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Placebo-controlled study finds low-dose zinc beneficial

The immune system needs small amounts of zinc to function. In particular, laboratory and animal studies have found that zinc can help play a role in the following:

• growth and development of T-cells
• activating the hormone thymulin, needed by the immune system
• maintaining the ability of T-cells and natural killer cells to destroy germs
• activating enzymes that protect cells from harmful substances

Clinical trials in low-income countries suggest that zinc supplements can help reduce the risk of pneumonia and diarrhea in HIV-negative children. Small clinical trials of zinc supplementation in HIV-positive people have yielded mixed results.

So a study team in Miami, led by researcher Mariana Baum, PhD, conducted an 18-month placebo-controlled trial of low-dose zinc supplements in HIV-positive people. Its findings are clear—compared to placebo, zinc helped to maintain CD4+ cell counts and reduced the proportion of people experiencing diarrhea by 50%.

Study details

Between 2002 and 2005, researchers recruited 231 HIV-positive people who were randomly assigned to receive one of the following interventions:

• 115 people – zinc 12 mg/day for women and 15 mg/day for men (the zinc group)
• 116 people – placebo (the placebo group)

Neither participants nor researchers, with the exception of a pharmacist and statistician, knew who received zinc or placebo.

Before being randomized, potential participants were assessed for zinc levels. Only those people with a zinc level of less than 0.75 mg/l in their blood were enrolled in the study. Additionally, because zinc levels temporarily fall during acute infections, participants had their blood levels of high sensitivity C-reactive protein (hsCRP) assessed at the start of and throughout the study. This can be a useful way to assess inflammation due to acute infections.

Participants were interviewed and examined at the start of the study and every six months. Blood and urine samples were also collected for analysis at regular intervals.

The main outcome of the study was to assess the impact of zinc on what the researchers termed “immunological failure,” which they defined as a CD4+ count falling below the 200-cell mark.

The average profile of participants at the start of the study was as follows:

• 27% females, 73% males
• age – 43 years
• HIV infection had been diagnosed 10 years previously
• 34% had AIDS
• 45% had a CD4+ count of 351 or more cells
• 62% reported the use of antiretroviral therapy (ART); however, only about 30% of ART users had a viral load below the 400-copy/ml mark
• 18% changed their anti-HIV medications during the study
• 25% were co-infected with hepatitis C virus

A majority of participants injected illicit substances, including cocaine and opiates. Additionally, there was a high rate of licit drug use, such as alcohol and tobacco.

Results—CD4+ cell counts

The following numbers of people completed the 18-month clinical trial:

• zinc supplement – 104 participants
• placebo – 94 participants

Taking into account factors such as age, gender, access to food, viral load and ART, people who received zinc compared to placebo were less likely to experience immunologic failure; that is, to have their CD4+ count fall below the 200-cell mark.

Results—Diarrhea

At the start of the study, 32% of participants reported experiencing diarrhea. Over time, the proportion of people who experienced diarrhea fell by more than 50% among people using zinc. This change was noted at the 12th month of the study and was sustained for the remainder of the study.

Results—Other infections

Some studies done in low-income countries have found that zinc supplementation reduces rates of TB (tuberculosis) and other lung infections. However, in the present study, the number of lung infections was too small to draw firm conclusions.

HIV viral load was not affected by zinc supplementation.

Results—Side effects and deaths

There were no side effects reported by participants. This is probably because a low level of zinc was used.

Eleven people who received zinc died, along with eight who received placebo. However, this difference in deaths was not statistically significant.

Sub-group analyses

Researchers conducted analyses on a subset of 40 people—20 who received placebo and 20 who received zinc—all of whom were taking ART and had a suppressed viral load. Among these people, four cases of immune failure occurred—a fall in the CD4+ count below the 200-cell mark. All four cases occurred in the placebo group. This difference between the zinc and placebo groups was statistically significant; that is, not likely due to chance alone.

A tough start

According to the study team, participants recruited for this trial had several factors associated with poor immunological reconstitution, including the following:

• poor access to ART
• failure of previous anti-HIV regimens
• intermittent use of ART
• low adherence to ART

Despite these barriers, according to the researchers, a low-dose zinc supplement provided “immunological and clinical benefits despite persisting detectable HIV viral load in the majority of participants.”

Adherence to zinc or placebo was higher than to ART, likely for the following reasons stated by the researchers:

• low pill burden
• lack of side effects
• regular monitoring and encouragement by study personnel

The Miami researchers stated that the results of their study can be generally extended to other HIV-positive populations where zinc deficiency has been documented, such as the following:

• drug users
• men who have sex with men
• children
• people in low-income countries

They encourage doctors to consider the use of low-dose zinc supplementation in addition to ART for their HIV-positive patients.

In an editorial in the journal Clinical Infectious Diseases, to accompany the results of the Miami study, Harvard University researchers agreed with this potential use of zinc.

—Sean R. Hosein

Created on: 05/25/2010

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