This publication is provided for historical reference only and the information may be out of date.
Research Focus for Clinicians
In response to a request from the public regarding the use of dietary supplements by patients currently undergoing pharmacologic cardiovascular treatment, a review was undertaken to evaluate the evidence regarding the benefits and harms of concomitant use of dietary supplements with cardiovascular drugs. The systematic review included 70 studies published through September 2011. The full report, listing all studies, is available at www.effectivehealthcare.ahrq.gov/dietary-supplements.cfm. This summary is provided to inform discussions with patients of options and to assist in decisionmaking along with consideration of a patient's values and preferences. However, reviews of evidence should not be construed to represent clinical recommendations or guidelines.
Background
Estimates suggest that approximately one-third to two-thirds of people suffering from heart failure or other forms of cardiovascular disease (CVD) use dietary supplements.1 These supplements are available in pharmacies, grocery stores, and health food stores and on the Internet. They are often consumed by patients without the knowledge of their health care providers and under the impression that they are safe and beneficial. Such claims of benefit are often unsubstantiated, however. These products do not require U.S. Food and Drug Administration (FDA) approval nor are there any FDA regulations that require evidence of purity, quality, or composition before marketing. Use of dietary supplements for CVD occurs in the setting where, in addition to lifestyle and dietary recommendations, patients receive pharmaceuticals (6.9 prescription drugs on average from 5.9 different drug classes2) to prevent or treat CVD. Patients may be at risk for drug-supplement or supplement-supplement interactions.
On one hand, patients taking supplements may be placed at risk for potential adverse effects from the supplements themselves or from interactions with other pharmacologically active agents. On the other hand, adding a dietary supplement to conventional cardiovascular drugs may confer benefits. Although a substantial amount of research describes drug-drug interactions in various populations, the evidence for drug-supplement interactions is unclear, especially in CVD populations. The evidence for benefits and adverse effects in patients with CVD has not been summarized previously.
- 1.
- Yeh GY, Davis RB, Phillips RS. Use of complementary therapies in patients with cardiovascular disease. Am J Cardiol. 2006 Sep 1;98(5):673–80. [PubMed: 16923460]
- 2.
- Choudhry NK, Fischer MA, Avorn J, et al. The implications of therapeutic complexity on adherence to cardiovascular medications. Arch Intern Med. 2011 May 9;171(9):814–22. [PubMed: 21555659]
Conclusion
Evidence for the use of dietary supplements in combination with cardiovascular drugs was insufficient to permit conclusions about clinical cardiovascular efficacy, effectiveness, and adverse effects (e.g., mortality, thrombotic events, and arrhythmia).
Evidence for most intermediate outcomes (e.g., lipid profile, blood pressure, international normalized ratio (INR), and bleeding and coagulation) was also insufficient or of low strength and suggested no effect. Where an effect on an intermediate outcome might be suggested, studies were often small, at risk of bias, and subject to the uncertainties associated with testing of agents of uncontrolled purity, quality, or composition.
Some findings with low strength of evidence, if acted on by a patient without consulting a physician, could lead to adverse effects.
Furthermore, the interactions of these agents with other noncardiovascular drugs that patients may be taking cannot be predicted from any of these studies. Comorbidities such as renal disease or liver disease that could affect the metabolism, actions, and safety of supplements were not studied.
Advertised claims for dietary supplements should be interpreted cautiously, and clinicians should ask their patients with CVD about their use of supplements, regardless of whether the supplement is to be taken to provide cardiovascular protection or for other purposes.
Details of the comparisons and findings are available online at www.effectivehealthcare.ahrq.gov/dietary-supplements.cfm.
Clinical Bottom Line
Supplement/Drug Combinations and Outcomes Studied
Gaps in Knowledge
- Future research with dietary supplements should involve substances for which the identity of the agents can be clearly ascertained and the chemical composition well characterized and ideally standardized. If the active ingredients or biologic activity is not known, studies to characterize these variables, identify mechanisms of action, and describe safety should precede clinical efficacy studies.
- As the extant literature is largely based on a few small efficacy studies of limited internal validity that examined intermediate outcomes, future supplement-cardiovascular drug interaction trials should focus on meaningful clinical outcomes, should be appropriately powered and rigorously conducted and reported, and should provide precise measurements of both clinical effectiveness and harms outcomes.
- Most studies were conducted in speciality settings, excluded patients with comorbidities or uncontrolled comorbidities, and did not include ethnic and racial minorities. Future trials should be representative of the population taking cardiovascular drugs in terms of comorbidities, setting, and racial distribution. They should also collect data and undertake subgroup analyses for age, sex, race, comorbidities (e.g., liver or renal compromise), and genotypic polymorphisms of the cytochrome P450 enzyme.
- A substantial number of pharmacokinetic interaction studies did not report and analyze pharmacokinetic outcomes according to FDA guidance for bioequivalence studies.
What To Discuss With Your Patients
Given these findings, clinicians may wish to inquire about supplement use among their patients with cardiovascular disease. Topics of discussion include:
- The importance of informing their clinician about a decision to take a supplement
- The high uncertainty about the benefits or potential side effects of dietary supplements used in combination with cardiovascular drugs
- The importance of continuing to take prescribed cardiovascular medication(s) if the patient decides to take a dietary supplement
- The fact that dietary supplements do not require FDA approval before being advertised and sold, and that there may be uncertainty about the purity, quality, or composition of the supplements
- The potential but uncharacterized risks for interactions with prescribed medicines or with other supplements
Resource for Patients
Taking Dietary Supplements With Heart, Blood Pressure, or Cholesterol Medicines, A Review of the Research for Adults is a free companion to this clinician research summary. It can help patients with cardiovascular disease who are considering taking dietary supplements in conjunction with their cardiovascular drugs talk with their health care professionals about their options. It provides information about:
- How much evidence is available concerning the cardiovascular benefits or harms of taking dietary supplements in conjunction with cardiovascular medications
- Warnings about the lack of regulation or standardization of supplement products sold in stores or on the Internet
- The importance of discussing the use of supplements with their doctor before adding them to cardiovascular medications, and questions to guide that discussion
Ordering Information
For electronic copies of Taking Dietary Supplements With Heart, Blood Pressure, or Cholesterol Medicines, A Review of the Research for Adults, this clinician research summary, and the full systematic review, visit www.effectivehealthcare.ahrq.gov/dietary-supplements.cfm. To order free print copies, call the AHRQ Publications Clearinghouse at 800-358-9295.
Source
The information in this summary is based on Dietary Supplements in Adults Taking Cardiovascular Drugs, Comparative Effectiveness Review No. 51, prepared by the University of Ottawa Evidence-based Practice Center under Contract No. 290-2007-10059-I for the Agency for Healthcare Research and Quality, April 2012. Available at www.effectivehealthcare.ahrq.gov/dietary-supplements.cfm. This summary was prepared by the John M. Eisenberg Center for Clinical Decisions and Communications Science at Baylor College of Medicine, Houston, TX.
Publication Details
Author Information and Affiliations
Authors
John M. Eisenberg Center for Clinical Decisions and Communications Science1.Affiliations
Publication History
Issued: April 10, 2013.
Copyright
Publisher
Agency for Healthcare Research and Quality (US), Rockville (MD)
NLM Citation
John M. Eisenberg Center for Clinical Decisions and Communications Science. Use Versus Nonuse of Dietary Supplements in Adults Taking Cardiovascular Drugs. 2013 Apr 10. In: Comparative Effectiveness Review Summary Guides for Clinicians [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2007-.