Patterns of Supplement Consumption and Interaction Risks Among Polymedicated Older Adults: A Descriptive Study ^†

Abstract

This study investigates the use of food supplements (FS) among polymedicated elderly individuals and assesses potential FS–drug interaction risks. A total of 98 community-dwelling older adults were surveyed and 18.4% reported FS use. FS were mostly used for musculoskeletal and cognitive support, with 71% having potential metabolic interactions via CYP enzymes or P-glycoprotein. Monthly costs reached €55. The findings reveal a complex interaction landscape and financial burden, underscoring the need for medication reviews and health literacy efforts to ensure safer FS use in older adults. This study aligns with One Health principles by linking clinical, social, and economic aspects of aging.

1. Introduction

The aging population is experiencing a marked increase in chronic conditions, often requiring the use of multiple medications—a phenomenon known as polypharmacy. Among older adults, defined commonly as individuals aged 65 years and above, polypharmacy is a growing concern due to its association with adverse drug events, hospitalizations, and reduced quality of life [1,2]. In parallel, there is a rising trend in the use of food supplements (FS), such as vitamins, minerals, and herbal products, often taken without professional guidance [3]. The use of FS by elderly polymedicated individuals raises concerns that go beyond pharmacological safety. Because these products are not classified as medicines, they fall outside reimbursement systems and regulatory frameworks, placing the full financial burden on users. For older adults, many of whom live on limited incomes, this can deepen existing social vulnerabilities and contribute to health inequities.

Due to the natural origin, FS are often perceived as inherently safe, but their concomitant use with prescription medications can lead to clinically significant interactions [4,5]. Older adults are particularly vulnerable due to age-related changes in drug disposition, along with the cumulative effects of polypharmacy [6]. Notably, FS such as St. John’s Wort, Ginkgo biloba, or calcium can interfere with drug absorption or metabolism, risking therapeutic failure or toxicity [7]. Others, such as Ephedra (banned in Europe and US but available through the internet), Yohymbe (Pausinystalia yohimbe), Kava (Piper methysticum), or green tea extract, can lead to potentially fatal outcomes, especially when used in high doses, combined with medications, or taken by vulnerable populations [8,9,10].

Despite the risks, there is a lack of systematic data on FS use in polymedicated older adults, particularly in community settings. This gap hampers efforts to identify high-risk combinations and implement preventive strategies. The present work aims to (1) describe the patterns of FS use among polymedicated older adults, including type, duration, motivation, and cost; and (2) identify potential FS–drug interactions using validated databases. It is anticipated that the work will provide evidence that informs clinical practice and health policy, supporting safer use of FS in a vulnerable population.

2. Materials and Methods

This cross-sectional study was part of the ESPIEM 2024/2025 cohort under the Healthy Ageing—Egas Moniz Interdisciplinary Project, aimed at promoting rational pharmacotherapy and understanding health behaviors in older adults. A convenience sample of community-dwelling individuals aged 65 or older and on polymedication was recruited by third-year pharmacy students through personal networks. Data were collected via standardized forms and included demographics, medication profile (number/types of chronic medicines), supplement use (product, ingredients, dose, duration, and motivation), and recommendation source (professional advice or self-initiated). Interaction risk was assessed using DrugBank [11] and Medscape Drug Interaction Checker [12] tools to evaluate the potential for supplement–drug interactions based on CYP enzymes and P-glycoprotein pathways. Supplement costs were estimated using reported dosages and market prices to reflect typical monthly expenses. Descriptive statistics were used to summarize supplement use patterns, potential interactions, and associated financial burden.

3. Results and Discussion

Among 98 polymedicated elderly individuals studied, 18 (18.4%) were taking FS, with a total of 21 distinct products reported. These were taken in addition to an average of 4.6 medications. All FS were oral solid dosage forms (mainly tablets and capsules), which did not appear to hinder use despite common dysphagia in the elderly. Women accounted for 66.7% of FS users. The most common indications were musculoskeletal support (43%) and cognitive enhancement (38%). While most supplements (57.2%) were recommended by health professionals, 38.1% were self-initiated (Figure 1). Use was often long-term, with 29% taking FS for 3–6 months and 43% for over 6 months.

The average monthly supplement cost was €18.23 per patient, reaching up to €55, an added burden for many on limited incomes.

Unlike medicines, FS are less strictly regulated, making their use in polymedicated older adults a concern due to potential clinically relevant interactions and heightened risk of adverse outcomes. In fact, fifteen FS (71%) showed potential CYP/P-gP interactions (

Table 1. Summary of bioactive constituents in the FS used by study participants (P1–P16), the potential modulatory effects with Cytochrome P450 (CYP) isoenzymes and P-glycoprotein (P-gP), and the concomitant medicines possibly affected [11,12].

P	FS	Bioactive	CYP ↑	CYP ↓	P-gP ↓	Drugs Affected (CYP/Transporter Involved)
1	A	Biotin	1B1	-	No	-
		Lutein	-	2C19	No	Simvastatin; Bromazepam; Pantoprazole (2C19)
		Resveratrol	1A2	1A2; 1A1; 1B1; 3A4; 2D6; 2B6; 2C19; 2C9	No	Betahistine (2D6); Simvastatin (3A4; 2D6; 2C19); Calcitriol (3A4); Acetylsalicylic acid (2C9); Bromazepam (1A2, 2C19; 3A4); Pantoprazole (2C19; 3A4); Spironolactone (3A4)
		Vitamin A	26A1	-	No	-
		Vitamin B1	4B1	-	No	-
		Riboflavin	-	CYP1A2; CYP2C19	No	Simvastatin (2C19); Bromazepam (1A2; 2C19); Pantoprazole (2C19)
		Vitamin B6	-	CYP1A1	No	-
		Vitamin D3	-	CYP1A1; CYP2C8	No	Simvastatin (2C8)
		Vitamin E	3A4	-	No	Simvastatin; Calcitriol; Bromazepam; Pantoprazole; Spironolactone (3A4)
2–4	B	Vitamin D3		1A1; 2C8	No	Atorvastatin (2C8)
5	C	Biotin	1B1	-	No	-
		Niacin	-	2D6; 3A4; 2E1	No	Bisoprolol (3A4; 2D6); Simvastatin (3A4; 2D6); Diazepam (3A4); Budesonide (3A4)
		Vitamin B6	-	1A1	No	-
6	D	DHA	-	2C9	No	-
7	E	Vitamin B6	-	1A1	No	-
		Vitamin D3	-	1A1; 2C8	No	-
8	F	DHA	-	2C9	No	Venlafaxine
		EPA	-	1A2	No	-
		Curcumin	-	3A4; 2C9; 2B6; 1A2; 2D6	Yes	Atorvastatin (3A4/P-gP); Venlafaxine (2D6; 3A4; 2C9/P-gP)
		Piperine	-	3A4	Yes	Atorvastatin (3A4/P-gP); Venlafaxine (3A4/P-gP)
		Vitamin E	3A4	-	No	Atorvastatin; Venlafaxine (3A4)
9	G	Vitamin D3	-	1A1; 2C8	No	Atorvastatin (2C8)
	H	EPA	-	1A2	No	-
		DHA	-	2C9	No	Candesartan (2C9)
10	I	Quercetin	-	2C8; 2D6; 2C9; 1A2; 2E1; 2C19	Yes	Alprazolam (2C9); Bisoprolol (2D6/P-gP)
11	J	DHA	-	2C9	No	Acetylsalicylic acid; Pitavastatin (2C9)
		EPA	-	1A2	No	-
		Vitamin E	3A4	-	No	Pantoprazole; Amlodipine; Silodosin (3A4)
12	K	Vitamin B1	4B1	-	No	-
		Riboflavin	-	1A2; 2C19	No	Esomeprazole (2C19); Simvastatin (2C19); Clozapine (1A2; 2C19); Vortioxetine (2C19)
		Niacin	-	2D6; 3A4; 2E1	No	Clonazepam (3A4); Esomeprazole (3A4); Simvastatin (3A4; 2D6); Clozapine (3A4; 2D6); Betahistine (2D6); Vortioxetine (3A4; 2D6)
		Vitamin B6	-	1A1	No	-
		Biotin	1B1	-	No	-
13	L	Pyridoxine	-	1A1	No	-
14	M	DHA	-	2C9	No	Trimipramine; Valsartan; Rosuvastatin (2C9)
		EPA	-	1A2	No	-
15	N	Niacin	-	2D6; 3A4; 2E1	No	Pantoprazole (3A4); Imatinib (3A4; 2D6)
		Riboflavin	-	1A2; 2C19	No	Pantoprazole (2C19); Imatinib (1A2; 2C19)
16	O	DHA	-	2C9	No	Omeprazole; Fluoxetine (2C9)
		EPA	-	1A2	No	Fluoxetine (1A2)

Interactions are classified based on how FS bioactives affect CYP enzymes and the P-gP transporter involved in drug disposition. Arrows indicate whether these pathways are induced (↑) or inhibited (↓), while “Yes” or “No” under P-gP denotes whether there is a documented transporter inhibition. Lack of interaction (-) means that no current evidence of significant effect exists.

), possibly affecting the metabolism, efficacy, and safety of co-medications. Despite the identification of potential clinically significant interactions, none of these were deemed to represent a life-threatening risk. However, many commonly prescribed drugs, such as statins, proton pump inhibitors, and benzodiazepines, presented interactions, potentially leading to altered efficacy or adverse outcomes. Therefore, clinicians should routinely ask about FS use and consider interactions when taking a medication history. Digital interaction tools and pharmacist-led reviews may enhance safety. Public health strategies should include FS risk education to support safer and more equitable use among older adults.

A key limitation of this study is the small number of FS users, which limits statistical power, generalizability, and subgroup (gender, comorbidities, or types of FS used) analysis. The low prevalence may also reflect underreporting, as some participants might not perceive supplements as relevant to their medication regimen or might withhold such information. Additionally, with such a small group of supplement users, the identification of potential supplement–drug interactions is necessarily limited, and clinically significant combinations may not have been captured. These limitations underscore the importance of future studies involving larger and more diverse elderly populations to better characterize supplement use patterns and associated risks in the context of polypharmacy.

4. Conclusions

The use of FS in older adults taking multiple medications reflects vulnerabilities in clinical, financial, and regulatory areas. The findings highlight the need for routine FS screening, the use of interaction tools, and integrated medication review strategies in practice. Public health policies should promote FS literacy and risk awareness, in line with One Health principles for safer ageing.