Aim To determine the associations of unprocessed red meat with serum C‐reactive protein and traditional lipid biomarkers among adults with different smoking status. Methods Using a cross‐sectional design, we analysed data collected from 5011 adults (men and women) who had provided information on dietary intakes and the proposed biomarkers for the 2005–2006 National Health and Nutrition Examination Survey (NHANES). Results We found positive associations between unprocessed red meat and serum C‐reactive protein and triglycerides and an inverse association between unprocessed red meat and high‐density lipoprotein (HDL) cholesterol in past smokers, but no associations in never smokers and current smokers. Among past smokers, the percent difference of biomarkers between participants with the highest and the lowest quintiles for the intakes of unprocessed red meat was 42% (P = 0.03) for CRP, 32% for triglycerides and −11% (P = 0.02) for HDL cholesterol. No association was found between unprocessed red meat and other lipid biomarkers. Conclusions Providing individualised nutritional guidelines according to smoking status is important. Our study provided evidence for developing specific guidelines on red meat for past smokers.

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The purpose of this study is twofold: 1) compare the effectiveness of non-quantitative food frequency questionnaire (NFFQ) to one-time or multiple 24-hr recalls on assessing the associations of vegetable and meat intakes with urinary nitrate; 2) to determine the associations of vegetable and meat intakes with urinary nitrate. Nitrate-related metabolic pathways have emerged as a fascinating topic because promising benefits of using nitrate supplement on several cardiovascular related outcomes in animal and small-scaled human intervention studies. In the past, most people consider that processed meat is the main source of nitrate exposure and nitrate is harmful. In fact, the major exogenous nitrate exposure comes from vegetables. Thus, we seek to untangle the mystery vegetable-nitrate and meat-nitrate associations in a large observational study. We conduct a cross-sectional analysis using the National Health and Nutrition Examination Survey (NHANES) during 2005-2006, among 7,683 participants. Urinary nitrate was measured, NFFQ and two-time 24-hr recalls were collected among these participants. We have found a positive association between vegetable intakes and urinary nitrate and an inverse association between red meat and processed meat intakes and urinary nitrate by using either non-quantitative NFFQ or averaged two-time 24-hr recalls. The magnitudes of the results were stronger when using NFFQ. Further, using NFFQ, we found that urinary nitrate intake increased by 26%, and decreased by 16% when comparing persons with the highest to the lowest quintile of vegetable intake and red and processed meat intake, respectively. Lastly, we found that the results from the 24-hr recall collected a few days after urine collection (but not the 24-hr recall on the day of urine collection) are consistent with NFFQ results. The trend of vegetable-urinary nitrate and red meat-urinary nitrate associations from NFFQ and averaged 24-hr recalls were consistent with our previous published findings using plasma nitrate measurement in the Health Professionals Follow-up Study, where only semi-quantitative FFQ (SFFQ) was administered. In summary, we conclude that dietary assessment with NFFQ,SFFQ, or average 24-hr recalls will yield similar results when evaluating red meat-circulating nitrate or vegetable-circulating nitrate associations. Measurement of circulating nitrate using either urine or plasma will yield similar results. Understanding how usual vegetable and red meat intake influences circulating nitrate in observational studies will provide valuable information for studying nitrate related pathways in the etiology of chronic disease and for designing long-term dietary intervention studies targeting circulating nitrate.

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ObjectiveOur study aimed to determine the associations between intakes of vegetables and red meat (processed and unprocessed) and circulating nitrate levels.DesignUsing a cross‐sectional study design.Setting and ParticipantsA secondary analysis using data from the National Health and Nutrition Examination Survey (NHANES) and from the Health Professionals Follow‐up Study (HPFS). 5,058 adults (men and women) in the 2005–2006 NHANES and 1,260 men from HPFS were analyzed.MeasurementsThe non‐quantitative food frequency questionnaire (NFFQ) and two 24‐hr recalls were collected and urinary nitrate was measured in the NHANES. Plasma nitrate was measured and a semi‐quantitative FFQ (SFFQ) was collected in the HPFS.ResultsUsing three dietary assessment instruments (NFFQ, SFFQ and average 24‐hr recalls), we found a similar trend when assessing the associations of vegetables and red meat with circulating (plasma and urinary) nitrate. Across instruments, circulating nitrate levels were 15–33% higher for participants in the highest, when compared to the lowest, quintile of vegetable intake (p<0.001). Circulating nitrate levels were 8–16% lower for participants in the highest, when compared to the lowest, quintile of red meat intake (p<0.001).ConclusionOur study has demonstrated a positive association between vegetable and circulating nitrate and an inverse association between red meat and circulating nitrate. As nitrate has been demonstrated to be beneficial for preventing several chronic diseases, our results provide valuable information for studying dietary etiologic factors associated with nitrate and chronic diseases.Support or Funding InformationNCI KO7 awardThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.