Introduction

White blood cells are key components of the immune system. They defend the body against a host of diseases and infections. Various studies have explored the possible influence of dietary nutrients on the white blood cell (WBC) count. If it can be demonstrated that nutrients affect the WBC count, they may offer an inexpensive way of modulating the immune system and in turn, the body's ability to fight against disease and infection. The sample sizes of previous studies, however, have been relatively small. The results have therefore been variable and conflicting. The purpose of this study is to continue to explore the dietary determinants of the WBC count, using a database that allows for a larger sample size, the 2005-2006 National Health and Nutrition Health Survey (NHANES).

Methods

The main outcome variable, WBC count, was recoded to the normal range for ages ≥ 18 years, of 4-11(±2). This was done in order to account for extreme values; particularly high and low values secondary to disease or infection. The population means and 95% confidence intervals were obtained using the statistical weights for the key variables of interest (Table 1). Multiple linear regression and backward elimination were used to predict the final model (Table 2). Variables with p < 0.1 were kept in the model. SAS 9.3 was used for all statistical analyses.

Table 1

Demographics and Physical Activity

 		Number
 		Weighted mean (SE)
 		95% CI
 
Gender*    
Male 2333 7.22(0.059) (7.10, 7.35) 
Female 2479 7.35(0.058) (7.22, 7.47) 
    
Race*    
Mexican American 1048 7.48(0.084) (7.30, 7.66) 
Other Hispanic 153 7.51(0.194) (7.09, 7.92) 
Non-Hispanic White 2239 7.39(0.062) (7.26, 7.52 ) 
Non-Hispanic Black 1179 6.54(0.055) (6.43, 6.66 ) 
Other race including multiracial 193 7.11(0.093) (6.91, 7.31) 
    
BMI(kg/m2)*    
Underweight 85 6.38(0.024) (5.86, 6.90 ) 
Normal 1424 7.02(0.060) (6.91, 7.14 ) 
Overweight 1542 7.17(0.070) (7.02, 7.32) 
Obese 1639 7.70(0.063) (7.57, 7.83) 
    
Physical activity*    
light intensity 599 7.12(0.140) (6.82 ,7.42 ) 
moderate intensity 6238 7.15(0.072) (7.00, 7.30 ) 
vigorous intensity 5714 7.03(0.083) (6.85 ,7.21 ) 
 		Number
 		Weighted mean (SE)
 		95% CI
 
Gender*    
Male 2333 7.22(0.059) (7.10, 7.35) 
Female 2479 7.35(0.058) (7.22, 7.47) 
    
Race*    
Mexican American 1048 7.48(0.084) (7.30, 7.66) 
Other Hispanic 153 7.51(0.194) (7.09, 7.92) 
Non-Hispanic White 2239 7.39(0.062) (7.26, 7.52 ) 
Non-Hispanic Black 1179 6.54(0.055) (6.43, 6.66 ) 
Other race including multiracial 193 7.11(0.093) (6.91, 7.31) 
    
BMI(kg/m2)*    
Underweight 85 6.38(0.024) (5.86, 6.90 ) 
Normal 1424 7.02(0.060) (6.91, 7.14 ) 
Overweight 1542 7.17(0.070) (7.02, 7.32) 
Obese 1639 7.70(0.063) (7.57, 7.83) 
    
Physical activity*    
light intensity 599 7.12(0.140) (6.82 ,7.42 ) 
moderate intensity 6238 7.15(0.072) (7.00, 7.30 ) 
vigorous intensity 5714 7.03(0.083) (6.85 ,7.21 ) 
*

P < 0.0001

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Table 2

Final Model

 		Estimate
 		95% CI
 
BMI (ref=normal)**   
Obese** 0.90 (0.70, 1.10) 
Overweight * 0.49 (0.23, 0.75) 
Underweight* -0.65 (-1.14, -0.17) 
Gender(ref=female)*   
Male* -0.21 (-0.41, -0.04) 
Physical Activity (ref=light intensity activity)*   
vigorous intensity activity -0.13 (-0.38, 0.12) 
moderate intensity activity -0.04 (-0.29, 0.20) 
Race (ref=Non-Hispanic White)**   
Mexican American -0.05 (-0.29, 0.19) 
Non-Hispanic Black** -1.04 (-1.24, -0.84) 
Other Hispanic 0.14 (-0.45, 0.73) 
Other Race – Including Multi-Racial* -0.48 (-0.91, -0.05) 
Mean Vit B1 intake/day(mg)* 0.20 (0.02, 0.37) 
Mean Vit K intake/day(mcg) -0.01 (-0.01, -0.00) 
Mean Iron intake/day(mg)* -0.02 (-0.04, -0.01) 
Mean Copper intake/day(mg)* -0.16 (-0.31, -0.02) 
Age** -0.02 (-0.02, -0.01) 
 		Estimate
 		95% CI
 
BMI (ref=normal)**   
Obese** 0.90 (0.70, 1.10) 
Overweight * 0.49 (0.23, 0.75) 
Underweight* -0.65 (-1.14, -0.17) 
Gender(ref=female)*   
Male* -0.21 (-0.41, -0.04) 
Physical Activity (ref=light intensity activity)*   
vigorous intensity activity -0.13 (-0.38, 0.12) 
moderate intensity activity -0.04 (-0.29, 0.20) 
Race (ref=Non-Hispanic White)**   
Mexican American -0.05 (-0.29, 0.19) 
Non-Hispanic Black** -1.04 (-1.24, -0.84) 
Other Hispanic 0.14 (-0.45, 0.73) 
Other Race – Including Multi-Racial* -0.48 (-0.91, -0.05) 
Mean Vit B1 intake/day(mg)* 0.20 (0.02, 0.37) 
Mean Vit K intake/day(mcg) -0.01 (-0.01, -0.00) 
Mean Iron intake/day(mg)* -0.02 (-0.04, -0.01) 
Mean Copper intake/day(mg)* -0.16 (-0.31, -0.02) 
Age** -0.02 (-0.02, -0.01) 
*

p <0.05

**

p <0.0001

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Results

Associations for age, gender, race and Body Mass Index (BMI) and WBC count, were consistent with previous studies and were all statistically significant (p< 0.0001). It has been shown that more intense physical activity usually leads to an increase in the WBC count. In this study, however, more vigorous forms of activity were associated with a lower WBC count (p < 0.0001). Increases in dietary copper and iron were associated with a subsequent decrease in the WBC count (Table 2, p < 0.05). An increase in vitamin K was also associated with a decrease in WBC count, however, it was not statistically significant (Table 2, p > 0.05). Increases in vitamin B1 were associated with an increase in WBC count (p < 0.05).

Conclusion

The results of this study suggest that further prospective studies are needed to investigate the role of these nutrients as determinants of the WBC count.

Disclosures:

No relevant conflicts of interest to declare.

Topics:
diet, leukocyte count, obesity, overweight, underweight, infections, copper, iron, thiamine, potassium intake

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2013 by The American Society of Hematology
2013
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