Relationship between systemic markers of inflammation and serum beta-carotene levels

Arch Intern Med. 2001 Aug 13-27;161(15):1903-8. doi: 10.1001/archinte.161.15.1903.

Abstract

Background: Low serum levels of beta-carotene have been associated with increased risk of cancer and cardiovascular disease. However, in clinical trials, supplementation of the diet with beta-carotene either had no benefit or caused harm. This pattern of findings raises the possibility that confounding by other factors might explain the association between serum beta-carotene level and disease risk.

Methods: We used data from 14 470 current smokers, ex-smokers, and never smokers aged 18 years or older who participated in the Third National Health and Nutrition Examination Survey to assess the relationship between serum beta-carotene and markers of inflammation (C-reactive protein and white blood cell count).

Results: After adjustment for beta-carotene intake and other factors, geometric mean levels of serum beta-carotene for individuals with undetectable (< 0.22 mg/dL), mildly elevated (0.22-0.99 mg/dL), and clinically elevated (> or =1.0 mg/dL) C-reactive protein levels were 18.0, 16.1, and 13.6 microg/dL, respectively, in never smokers; 18.1, 15.7, and 13.9 microg/dL in ex-smokers; and 11.3, 10.2, and 9.4 microg/dL in current smokers (P< .001 for all). In corresponding analyses, white blood cell count was also inversely related to serum beta-carotene concentration (P< .05 for all).

Conclusions: The strong and inverse association of serum beta-carotene level with C-reactive protein level and white blood cell count suggests that the relationship between serum beta-carotene concentration and disease risk might be confounded by inflammation. More broadly, for beta-carotene and likely other nutrients, it seems unwise to interpret biomarker data as prima facie evidence of dietary intake without a more complete understanding of the physiologic processes that affect nutrient levels.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Biomarkers / blood
  • C-Reactive Protein / metabolism*
  • Confounding Factors, Epidemiologic
  • Female
  • Humans
  • Inflammation / blood*
  • Leukocyte Count
  • Male
  • Middle Aged
  • Risk Factors
  • Smoking / blood
  • beta Carotene / blood*

Substances

  • Biomarkers
  • beta Carotene
  • C-Reactive Protein