What are the guidelines for safely using dietary supplements?

Guidelines for Safe Use of Dietary Supplements

For most healthy individuals, dietary supplements are unnecessary and potentially harmful—prioritize obtaining nutrients from a well-balanced diet rather than supplements, and only use supplements under medical supervision when specific deficiencies or medical conditions are documented. 1

Core Safety Principles

Regulatory Reality and Inherent Risks

• Dietary supplements lack FDA premarket approval for safety or efficacy, meaning manufacturers can market products without demonstrating they are safe or effective under the Dietary Supplement Health and Education Act of 1994. 1
• The actual content, purity, and efficacy of supplements are often unclear since they do not meet FDA premarket approval standards that apply to drugs. 1
• Patients should never assume "natural" means "safe"—dietary supplements are not inherently safer than prescription medications despite marketing claims. 1
• When supplements are used, choose only products with third-party certification (US Pharmacopeia verified or NSF certified) to ensure manufacturing standards. 2

When Supplements May Be Appropriate

• A standard multivitamin containing approximately 100% of the Daily Value may be beneficial during periods when eating a nutrient-adequate diet is difficult (such as during cancer treatment), but this does not extend to high-dose supplementation. 2
• Supplements are necessary only in cases of documented nutrient deficiency, and even then, their use should be recommended and monitored by a physician. 3
• Without underlying nutritional deficiencies, there is no benefit from herbal or other supplementation for most individuals. 1

Absolute Contraindications

High-Risk Populations

• Pregnant women must avoid high-dose vitamin A (>3000 mcg/day) due to teratogenic risk and potential fetal harm. 4
• Beta-carotene supplementation is contraindicated in heavy smokers, as two major trials demonstrated higher incidence of lung cancer and increased all-cause mortality in this population. 4
• Couples unwilling to comply with adequate contraception should not receive retinoid-containing supplements. 4

Medical Conditions

• Patients with known allergies to any supplement ingredient must avoid that supplement. 4
• Patients with history of hypercalcemia should avoid excessive vitamin D supplementation, which can lead to toxicity. 4
• Patients with uncontrolled autoimmune diseases should exercise caution with immune-modulating supplements. 4

Context-Specific Guidelines

Perioperative Management

The Society for Perioperative Assessment and Quality Improvement provides specific timing recommendations for surgical patients: 2

• Discontinue most supplements 2 weeks before surgery, including those affecting blood glucose (American ginseng, bitter melon, chromium, fenugreek), those with multiple drug interactions (Echinacea, feverfew, goldenseal, grapefruit extract), and St. John's wort (due to CYP3A4 induction).
• Hold serotonergic supplements (5-hydroxytryptophan, L-tryptophan, S-adenosylmethionine) for 24 hours before surgery due to rapid metabolism and potential interactions with perioperative medications like meperidine or tramadol.
• Cannabis products should be discontinued at minimum 3 days before elective surgery, ideally 2 weeks, due to sympathetic hyperactivity, airway irritability, impaired temperature regulation, and increased risk of perioperative coronary vasospasm.
• Garcinia cambogia and kratom should be discontinued due to hepatotoxicity risk and opioid agonist properties, respectively.

Kidney Donors

For living kidney donors, the American Journal of Kidney Diseases recommends the highest level of caution: 2

• Discourage all dietary supplements (excluding multivitamins and minerals) at any point during kidney donor evaluation due to unknown effects on kidney function and metabolic parameters.
• Certain supplements have documented nephrotoxic potential, including aristolochic acid (direct nephrotoxicity causing tubulointerstitial disease), kava (altered renal hemodynamics), and turmeric (alterations in renal blood flow).
• Creatine supplementation can interfere with creatinine clearance measurements, leading to misclassification of kidney function.

Rheumatoid Arthritis Management

The 2022 American College of Rheumatology guideline takes a clear stance: 2

• Conditionally recommend following established dietary recommendations without adding dietary supplements based on very low to moderate certainty evidence showing no consistent, clinically meaningful benefit on physical function, pain, or disease activity.
• Support a "food first" approach, though recognize supplements may serve roles for bone health (vitamin D) and cardiovascular health (fish oil) in specific circumstances.

Cancer Survivors

The American Cancer Society provides nuanced guidance: 2

• High-dose vitamins, minerals, and supplements can cause physical harm—doses greatly exceeding the Recommended Dietary Allowance should be taken with extreme caution.
• High-dose beta-carotene supplements actually increase (not decrease) lung cancer rates in clinical trials, despite observational studies suggesting dietary beta-carotene was protective.
• Beta-carotene supplements may increase colorectal adenoma recurrence in persons who smoke cigarettes or consume alcohol.
• It remains prudent to obtain potentially beneficial compounds from food rather than supplements, as few studies have examined supplement effects on cancer recurrence and survival.

Critical Drug Interactions and Monitoring

Medication Interactions

• Supplements can interact with medications in complex ways, particularly problematic in elderly patients taking multiple medications. 4
• St. John's wort induces CYP3A4, reducing plasma concentrations of drugs metabolized by this enzyme. 2
• The prescribing physician must specifically ask about dietary supplement use during clinical encounters, as most patients do not voluntarily disclose supplement use to their physicians. 1, 5

Monitoring Requirements

• When vitamin D supplementation is used, the Endocrine Society recommends monitoring serum calcium and phosphorus levels. 4
• Supplements should be used with adherence to dosages recommended in the Dietary Reference Intakes of the Institute of Medicine. 1
• Regularly review and re-evaluate patients taking supplements to determine whether continuation is appropriate. 2

Common Pitfalls to Avoid

Dosing Errors

• Vitamins A and D may be harmful in higher doses—potential harms may outweigh potential benefits when doses greatly exceed recommendations. 4
• Nine customers in one survey were taking megadoses of vitamin A, which has previously reported toxicities. 5
• Imprecision in content and concentration of ingredients poses theoretical risks not reflected in clinical trials. 4

False Assumptions

• The pattern of supplement use suggests physicians are not adequately addressing preventive and wellness issues, leading patients to self-medicate with supplements. 5
• Most dietary supplement users are white, female, college-educated, have health insurance, and have a regular physician—yet they do not typically consult their physician about supplements. 5
• Dietary supplements must be used cautiously and should not replace a well-balanced diet, as excessive intake can pose serious health risks. 1

Practical Clinical Approach

For general nutritional support, prioritize a diet high in fruits, vegetables, whole grains, and legumes rather than relying on supplements. 1 Only individuals with documented nutritional deficiencies or specific medical conditions requiring supplementation should use dietary supplements, under medical supervision with dosing determined by the body's actual needs. 1