Evidence for using zinc supplements with antihypertensives

Routine use of zinc supplements is unnecessary for people taking blood pressure lowering medicines (or ‘antihypertensives’). There is evidence that long-term treatment with certain types of antihypertensives may reduce zinc levels, but it is unclear how often this causes zinc deficiency.

Limitations of evidence

Evidence for any benefit of zinc supplementation in the absence of zinc deficiency is limited.1 People taking anithypertensives should only be considered for a zinc supplement if they are deficient in zinc.

Results from the only trial investigating zinc supplementation with an antihypertensive (hydrochlorothiazide) were inconclusive.

While some studies have found reduced blood zinc levels in people taking antihypertensives2 — namely ACE inhibitors, angiotensin II–receptor antagonists and thiazide diuretics — it is unclear how frequently zinc deficiency occurs with these medicines. Zinc depletion has not been seen with other types of antihypertensives.3

Reliable data on the rate of zinc deficiency in Australia are not available.4 For comparison, a survey of the US population found that 1–3% of people aged 3–74 years were zinc deficient.5

Thiazide diuretics can increase the excretion of zinc in the urine.2 But a zinc supplement is only necessary if someone shows symptoms of zinc deficiency after long-term treatment.3

There has been one trial of zinc supplementation for people taking hydrochlorothiazide (a type of thiazide diuretic) but it had inconclusive results.6 There are no trials of zinc supplementation with other antihypertensives.

Studies investigating the effect of ACE inhibitors or angiotensin-II receptor antagonists on zinc levels have had inconsistent results.2 People taking these medicines for prolonged periods should be aware of the symptoms of zinc deficiency, especially if they have other risk factors.

People who may be deficient in zinc should see their doctor first

People with symptoms or risk factors for zinc deficiency should be referred to their doctor for further investigation.

Symptoms of zinc deficiency include an impaired sense of taste or smell, hair loss, poor wound healing and an eczema-like skin rash.3,7

A diet low in zinc is relatively common4 and is a major cause of zinc deficiency.7 People whose diet may not contain enough zinc may benefit from dietary advice.

Among those likely to be taking an antihypertensive, people in residential aged care and possibly people with diabetes, are the groups at increased risk of zinc deficiency.4 Other people who may be at risk include those with coeliac disease or malabsorption syndromes.7

Supplements can have side effects and interactions

Zinc supplements often cause nausea7, although low doses at the level of 20 mg elemental zinc per day do not usually cause adverse effects. There may be a higher risk of adverse effects for people with certain medical conditions, including diabetes, bleeding disorders, or immune disorders.1

Zinc supplements can affect the absorption of tetracycline and quinolone antibiotics, so they need to be taken at least 2 hours apart from these other medicines.1,8

References
  • Natural Standard. Somerville, MA, USA: 2011. naturalstandard.com (accessed 27 September 2011).
  • Cohen N, Golik A. Zinc balance and medications commonly used in the management of heart failure. Heart Fail Rev 2006;11:19-24. www.ncbi.nlm.nih.gov/pubmed/16819574
  • Natural Medicines Comprehensive Database. Stockton, CA, USA: Therapeutic Research Faculty, 2011. naturaldatabase.therapeuticresearch.com (accessed 29 September 2011).
  • Gibson R, Heath A-L. Population groups at risk of zinc deficiency in Australia and New Zealand. Nutrition & Dietetics 2011;68:97-108.
  • Pilch SM, Senti FR. Analysis of zinc data from the second National Health and Nutrition Examination Survey (NHANES II). J Nutr 1985;115:1393-7. www.ncbi.nlm.nih.gov/pubmed/4056936
  • Khedun SM, Naicker T, Maharaj B. Zinc, hydrochlorothiazide and sexual dysfunction. Cent Afr J Med 1995;41:312-5. www.ncbi.nlm.nih.gov/pubmed/8556776
  • Therapeutic Guidelines: Gastrointestinal Writing Group. Therapeutic Guidelines: Gastrointestinal. Version 5 ed. Melbourne: Therapeutic Guidelines Ltd, 2011.
  • Rossi S, ed. Australian Medicines Handbook. Adelaide, 2011.