Lao Zinc Study: Effects of Two Forms of Daily Preventive Zinc Versus Therapeutic Zinc Supplementation

Zinc is an essential nutrient that is required for children's normal growth and resistance to infections, including diarrhea and pneumonia, two major causes of child mortality. Current strategies for controlling the growth and infection-related complications of zinc deficiency include: 1) daily or weekly preventive zinc supplementation, and 2) therapeutic zinc supplementation for 10-14 days in relation to episodes of diarrhea. Information is needed on the relative impact of these intervention strategies on children's growth and risk of new episodes of diarrhea (and other infections).

Preventive zinc supplements can be delivered either as a single nutrient (zinc) supplement or as a multiple micronutrient (MMN) supplement, such as micronutrient powders (MNP) added to young children's complementary food. Available research indicates that zinc delivered in MNP at the currently recommended dose (4.1-5 mg/d) has not had a measurable impact on zinc-related functional outcomes, like growth and prevention of infection. Moreover, some studies of MMN supplements have detected a greater incidence of diarrhea in the MMN group than in the non-intervention or placebo control groups. Thus, despite the beneficial effects of MNP on prevention of anemia and enhancing iron status, questions have been raised about the desirability of providing zinc in MNP (containing iron and other nutrients) versus a single nutrient formulation offered between meals. For these reasons, the present study is designed to compare both the zinc delivery plan (i.e., preventive versus therapeutic supplementation) as well as the form of delivering zinc (i.e., as a dispersible tablet given between meals or as a MNP given with meals) and to permit assessment of any adverse effects of MNP on the incidence of diarrhea.

The study will be conducted as a community-based, randomized, placebo-controlled trial with four study groups in rural communities of Khammouane Province in Central Lao PDR.

The project team will enroll a total of ~3,400 children whose ages will range from 6-23 months. Children will be randomly assigned to one of four study group: 1) preventive zinc supplementation provided as LI-MNP plus ORS and placebo tablets for treatment of diarrhea; 2) placebo preventive supplementation provided as placebo powder plus ORS and placebo tablets for diarrhea ; 3) preventive zinc supplementation provided as dispersible zinc tablets (containing 7 mg zinc, to be given between meals) plus ORS and placebo tablets for diarrhea; and 4) therapeutic zinc supplementation provided as dispersible tablets (containing 20 mg zinc) for diarrhea plus ORS and placebo preventive tablets.

The major outcomes that will be monitored include adherence to the interventions; physical growth; incidence, duration and severity of episodes of diarrhea; changes in MN status; immune function; environmental enteric dysfunction; parasite burden; hair cortisol concentration; neuro-behavioral development; and the occurrence of any adverse events.

Inclusion criteria

• Signed informed consent from at least one parent or primary caregiver
• Age 6-23 months initially
• Permanent resident of study area
• Planned availability during the period of the study
• Acceptance of home visitors

Exclusion criteria

• Weight-for-height z-score (WHZ) <-3Z with respect to WHO 2006 standards
• Presence of bipedal edema
• Severe illness warranting hospital referral
• Congenital abnormalities potentially interfering with growth
• Chronic medical condition (e.g. malignancy) requiring frequent medical attention
• Known HIV infection of index child or child's mother
• Hemoglobin <70 g/L
• Currently consuming zinc supplements
• Current participation in any other clinical trial