Does BMI Predict Zinc Deficiency and Its Association with Anemia?

Background:

Zinc (Zn) is an essential micronutrient and is involved in erythropoiesis. It is involved in iron metabolism, heme synthesis, erythroid cell growth, erythropoietin signaling, and erythroid differentiation. Zn deficiency has been recognized in malnourished and morbidly obese individuals. Given the prevalence of malnourishment and obesity worldwide, it is critical to understand the relationship between BMI, Zn, and erythropoiesis.

This descriptive, retrospective study examined 125 patients with chronic anemia and Zn deficiency. These patients were further divided into subgroups based on BMI. Changes in hemoglobin (HGB) and plasma Zinc concentration (pZc) were monitored over 12 months after oral Zn replacement. This study was completed at an academic outpatient hematology center in California.

Objectives:

Primary endpoint: Describe baseline pZc and HGB differences between BMI ranges.

Secondary endpoints: determine HGB and pZc changes after Zn replacement at 1, 3, 6, and 12 months, and determine the rate of anemia resolution after replacement of Zn.

Methods:

One hundred-and-twenty-five patients with chronic anemia (HGB <12 g/dL for women, HGB <13 g/dL for men for >3 months) over the age of 18 were identified to have Zn deficiency (pZc <65 ug/dL). Zn Sulfate 220 (50)mg capsule was given daily.

Patients were placed into subgroups according to their BMI, where BMI <18 was underweight, 18-25 was normal, 25-30 was overweight, and >30 was obese. A retrospective analysis was completed for prior medical history, lab data, including HGB and pZc was tabulated at the time markers of 1, 3, 6, and 12 months following initiation of Zn replacement. Data was analyzed with ANOVA between subgroups, T-Test from baseline lab values to post treatment lab values, and CHI-squared in all patients.

Results

The mean age was 62.5, women accounted for 60% of the patients. The mean BMI was 26.8, with lowest BMI of 13.3 and highest BMI of 58.0. Mean baseline WBC was 6.8 x10³/uL, HGB 9.8 g/dL, MCV 90.1 fl, Plts 219 x10³/uL.

Baseline pZc was compared across BMI ranges where the mean pZc was 52.5 ug/dL (p = 0.11 between subgroups). Mean baseline underweight pZc was 54 ug/dL. Mean baseline normal BMI pZc was 50.4 ug/dL. Overweight subgroup baseline pZc was 53.6 ug/dL, and obese subgroup pZc was 53.9 ug/dL.

HGB means were compared across patient subgroups based on BMI using ANOVA analysis. Mean baseline HGB prior to Zn replacement was 9.8 g/dL with p = 0.67 between subgroups. At 1 month, the mean HGB was 10.3 g/dL with p = 0.94 between subgroups. At 3 months, mean HGB was 10.8 g/dL with p = 0.99 between subgroups. At 6 months the mean HGB was 11.3 g/dL with p = 0.21 between subgroups. At 12 months the mean HGB was 11.4 g/dL with p = 0.27 between subgroups.

Among the 125 subjects, the mean HGB prior to replacement was 9.8 g/dL and mean pZc of 52.5 ug/dL. Following 1 month of zinc replacement, the mean HGB was 10.3 g/dL (p = 0.03, n=104) and mean pZc of 68 ug/dL (p = 9x10^-13, n = 40). At 3 months mean HGB was 10.7 g/dL (p = 4.2x10^-5, n = 108) with pZc of 70.3 ug/dL (p = 1.7x10^-18, n = 51). At 6 months the mean HGB was 11.3 g/dL (p = 6.6x10^-10, n = 96) with pZc of 74.7 ug/dL (p = 9.1x10^-14, p = 48). At 12 months the mean HGB was 11.4 g/dL (p= 2.2x10^-5, n = 77 with median pZc of 67.9 ug/dL (p = 8.9x10^-14, n = 33). Anemia resolution was reached in 53 of the 125 subjects (42%) where Zn deficiency resolution was reached in 62 of 84 (63.8%) patients.

Conclusions:

Patients with Zn deficiency were not found to have different baseline HGB levels when compared across different BMI ranges. BMI was not shown to have a statistically significant correlation to HGB levels after replacement. Overall Zn replacement significantly improved HGB levels in patients with Zn deficiency and chronic anemia where statistically significant increases in HGB were found at 6 and 12 month time markers. PZc was found to be significantly higher after 3 months. Prospective studies are needed to understand the mechanisms driving Zn deficiency, the specific mechanism for erythropoiesis in Zn deficiency, Zn deficiency screening guidelines and replacement duration and dose.

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