Educational content, not medical advice. It explains general science and does not replace a conversation with a qualified clinician about your own health, tests or treatment.
A careful starting point
Companies now offer nutrigeneticNutrigenomicsResearch into how genetic make-up relates to diet, and how nutrition influences gene activity. tests directly to consumers, suggesting diets based on a limited set of genetic markers.[1] The strength of the science behind such advice varies enormously: for some single-gene conditions the link between genes and diet is well established, but for most everyday traits it is not.[1][2]
How strong is the evidence?
Phenylketonuria dietStrong
Variants in the PAH gene cause PKU. A low-phenylalanine diet is a established management approach, and most cases are found by newborn screening.
Where the evidence is strong
Phenylketonuria (PKU)
PKU is caused by variants in the PAH gene, which provides instructions for an enzyme that processes the amino acid phenylalanine. It can often be managed by following a diet low in phenylalanine, and most cases are detected shortly after birth by newborn screening.[3]
Digesting lactose as an adult
About 65 percent of people have a reduced ability to digest lactose after infancy. Activity of the LCT gene, which makes the enzyme lactase, is controlled by a regulatory element within a nearby gene called MCM6, and which variants of it a person inherits determines whether they can digest lactose into adulthood.[4]
Single-gene conditions like these are where a nutritional genomic approach is reliable.[1]
Where the evidence is weak
Most traits of interest are complex. Many are polygenic — the result of small contributions from many genes — and the effect sizes of individual variants are commonly small.[2]
A 2015 meta-analysis looked at 38 genes included in commercially available nutrigenomic tests, using data from more than 500,000 people. It found no specific, statistically significant association for any of the 38 genes and concluded that such tests could not be recommended at that time.[6]
A 2020 review concludes that precision nutrition is at a very early stage and in most cases lacks sufficient science to be implemented. It quotes the Academy of Nutrition and Dietetics’ 2014 position that using nutrigenetic testing to provide dietary advice “is not ready for routine dietetics practice”.[2]
Pharmacogenomics: genes and medicines
PharmacogenomicsPharmacogenomicsThe study of how a person’s genes affect their response to drugs. is the study of how a person’s genes affect their response to drugs. Conditions that affect drug response include clopidogrel resistance, warfarin sensitivity and resistance, and thiopurine S-methyltransferase (TPMT) deficiency.[7]
The U.S. Food and Drug Administration keeps a table of medicines whose labelling includes pharmacogenomic information. The labelling for some, but not all, of these products includes specific actions to be taken based on the biomarker.[5]
Examples from the FDA table
| Drug | Biomarker | Label sections (FDA) |
|---|---|---|
| Abacavir | HLA-B | Boxed Warning, Dosage and Administration, Contraindications, Warnings and Precautions |
| Clopidogrel | CYP2C19 | Boxed Warning, Warnings and Precautions, Clinical Pharmacology |
| Codeine | CYP2D6 | Boxed Warning, Warnings and Precautions, Use in Specific Populations, Patient Counseling Information |
| Capecitabine | DPYD | Boxed Warning, Dosage and Administration, Warnings and Precautions, Clinical Pharmacology, Patient Counseling Information |
| Carbamazepine | HLA-B | Boxed Warning, Warnings, Precautions |
| Warfarin | CYP2C9; VKORC1 | Dosage and Administration, Drug Interactions / Clinical Pharmacology |
| Azathioprine | TPMT; NUDT15 | Dosage and Administration, Warnings, Precautions, Adverse Reactions, Clinical Pharmacology |
| Mercaptopurine | TPMT; NUDT15 | Dosage and Administration, Warnings and Precautions, Adverse Reactions / Clinical Pharmacology |
The FDA notes that labelling for some, but not all, products includes specific actions based on the biomarker. See the live FDA table for the current list.
Making sense of a result
Classification frameworks for disease-causing variants are not designed for pharmacogenomic variants, which need their own interpretation.[8] Any genetic result, whether about diet, medicines or disease risk, is best discussed with a qualified clinician or genetic counsellor who knows your personal and family history.
Sources
Every source below was read and checked when this article was written. Links open the original publisher.
- [1]Floris M, Cano A, Porru L, et al. Direct-to-Consumer Nutrigenetics Testing: An Overview. Nutrients 12, 2020. pmc.ncbi.nlm.nih.gov/articles/PMC7071525(opens in a new tab)
- [2]Mullins VA, Bresette W, Johnstone L, et al. Genomics in Personalized Nutrition: Can You “Eat for Your Genes”?. Nutrients 12, 2020. pmc.ncbi.nlm.nih.gov/articles/PMC7599709(opens in a new tab)
- [3]Phenylketonuria. MedlinePlus Genetics (U.S. National Library of Medicine). medlineplus.gov/genetics/condition/phenylketonuria(opens in a new tab)
- [4]Lactose intolerance. MedlinePlus Genetics (U.S. National Library of Medicine). medlineplus.gov/genetics/condition/lactose-intolerance(opens in a new tab)
- [5]Table of Pharmacogenomic Biomarkers in Drug Labeling. U.S. Food and Drug Administration. www.fda.gov/drugs/science-and-research-drugs/table-pharmacogenomic-biomarkers-drug-labeling(opens in a new tab)
- [6]Pavlidis C, Lanara Z, Balasopoulou A, et al. Meta-Analysis of Genes in Commercially Available Nutrigenomic Tests Denotes Lack of Association with Dietary Intake and Nutrient-Related Pathologies. OMICS: A Journal of Integrative Biology, 2015. pubmed.ncbi.nlm.nih.gov/26348710(opens in a new tab)
- [7]What is pharmacogenomics?. MedlinePlus Genetics (U.S. National Library of Medicine). medlineplus.gov/genetics/understanding/genomicresearch/pharmacogenomics(opens in a new tab)
- [8]Richards S, Aziz N, Bale S, et al. Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the ACMG and AMP. Genetics in Medicine, 2015. pmc.ncbi.nlm.nih.gov/articles/PMC4544753(opens in a new tab)