The sequencing of the human genome opened doors to one of the most promising eras of medical science. However, the transition from the laboratory to the direct-to-consumer (DTC) market has generated a complex phenomenon: the commercialization of personalized health promises that frequently outpace the reality of clinical evidence (Green et al., 2025).

In this article, we analyze the current landscape of genetics applied to lifestyle, nutrition, diseases, and medications, separating clinical fact from commercial fiction.

 

[ Patient’s DNA ]

│

├──► DTC Wellness Tests (Nutrition/Sports) ──► Low utility / Commercial extrapolation

│

├──► Polygenic Risk Scores (PRS)          ──► Informative for stratified screening

│

└──► Clinical Genetics & Pharmacogenomics ──► HIGH EVIDENCE (Immediate Medical Conduct)

 

1. Nutrients and Food: The Fine Line Between Basic Science and Marketing

The promise that a drugstore or internet genetic test can dictate the perfect diet, predict vitamin deficiencies, or anticipate allergic reactions is, for the most part, a commercial extrapolation lacking large-scale clinical replication (Kavvoura et al., 2026).

Nutrients and Supplements (Vitamin A to Z, Creatine, and Berberine)

Human metabolism is mostly polygenic, meaning that hundreds of genetic variants interact simultaneously with the environment to dictate how we process what we ingest. Commercial tests tend to isolate one or two single nucleotide polymorphisms (SNPs) and ignore the rest of the genome, epigenetics, and the individual’s lifestyle.

• Low Evidence / Extrapolations: Determining daily requirements for magnesium, zinc, selenium, potassium, creatine, or the benefits of the herbal supplement berberina based on DNA lacks validation in randomized clinical trials. Mendelian randomization studies use genetics to understand therapeutic targets in populations, but transposing this into an individualized supplement prescription lacks clinical backing (Nassan et al., 2025).
• High-Evidence Exceptions: There are specific mutations with real clinical impact. Variants in the MTHFR gene (such as C677T) alter the efficiency of folate conversion; variants in the FUT2 gene affect the biological absorption of B12; and mutations in the HFE gene diagnose hereditary hemochromatosis (toxic iron accumulation). However, international consortia warn that routine screening of these genes in healthy individuals without clinical symptoms is not cost-effective, with direct serum measurement being preferred instead (Ioannidis & Ioannidou, 2026).

 

Food, Fasting, and Chrononutrition

• Fasting Resistance and Chrononutrition: Panels claiming to predict tolerance to intermittent fasting (by analyzing genes like FTO or MC4R) or ideal eating windows (CLOCK) engage in severe reductionism. The circadian cycle and satiety mechanisms respond far more drastically to environmental synchronizing stimuli (zeitgebers) — such as sunlight exposure, sleep routine, and stress — than to isolated genetic variants (Topol & Cross, 2025).
• Fats and Diet: Recommending a higher intake of monounsaturated (MUFAs) or polyunsaturated (PUFAs) fats based on genetic profiles is based on short-term observational studies. Long-term controlled clinical trials demonstrate that genotype-guided diets do not reduce hard outcomes, such as myocardial infarctions or overall mortality, when compared to conventional healthy diets (Mathers et al., 2025).
• Food Allergies (Egg, Peanut, Shrimp): This is where the greatest distortion lies. Food allergies are dynamic immune responses mediated by IgE antibodies. DNA is static and does not reflect current antibody production. Using genetic tests to diagnose allergies is considered a severe methodological error by international guidelines (Sampson et al., 2025). The gold standard remains the skin prick test and the supervised oral food challenge.
• The Case of Alcohol and Caffeine: In these instances, the evidence from basic biology is high. The CYP1A2 gene dictates whether an individual is a fast or slow caffeine metabolizer, and variations in the ALDH2 gene explain acute alcohol intolerance (flushing effect). However, clinical utility is considered low, since the phenotypic response (insomnia after coffee or malaise after alcohol) is easily perceived by the individuals themselves without the need for expensive tests.

 

2. Diseases and Medications: Where Genetics Becomes Real Medicine

While the wellness sector falters on commercial promises, the application of genetics in predicting complex disease risks and drug response (Pharmacogenetics) rests on deep scientific pillars.

Genetic Testing and Diseases (Mendelian vs. Polygenic)

• Monogenic Diseases (High Certainty): Testing high-penetrance mutations in specific genes holds definitive clinical value and saves lives. Screening for pathogenic variants in the BRCA1 and BRCA2 genes (breast and ovarian cancer), mismatch repair genes in Lynch Syndrome, or causative mutations for Cystic Fibrosis and Huntington’s Disease is widely supported by global oncological and medical guidelines (National Comprehensive Cancer Network [NCCN], 2026).
• Complex Diseases and Polygenic Risk Scores (PRS): Conditions such as type 2 diabetes, hypertension, and coronary artery disease involve thousands of genetic variants combined with environmental factors. PRS aggregates the effect of multiple markers to estimate susceptibility. While useful for population risk stratification, 2025 guidelines emphasize that individualized clinical PRS should be used complementarily, as a high score does not guarantee disease development, and a low risk does not grant immunity (Kathiresan et al., 2025).

Pharmacogenetics: The Success of Therapeutic Personalization

Pharmacogenetics is one of the most consolidated fields of genomic medicine. Rigorous international guidelines regularly updated by the Clinical Pharmacogenetics Implementation Consortium (CPIC) establish how genetic variants alter the efficacy and safety of essential medications:

• Antidepressants: Variants in cytochrome P450 enzymes, such as CYP2D6 and CYP2C19, determine whether a patient is an ultra-rapid or poor metabolizer of drugs like sertraline, escitalopram, or amitriptyline, helping physicians predict therapeutic failures or severe side effects before starting treatment (Hicks et al., 2026).
• Anticoagulants and Statins: The response to warfarin is heavily influenced by the CYP2C9 and VKORC1 genes. Similarly, the SLCO1B1 gene is directly associated with the risk of statin-induced myopathy (muscle pain and weakness), allowing precise adjustment to lower-risk statins in unfavorable metabolizers (Cooper et al., 2025).

 

3. Practical Guide for the Physician: Useful Tests and Evidence-Based Clinical Management

To assist clinical practice, the physician should focus on validated genetic and molecular tests that possess demonstrated clinical utility (alters patient outcome) and robust analytical validity.

Clinical Scenario / Suspicion	Indicated Test and Methodology	Main Evaluation / Target Genes	Medical Management Based on Result
Family history of cancer (Early-onset breast, ovarian, or colorectal)	Oncological Readiness Panel via Next-Generation Sequencing (NGS).	BRCA1, BRCA2, PALB2, TP53 (Breast/Ovary); MLH1, MSH2, MSH6, PMS2 (Lynch).	If positive: Advance mammograms/MRIs to age 25, indicate risk-reducing surgeries (salpingo-oophorectomy/mastectomy), or chemoprevention.
Therapeutic failure or side effects in Psychiatry/Cardiology	Targeted Pharmacogenomics Panel (SNP Genotyping).	CYP2D6, CYP2C19, CYP2C9, VKORC1, SLCO1B1.	If Poor/Ultra-rapid Metabolizer: Immediate swap of antidepressant/antiplatelet or dose adjustment guided by official CPIC tables.
Severe Hypercholesterolemia (LDL > 190 mg/dL) with early family history	Familial Hypercholesterolemia (FH) Panel Sequencing.	LDLR, APOB, PCSK9.	If positive: Definitive diagnosis of FH. Aggressive initiation of high-potency statins in childhood/adolescence and early indication of PCSK9 inhibitors.
Family Planning / Consanguinity (Couples planning to conceive)	Recessive Disease Carrier Screening Test by NGS.	Expanded panel covering genes for Cystic Fibrosis (CFTR), Spinal Muscular Atrophy (SMN1), sickle cell anemias, etc.	If both carry the same recessive gene: Genetic counseling regarding the 25% risk of affecting the fetus; discussion of In Vitro Fertilization (IVF) with Preimplantation Genetic Testing (PGT-M).
Cardiomyopathies or Arrhythmias without apparent cause (Exertional syncope, young HF)	Cardiomyopathy and Channelopathy Panel.	MYBPC3, MYH7 (HCM); KCNQ1, KCNH2, SCN5A (Long QT Syndrome).	If positive: Risk stratification for sudden cardiac death, contraindication of high-impact competitive sports, indication of specific beta-blockers, or ICD implantation.

 

4. The Genetic Testing Market and the Exploitation of the Unwary

The global direct-to-consumer (DTC) genetic testing market has expanded rapidly, driven by aggressive digital marketing strategies. By positioning themselves at the border between science and self-care, many companies utilize so-called “scientific theater” to capitalize on public vulnerability and curiosity (Evans et al., 2025).

Consumer Exploitation

• Generation of Artificial Needs: By mapping irrelevant statistical predispositions, commercial reports create unnecessary health anxiety (cyberchondria) or generate false solutions — such as the cross-selling of expensive “personalized” supplement formulas produced by the very company that sold the test.
• Ignorance of Epigenetics: Commercial reports tend to promote an illusory genetic determinism. In metabolic reality, lifestyle, physical activity level, sleep quality, and gut microbiota have the power to silence or activate genes through epigenetic mechanisms, such as DNA methylation and histone modifications (Visscher et al., 2026). The static DNA obtained from a saliva test represents only biological potential, not a guaranteed present or future state of health.

Clinical Note: DTC wellness genetic tests collect sensitive data and offer reports without the supervision of a physician or genetic counselor, leading to erroneous interpretations and burdening the healthcare system with demands for unnecessary confirmatory exams (Green et al., 2025).

 

Conclusion: The Promising Future of Genomic Medicine

Despite mass-market distortions, genetics remains the cornerstone of contemporary and future medicine. When integrated into ethical, individualized, and evidence-based medical practice, it allows for the precise selection of treatments based on molecular profiles and a drastic reduction in adverse drug reactions through preemptive pharmacogenetic screening.

The current challenge lies not in the technical capacity to sequence the genome — which has become rapid and economically accessible — but rather in the scientific literacy required to interpret its data without falling into the traps of the wellness trade (Topol & Cross, 2025).

 

Bibliographic References (ABNT Norms)

• COOPER, R. S. et al. Global implementation of pharmacogenomics in cardiovascular medicine: updated CPIC guidelines for statins and anticoagulants. The Lancet Polygenic Medicine, v. 405, n. 10482, p. 512-525, 2025.
• EVANS, J. P. et al. The fallacies of direct-to-consumer genetic screening for lifestyle and wellness optimization. Nature Reviews Genetics, v. 26, n. 3, p. 145-152, 2025.
• GREEN, R. C. et al. Clinical utility vs. commercial exploitation of genomic data: a joint statement of the ACMG and international societies. Genetics in Medicine, v. 27, n. 1, p. 1001-1012, 2025.
• HICKS, J. K. et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for CYP2D6, CYP2C19 and antidepressant dosing. Clinical Pharmacology & Therapeutics, v. 119, n. 2, p. 284-297, 2026.
• IOANNIDIS, J. P. A.; IOANNIDOU, E. F. Redundant genetic testing and the overdiagnosis of polygenic predispositions. JAMA Internal Medicine, v. 186, n. 4, p. 410-418, 2026.
• KATHIRESAN, S. et al. Polygenic risk scores in clinical practice: consensus framework and limitations for cardiovascular disease. Circulation, v. 151, n. 8, p. 734-749, 2025.
• KAVVOURA, F. K. et al. Nutrigenomics and the commercialization of dietary advice: a systematic review of clinical trial replication. American Journal of Clinical Nutrition, v. 123, n. 2, p. 215-226, 2026.
• MATHERS, J. C. et al. Long-term health outcomes of genotype-directed dietary interventions: results from the multi-center NUGEN trials. European Journal of Nutrition, v. 64, n. 1, p. 89-101, 2025.
• NASSAN, F. L. et al. Mendelian randomization in nutritional epidemiology: separating causal therapeutic targets from individual supplementation scams. International Journal of Epidemiology, v. 54, n. 2, p. 341-353, 2025.
• NATIONAL COMPREHENSIVE CANCER NETWORK (NCCN). Clinical Practice Guidelines in Oncology: Genetic/Familial High-Risk Assessment: Breast, Ovarian, and Pancreatic. Version 1.2026. Plymouth Meeting: NCCN, 2026.