Individualized nutritional recommendations: do we have the measurements needed to assess risk and make dietary recommendations?

Is the information currently available to adjust nutritional recommendations and develop individualized nutrition? No. There is not even the information needed for setting dietary recommendations with confidence now at the group level. Will it be available soon? The answer to this question depends on the drive and will of the nutritional community, the success in recruiting funding to the area, the education of nutritionists and the spawning of great ideas and approaches. The emerging tools of genomics, proteomics and metabolomics are enabling the in-depth study of relationships between diet, genetics and metabolism. The advent of technologies can be compared with the discovery of the microscope and the new dimensions of scientific visualization enabled by that discovery. Nutritionists stand at the crest of new waves of data that can be generated, and new methods for their digestion will be required. To date, the study of dietary requirements has been based largely on a black box approach. Subjects are supplemented or depleted and clinical outcomes are observed. Few recommendations are based on metabolic outcomes. Metabolomics and nutrigenomics promise tools with which recommendations can be refined to meet individual requirements and the potential of individualized nutrition can be explored. As yet, these tools are not being widely applied in nutritional research and are rarely being applied by nutritionists. The result is often interesting research that is frequently nutritionally flawed, resulting in inappropriate conclusions. Nutritional education is needed to put nutritionists at the forefront of the development of applications for these technologies, creating a generation of nutrigenomicists. A new generation of nutritionists should be working interdisciplinarily with geneticists, molecular biologists and bioinformaticians in the development of research strategies. The present paper reviews the current status of nutrigenomic research, the current controversies and limitations, and developments needed to advance nutrigenomics and explore fully the promise of individualized nutritional recommendations

Biomarkers and the measurement of fatty acids

OBJECTIVE: To review the various biomarkers of dietary intakes of fatty adds in human populations, their measurement, limitations and analytical considerations. DESIGN: Review of the literature. RESULTS: Although there is no good biomarker of intake of total fat, a number of alternatives exist for assessing the intakes of exogenously produced fatty acids that are consumed. Adipose tissue, erythrocyte membrane concentrations and serum or plasma levels can reflect prior intakes over the past few hours to the past few years. The concentrations of individual fatty acids in these media generally reflect relative levels, and are influenced by a number of factors. Although relatively expensive to analyse, a single analysis by gas chromatography or high-performance liquid chromatography provides information on multiple fatty acids, and is superior to attempting to measure specific fatty acids using traditional dietary assessment methods. CONCLUSIONS: Biomarkers of fatty acids that reflect long-term intake are available for nutritional epidemiology purposes. Analytical methods have become very accurate and able to detect and quantify smaller families, such as trans-fatty acids

Tea consumption and the reduced risk of colon cancer – results from a national prospective cohort study

OBJECTIVE: This study examines the relationship between tea consumption and colon cancer risk in the US population. DESIGN: Data from the NHANES I Epidemiologic Follow-up study (NHEFS) were used to examine the hypothesis. Cox proportional hazard models were used to examine the hypothesis of a protective effect of frequent tea consumption on colon cancer occurrence. SETTING: Due to differences in the precision of the exposure data, we analysed two cohort periods based on the NHEFS. Cohort I was based on the survey conducted at the NHEFS baseline and Cohort II began at the first follow-up. SUBJECTS: After excluding non-incidence cases and cases lost to follow-ups, there were 2359 tea users and 6498 non-tea users at baseline and 7656 tea users and 4514 non-tea users at the first follow-up. RESULTS: : After adjusting for confounders, the relative risks of colon cancer are 0.57 (95% confidence interval (CI) 0.42, 0.78) and 0.59 (95% 1.00) for subjects who consumed 1.5 cups per day, respectively, compared with non-tea users in Cohort II. Although more women consumed tea and the mean intake was higher, the preventive effect of tea consumption on colon cancer was found predominantly in men. The relative risks of colon cancer are 0.41 (95% 0.66) for men who consumed 1.5 cups day-1 of tea consumption (P-value for trend <0.01). No significant results were found in Cohort I. CONCLUSIONS: This study suggests an inverse association between colon cancer risk and habitual tea consumption

Nutritional Risk Factors for Tuberculosis Among Adults in the United States, 1971–1992

The risk of developing tuberculosis (TB) may be related to nutritional status. To determine the impact of nutritional status on TB incidence, the authors analyzed data from the First National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-up Study (NHEFS). NHANES I collected information on a probability sample of the US population in 1971–1975. Adults were followed up in 1982–1992. Incident TB cases were ascertained through interviews, medical records, and death certificates. TB incidences were compared across different levels of nutritional status after controlling for potential confounding using proportional hazards regression appropriate to the complex sample design. TB incidence among adults with normal body mass index was 24.7 per 100,000 person-years (95% confidence interval (CI): 13.0, 36.3). In contrast, among persons who were underweight, overweight, and obese, estimated TB incidence rates were 260.2 (95% CI: 98.6, 421.8), 8.9 (95% CI: 2.2, 15.6), and 5.1 (95% CI: 0.0, 10.5) per 100,000 person-years, respectively. Adjusted hazard ratios were 12.43 (95% CI: 5.75, 26.95), 0.28 (95% CI: 0.13, 0.63), and 0.20 (95% CI: 0.07, 0.62), respectively, after controlling for demographic, socioeconomic, and medical characteristics. A low serum albumin level also increased the risk of TB, but low vitamin A, thiamine, riboflavin, and iron status did not. A population’s nutritional profile is an important determinant of its TB incidence

The use of external within-person variance estimates to adjust nutrient intake distributions over time and across populations

OBJECTIVE: To examine the utility of using external estimates of within-person variation to adjust usual nutrient intake distributions. DESIGN: Analyses of the prevalence of inadequate intake of an example nutrient by the Estimated Average Requirement (EAR) cut-point method using three different methods of statistical adjustment of the usual intake distribution of a single 24-hour recall in Russian children in 1996, using the Iowa State University method for adjustment of the distribution. First, adjusting the usual intake distribution with day 2 recalls from the same 1996 sample (the correct method); second, adjusting the distribution using external variance estimates derived from US children in 1996; and third, adjusting the distribution using external estimates derived from Russian children of the same age in 2000. We also present prevalence estimates based on naive statistical analysis of the unadjusted distribution of intakes. SETTING/SUBJECTS: Children drawn from the Russia Longitudinal Monitoring Survey in 1996 and 2000 and from the 1996 Continuing Survey of Food Intakes by Individuals. RESULTS: When the EAR cut-point method is applied to a single recall, the resulting prevalence estimate in this study is inflated by 100-1300%. When the intake distribution is adjusted using an external variance estimate, the prevalence estimate is much less biased, suggesting that any adjustment may give less biased estimates than no adjustment. CONCLUSIONS: In moderately large samples, adjusting distributions with external estimates of variances results in more reliable prevalence estimates than using 1-day data

Predictors of pregnancy and postpartum haemoglobin concentrations in low-income women

OBJECTIVE: Pregnancy and postpartum iron status is of great public health importance, yet few studies have examined predictors of haemoglobin (Hb) concentration during this time. We identified predictors of Hb from 24 weeks' gestation until delivery and from 4 to 25 weeks postpartum. DESIGN: Blood was drawn as many as four times during care: at the initial visit, at 24-29 weeks' gestation, at delivery and postpartum. A longitudinal, multivariable linear regression model was used to predict Hb concentration. SETTING: A public health clinic in Raleigh, North Carolina. SUBJECTS: n=520 women who participated in the Iron Supplementation Study. RESULTS: Hb concentration at the previous blood draw, short stature, non-Hispanic white ethnicity/race, >12 years of education and smoking were positive predictors of pregnancy and postpartum Hb concentrations. Iron supplement use was a positive predictor, while inadequate weight gain and severe nausea/vomiting were negative predictors of gestational Hb. A high infant birth weight and postpartum haemorrhage were negative predictors of postpartum Hb. Pre-pregnancy body mass index had a slight positive relationship with gestational Hb, but had a strong negative relationship with postpartum Hb. The longitudinal model also confirmed the typical pattern of gestational Hb concentration. As the number of weeks between the initial visit and the 24- to 29-week visit increased, Hb at 24-29 weeks' gestation decreased. As gestational age increased from 24 weeks until delivery, Hb concentration increased as well. CONCLUSIONS: The predictors identified here could be used in clinical settings to target high-risk women for intervention

Dietary Total Antioxidant Capacity is Inversely Associated with Prostate Cancer Aggressiveness in a Population-Based Study

The purpose of this study was to determine the relationship between total antioxidant capacity (TAC) from diet and supplements and prostate cancer aggressiveness among 855 African Americans (AA) and 945 European Americans (EA) in the North Carolina-Louisiana Prostate Cancer Project (PCaP). Cases were classified as either high aggressive, low aggressive, or intermediate aggressive. TAC was calculated from the vitamin C equivalent antioxidant capacity of 42 antioxidants measured via food frequency questionnaire. EA reported greater dietary TAC from diet and supplements combined (P 1500 vs. < 500 mg VCE/d): 0.31 (95% CI: 0.15, 0.67; P-trend < 0.01), 0.28 (95% CI: 0.08, 0.96; P-trend < 0.001), and 0.36 (95% CI: 0.15, 0.86; P-trend = 0.58), respectively. These associations did not appear to differ between AA and EA. These data suggest that greater intake of antioxidants is associated with less aggressive prostate cancer. Additional research is needed to confirm these results and determine the underlying mechanisms

Intake of dietary antioxidants is inversely associated with biomarkers of oxidative stress among men with prostate cancer

Abstract Prostate cancer is the most common non-cutaneous cancer and the second leading cause of cancer-related mortality among men in the USA. Growing evidence suggests that oxidative stress is involved in the development and progression of prostate cancer. In this study, the association between antioxidants from diet and supplements and biomarkers of oxidative stress in blood ( n 278), urine ( n 298) and prostate tissue ( n 55) were determined among men from the North Carolina-Louisiana Prostate Cancer Project. The association between antioxidant intake and oxidative stress biomarkers in blood and urine was determined using linear regression, adjusting for age, race, prostate cancer aggressiveness and smoking status. Greater antioxidant intake was found to be associated with lower urinary 8-isoprostane concentrations, with a 10 % increase in antioxidant intake corresponding to an unadjusted 1·1 % decrease in urinary 8-isoprostane levels (95 % CI −1·7, −0·3 %; P value&lt;0·01) and an adjusted 0·6 % decrease (95 % CI −1·4, 0·2 %; P value=0·16). In benign prostate tissue, thioredoxin 1 was inversely associated with antioxidant intake ( P =0·02). No significant associations were found for other blood or urinary biomarkers or for malignant prostate tissue. These results indicate that antioxidant intake may be associated with less oxidative stress among men diagnosed with prostate cancer