tests available will probably provide them with unproven predictions. Guidance from a professional, especially when dealing with complex conditions, therefore becomes important. Furthermore, it is not clear yet to behavioral scientists how to properly motivate patients to include new foods tailored to their specific needs. According to recent research, tests alone often don’t provide sufficient motivation.

Tailored diets have limitations, and some nutrition experts have observed that when restrictive diets are followed for a prolonged period of time, they can result in an impoverished gut microbiome, which has been linked to poor health outcomes. A study of European patients with Inflammatory Bowel Disease showed that their fecal microbiome contained 25 percent less microbial genes compared to healthy individuals. This suggests that less gut variety does not bode well for health. In contrast, rich microbiota (supported by a diverse diet) has been linked to good health.

As a health professional, you need to be able to relay this information to your patients before they make any drastic decisions about their new diet—especially when encouraged by the results of an at-home nutrigenomics test that potentially lacks scientific rigor.

Sources:

Braicu C, Mehterov N, Berindan-Neagoe I, et al. Review: Nutrigenomics in cancer: Revisiting the effects of natural compounds. Seminars in Cancer Biology. 2017

Joffe Y, Houghton C. A Novel Approach to the Nutrigenetics and Nutrigenomics of Obesity and Weight Management. Current Oncology Reports. 2016;18(7):1-6

Nock T, Chouinard-Watkins R, Plourde M. Review: Carriers of an apolipoprotein E epsilon 4 allele are more vulnerable to a dietary deficiency in omega-3 fatty acids and cognitive decline. BBA - Molecular And Cell Biology of Lipids. 2017;1862(Part A):1068-1078

Pavlidis C, Patrinos G, Katsila T. Nutrigenomics: A controversy. Applied & Translational Genomics. 2015; 4:50-53.

Saukko P, Reed M, Britten N, Hogarth S. Negotiating the boundary between medicine and consumer culture: Online marketing of nutrigenetic tests. Social Science & Medicine. 2010; 70:744-753

Qin J, Li R, Wang J, et al. A human gut microbial gene catalogue established by metagenomic sequencing. Nature. 2010; 464(7285):59-65

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