“Unfortunately, the promise, or more accurately the ‘hype’ of such advertising far exceeds the reliable knowledge from the underlying science.”
K. R. Pelletier, PhD, MD; University of California, San Francisco
Many are interested in the promises of genetic testing companies and doctors promising clear information about what to eat, or predictions of longevity, or of diseases from a simple genetic test. Is that realistic? What is Epigenetics and Nutrigenomics? To begin, review this quote from a study about the field of genetics:
“Efforts to unveil the etiology of human disease often recapitulate the nature versus nurture debate. But today’s biologists concede that neither nature nor nurture alone can explain the molecular processes that ultimately govern human health. The presence of a particular gene or mutation in most cases merely connotes a predisposition to a particular disease process. Whether that genetic potential will eventually manifest as a disease depends on a complex interplay betweenthe human genome and environmental and behavioral factors. This understanding has helped spawn numerous multidisciplinary gene-based approaches to the study of health and disease.”
What is Nutrigenomics?
One such endeavor is nutrigenomics, the integration of genomic science with nutrition and, when possible, other lifestyle variables such as cigarette smoking and alcohol consumption. Although genes are critical for determining function, nutrition modifies the extent to which different genes are expressed and thereby modulates whether individuals manifest the potential established by their genetic background (or not).
Nutrigenomics therefore initially referred to the study of the effects of nutrients on the expression of an individual’s genetic makeup. More recently, this definition has been broadened to encompass nutritional factors that protect the genome from damage. Ultimately, nutrigenomics is concerned with the impact of dietary components on the genome.
A common, popular definition of nutrigenomics found on Wikipedia states, “Nutritional genomics, also known as nutrigenomics, is a science studying the relationship between human genome, nutrition and health. People in the field work toward developing an understanding of how the whole body responds to a food via systems biology, as well as single gene/single food compound relationships.”
Science of Nutrigenomics
Science in the field of nutrigenomics continues to develop. Studies evaluate the role of genetics on illness and the genetics of how the human body changes to environment, behavior, nutrition, exercise and other influences of life. Testing outside the research laboratory, which we refer to as genetic testing, or more accurately “epigenetic assays,” are the new buzzword in direct to consumer (D2C) testing services that attempt to inform about the relationship between lifestyle activities and genetic expression. There are over 20 companies now offering such testing ranging from national weight loss companies to small start-ups. There is a daily march of new companies advertising these services on the internet and in vendor advertising. What these vendors all have in common is the promise of personalized nutrition based upon genetic testing. Prices of such assessments range from a $50 to over $25,000. Cost neither predicts quality nor accuracy. Unfortunately, the promise, or more accurately the “hype,” of such advertising far exceeds the reliable knowledge from the underlying science.
Types of Genetic Testing
To be more specific, there are two basic approaches in genetic testing. One approach is true genetic assessment as represented by the complete mapping of the Human Genome. This type of testing is used for diagnosis of diseases and to evaluate if a medication may be more beneficial in the treatment of disease.
By contrast, the second approach is the domain of epigenetic assays which is the basis for the current barrage of vendor claims and sales of testing services.
Epigenetic assays assume the actual gene itself is unchanging unless it is damaged by radiation and/or petrochemical exposure. What epigenetics attempts to measure is the influence on the gene that effects the expression of genetic predisposition due to factors including such lifestyle factors as aging, nutrition and diet, stress, sleep quality, and exercise as well as environmental and psychosocial factors such as the presence or absence of social support.
Health Prediction Using Epigenetic Testing
draftThere is excellent, basic science evidence that each of these factors do impact gene expression, but the question is whether such subsequent health predictions based on testing gene expression are reliable and/or accurate. That answer is a definite “No,” despite vendor claims to the contrary.
Addressing the realm of objective outcomes of such recommendations, there is literally no scientific evidence of adherence to the guidelines and/or long-term outcomes.
Within the realm of epigenetic testing, there are 2 basic approaches. One approach is a disease prediction model which provides a statistical probability of manifesting disease ranging
from diabetes to CHD, cancer, and Alzheimer’s. These “predictions” are probabilities, not certainties, but they can raise false concern among the individual who has been tested. Recently, the FDA has been more active in challenging vendor claims and services in this realm.
By contrast, the second approach is an epigenetic model is based on specific “biomarkers” that are in, above, or below normal and/or optimal ranges.
This is where personalized nutrition/diet assays have flourished and are trying to directly connect one genomic biomarker to one nutritional or lifestyle factors. As with the disease prediction model,
the recommendations derived from such epigenetic testing are sorely lacking and/or completely invalid.
No single epigenetic assay can accurately provide an individual dietary guideline for general nutrition or weight loss based solely on genetic profiles.
Pelletier, KR. Change Your Genes-Change Your Life: Creating Optimal Health with the New Science of Epigenetics: (San Francisco: Origin Press, 2018)