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Lower Toenail Chromium in Men With Diabetes and Cardiovascular Disease Compared With Healthy Men

¹ Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts
² Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts
³ Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts
⁴ Research Reactor Center, University of Missouri, Columbia, Missouri

Address correspondence and reprint requests to Swapnil Rajpathak, Departments of Epidemiology and Nutrition, Harvard School of Public Health, 655 Huntington Ave., Boston, MA 02120. Email: srajpath{at}hsph.harvard.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS CONCLUSIONS References

 
OBJECTIVE—Chromium may improve insulin sensitivity, which can modify the risk of diabetes and cardiovascular disease (CVD). Therefore, we evaluated the association between toenail chromium and CVD in diabetic men.

RESEARCH DESIGN AND METHODS—We performed cross-sectional and nested case-control analyses among men aged 40–75 years within the Health Professionals Follow-up Study. The cross-sectional analysis compared men with diabetes only (n = 688), diabetes with prevalent CVD (n = 198), and healthy control subjects (n = 361). The nested case-control study included 202 men with baseline diabetes who developed incident CVD and 361 matched control subjects.

RESULTS—Mean toenail chromium (µg/g) was 0.71 in healthy control subjects, 0.61 in diabetes-only subjects, and 0.52 in diabetic subjects with prevalent CVD (P for trend = 0.003). In the cross-sectional analysis, the multivariate odds ratio (OR) between extreme quartiles was 0.74 (95% CI 0.49–1.11; P for trend = 0.18), comparing diabetes only with healthy control subjects. A similar comparison between diabetic subjects with prevalent CVD and healthy control subjects yielded an OR of 0.45 (0.24–0.84; P for trend = 0.003). In the nested case-control study, comparing diabetic men with incident CVD with healthy control subjects, the multivariate OR was 0.65 (0.36–1.17; P for trend = 0.16) between extreme quartiles. When we combined prevalent and incident CVD cases among diabetic men and compared them with healthy control subjects, the OR was 0.62 (0.39–1.01; P for trend = 0.02) between extreme quartiles.

CONCLUSIONS—Our results suggest that diabetic men with CVD have lower toenail chromium than healthy control subjects. However, this study could not distinguish between the effects of chromium on diabetes and those on CVD. Long-term clinical trials are needed to determine whether chromium supplementation is beneficial for preventing CVD among diabetic patients.

Abbreviations: CABG, coronary artery bypass graft • CVD, cardiovascular disease • PTCA, percutaneous transluminal coronary angioplasty • SRM, standard reference material

	INTRODUCTION

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Most of the research on dietary factors affecting the risk of cardiovascular disease (CVD) in people with diabetes has been focused on macronutrients. However, micronutrients, including trace elements such as chromium, may also play a role in the etiology of CVD (1). Although the mechanism of action is largely unknown, chromium can improve insulin sensitivity and therefore may be involved in carbohydrate and lipid metabolism (2,3). Chromium is a transition metal, and its trivalent state is the most prevalent form in organic complexes. Chromium supplements are widely consumed in the U.S. (4), but clinical studies of their efficacy have been inconclusive (5). In addition, epidemiological data on chromium intake and the risk of CVD are limited, partly because of the difficulty in estimating dietary chromium considering its wide variability in food sources. Hence, a sensitive and time-integrated biomarker for chromium intake is required in epidemiological studies. Results from two case-control studies suggest an inverse association between chromium levels in toenails and the risk of myocardial infarction in the general population (6,7). Because the risk of CVD is substantially higher in individuals with diabetes than in those without diabetes (8), we conducted this study to evaluate the association between toenail chromium and CVD among men with diabetes within the Health Professionals Follow-up Study.

	RESEARCH DESIGN AND METHODS

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The Health Professionals Follow-up Study is a prospective cohort study of 51,529 men aged 40–75 years in 1986 evaluating the role of diet in chronic diseases. At baseline, all participants completed a mailed questionnaire concerning their diet and medical history. A follow-up questionnaire is sent every 2 years to obtain updated information on incident medical conditions including CVD. In 1987, 33,737 of the participants provided samples of toenail clippings; these were stored for analyses of trace elements. Chromium levels were assayed for all men with baseline diabetes and the matched control subjects selected for this study. The study was approved by the institutional review board for the protection of human subjects at the Harvard School of Public Health.

For the cross-sectional analyses, we used data provided in the baseline year of 1986. The study participants were divided into three groups: men with diabetes only (n = 688), men with diabetes and prevalent CVD (n = 198), and healthy control subjects (n = 361). The diabetes-only group consisted of men who had self-reported diabetes but had never been diagnosed with CVD. We defined CVD as fatal or nonfatal myocardial infarction, coronary artery bypass graft (CABG), percutaneous transluminal coronary angioplasty (PTCA), or stroke. The second group included subjects who self-reported both diabetes and CVD at baseline. The healthy control group consisted of the matched control subjects who we selected for the nested case-control study (see below). The diagnosis of diabetes was based on self-reports from the mailed questionnaire at baseline. The validity of self-reported diabetes in this cohort has been verified in a subsample of 71 men (9). A physician blinded to the reported information on the supplementary questionnaire reviewed the medical records according to standard diagnostic criteria. Of the 71 patients, 12 had incomplete records and, among the remaining 59 case subjects, the diagnosis of type 2 diabetes was confirmed in 57 (97%).

The case subjects in the nested case-control analysis included all men with baseline diabetes who developed incident CVD during the follow-up period from the date of return of the toenail samples in 1987 until 1998 (n = 202). Control subject selection involved 1:2 matching based on age (within 1 calendar year), smoking status (past, never, or current), and date of toenail return (within 1 month). These control subjects were selected from subjects free of chronic disease at the time of case diagnosis (i.e., risk-set sampling) (10). Since the selection criteria for the healthy control subjects were stringent, we obtained only 1 control for 43 case subjects, and hence, the total number of control subjects was 361. The comparison between diabetic men with CVD and healthy control subjects was designed a priori because it could provide the strongest contrast in toenail chromium levels. Since we did not have a group with CVD without diabetes in either cross-sectional or nested case-control analyses, we were unable to assess the impact of chromium on diabetes separately from that on CVD.

Assessment of outcomes
The primary outcome in the nested case-control study was incident CVD (defined above). Medical records were reviewed by physicians blinded to the questionnaire data. Confirmation of nonfatal myocardial infarction was based on World Health Organization criteria as follows: symptoms plus either diagnostic electrocardiographic changes or elevated cardiac-enzyme levels. Men who were hospitalized for myocardial infarctions but whose medical records were not available were designated as probable case subjects. We included both the confirmed and probable case subjects in our study. Death from CVD was confirmed if it was listed in the hospital records, autopsy reports, or on the death certificate as the underlying cause of death. When medical records were not available or telephone interviews were not feasible, the diagnosis of CVD was corroborated by correspondence with the subject, family member, or personal physician. Information on CABG and PTCA was based on self-reports only. Among the men who reported diabetes at baseline, 198 reported prevalent CVD (myocardial infarction, 131; stroke, 21; and CABG/PTCA, 46). Among the baseline diabetic men who did not report CVD in 1986, we documented 202 cases of CVD (myocardial infarction, 108; stroke, 17; and CABG/PTCA, 77) during the follow-up period.

Assessment of exposure
Toenails incorporate trace elements as they grow, and a sample from each toe reflects their incorporation over a period of 1 year (11). The level of chromium in the toenails was analyzed by instrumental neutron–activation analysis at the University of Missouri Research Reactor Center and is the most sensitive method for such estimations (12). Initially, the toenail samples were washed in a sonicator with deionized water to remove any contamination. The laboratory personnel were unaware of the disease status of the participant who provided the sample. In a quality-control study, we used organic standard reference material (SRM) obtained from the National Institutes of Standards and Technology (NIST SRM 1571 Orchard Leaves) with a certified chromium value of 2.6 ± 0.3 µg/g. This was analyzed in duplicate in 18 analytic batches. The mean (±SD) of the chromium concentration measured in these 36 replicate SRM samples was 2.610 ± 0.316 µg/g; this is in good agreement with the certified values. The toenail samples from the case and control subjects in the nested case-control study were analyzed together but in random order. The samples from baseline diabetic men in the cross-sectional analysis were analyzed together but separately from the nested case-control study batches.

Assessment of potential confounders
Anthropometric, lifestyle, and dietary data were obtained from the questionnaires mailed in 1986, which included a semiquantitative food frequency questionnaire. The average nutrient intake from the food frequency questionnaire was computed using the Harvard University food composition database derived from U.S. Department of Agriculture sources, manufacturers’ data, and published reports. BMI was calculated as the ratio of self-reported body weight in kilograms to height in meters squared (kg/m²). Physical activity was expressed as metabolic equivalent hours based on the self-reported types and durations of activities during the previous year. One metabolic equivalent hour is equivalent to the energy expended sitting quietly for 1 h (13). The reproducibility and validity of the dietary and physical activity data have been reported in detail elsewhere (14–16).

Statistical analysis
All statistical analyses were performed with SAS software (SAS, Cary, NC). For all analyses, we categorized chromium levels into quartiles based on the distribution of the reference group. Since the concentration of a trace element is correlated with the weight of the sample, the estimated levels of chromium in toenails are adjusted for their weight and expressed in micrograms per gram of toenail sample (µg/g). The reported geometric mean of toenail chromium is the antilog of a log-transformed form of this variable.

To examine the association between the quartiles of chromium and the risk of CVD, we used unconditional logistic regression adjusted for the matching factors (i.e., age, smoking, and date of toenail return) and other potential confounders such as BMI, physical activity, alcohol intake, hypertension, hypercholesterolemia, and family history of myocardial infarction. We estimated the odds ratios (ORs) and 95% CIs using the lowest quartile as the reference category. We also adjusted for nutrients as quartiles of a dietary composite score created with quartile scores of six variables (marine -3, trans fatty acids, folate, cereal fiber, polyunsaturated/saturated fat ratio, and glycemic load) (17). In addition, we controlled for mercury and selenium levels in toenails, as these elements have been associated with the risk of CVD in previous studies (18,19). Tests for trend were conducted by assigning an ordinal score to each quartile. All P values reported are two tailed, and values below 0.05 were considered statistically significant.

	RESULTS

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS CONCLUSIONS References

 
Table 1 shows age-standardized characteristics at baseline among healthy control subjects according to the quartiles of chromium levels.

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS CONCLUSIONS References

 
Overall, we found lower levels of toenail chromium among men with diabetes and CVD compared with healthy control subjects. The results from the nested case-control analyses were consistent with those from the cross-sectional analyses.

Trivalent chromium is a cofactor for insulin action. When patients receiving total parenteral therapy were supplemented with chromium, their diabetes symptoms reversed and they required smaller doses of exogenous insulin (20). In atherosclerotic rabbits, an injection of chromium chloride results in a marked reduction in the plaques covering the aortic intimal surface, in aortic weight, and in cholesterol content (21). In the last decade, numerous supplementation studies in humans have examined the role of chromium in glucose intolerance, lipid levels, and type 2 diabetes. A recent meta-analysis of clinical trials concluded that there was no appreciable effect of chromium supplementation on glucose or insulin concentrations in nondiabetic subjects, and the results in studies among people with diabetes were inconclusive (5). The equivocal evidence has led to a substantial controversy about the role of chromium in human nutrition.

Epidemiological studies assessing the role of chromium in CVD are limited. Rimm et al. (6) reported a nested case-control study in which higher levels of chromium in toenails were associated with lower risk of myocardial infarction in men. After controlling for potential confounders, the OR for myocardial infarction comparing the extreme quintiles was 0.69 (95% CI 0.44–1.08; P for trend = 0.01). Another case-control study in Europe by Guallar et al. (7) found a similar inverse association between chromium in toenails and the risk of first myocardial infarction; the multivariate OR for the highest quintile was 0.65 (0.42–0.99; P for trend = 0.04). Both of these studies included subjects who were apparently healthy at baseline.

Diet is the main source of chromium in humans. Absorption of chromium is poor and can be affected by other dietary components (22). In self-selected western diets, the average daily intake is lower (men 33 µg, women 25 µg) than the estimated adequate intake of 50–200 µg/day (23). The foods high in chromium are whole grains and most fruits and vegetables, but they vary widely (24). In contrast, polished rice, fish, dairy products, and refined flour are poor sources. Chromium in the diet is affected by many factors such as source, processing, and method of preparation. Thus, data on food composition are unlikely to provide a valid measure of the chromium status. This problem in exposure assessment makes it difficult to conduct epidemiological studies with chromium. Few epidemiological studies have used toenails to evaluate the role of trace elements in chronic disease, e.g., in cancer (25,26) and cardiovascular disease (27,28).

Our study has several limitations. Contamination of samples may be a problem in the measurement of trace elements and can produce erroneously high levels of chromium in toenails. However, we washed the samples in a sonicator with deionized water before the analysis to ensure minimal contamination. Because a single measurement is prone to random errors, the effects are likely to be underestimated. The cross-sectional study is prone to the bias of "reverse causation" and chronic medical disorders such as diabetes or CVD could lower the levels of chromium in toenails, although there are no data in this area. We conducted a prospective nested case-control analysis simultaneously to examine the consistency of our findings. The prospective design has an advantage because the toenail samples were collected before the diagnosis of CVD; hence, the levels of chromium in toenails are unlikely to be affected by CVD status. The comparison between diabetic men with CVD and healthy control subjects cannot distinguish the effects of chromium on diabetes from those on CVD. Future studies should be designed to specifically address the role of chromium in diabetes separately from its role in CVD among people with diabetes. Furthermore, it is not yet established whether toenail levels of chromium adequately reflect dietary intake.

In conclusion, our results suggest that levels of toenail chromium are lower among men with diabetes and CVD than in healthy control subjects. Whether chromium supplementation is beneficial for preventing CVD among people with diabetes needs to be determined in long-term clinical trials.

	Acknowledgments

 
This study was supported by research grants HL35464 and CA55075 from the National Institutes of Health. The work of F.H. is supported in part by the American Heart Association’s Established Investigator Award. We thank Nutrition 21, New York, for their unrestricted funding for the measurement of toenail chromium levels and data analysis.

	Footnotes

 
F.B.H. has received funding from Nutrition21.

A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

Received for publication March 23, 2004. Accepted for publication May 26, 2004.

	References

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1. Simonoff M: Chromium deficiency and cardiovascular risk. Cardiovasc Res 18:591–596, 1984[Medline]
   
2. Anderson RA: Chromium, glucose intolerance and diabetes. J Am Coll Nutr 17:548–555, 1998[Abstract/Free Full Text]
   
3. Offenbacher EG, Pi-Sunyer FX: Beneficial effect of chromium-rich yeast on glucose tolerance and blood lipids in elderly subjects. Diabetes 29:919–925, 1980[Abstract]
   
4. Nielsen F: Controversial chromium: does the superstar mineral of the Mountebanks receive appropriate attention from clinicians and nutritionists? Nutr Today 31:226–233, 1996
   
5. Althuis MD, Jordan NE, Ludington EA, Wittes JT: Glucose and insulin responses to dietary chromium supplements: a meta-analysis. Am J Clin Nutr 76:148–155, 2002[Abstract/Free Full Text]
   
6. Rimm EGE, Giovannucci E, Ascherio A, Stampfer M, Willett W, Hu F: Toenail chromium levels and risk of coronary heart disease among normal and overweight men. AHA-Epidemiology Meeting Abstract, 2002
   
7. Guallar EJF, van’t Veer P, Bode P, Riemersma R, Gomez-Aracena J, Kark J, Arab L, Kok F, Martin-Moreno JM: Low teonail chromium and increased risk of myocardial infarction. Am J Epidemiol. In press
   
8. Gary P: Cardiovascular disease in diabetes. In Pickup’s Textbook of Diabetes. Oxford, U.K. Blackwell Science, 1997, p. 57.51–20
   
9. Hu FB, Leitzmann MF, Stampfer MJ, Colditz GA, Willett WC, Rimm EB: Physical activity and television watching in relation to risk for type 2 diabetes mellitus in men. Arch Intern Med 161:1542–1548, 2001[Abstract/Free Full Text]
   
10. Prentice RL, Breslow NE: Retrospective studies and failure time models. Biometrika 65:153–158, 1978[Abstract/Free Full Text]
    
11. Longnecker MP, Stampfer MJ, Morris JS, Spate V, Baskett C, Mason M, Willett WC: A 1-y trial of the effect of high-selenium bread on selenium concentrations in blood and toenails. Am J Clin Nutr 57:408–413, 1993[Abstract/Free Full Text]
    
12. Cheng T-P, Morris JS, Koirtyohann SR, Spate VL, Baskett CK: The analysis of human nails for 24 elements via k0 and cyclic neutron activation analysis. Nuel Instr Methods Phys Res 457–460, 1994
    
13. Ainsworth BE, Haskell WL, Whitt MC, Irwin ML, Swartz AM, Strath SJ, O’Brien WL, Bassett DR Jr, Schmitz KH, Emplaincourt PO, Jacobs DR Jr, Leon AS: Compendium of physical activities: an update of activity codes and MET intensities. Med Sci Sports Exerc 32 (Suppl. 9):S498–S504, 2000
    
14. Rimm EB, Giovannucci EL, Stampfer MJ, Colditz GA, Litin LB, Willett WC: Reproducibility and validity of an expanded self-administered semiquantitative food frequency questionnaire among male health professionals. Am J Epidemiol 135:1114–1136, 1992[Abstract/Free Full Text]
    
15. Chasan-Taber S, Rimm EB, Stampfer MJ, Spiegelman D, Colditz GA, Giovannucci E, Ascherio A, Willett WC: Reproducibility and validity of a self-administered physical activity questionnaire for male health professionals. Epidemiology 7:81–86, 1996[Medline]
    
16. Giovannucci E, Colditz G, Stampfer MJ, Rimm EB, Litin L, Sampson L, Willett WC: The assessment of alcohol consumption by a simple self-administered questionnaire. Am J Epidemiol 133:810–817, 1991[Abstract/Free Full Text]
    
17. Stampfer MJ, Hu FB, Manson JE, Rimm EB, Willett WC: Primary prevention of coronary heart disease in women through diet and lifestyle. N Engl J Med 343:16–22, 2000[Abstract/Free Full Text]
    
18. Guallar E, Sanz-Gallardo MI, van’t Veer P, Bode P, Aro A, Gomez-Aracena J, Kark JD, Riemersma RA, Martin-Moreno JM, Kok FJ: Mercury, fish oils, and the risk of myocardial infarction. N Engl J Med 347:1747–1754, 2002[Abstract/Free Full Text]
    
19. Alissa EM, Bahijri SM, Ferns GA: The controversy surrounding selenium and cardiovascular disease: a review of the evidence (Review). Med Sci Monit 9:RA9–RA18, 2003[Medline]
    
20. Anderson RA: Chromium and parenteral nutrition. Nutrition 11 (Suppl. 1):83–86, 1995
    
21. Abraham AS, Brooks BA, Eylath U: Chromium and cholesterol-induced atherosclerosis in rabbits. Ann Nutr Metab 35:203–207, 1991[Medline]
    
22. Lukaski HC: Chromium as a supplement. Annu Rev Nutr 19:279–302, 1999[Medline]
    
23. Anderson RA, Kozlovsky AS: Chromium intake, absorption and excretion of subjects consuming self-selected diets. Am J Clin Nutr 41:1177–1183, 1985[Abstract/Free Full Text]
    
24. Anderson RA, Bryden NA, Polansky MM: Dietary chromium intake: freely chosen diets, institutional diet, and individual foods. Biol Trace Elem Res 32:117–121, 1992[Medline]
    
25. Garland M, Morris JS, Colditz GA, Stampfer MJ, Spate VL, Baskett CK, Rosner B, Speizer FE, Willett WC, Hunter DJ: Toenail trace element levels and breast cancer: a prospective study. Am J Epidemiol 144:653–660, 1996[Abstract/Free Full Text]
    
26. Hartman TJ, Taylor PR, Alfthan G, Fagerstrom R, Virtamo J, Mark SD, Virtanen M, Barrett MJ, Albanes D: Toenail selenium concentration and lung cancer in male smokers (Finland). Cancer Causes Control 13:923–928, 2002[Medline]
    
27. Yoshizawa K, Ascherio A, Morris JS, Stampfer MJ, Giovannucci E, Baskett CK, Willett WC, Rimm EB: Prospective study of selenium levels in toenails and risk of coronary heart disease in men. Am J Epidemiol 158:852–860, 2003[Abstract/Free Full Text]
    
28. Yoshizawa K, Rimm EB, Morris JS, Spate VL, Hsieh CC, Spiegelman D, Stampfer MJ, Willett WC: Mercury and the risk of coronary heart disease in men. N Engl J Med 347:1755–1760, 2002[Abstract/Free Full Text]
    

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