Coles CL, et al. Infectious etiology modifies the treatment effect of zinc in severe pneumonia. Am J Clin Nutr. 2007;86(2):39.
In order to determine if the etiology of pneumonia (bacterial versus nonbacterial pneumonia) alters the efficacy of zinc adjuvant therapy, a randomized, double-blind, placebo-controlled study of 299 children (2-23 mo) hospitalized for severe pneumonia was performed. C-reactive protein (CRP) concentrations were used to determine the etiology of pneumonia. In those with suspected bacterial pneumonia, the zinc-treated group required an additional 20 hours to recover, resulting in a longer hospital stay as compared to the placebo group. No difference in time of recovery was detected in patients with nonbacterial pneumonia. Therefore, this study suggests that zinc adjuvant therapy for patients with bacterial pneumonia may increase the time to recovery and length of hospital stay. However, because the etiology of pneumonia was determined by CRP concentration, it is possible that some subjects may have been misclassified.
Lin LC, et al. Effects of zinc supplementation on clinical outcomes in patients receiving radiotherapy for head and neck cancers: a double-blinded randomized study. Int J Radiat Oncol Biol Phys. 2008;70(2):368-373.
One hundred subjects with cancers of the head and neck regions and undergoing radiotherapy or chemo radiotherapy participated in this study to determine if zinc supplementation (25 mg Pro-Z, 3 times daily) could affect survival, including overall survival, disease-free survival, local-free survival, and metastasis-free survival. Three-year local-free survival was minimally affected by zinc supplementation as compared to the placebo group. However, in patients with Stages III-IV disease who simultaneously received chemo radiotherapy, zinc supplementation significantly enhanced 3-year local-free survival possibly due to decreased radiotherapy-induced mucositis and dermatitis, resulting in less interruption of the chemo radiotherapy regimen. Additional studies with more participants and longer follow-up periods are necessary.
Gonzalez, et al. Zinc intake from supplements and diet and prostate cancer. Nutr Canc. 2009;61(2):206-215.
In a ten year, prospective study of 35,242 men who completed a baseline dietary and supplements questionnaire, 832 subjects developed invasive prostate cancers. Analysis showed that a ten year average intake of >15 mg/day of supplemental zinc did not reduce overall prostate cancer risk compared to non-supplementation (p=0.44). However, the risk of advanced prostate cancer was found to significantly decrease with intake of > 15 mg/day supplemental zinc vs. non-use (p=.04). The authors concluded that long-term supplemental zinc intake was associated with reduced risk of clinically relevant advanced disease. However, because study results regarding zinc supplementation and prostate cancer have been inconsistent, further research is needed.
Kelishadi R, et al. Effect of zinc supplementation on markers of insulin resistance, oxidative stress, and inflammation among prepubescent children with metabolic syndrome. Metab Syndr Relat Disord. 2010;8(6):505-510.
This was a triple-blinded, randomized, crossover trial that enrolled 60 obese children. Participants were randomized into two groups of 30 subjects. Each group received either 20 mg/day of elemental zinc or placebo for 8 weeks. After a 4 week washout period, the groups were crossed over. Blood pressure, fasting plasma glucose, lipid profile, insulin, apolipoproteins A-1 and B, high sensitivity C-reactive protein (hs-CRP), leptin, oxidized low-density lipoprotein, and malondialdehyde levels were measured during all study phases. After receiving zinc, a significant decrease in ApoB/ApoA-1 ratio, ox-LDL, leptin, malondialdehyde, total and LDL-cholesterol levels was documented (p<0.05), whereas no significant change in these parameters was detected in the placebo group. Levels of hs-CRP, markers of insulin resistance, mean weight, BMI, and BMI Z-score also decreased significantly after receiving zinc (p<0.05), whereas these values increased after receiving placebo. The authors suggest that the effect of zinc supplementation on childhood obesity should be further investigated.