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. Author manuscript; available in PMC: 2021 Nov 1.
Published in final edited form as: Ethn Health. 2018 Jul 2;25(8):1132–1144. doi: 10.1080/13557858.2018.1492707

ANTIOXIDANT INTAKE IN RELATION TO SERUM C-REACTIVE PROTEIN IN MID-LIFE AND OLDER AFRICAN AMERICANS

Katherine M Rancaño 1, Penny A Ralston 2, Jennifer L Lemacks 3, Iris Young-Clark 4, Jasminka Z Ilich 5
PMCID: PMC6375798  NIHMSID: NIHMS1512422  PMID: 29962216

Abstract

Objective:

African Americans (AAs) experience greater prevalence of cardiovascular disease (CVD) compared to other ethnic/racial groups. Low-grade chronic inflammation (often quantified by serum C-reactive protein CRP) is a well-documented risk factor for CVD. A healthy diet is plentiful in antioxidant nutrients and is associated with a lower inflammatory status and CVD risk. Our objective was to examine the relationship between dietary intake of antioxidants (carotenoids, vitamins A, C, E, and selenium) and serum CRP concentrations in mid-life and older AAs, while controlling for confounders.

Methods:

Data were from the baseline phase of a longitudinal church-based intervention study to reduce CVD risk in AAs. Anthropometrics were measured in a standard manner. Fasting serum samples were analyzed with ELISA for CRP. Multiple-pass 24-hour dietary recalls were used to assess intake; self-reported questionnaires were used to collect demographics. Statistical analyses were performed using SPSS Statistics 21 with the level of significance set at p<0.05.

Results:

A total of n=73 participants (n=51 females) were included in the analyses. The females and males, respectively were 58.9±10.3 and 59.4±9.7 years old, with BMI of 34.6±8.3 and 35.6±9.3 kg/m2 (Mean±SD). The mean serum CRP was above 0.6 mg/dL, although slightly lower in males. Males consumed more energy (kcal) and met RDA for selenium, whereas females met RDA for vitamin C. Both groups met RDA for vitamin A. All other dietary variables fell below the RDA or had no RDA established. Results from the binary logistic regression did not show significant association between dietary antioxidants and serum CRP in males or females. However, among females, for every unit increase in BMI, there was a 15% increase in serum CRP (OR=1.15, p=0.04).

Conclusions:

Our study does not support the inverse relationship between antioxidants intake and CRP, but does support the evidence for obesity-induced inflammation and suggests the association can be applied to AA women.

Keywords: African Americans, antioxidants, cardiovascular disease, C-reactive protein

INTRODUCTION

Cardiovascular disease (CVD) is the leading cause of death in the United States (U.S.), contributing to one in four deaths each year (cdc.gov 2017). The burden of CVD is different across ethnic/racial groups with African Americans experiencing a greater prevalence (46.0% males 47.7% females) and age-adjusted mortality rate (352.4 males, 241.3 females per 100,000) when compared to Caucasians (37.7% males, 35.1% females and 266.1 males, 182.1 females per 100,000), respectively (Benjamin 2017). Low-grade chronic inflammation is a well-documented risk factor for obesity and osteoporosis (Ilich 2014), as well as for CVD and may partially explain the observed disparity in CVD morbidity and mortality among African Americans compared to other racial/ethnic groups (Khan 2016; Danesh 2000). The standard procedure to quantify low-grade chronic inflammation is by measuring serum levels of C-reactive protein (CRP) which increases in response to inflammation. Serum CRP concentration greater than 0.3mg/dL has been associated with a “high risk” for a cardiovascular event (Ridker 2007). Studies have consistently shown serum CRP tends to be higher in African Americans (Albert 2004; Cushman 2009; Khera 2005) and females (Lakoski 2006) when compared to Caucasians and males. It also tends to increase with age and body mass index (BMI) (Woloshin 2005).

Therefore, higher serum CRP in African Americans, as a consequence of heighten low-grade chronic inflammation, may be the first sign to point to the magnified burden of CVD in this population, particularly among females, and mediated by the lower socioeconomic status (Cozier 2016; Khan 2016). Given the prevalence of CVD in African Americans and the effects of gender, age, and BMI on serum CRP levels, it is crucial to investigate avenues that mediate low-grade chronic inflammation in this population in order to better understand, and even more importantly, diminish its impact on CVD.

Diet is one of the most salient modifiable risk factors for CVD and a healthy dietary pattern has shown significant anti-inflammatory effects in diverse populations in the U.S. (Barbaresko 2013). Even in young girls, a poor diet (low in fruits and vegetables) was associated with higher CRP levels (Navaro 2017). A healthy diet is plentiful in antioxidant-rich foods, such as fruits, vegetables, legumes, and nuts, and is associated with a lower inflammatory status and a lower risk for CVD (Barbaresko 2013; Hu 2000; Lobo 2010; Alehagen 2015). It is well known that diet and dietary patterns differ significantly by age, gender, and racial/ethnic groups. For example, a lower percentage of African American adults consume a diet that meets Dietary Guidelines for Americans (DGA) (DGA, 20015–2020) or Recommended Dietary Allowances (RDA) (NIH, 2018) when compared to non-Hispanic whites and Mexican Americans (Kirkpatrick 2012). Moreover, food choice in African Americans is further complicated by cultural, environmental, and socioeconomic factors which often make consumption of a “healthy” diet more challenging (James 2004). Gender is also a determining factor in dietary intake of antioxidant-rich foods, with males consuming less fruits and vegetables despite their overall higher total energy intake (Baker 2003). Lastly, with aging, total energy intake tends to decrease as a result of reduced appetite, difficulties in chewing, and a reduced taste acuity, which results in an overall lower adherence to recommended nutrient intakes (JafariNasabian 2017; Nutrition Insights 2017; Wakimoto 2001). Poor dietary habits across ethnic/racial groups and gender, among other adverse consequences, may result in a reduced ability to resolve inflammation and therefore disproportionately increase the risk for chronic disease (Ilich 2014).

Diet quality (DQ) (Alkerwi 2014) is often measured by adherence to DGA (DGA, 2015–2020), the later emphasizing the consumption of variety of fruits, vegetables and whole grains as part of the “healthy eating pattern”. Similarly, DQ refers to a diet naturally rich in foods that provide antioxidant nutrients and can mediate serum CRP levels via anti-oxidative pathways, as shown in some studies among African American males and females (Hebert 2013; Kuczmarski 2013; Qian 2007). A cross-sectional analysis using NHANES data examined the effect of specific dietary constituents on serum high-sensitivity CRP and observed a lower age-, gender-, and race-adjusted mean intake of dietary antioxidants (specifically vitamins A, C, and E) across quarters of serum CRP (Mazidi 2017). Total Antioxidant Capacity (TAC) and individual antioxidant nutrients such as carotenoids, vitamin A, C, E, and selenium, have been shown to mediate serum CRP levels in U.S. and European adults (Block 2009; Erlinger 2001; Floegel 2011; Ford 2003; Humenikova 2006; Roberts 2007; Yang 2013; Alehagen 2015; Mazidi 2017). Floegel (2011) examined the antioxidant intake, from both diet and supplements, and found carotenoids, vitamin C, and E were associated with reduced odds of elevated serum CRP. Several studies have found similar results with carotenoids (Erlinger 2001; Ford 2003, Humenikova 2006), vitamin A (Erlinger 2001; Humenikova 2005; Mazidi 2017), vitamin C (Block 2009; Erlinger 2001; Humenikova 2006; Mazidi 2017) and selenium (Ford 2003). Associations between vitamin E and serum CRP have been controversial (Block 2009; Erlinger 2001; Humenikova 2006); however, some studies have shown an anti-inflammatory effect in adult men and women (Floegel 2011; Roberts 2007; Yang 2013). Regarding selenium, a large randomized clinical trial in European older adults with the median follow-up of 5.2 years, showed that supplementation with selenium and coenzyme Q10 had lowering effect on CRP as well as overall reduction of cardiovascular mortality (Alehagen 2015).

To our knowledge, the relationship between dietary antioxidant intake and serum CRP levels has not been exclusively evaluated in African American adults. Thus, the purpose of this study was to examine the relationship between dietary intake of antioxidants (carotenoids, vitamins A, C, E, and selenium) and serum CRP concentrations in mid-life and older African Americans. We hypothesized that a higher intake of dietary antioxidants would be associated with a lower concentration of serum CRP. In order to account for any confounders, we also examined the relationship between serum C-reactive protein levels and possible confounding variables (age, BMI, marital and educational status) as well as the relationship between dietary antioxidants (carotenoids, vitamin A, C, E, and selenium) intake and above listed confounding variables.

METHODS

Study Population

Clinical baseline data from a larger, longitudinal church-based intervention study to reduce CVD risk in mid-life and older African Americans were used for this analysis. The larger study, described in Ralston et al. (2014, 2017) included a total sample of n=221 participants. and a clinical subsample of n=104. Within the baseline clinical subsample, due to missing data, we used data for n=73 participants, to include: anthropometric data, biochemical markers, 24-dietary recalls and other self-reported questionnaires for demographic information. As per inclusion criteria, the cut-off age for recruitment was ≥45 years. The Florida State University Institutional Review Board approved protocol for the original study (HSC No. 2017.21791).

Anthropometric Measurements

Weight was recorded in pounds to the nearest tenth and converted to kilograms (kg), in normal indoor clothing, without shoes using an electric platform balance Tanita BWB-800 digital scale (Arlington Heights, Illinois). Height (standing stature) was recorded in centimeters (cm) without shoes using a Charder HM200P portable stadiometer (Issaquah, Washington), as described previously (Carter et al. 2016). BMI (kg/m2) was calculated from weight and height.

Biochemical Parameters

Overnight fasting blood samples were obtained by venous puncture and after serum was separated from red blood cells, it was frozen at −80° C until analyzed. The high-sensitive C-reactive protein (hs-CRP) was measured by immunoassays using the ELISA kits (Enzo Life Sciences, Inc, Farmingdale, NY) according to the manufacturers’ instructions, with sensitivity of 12 ng/mL (0.0012 mg/dL).

Dietary Recalls

Dietary intake was determined using the multiple-pass 24-hour dietary recall protocol approximately two to four weeks after completion of baseline data collection (Johnson 2002). Three unannounced dietary recalls were taken on non-consecutive days (two weekdays and one weekend). The average of the three recalls was computed and used for analysis. Dietary recalls were analyzed using the Food Processor; Nutrition and Fitness Software (Salem, OR: Esha Research, Inc.). The emphasis was placed on the analysis of vitamin A and its precursors carotenoids, vitamin C, vitamin E, and selenium, all known to provide major oxidative protection (Alehagen 2015; Navaro 2017). Among carotenoids, beta-carotene, being the most abundant carotenoid in Western diet, and the one with the highest potency to convert into vitamin A (Tang 2010), was examined separately. Other carotenoids included into analysis under “carotenoids” were alpha-carotene, cryptoxanthin, lutein, zeaxanthin and lycopene, known to exert antioxidative properties but have lower potency as vitamin A precursors (Tang 2010).

Self-Reported Questionnaires

Information about demographic characteristics (age, gender, marital and educational status) were collected using a self-administered questionnaire (“What year were you born?”, “What is your gender?” coded as female= 1, male= 2). Year of birth was subsequently used to calculate age. Other background characteristics included educational level (“What is your educational level?” ranging from some high school, coded as 1, to master’s degree or above, coded as 5) and marital status (“What is your marital status?” single/divorced/widowed or separated, coded as 1, and married coded as 2).

Statistical analysis

All statistical analyses were performed using IBM SPSS Statistics 21, 2012 (Armonk, NY) and p<0.05 was deemed significant. Pearson correlation was used to determine the correlation between potential confounding variables, age and BMI, and serum CRP and dietary antioxidant intake. Binary logistic regression analysis was used to evaluate the association between dietary antioxidant intake and serum CRP and statistical models were adjusted for confounders. We conducted analyses on the whole population and separately on men and women. Due to the bipolarity of the data, serum CRP values were transformed into a dichotomous variable (low-moderate: 0.0–0.199 mg/dL; moderate-high ≥0.200 mg/dL). Dietary antioxidant variables were energy-adjusted using the energy density method (Willett 1997).

RESULTS

Of n=104 participants, n=73 had the complete sets of data and were included in the analyses (females n=51, males n=22). Thirty-one participants were excluded due to missing data and one participant was removed due to a coding error. Majority of participants were married (56.8%, n=42; 31.1%, n=23 compared to males 25.7%, n=19). Regarding the educational level, 54.8% (n=40 participants (41.1%, n=30 females vs. 13.7%, n=10 males) had completed high school or some college. However, those variables did not show statistical difference in any calculations, and thus they were not included in the logistic regression. Descriptive statistics, presented in Table 1, showed males were slightly older than females, had a higher mean BMI, but had a lower mean serum CRP concentration than females. As expected, males consumed more energy than females and met RDA for selenium, whereas females met RDA for vitamin C. Both males and females met RDA for vitamin A. All other dietary variables fell below the RDA or had no RDA established (NIH 2018) (Table 2).

Table 1:

Descriptive characteristics of the participants (mean±SD)

Variables Females, n=51 Males, n=22
Age (years) 58.9±10.3 59.4±9.7
Height (cm) 163.5±8.1 173.3±11.1
Weight (kg) 93.0±25.5 107.5±33.3
BMI (kg/m2) 34.6±8.3 35.6±9.3
C-Reactive protein (mg/dL) 0.7±0.8 0.6±0.9
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Table 2:

Average daily dietary intake of total energy and antioxidant nutrients in participants (mean±SD)

Daily Dietary Intake of
Nutrients		 Females
n=51		 Males
n=22		 Dietary
Reference Intake
(RDA)
Energy (kcal/day) 1422.±373.5 1806.5±431.8 NA
Vitamin A (IU/day) 4843.8±3634.9 5977.1±5532.5 3,000 (men)
2,334 (women)
Carotenoids (RE/day) 354.2±320.4 450.2±528.9 NA
Beta-carotene (mcg/day) 1725.4±1866.5 2358.8±3164.8 NA
Vitamin C (mg/day) 80.5±60.4 83.4±60.2 90 (men)
75 mg/d (women)
Vitamin E (mg/day) 2.9±2.5 3.6±3.1 15
Selenium (mcg/day) 46.8±18.6 68.8±32.2 55
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NA = Not available

For females, Pearson’s correlation analysis showed a positive trend for the relationship between serum CRP and BMI (r=0.256, p=0.06). Females also demonstrated a negative trend between BMI and dietary carotenoids (r=−0.254, p=0.07) and ß-carotene (r=−0.268, p=0.06) and a significant positive correlation between age and ß-carotene (r=0.317, p=0.02). Females also had a slight positive trend between age and vitamin A (r=0.263, p=0.06) and carotenoid intake (r=0.241, p=0.09). For males, there was a negative trend between vitamin E and BMI (r= −0.412, p=0.06) (Table 3)

Table 3:

Pearson correlations (r) for dietary antioxidant intake and covariates in participants

Females (n=51) Males (n=22)
Nutrients BMI Age BMI Age
Vitamin A (IU) −0.195 0.263 −0.133 0.232
Carotenoids (RE) −0.254 0.241 −0.138 −0.015
Beta-carotene (mcg) −0.268 0.317 * −0.148 −0.007
Vitamin C (mg) 0.024 0.186 −0.169 0.109
Vitamin E (mg) −0.121 0.178 −0.412 −0.163
Selenium (mcg) −0.171 0.061 −0.113 −0.182
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*

Indicates statistical significance at p<0.05

Results from the binary logistic regression analysis did not show a significant association between dietary antioxidant intake and serum CRP concentrations in males or females (Table 4) or in the whole population controlled for gender in addition to age and BMI (data not presented). However, among females, the odds for having moderate-high levels of serum CRP was 15% higher for every one-unit increase in BMI (OR=1.15, p=0.04) (Table 4).

Table 4:

Logistic regression with serum CRP concentrations and dietary antioxidants and covariates in participants

Females (n=51)
Nutrients β S.E. OR (95% CI) P value
Vitamin A 0.001 0.001 1.001 0.283
Carotenoids −0.0002 0.006 0.998 0.724
β-carotene −0.0638 0.913 0.528 0.485
Vitamin C −2.492 1.422 0.083 0.080
Vitamin E −1.559 1.493 0.210 0.296
Selenium −0.015 0.033 0.985 0.650
Age 0.002 0.041 1.002 0.970
BMI 0.141 0.070 1.151 0.043*
Males (n=22)
Nutrients β S.E. OR (95% CI) P value
Vitamin A −4.810 3.145 0.008 0.126
Carotenoids 0.022 0.019 1.023 0.241
β-carotene −0.003 0.003 0.997 0.345
Vitamin C 0.011 0.018 1.011 0.545
Vitamin E 1.278 2.097 3.591 0.542
Selenium 4.000 3.201 54.610 0.211
Age 0.011 0.073 1.012 0.876
BMI 0.046 0.064 1.048 0.471
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*

Indicates statistical significance at p<0.05

DISCUSSION

The purpose of this study was to investigate the relationship between dietary intake of antioxidants (carotenoids, vitamins A, C, E, and selenium) and serum CRP (as one of the CVD risk factors) in mid-life and older African American males and females at baseline enrolled in a longitudinal church-based intervention (Ralston 2014, 2017). On average, participants were in their late fifties and the majority was less than 60 years old (males: 63.6%, females: 60.8%). They were classified as obese with average BMI ≥ 30. The mean serum CRP level was greater than 0.3 mg/dL (threshold for CVD risk) which signified participants may had an elevated risk for CVD (Hebert 2013). Furthermore, serum CRP concentrations were higher in females than males, a trend consistent throughout the literature (Albert 2004; Cusman 2009; Khera 2005). However, our main hypothesis was not confirmed, as we did not find significant negative relationship between the dietary antioxidants intake and serum CRP.

We found males met RDA requirements for most of the dietary antioxidants evaluated, except for vitamin C and E. Females did not meet RDA for vitamin E and selenium. The mean dietary antioxidant intake was lower in the current study when compared to previous studies that assessed antioxidant intake in African Americans. Studies using 24-hour dietary recalls reported a higher mean intake for vitamin A, beta-carotene, vitamin C, vitamin E, and selenium in both African American males and females (Kant 2007; Watters 2007).

The studies which observed an inverse association between dietary antioxidant intake and serum CRP levels in US adults (Block 2009; Erlinger 2001; Floegel 2011; Ford 2003; Humenikova 2006; Roberts 2007; Yang 2013) provide a strong evidence that a higher intake of dietary antioxidants can help lower circulating levels of serum CRP and potentially reduce the risk for CVD. However, unlike the current study, the participants in these studies were given high doses of the antioxidant nutrients (Block 2009; Roberts 2007; Ford 2003); the serum nutrient biomarkers were used in analyses (Erlinger 2001; Humenikova 2006); or TAC was calculated (Yang 2013).

Floegel et al. (2011) evaluated the association between dietary antioxidant intake from diet and supplements and serum CRP in US adults. Among participants in the highest quintile for dietary antioxidant intake, the odds of having serum CRP levels >0.3 mg/dL was 26%, 29% and 30%, lower for vitamin C, E, and selenium respectively, when compared to the lowest quintile for dietary antioxidant intake. However, in this study the mean nutrient intake in the highest quintile was substantially higher (vitamin C 228 1 mg/day; vitamin E 12.2 mg/day; selenium 177.4 µg/d) than the mean intake in our study sample. In a crossover, randomized control trial, Valtuena et al. (2008) randomized older adults (mean age was 62 and 60 years-old for males and females, respectively) to a high- or low-TAC diet for two weeks and observed a statistically significant greater decrease in serum CRP in participants consuming a high-TAC diet compared to the low-TAC diet. Similarly to Floegel et al. (2011), the mean intake of vitamin C (423±197 mg/day) and E (16.2 ± 4.7 mg/day) in the high-TAC diet was substantially higher than the mean intake for vitamin C and E in our study sample (Valtuena 2008). Therefore, the possible reason we did not observe a significant association between dietary antioxidant intake and serum CRP levels was because the mean antioxidant intake in our population may have been insufficient to produce an anti-inflammatory effect, even though the intake largely met participants’ nutrient requirements (NIH 2018).

Other studies have also found null results for the association between dietary antioxidant intake and serum CRP. A cross-sectional analysis using participant data from the Multi-Ethnic Study of Atherosclerosis Study, a racially and ethnically diverse sample of mid-life and older adults (45–84 years old), did not observe a significant association between dietary intake of vitamin C, E, and selenium and circulating levels of serum CRP (de Oliveira 2011). The mean intake of these nutrients was also slightly higher than our study sample. Another cross-sectional analysis, which used NHANES III data, found dietary antioxidant intake of vitamin E, C, A, and beta-carotene was not statistically significantly correlated with serum CRP, whereas, serum biomarkers for vitamin C, vitamin A, and beta-carotene were significantly inversely correlated with serum CRP (Humenikova 2006). This study did not, however, adjust for race/ethnicity.

Our findings are slightly contradictory to previous studies which found the diet of African Americans to be suboptimal (Benjamin 2017; Kirkpatrick 2012). Kirkpatrick et al. (2012) measured DQ by calculating the Healthy Eating Index score, which compares intake with adherence to DGA, and found suboptimal dietary patterns in African Americans. However, they did not evaluate dietary intake of specific nutrients. Kuczmarski (2013) assessed DQ by calculating the Mean Adequacy Ratio (MAR), which uses the Institute of Medicine’s (IOM) RDA values as the reference (NIH 2018). African Americans aged 51–64 years-old had a significantly lower MAR score than Caucasians within the same age group. Additionally, dietary intake of vitamin A, E, and C fell below RDA for both African Americans and Caucasians aged 51–64 years old. Differences by race were only observed in the younger age group (30–50 years-old) (NIH 2018). Although evaluating a small set of dietary nutrients does not provide a complete assessment of DQ, the dietary antioxidant intake of our study sample likely met nutrient requirements.

We found a positive trend between BMI and elevated serum CRP in females. This result is comparable to findings from Albert (2004), who reported the interaction between BMI and serum CRP was strongest among African American women. Given the higher risk for CVD and the association between BMI and serum CRP in African Americans, it may be reasonable to conclude that a higher prevalence of obesity in this population in part leads to elevated systemic inflammation and thus increases their risk for chronic disease. However, caution must be taken in the interpretation of this finding because several factors, other than gender and racial/ethnic group, play a significant role in the development of obesity and chronic inflammation. Factors such as high perceived stress (Wickrama 2013), lower life satisfaction (Mendez 2018), socioeconomic status, and environmental context all play a part in inflammatory status and risk for chronic disease (Slopen 2010). Moreover, given the cross-sectional design of our study, we cannot infer the causation of the relationship between BMI or dietary intake with serum CRP levels. Our study did not find a significant association between age and serum CRP for males or females. However, previous studies have found age to be associated with elevated serum CRP, especially for those greater than 80 years-old (Lakoski 2006; Woloshin 2005). We may have not observed this trend in the present study due to the narrow age range of our sample and having no participants ≥ 80 years.

There was a significant, positive correlation between age and dietary ß-carotene among females. These results are in accordance with previous research which found an increase in dietary carotenoids across the lifespan, with the exception of adults ≥ 80 years-old (Kirkpatrick 2012). However, there were no statistically significant correlations (just trends) between age and vitamin A (p = 0.06) and other carotenoids (p = 0.08). ß-carotene is the main precursor of vitamin A and is a type of carotenoid. However, since ß-carotene is just one of several carotenoids, the observed age-related increase in African American women may be specific to ß-carotene and not apply to total carotenoid or total vitamin A intake. We did not observe any significant trends between dietary antioxidant nutrients and age for men in this study; however, this could be a result of the small sample size and limited statistical power, as well as the narrow age range. Among females, there was a borderline significant, negative correlation between BMI and ß-carotene and a trend towards significance between total carotenoids and BMI. Among males, we observed a negative trend between BMI and dietary vitamin E. These findings may be indicative of dietary habits associated with overweight. For example, foods that are rich in carotenoids and vitamin E, such as fruits, vegetables and nuts tend to have less energy per unit of weight and may result in better weight management and weight loss. However, we did not observe similar correlations between BMI and other dietary antioxidants.

We found the risk for moderate-high levels of serum CRP was 15% higher for every one-unit increase in BMI among females. Our results are in accordance with previous research reporting a significant association between obesity and chronic inflammation. Obesity is closely related to chronic inflammation and this relationship has been observed in both men and women of diverse racial/ethnic backgrounds. Although we found a significant association between BMI and serum-CRP in women, we did not observe this association in men, probably due to the small sample size.

There were several strengths to the current study. To our knowledge, this study is the first to exclusively investigate the association between dietary antioxidant intake and serum CRP levels in mid-life and older African Americans. Previous research evaluating dietary antioxidants and serum CRP levels did not adjust statistical models for gender, whereas we conducted a stratified analysis. We believe stratification was necessary given the significant differences in serum CRP concentrations by gender in African Americans. However, the small sample size is a limitation, especially for males in the study. The method used to assess dietary antioxidant intake was both a strength and limitation to this study. By using the average of three 24-hour dietary recalls, we followed standard procedures for estimating usual dietary intake. However, 24-hour dietary recalls, like all dietary assessment tools, are subject to under- and over-reporting of energy and nutrient intake. The most accurate and straight-forward method would have been to analyze serum concentrations of tocopherol (for vitamin E), ascorbate (for vitamin C), selenium, etc., as they reflect the bioavailability and true presence of metabolized antioxidant nutrients (Sies, 2007). However, this method is more expensive and not available in many research labs. Determining TAC is another method of calculating the total antioxidant potential of a diet, although it has been scrutinized. Food components undergo complex metabolic pathways generating various molecules which do not necessarily reflect the ultimate health outcomes/benefits of antioxidant nutrients (Sies 2007). Therefore, both methods offer advantages and disadvantages. Additionally, previous studies estimating antioxidant status using serum concentrations (Block 2009; Erlinger 2001; Ford 2003; Humenikova 2006) or by calculating TAC (Floegel 2011; Yang 2013) either did not separate by gender or did not exclusively include African Americans, rendering no comparison with our study, even if we had performed the TAC and serum analyses.

CONCLUSION

The dietary antioxidant intake of mid-life to older African American women and men in this study met (more or less) the recommendations provided by the Institute of Medicine (NIH 2018), however, intake may not have been sufficient to modify inflammatory biomarkers. This study supports existing evidence for obesity-induced inflammation and suggests the association can be applied to African American women. Future research should expand upon our findings by evaluating the association between dietary antioxidants and inflammation in a larger sample and include additional measures of inflammation, such as inflammatory cytokines. Moreover, in light of the limited clinical and public health utility of recommending an increase in “dietary antioxidant intake,” it would be insightful to assess the effects of food groups and dietary patterns on inflammation in African Americans.

Key messages:

Diet rich in fruits, vegetables, grains and nuts, containing antioxidant nutrients should be practiced for better overall health, management of weight and possibly lower serum CRP in African Americans.

Maintaining the healthy weight might lead to reduced low-grade chronic inflammation in African Americans and subsequent reduction in CRP.

Acknowledgments:

The authors are in debt to all the participants of the study.

Funding agency: This study was supported by the National Institute on Minority Health and Health Disparities, National Institutes of Health Award Number 1R24MD002807 (P.I. Penny A. Ralston). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute on Minority Health and Health Disparities or the National Institutes of Health.

Footnotes

Disclosure:

All authors declare no conflict of interest

Contributor Information

Katherine M. Rancaño, Friedman School of Nutrition Science and Policy, Tufts University, katherine.rancano@tufts.edu.

Penny A. Ralston, Center on Better Health and Life for Underserved Populations, Florida State University, pralston@fsu.edu.

Jennifer L. Lemacks, Department of Nutrition & Food Systems, The University of Southern Mississippi, Jennifer.Lemacks@usm.edu.

Iris Young-Clark, Center on Better Health and Life for Underserved Populations, Florida State University, iyoungclark@fsu.edu.

Jasminka Z. Ilich, Collaborating Faculty, Center on Better Health and Life for Underserved Populations, Affiliate, Institute for Successful Aging, Florida State University, jilichernst@fsu.edu.

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