Study design and hypothesis testing: issues in the evaluation of evidence from research in nutritional epidemiology

Adherence to 2020 to 2025 Dietary Guidelines for Americans and the Risk of New-Onset Female Gout

IMPORTANCE

Female-specific gout data are scarce despite perceived differences from males in its risk factors and disproportionate worsening in disease and comorbidity burden globally. The 2020 to 2025 Dietary Guidelines for Americans recommend multiple healthy eating patterns for prevention of cardiovascular-metabolic outcomes, which may also be relevant to the prevention of female gout.

OBJECTIVE

To examine the associations of dietary scores for the latest guideline-based healthy eating patterns with risk of incident female gout.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study included 80 039 US women in the Nurses' Health Study followed up through questionnaires every 2 years starting from 1984. Participants had no history of gout at baseline, and the study used questionnaire responses through 2018. Statistical analyses were performed over September 2020 to August 2021.

EXPOSURES

Four healthy eating patterns: Dietary Approaches to Stop Hypertension (DASH), Alternate Mediterranean Diet Score, Alternative Healthy Eating Index (AHEI), and Prudent, plus Western (unhealthy) for comparison, with scores derived from validated food frequency questionnaires.

MAIN OUTCOMES AND MEASURES

Incident, physician-diagnosed female-specific gout.

RESULTS

During 34 years of follow-up, we documented 3890 cases of incident female gout. Compared with the least-adherent quintile, women most adherent to healthy diets had significantly lower risk of incident gout, with multivariable-adjusted hazard ratios (HRs) 0.68 (95% CI, 0.61-0.76) (DASH), 0.88 (95% CI, 0.80-0.98) (Mediterranean), 0.79 (95% CI, 0.71-0.89) (AHEI), and 0.75 (95% CI, 0.73-0.90) (Prudent); all P for trend ≤.009. Conversely, women with highest-quintile Western diet score had 49% higher risk of gout (HR, 1.49; 95% CI, 1.33-1.68], P <.001). When combined, the most DASH-diet adherent women with normal body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) had a 68% lower risk of gout compared with the least adherent women with overweight or obese BMI; the corresponding risk reduction was 65% combining high DASH diet adherence with no diuretic use.

CONCLUSIONS AND RELEVANCE

These large-scale, long-term prospective cohort findings extend the pleotropic benefits of the 2020 to 2025 Dietary Guidelines for Americans to female gout prevention, with multiple healthy diets that can be adapted to individual food traditions, preferences, and comorbidities.

Nutrition interventions to treat low muscle mass in cancer

Many patients with cancer experience poor nutritional status, which detrimentally impacts clinical outcomes. Poor nutritional status in cancer is primarily manifested by severe muscle mass (MM) depletion, which may occur at any stage (from curative to palliative) and often co-exists with obesity. The objective of this article was to discuss gaps and opportunities related to the role of nutrition in preventing and reversing low MM in cancer. It also provides a narrative review of relevant nutritional interventions for patients capable of oral intake. The impact of nutrition interventions to prevent/treat low MM in cancer is not well understood, potentially due to the limited number of studies and of clinically viable, accurate body composition assessment tools. Additionally, the type of study designs, inclusion criteria, length of intervention, and choice of nutritional strategies have not been optimal, likely underestimating the anabolic potential of nutrition interventions. Nutrition studies are also often of short duration, and interventions that adapt to the metabolic and behavioural changes during the clinical journey are needed. We discuss energy requirements (25-30 kcal/kg/day) and interventions of protein (1.0-1.5 g/kg/day), branched-chain amino acids (leucine: 2-4 g/day), β-hydroxy β-methylbutyrate (3 g/day), glutamine (0.3 g/kg/day), carnitine (4-6 g/day), creatine (5 g/day), fish oil/eicosapentanoic acid (2.0-2.2 g/day EPA and 1.5 g/day DHA), vitamin/minerals (e.g. vitamin D: 600-800 international units per day), and multimodal approaches (nutrition, exercise, and pharmaceutical) to countermeasure low MM in cancer. Although the evidence is variable by modality type, interventions were generally not specifically studied in the context of cancer. Understanding patients' nutritional requirements could lead to targeted prescriptions to prevent or attenuate low MM in cancer, with the overall aim of minimizing muscle loss during anti-cancer therapy and maximizing muscle anabolism during recovery. It is anticipated that this will, in turn, improve overall health and prognostication including tolerance to treatment and survival. However, oncology-specific interventions with more robust study designs are needed to facilitate these goals.

How does 'park and ride' perform? An evaluation using longitudinal data

The efficiency of park and ride (PnR) lots has not been investigated in serious depth in prior literature. This study examines the effect of various factors on the utilization rate of PnR lots with panel Tobit models. The examined factors consist of land use features, roadway design features, transit ridership, sociodemographic attributes, travel characteristics, policy tools, gasoline prices, and weather conditions. The data is drawn from PnR lots in King County, Washington. Results show that: (1) degree of mixed land use, road density, employment density, percentages of people aged between 18 and 34 and people over 65, the percentage of white people, the percentage of poor people, and transit ridership are positively associated with the utilization rate of PnR lots; (2) the percentage of drive lanes in total roadway miles, the percentage of males, and the mode share percentage of driving are negatively correlated with the utilization rate of PnR lots; (3) various policy interventions, including countermeasures for preserving transit after the economic recession, congestion reduction charge, and bus-rail integration, are all positively correlated with the utilization rate of PnR lots. Contextualized to US cities, PnR is a practical way to attract bus riders, especially young adults, senior citizens, and low-income people to public transit. Dense urban development is encouraged for the full utilization of PnR lots. Additionally, the integration between bus and rail appears to be an effective policy tool to promote PnR utilization.

Promoting active student travel: A longitudinal study

This study investigates the effects of sidewalk modification and bike lane accommodation on students' active travel to schools. The modeling framework assumes that a student's choice for the mode of travel to school is impacted by numerous factors such as neighborhood crime rates, traffic safety, built environment amenities, and socio-demographic factors. A generalized linear model is employed to capture longitudinal changes in the mode share of students who walk or bike to school based on data collected from 53 schools in the city of Seattle, Washington. The modeling results indicate that (1) enhanced sidewalk modifications and bike lane accommodations encourage students walking and biking to school; (2) the implementation of Seattle's student assignment plan helps promote students walking to school possibly due to the change from school choice to neighborhood-based school assignment; (3) the size of the school attendance area is not significantly correlated with students' active travel activities, while the size of school enrollment is negatively associated with walking; (4) in school areas with high employment density, biking to school may be a more attractive option for students; (5) greater crosswalk density may encourage more students to walk to school; (6) the density of bike crashes is negatively associated with students biking to school. In terms of policy implications, transport planners should continually promote walking and biking supportive environments and implement policies to encourage active student travel.

Macronutrient composition and food groups associated with gestational weight gain: the GUSTO study

PURPOSE

To examine the associations of energy, macronutrient and food intakes with GWG on 960 pregnant women from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) mother-offspring cohort.

METHODS

Dietary intake was assessed at 26-28 weeks' gestation with a 24-hour recall and 3-day food diary. GWG z-scores were calculated from first (4-13 weeks' gestation) and last (30-40 weeks gestation) measured weights; inadequate and excessive GWG were defined using the Institute of Medicine recommendations based on weights between 15 and 35 weeks' gestation. Associations were examined using substitution models for macronutrient composition, with linear or multinomial logistic regressions.

RESULTS

Mean ± SD daily energy intake was 1868 ± 598 kcal, and percentage energy intakes were 51.8 ± 8.9% from carbohydrate, 15.7 ± 3.9% from protein and 32.6 ± 7.7% from fat. Higher energy intake (per 500 kcal increment) was associated with 0.18 SD higher GWG. In isocaloric diets, higher-carbohydrate and lower-fat intakes (at 5% energy substitution) were associated with 0.07 SD higher GWG, and 14% higher likelihood of excessive GWG. Concordantly, the highest tertile of carbohydrate-rich foods intake was associated with 0.20 SD higher GWG, but the highest tertile of fruit and vegetable intake was independently associated with 60% lower likelihood of inadequate GWG. Additionally, the highest tertile of dairy intake was associated with 0.18 SD lower GWG; and the highest tertile of plant-based protein foods intake was associated with 60% and 34% lower likelihood of inadequate and excessive GWG.

CONCLUSIONS

Balancing the proportions of carbohydrates and fat, and a higher intake of plant-based protein foods may be beneficial for achieving optimal GWG.

Recognition of phenylthiocarbamide (PTC) in taste test is related to blood group B phenotype, females, and risk of developing food allergy: a cross-sectional Brazilian-based study

Anti-nutritional factors, including hemagglutinins, are natural substances that reduce nutritional bioavailability and/or generate adverse physiological effects. Most are bitter toxic compounds, but present chemo-protective properties at low concentrations. Responses to phenylthiocarbamide (PTC) allow for an evaluation of humans' perception of bitter taste, a perception that has evolutionary advantages. Therefore, we hypothesized that relationships between food preference, dietary exposures and disease risk could reflect possible associations not only with the recognition threshold for the bitter taste of PTC, but also with ABO/Rh blood group phenotypes. To test this hypothesis, 375 volunteers of both genders, aged 16-49 years, were recruited. Data were obtained from laboratory tests and questionnaires. PTC test followed literature; blood typing used commercially available sera. Allele frequencies calculated from phenotypes were: T=0.51, t=0.49 (PTC); I^A=0.22, I^B=0.08, i=0.70 (ABO); D=0.57, d=0.43 (Rh). Associations with the recognition threshold for bitter taste were found for blood group B, females, and risk of developing food allergy for bitter taste at PTC dilution 1 (the highest concentration) (OR=3.862; 95%CI=1.387-10.756; p=0.016); for each more diluted PTC solution, the chance of food allergy fell 25.2% (95%CI = 0.764-0.836), while for each more concentrated solution the chance of food allergy increased 20.1% (p=0.000). There were also nominally significant differences among PTC tasting, ABO/Rh, genders and age-groups in relation to food preferences. Results demonstrated that the ability to recognize PTC in taste test is related to blood group B, females, and risk of developing food allergy, thus confirming the research hypothesis, and presenting original and important associations.

Short term elevation in dietary protein intake does not worsen insulin resistance or lipids in older adults with metabolic syndrome: a randomized-controlled trial

Background

There is a great deal of controversy as to whether higher protein intake improves or worsens insulin sensitivity in humans. The purpose of the study was to determine the influence of a short-term elevation in dietary protein on hepatic and peripheral insulin sensitivity in twelve older subjects (51–70 yrs) with metabolic syndrome.

Methods

Individuals were randomly assigned to one of the dietary groups: recommended protein intake (RPI, 10% of daily calorie intake) or elevated protein intake (EPI, 20% of daily calorie intake) for 4 weeks. Prior to and immediately following the dietary intervention, subjects were studied with primed continuous infusion of [6,6-²H₂]glucose and [1-¹³C]glucose dissolved in drink during the dual tracer oral glucose tolerance test (DT OGTT) to determine hepatic and peripheral insulin sensitivity. Plasma lipids were measured pre- and post-dietary intervention.

Results

In both intervention groups: 1) hepatic insulin sensitivity as assessed by the endogenous glucose rate of appearance (glucose R_a), 2) peripheral insulin sensitivity as assessed by the metabolic clearance rate of glucose normalized to plasma glucose concentration (MCR) and/or the rate of glucose utilization (R_d) or 3) glucose/insulin AUC were unaffected by the diets. Moreover, fasting lipid was not affected by RPI or EPI.

Conclusion

Our findings suggest that a short-term elevation in EPI with correspondingly higher branched chain amino acid (BCAA) contents has no detrimental impact on hepatic and peripheral insulin sensitivity or plasma lipid parameters in older adults with metabolic syndrome.

Trial registration

ClinicalTrials.gov Identifier: NCT02885935; This trial was registered retrospectively (Study start date, April 01, 2013, date of registration, August 26, 2016).

Electronic supplementary material

The online version of this article (doi:10.1186/s40795-017-0152-4) contains supplementary material, which is available to authorized users.

Diet, nutrition, and cancer: past, present and future

Despite the potentially important roles of diet and nutrition in cancer prevention, the evidence to support these roles is widely perceived by the public and health professionals as being inconsistent. In this Review, we present the issues and challenges in conducting and interpreting diet-cancer research, including those relating to the design of epidemiological studies, dietary data collection methods, and factors that affect the outcome of intervention trials. Approaches to improve effect estimates, such as the use of biomarkers to improve the accuracy of characterizing dietary exposures, are also discussed. Nutritional and dietary patterns are complex; therefore, the use of a reductionist approach to investigations, by focusing on specific nutrients, can produce misleading information. The effects of tumour heterogeneity and the failure to appreciate the nonlinear, U-shaped relationship between micronutrients and cancer in both observational studies and clinical trials are discussed. New technologies and investigational approaches are enabling the exploration of complex interactions between genetic, epigenetic, metabolic, and gut-microbial processes that will inform our knowledge of the diet-cancer relationship. Communicating the status of the evolving science in the context of the overall scientific evidence base, and evidence-based dietary recommendations for cancer prevention, should be emphasized in guidance for the public and for individual patients.

Nut Consumption and Cardiovascular Risk in Older Chinese: The Guangzhou Biobank Cohort Study

Objectives

In Western contexts nut consumption is associated with better health. We examined the associations of nut consumption with cardiovascular disease risk in the non-Western setting of Southern China.

Methods

In the Guangzhou Biobank Cohort Study we used multivariable linear regression to examine the associations of baseline nut (mainly peanuts) consumption (none (n = 6688), <3 portions/week (n = 2596) and ≥3 portions/week (n = 2444)) with follow-up assessment of Framingham cardiovascular disease score (excluding smoking) and its components in older Chinese (≥50 years) (follow-up 57.8%).

Results

Nut consumption was not associated with Framingham score (≥3 portions/week compared to none: 0.02 95% confidence interval (CI) -0.11 to 0.15), systolic blood pressure (-0.66 mmHg 95% CI -1.94, 0.62), diastolic blood pressure (-0.69 mmHg 95% CI -1.44, 0.07), HDL-cholesterol (-0.01 mmol/L 95% CI -0.02, 0.005), LDL-cholesterol (-0.01 mmol/L 95% CI -0.05, 0.02) or fasting glucose (0.04 mmol/L 95% CI -0.02, 0.09), adjusted for baseline values, energy intake, age, sex, phase of recruitment, socio-economic position, lifestyle and baseline health status.

Conclusions

Observations concerning the benefits of nut consumption may be contextually specific, perhaps depending on the type of nut consumed.

Limitations of observational evidence: implications for evidence-based dietary recommendations

Data from randomized controlled trials (RCTs) provide the strongest evidence for establishing relations between exposures, including dietary exposures, and health outcomes. However, not all diet and health outcome relations can be practically or ethically evaluated by using RCTs; therefore, many dietary recommendations are supported by evidence primarily from observational data, particularly those from prospective cohort studies. Although such evidence is of critical importance, limitations are often underappreciated by nutrition scientists and policymakers. This editorial review is intended to 1) highlight some of these limitations of observational evidence for diet-disease relations, including imprecise exposure quantification, collinearity among dietary exposures, displacement/substitution effects, healthy/unhealthy consumer bias, residual confounding, and effect modification; and 2) advocate for greater caution in the communication of dietary recommendations for which RCT evidence of clinical event reduction after dietary intervention is not available.

Design of clinical trials evaluating dietary interventions in patients with functional gastrointestinal disorders

Clear guiding principles for the design and conduct of dietary intervention trials in functional gastrointestinal disorders (FGID) are lacking. This narrative review examines the specific challenges associated with the design and reporting in dietary intervention trials. Dietary intervention trials need to address the collinearity between food, nutrients, and bioactive components that obscure the relationship between food and their effects in the gut. Randomized, double-blinded, placebo-controlled studies remain the gold standard for dietary trials, but are limited by difficulties in adequate masking of study food or inappropriate choice of placebo food/diets. Provision of study diets as the preferred delivery method can somewhat address these limitations, although allowing good adherence compared with education-based dietary interventions. Issues associated with participant expectancies and dietary behaviors can alter the true effectiveness of a diet. In addition, failure to adjust for or report baseline intake of nutrients of interest can reduce their magnitude of benefit. Bias in subjective reports and choice of measurement tools can preclude accurate assessment of food-intake data. In the design of elimination and rechallenge studies, sufficient time period and adequate exclusion of dietary triggers are essential to ensure symptoms are well-controlled before rechallenging. The route and frequency of challenging, design of test food, and/or placebo should match the aims of the rechallenge phase. Long-term efficacy data of such therapeutic diets has been poorly documented in most studies. Standardized guidelines that address many of the challenges outlined above are suggested to strengthen the quality of evidence for dietary therapies in FGID.

Dietary fiber and the risk of precancerous lesions and cancer of the esophagus: a systematic review and meta-analysis

Dietary fiber has several anticarcinogenic effects and is thought to be protective against esophageal cancer. The aim of this systematic review was to quantify the association between dietary fiber and the risk of esophageal cancer by investigating histological subtypes of esophageal cancer and the stage at which fiber may influence the carcinogenic pathway. Systematic search strategies were used to identify relevant studies, and adjusted odds ratios (ORs) were combined using random-effects meta-analyses to assess the risk of cancer when comparing extreme categories of fiber intake. Ten relevant case-control studies were identified within the timeframe searched. Pooled estimates from eight studies of esophageal adenocarcinoma revealed a significant inverse association with the highest fiber intakes (OR 0.66; 95% confidence interval [CI] 0.44-0.98). Two studies also identified protective effects of dietary fiber against Barrett's esophagus. Similar, though nonsignificant, associations were observed when results from five studies of fiber intake and risk of squamous cell carcinoma were combined (OR 0.61; 95%CI 0.31-1.20). Dietary fiber is associated with protective effects against esophageal carcinogenesis, most notably esophageal adenocarcinoma. Potential methods of action include modification of gastroesophageal reflux and/or weight control.

Energy underreporting in African-American girls: a longitudinal analysis

BACKGROUND

The objective of this study was to determine the longitudinal prevalence and predictors of dietary underreporting in African-American preadolescent girls and the association of baseline dietary underreporting with changes in BMI over a 2-year period as part of the Girls health Enrichment Multi-site Studies (GEMS).

METHODS

Energy was summarized at baseline, 12 months, and 24 months and computed as a 3-day average of 24-hour dietary recalls. Physical activity was assessed by accelerometer, basal metabolic rate was estimated using the World Health Organization's prediction equation, and caloric underreporting was based on the Goldberg equation.

RESULTS

We classified 48% of the girls at baseline as underreporters; with underreporting increasing over time (61% at 12 months; 66% at 24 months). Intervention treatment assignment did not affect the prevalence of underreporting over time. The consistency of underreporting (or not) stayed stable over time. Across all three time points, a higher BMI predicted underreporting. Baseline dietary underreporting and baseline BMI were found to be the major predictors of change in BMI, whereas baseline dietary variables did not predict change in BMI.

CONCLUSIONS

Dietary underreporting was extremely common in this sample of AA preadolescent girls and predictive of change in BMI. Given the magnitude and consistency of dietary underreporting along with the fact that no dietary variables predicted change in BMI, measurement of dietary intake in preadolescents, even with sophisticated measurement methodologies, appears biased. The best use of dietary recalls may not be to estimate dietary intake but rather to determine underreporting.

Methodological diversity and integration in health communication inquiry

Research on health communication is complicated by myriad individual, organizational, and societal factors that influence health-related decisions and behaviors, making it difficult to control for secular trends (uncontrolled social and environmental influences) that affect health care and health promotion practices. Sophisticated research on health communication must take into account the numerous situational, psychological, and societal factors to fully examine the often hidden dynamics of health care and health promotion. This essay examines major research challenges, strategies, and opportunities for making sense of the complexities of health communication processes, recommending the power of methodological diversity and integration for health research.

Influence of observational study design on the interpretation of cancer risk reduction by carotenoids

Recently published literature has been reviewed to determine whether lycopene, beta-carotene, alpha-carotene, and beta-cryptoxanthin are associated with reductions in cancer risk and whether study findings differ by study design. A total of 57 publications meeting pre-defined inclusion and exclusion criteria were identified, with the majority (55) being observational studies. None of the intervention studies supported a significant reduction in cancer risk with carotenoid (beta-carotene) supplementation. The majority of observational studies did not support significant reductions in cancer risk with increased carotenoid dietary intakes/circulating levels. A larger percentage of case-control studies supported significant associations between increased dietary intakes/circulating levels of carotenoids relative to prospective (cohort and nested case-control) studies. Compared to prospective studies, case-control studies cannot be used to establish temporality and may be more susceptible to selection and recall biases. Thus, diet-disease relationships suggested by case-control studies should ideally be confirmed by additional evidence from prospective studies.

An international case-control study of adult diet and brain tumor risk: a histology-specific analysis by food group

PURPOSE

Existing studies of diet and adult brain tumors have been limited by small numbers in histology-specific subgroups. Dietary data from an international collaborative case-control study on adult brain tumors were used to evaluate associations between histology-specific risk and consumption of specific food groups.

METHODS

The study included 1548 cases diagnosed between 1984 and 1991 and 2486 control subjects from 8 study centers in 6 countries. Of the 1548 cases, 1185 were gliomas, 332 were meningiomas, and 31 were other tumor types. Dietary consumption was measured as average grams per day.

RESULTS

We found inverse associations between some vegetable groups and glioma risk, the strongest for yellow-orange vegetables (odds ratio [OR], 0.7, 95% confidence interval [CI], 0.5-0.9 for the 4th vs. 1st quartile of consumption, p for trend<0.001), and the association was limited to specific glioma subtypes. There was no association with cured meat. Non-cured meat was associated with a modest increase in glioma risk (OR, 1.3; 95% CI, 1.0-1.7 for 4th quartile vs. 1st quartile, p for trend=0.01). We also found positive associations between egg, grain, and citrus fruit consumption and glioma but not meningioma risk.

CONCLUSIONS

Our study suggests that selected dietary food groups may be associated with adult gliomas and its subtypes but not meningiomas.

Artigos de revisão: contribuições com enfoque em ciência da nutrição

O objetivo deste trabalho é contribuir com a produção científica de artigos de revisão com base em pesquisas quantitativas, cuja finalidade é atualização do conhecimento sobre determinado tema, dirigindo-se especialmente aos pesquisadores iniciantes. Aborda a utilização de alguns instrumentos teórico-metodológicos para produção de textos, a priorização nos cuidados necessários quanto à leitura dos artigos consultados, o enriquecimento do conhecimento e a forma de reprodução desse conhecimento adquirido. Também alerta para os diversos aspectos que podem envolver a discussão sobre o tema escolhido, ressaltando e exemplificando a abrangência dos recursos metodológicos que precisam ser respeitados, mesmo em artigos de revisão de literatura. Conclui, orientando o compromisso com a qualidade que o desenvolvimento da pesquisa exige, e a preparação do material resultante da mesma em forma de pesquisa científica.

Proposed criteria for assessing the efficacy of cancer reduction by plant foods enriched in carotenoids, glucosinolates, polyphenols and selenocompounds

BACKGROUND AND AIMS

The cancer-protective properties of vegetable consumption are most likely mediated through 'bioactive compounds' that induce a variety of physiologic functions including acting as direct or indirect antioxidants, regulating enzymes and controlling apoptosis and the cell cycle. The 'functional food' industry has produced and marketed foods enriched with bioactive compounds, but there are no universally accepted criteria for judging efficacy of the compounds or enriched foods.

SCOPE

Carotenoids, glucosinolates, polyphenols and selenocompounds are families of bioactive compounds common to vegetables. Although numerous studies have investigated the agricultural and human health implications of enriching foods with one or more of these compounds, inadequate chemical identification of compounds, lack of relevant endpoints and inconsistencies in mechanistic hypotheses and experimental methodologies leave many critical gaps in our understanding of the benefits of such compounds. This review proposes a decision-making process for determining whether there is reasonable evidence of efficacy for the both the compound and the enriched food. These criteria have been used to judge the evidence of efficacy for cancer prevention by carotenoids, polyphenols, glucosinolates and selenocompounds.

CONCLUSIONS

The evidence of efficacy is weak for carotenoids and polyphenols; the evidence is stronger for glucosinolates and lycopene, but production of enriched foods still is premature. Additionally there is unacceptable variability in the amount and chemical form of these compounds in plants. The evidence of efficacy for selenocompounds is strong, but the clinical study that is potentially the most convincing is still in progress; also the variability in amount and chemical form of Se in plants is a problem. These gaps in understanding bioactive compounds and their health benefits should not serve to reduce research interest but should, instead, encourage plant and nutritional scientists to work together to develop strategies for improvement of health through food.

Nutritional genomics

Nutritional genomics has tremendous potential to change the future of dietary guidelines and personal recommendations. Nutrigenetics will provide the basis for personalized dietary recommendations based on the individual's genetic make up. This approach has been used for decades for certain monogenic diseases; however, the challenge is to implement a similar concept for common multifactorial disorders and to develop tools to detect genetic predisposition and to prevent common disorders decades before their manifestation. The preliminary results involving gene-diet interactions for cardiovascular diseases and cancer are promising, but mostly inconclusive. Success in this area will require the integration of different disciplines and investigators working on large population studies designed to adequately investigate gene-environment interactions. Despite the current difficulties, preliminary evidence strongly suggests that the concept should work and that we will be able to harness the information contained in our genomes to achieve successful aging using behavioral changes; nutrition will be the cornerstone of this endeavor.

Systematic review of fibroadenoma as a risk factor for breast cancer

Fibroadenoma (FA) is a common breast lesion occurring in 25% of asymptomatic women. Several studies considered FA as a risk factor for breast cancer, prompting a systematic review of the literature. We selected cohort and case-control studies. Seven studies satisfied the selection criteria. Dupont et al. (1994) and McDivitt et al. (1992) were considered to provide the strongest evidence, showing the relative risk for excised FA without hyperplasia in the range 1.48-1.7, with hyperplasia 3.47-3.7, and with hyperplasia and atypia 6.9-7.29, persisting for more than 20 years. Five studies by Levi et al. (1994), Ciatto et al. (1997), Moskowitz et al. (1980), Carter et al. (1988), and Levshin et al. (1998), were considered to provide weaker evidence, although they showed similar results. None of the results could be used to quantify the risks of excised, non-excised, and asymptomatic FA. More care should be taken in managing patients with complex FAs and FAs with hyperplasia with or without atypia. Core biopsy may be a better option in diagnosis of FAs. Regular screening may be advisable in patients with FAs and a family history of breast cancer in a first-degree relative. More rigorous research is needed in this area.

Physical activity and cancer: lessons learned from nutritional epidemiology

Convincing epidemiologic evidence currently exists for an association between physical activity and the prevention of colon and breast cancer Physical activity may also reduce the risk of cancer at several other sites. With increasing research on this topic, it is apparent that studies of physical activity and cancer have numerous methodological similarities with studies of nutrition and cancer Lessons learned from nutritional epidemiology that can be applied to studies of physical activity and cancer prevention and recommendations for future research are discussed in this review.

Antioxidants and breast cancer

A recent prospective study found that consumption of fruits and vegetables high in specific carotenoids and vitamins reduced breast cancer risk among premenopausal women. This observed protection might not be due to the anticarcinogenic mechanism of a single nutrient. Further prospective studies relating blood and dietary micronutrients to breast cancer risk are warranted.

The role of epidemiology in determining when evidence is sufficient to support nutrition recommendations. Summary statement

This statement summarizes the key points of discussion among a group of nutritional epidemiologists who met in Washington, DC, for 2 d in October of 1997 to reflect on the role of nutritional epidemiology in the development of dietary recommendations for the public. Although imprecision in the measurement of diet places limits on nutritional epidemiology, no other field of nutritional science can provide direct information on relations between nutrition and health in free-living human populations. Among the nutritional sciences, therefore, epidemiology was regarded as being critically important. Nutritional epidemiology can be improved in the future by the development of more precise measures of long-term dietary exposures, both by improved methods of self-reporting of diet and by the development of more useful biomarkers of long-term nutritional status. There is a need as well to reconsider the applicability of causal criteria as applied to nutritional epidemiology, because many of the important associations between dietary behaviors and chronic diseases cannot necessarily be expected to be either strong or to manifest linear dose-response relations. In the future, scientific evidence from the rapidly growing field of nutritional epidemiology will likely play an increasingly important role in developing nutrition policy and advice for the public.