Effects of trace components of dietary fat on cholesterol metabolism: phytosterols,oxysterols, and squalene

The effect of dietary fats on serum cholesterol is widely assumed to be due solely to the fatty acids and cholesterol they contain. Phytosterols, sterol oxidation products, and sterol precursors such as squalene, however, are often present in dietary fats. Little is known of the physiology of these substances in natural foods and most published diet studies do not consider them at all. Supplementation of the diet with high-dose phytosterols is now recommended for prevention of heart disease, but both recent and old data strongly suggest that the lower levels of phytosterols naturally present in vegetable fats may also reduce cholesterol absorption and serum cholesterol substantially. Moreover, unmeasured phytosterols may confound otherwise well-controlled diet studies because there is an inverse correlation between phytosterol and saturated fatty acid content of vegetable fats. Sterol oxidation products, many of which are found in foods, are potent regulators of lipoprotein and cholesterol transport pathways in vitro. Squalene is a phytosterol precursor abundant in olive oil that is at least partly absorbed and then quantitatively converted to cholesterol. The effects of dietary triglyceride-derived fatty acids have not been experimentally separated from the effects of trace fat components in most clinical studies. A better understanding of the activity of sterol-related dietary components is needed to reduce variability in diet studies, accurately assess the effects of dietary fatty acids and to maximize the effectiveness of dietary treatment for hypercholesterolemia.     

Effects of dietary fiber and its components on metabolic health

Dietary fiber and whole grains contain a unique blend of bioactive components including resistant starches, vitamins, minerals, phytochemicals and antioxidants. As a result, research regarding their potential health benefits has received considerable attention in the last several decades. Epidemiological and clinical studies demonstrate that intake of dietary fiber and whole grain is inversely related to obesity, type two diabetes, cancer and cardiovascular disease (CVD). Defining dietary fiber is a divergent process and is dependent on both nutrition and analytical concepts. The most common and accepted definition is based on nutritional physiology. Generally speaking, dietary fiber is the edible parts of plants, or similar carbohydrates, that are resistant to digestion and absorption in the small intestine. Dietary fiber can be separated into many different fractions. Recent research has begun to isolate these components and determine if increasing their levels in a diet is beneficial to human health. These fractions include arabinoxylan, inulin, pectin, bran, cellulose, β-glucan and resistant starch. The study of these components may give us a better understanding of how and why dietary fiber may decrease the risk for certain diseases. The mechanisms behind the reported effects of dietary fiber on metabolic health are not well established. It is speculated to be a result of changes in intestinal viscosity, nutrient absorption, rate of passage, production of short chain fatty acids and production of gut hormones. Given the inconsistencies reported between studies this review will examine the most up to date data concerning dietary fiber and its effects on metabolic health.     

Nutrition and disease: challenges of research design

This review discusses research methodology in the relation between diet and disease. Medical research can be divided into two types: complex research (the detailed study of disease mechanisms using such methods as biochemistry and molecular genetics) and simple research (the investigation of the factors that cause or prevent disease using methods such as epidemiology, intervention trials, and analagous studies on animals). Although complex research has received the bulk of resources, the large majority of our information of practical value has come from simple research. This general principle is illustrated in the area of diet and disease by examples from various areas: selenium, carotenoids, and cancer; vitamin E, omega-3 fatty acids, and coronary heart disease; dietary fat and obesity; dietary sodium and hypertension; and alcohol and stroke. Discussion then turns to aspects of the design of cohort (prospective) studies. Because of problems of sample size and relative lack of diversity, previous studies often failed to give clear-cut results. Suggestions are made concerning the design of cohort studies, notably the use of much larger numbers of subjects and with greater diversity in their diets. The problem of confounding also is discussed. Lifestyle factors often cluster together but cohort studies may not have fully unraveled this.     

Diet components can suppress inflammation and reduce cancer risk

Epidemiology studies indicate that diet or specific dietary components can reduce the risk for cancer, cardiovascular disease and diabetes. An underlying cause of these diseases is chronic inflammation. Dietary components that are beneficial against disease seem to have multiple mechanisms of action and many also have a common mechanism of reducing inflammation, often via the NFκB pathway. Thus, a plant based diet can contain many components that reduce inflammation and can reduce the risk for developing all three of these chronic diseases. We summarize dietary components that have been shown to reduce cancer risk and two studies that show that dietary walnut can reduce cancer growth and development. Part of the mechanism for the anticancer benefit of walnut was by suppressing the activation of NFκB. In this brief review, we focus on reduction of cancer risk by dietary components and the relationship to suppression of inflammation. However, it should be remembered that most dietary components have multiple beneficial mechanisms of action that can be additive and that suppression of chronic inflammation should reduce the risk for all three chronic diseases.     

Carotenoid concentrations in vegetables and fruits common to the Costa Rican diet

The intake of vegetables and fruits has been shown to reduce the risk of multiple diseases in many different populations. Various components of these foods have been investigated to explain the protective effects. Carotenoids, a class of phytochemicals found in these foods, have been investigated for links between their oxidative, provitamin A, and cellular properties and disease risk reduction. Many nutrition-based studies employ dietary questionnaires to estimate intakes for associations with disease. Reliable assessments of the components of these foods are necessary for accurate quantification of intake. While databases have been published, they vary greatly due to differences in methodology, growth conditions, and handling. In addition, data relevant to foods grown and consumed in Latin America and Costa Rica are scarce. In this paper, we employ a quality-controlled method for analyzing foods to obtain data on vegetables and fruits that are common to the Costa Rican diet. The data is presented in tables and compared to databases from the United States and Europe.     

Can soyabean isoflavones mimic the effects of energy restriction on healthy ageing?

Energy restriction is the only known robust dietary measure effective in increasing lifespan across a wide variety of species. Our current research indicates a role for the best-established dietary mimetic of energy restriction, the red grape polyphenol resveratrol, in altering information carried by DNA at a level superimposed on the information provided by the sequence of bases, known as epigenetic marking. These effects appear to share a common pathway with some of the effects of energy restriction that involve the protein Sirt1. Preliminary observations made in human intestinal cells reveal that isoflavones found in the soyabean may share some of these functional properties and so highlight the potential for a diet rich in these compounds to promote healthy ageing.     

Certain dietary patterns are beneficial for the metabolic syndrome: reviewing the evidence

The metabolic syndrome (MetS) is a global public health issue of increasing magnitude. The Asia-Pacific region is expected to be hardest hit due to large population numbers, rising obesity, and insulin resistance (IR). This review assessed the protective effects of dietary patterns and their components on MetS. A literature search was conducted using prominent electronic databases and search terms that included in combination: diet, dietary components, dietary patterns, and metabolic syndrome. Articles were restricted to prospective studies and high quality randomized controlled trials that were conducted on humans, reported in the English language, and within the time period of 2000 to 2012. Traditional factors such as age, gender, physical activity, and obesity were associated with risk of MetS; however, these potential confounders were not always accounted for in study outcomes. Three dietary patterns emerged from the review; a Mediterranean dietary pattern, dietary approaches to stop hypertension diet, and the Nordic Diet. Potential contributors to their beneficial effects on prevalence of MetS or reduction in MetS components included increases in fruits, vegetables, whole grains, dairy and dairy components, calcium, vitamin D, and whey protein, as well as monounsaturated fatty acids, and omega-3 fatty acids. Additional prospective and high quality randomized controlled trial studies that investigate Mediterranean dietary pattern, the dietary approaches to stop hypertension diet, and the Nordic Diet would cement the protective benefits of these diets against the MetS.     

The Mediterranean diet: effects on proteins that mediate fatty acid metabolism in the colon

A Mediterranean diet appears to have health benefits in many domains of human health, mediated perhaps by its anti-inflammatory effects. Metabolism of fatty acids and subsequent eicosanoid production is a key mechanism by which a Mediterranean diet can exert anti-inflammatory effects. Both dietary fatty acids and fatty acid metabolism determine fatty acid availability for cyclooxygenase- and lipoxygenase-dependent production of eicosanoids, namely prostaglandins and leukotrienes. In dietary intervention studies and in observational studies of the Mediterranean diet, blood levels of fatty acids do reflect dietary intakes but are attenuated. Small differences in fatty acid levels, however, appear to be important, especially when exposures occur over long periods of time. This review summarizes how fat intakes from a Greek-style Mediterranean diet can be expected to affect fatty acid metabolizing proteins, with an emphasis on the metabolic pathways that lead to the formation of proinflammatory eicosanoids. The proteins involved in these pathways are ripe for investigation using proteomic approaches and may be targets for colon cancer prevention.     

Functional foods and health: a US perspective

Linkages between diet habits and the quality of life continue to surface on numerous fronts. Collectively these epidemiological, pre-clinical and clinical studies provide rather compelling evidence that numerous essential and non-essential dietary components are capable of influencing growth, development and performance and disease prevention. Scientific discoveries and widespread interest in the potential medicinal benefits of foods and food components have fostered a variety of content, health and structure-function claims. Unfortunately, defining the ideal diet is complicated by the numerous and diverse components that may influence biological processes. Inconsistencies in the literature may reflect the multi-factorial nature of these processes and the specificity that individual dietary constituents have in modifying genetic and epigenetic events. New and emerging genomic and proteonomic approaches and technologies offer exciting opportunities for identifying molecular targets for dietary components and thus determining mechanisms by which they influence the quality of life. All cells have unique 'signatures' that are characterized by active and inactive genes and cellular products. It is plausible that bridging knowledge about unique cellular characteristics with molecular targets for nutrients can be used to develop strategies to optimize nutrition and minimize disease risk.     

Strategies for cancer prevention: the role of diet

Linkages between diet habits and cancer risk have surfaced from a multitude of epidemiological and preclinical studies. Collectively these studies provide rather compelling evidence that dietary components modify the incidence and biological behavior of tumors. While the risk of breast, prostate, colon, lung and liver cancers are frequently associated with dietary patterns, inconsistencies are not uncommon. These inconsistencies likely reflect the multi-factorial and complex nature of cancer and the specificity that individual dietary constituents have in modifying cancer related genetic pathways. The complexity of defining the role of diet is underscored by the numerous and diverse essential and non-essential components that may alter one or more phases of the cancer process. The explosive increase in the recognition of genes and pathways for regulating cell growth and development, and evaluating the response to hormones and other chemicals synthesized by the body, offers exciting opportunities for unraveling the molecular targets by which dietary components influence cancer prevention. It is recognized that all cells have unique 'signatures' that are characterized by active and inactive genes and cellular products. It is certainly plausible that bridging knowledge about these unique cellular characteristics with the molecular targets for nutrients can be used to assist in optimizing nutrition and minimizing cancer risk.     

Acne: The Role of Medical Nutrition Therapy

Acne is a common disease in Westernized nations, particularly among adolescents and young adults. Acne has substantial effects on quality of life, making treatment essential. Medical nutrition therapy as a potential treatment for acne is not new, although the literature examining diet and acne during the past 100 years is mixed. During the late 1800s and early 1900s, diet was commonly used as an adjunct treatment for acne. During the 1960s, however, the diet–acne connection fell out of favor. In recent years, dermatologists and registered dietitians have revisited the idea and become increasingly interested in the role of medical nutrition therapy in acne treatment. This article reviews the history and existing literature examining the association between diet and acne. Although the total number of studies conducted within the past 40 years is relatively small, the growing body of epidemiologic and experimental evidence suggests a relationship between diet and acne. Compared with other dietary factors, more research examines dietary glycemic load. The evidence is more convincing for high glycemic load diets, compared with other dietary factors. To date there are no randomized controlled trials investigating the relationship between frequent dairy or milk consumption and acne. Similarly, the number of research studies examining the relationship between dietary fat and/or n-3 fatty acids is sparse and the evidence is less robust. Taken together, several methodologic limitations need to be addressed, and additional research, preferably randomized controlled trials, is warranted before comprehensive evidence-based guidelines can be established. While dermatologists and registered dietitians continue to debate and research the potential relationship between diet and acne, the best dietary approach is to address each acne patient individually, carefully considering the possibility of dietary counseling.     

The biomarkers detecting early changes in the human organism exposed to occupational carcinogens

Epidemiological studies and clinical data confirm that occupational exposure to carcinogenic agents plays an important role in cancer etiology. Recent tremendous progress in understanding of the mechanisms of carcinogenesis, and also introduction of new tests to recognize changes occurring in the exposed organism have made it possible for the occupational medicine to detect the earliest cancer stages which occur during the latent phase of the disease. Detecting pre-neoplastic changes which precede an overt form of cancer and identification of measurable indicators of those changes has been one of the fundamental aims of molecular biology research. Biomarkers may serve as a research tool which makes it possible to achieve this aim. Suitably selected biomarker sets can provide information on the extent of the exposure to carcinogenic agents (biomarkers of exposure), detect early changes produced by the agents in the exposed organism (biomarkers of effects), and identify people with particularly high cancer risk (biomarkers of susceptibility). It will soon be possible to use molecular biomarkers, capable of detecting increased cancer risk at the molecular level of cell structure, in prophylactic action intended to reduce cancer incidence. Molecular biomarkers are capable of recording very early health effects of exposure to carcinogens, thus making it possible to determine cancer risk at a very early stage of cancer development.     

Socio-economic and dietary influences on leg length and trunk length in childhood: a reanalysis of the Carnegie (Boyd Orr) survey of diet and health in prewar Britain (1937–39)

Social class differences in height have been recognised for many centuries. However, few studies have examined the extent to which these differences are made up of differences in leg length or trunk length. This paper reanalyses cross-sectional information on children examined in Britain in the 1930s. We assess associations between socio-economic status and diet and the components of childhood stature. The analyses were based on the records of 2990 children aged 2 years to 14 years 9 months who were examined in the Carnegie (Boyd Orr) survey of diet and health (1937–39). z -Scores for the measures of childhood stature were calculated using polynomial regression techniques with the study population as the standard. Univariable and multivariable statistical techniques were used to assess the relationships between childhood height, leg length and trunk length, and dietary and socio-economic factors measured at the level of the household. Leg length was the component of stature most strongly associated with measures of childhood diet and socio-economic status. A greater part of the difference in stature between socio-economic groups was caused by differences in leg length rather than trunk length. In multiple regression analyses, district of residence and family food expenditure were generally the two factors most strongly related to stature. In a subsample of the surveyed children, for whom birthweight information was available, trunk length and leg length were equally strongly related to birthweight. Leg length appears to be a particularly sensitive indicator of childhood socio-economic circumstances. Although contemporary studies highlight the importance of biological factors in determining childhood height, the data analysed in this study suggest that socio-economic circumstances were also important in explaining height differentials in prewar Britain.     

A critical review of predefined diet quality scores

The literature on predefined indexes of overall diet quality is reviewed. Their association with nutrient adequacy and health outcome is considered, but our primary interest is in the make-up of the scores. In total, twenty different indexes have been reviewed, four of which have gained most attention, and many others were based on those four. The various scores differ in many respects, such as the items included, the cut-off values used, and the exact method of scoring, indicating that many arbitrary choices have been made. Correlations in intake between dietary components may not be adequately addressed. In general, diet quality scores show an association with mortality or disease risk, but these relations are generally modest. Existing indexes do not predict morbidity or mortality significantly better than individual dietary factors. Although conclusions from the review may provide guidance in the construction of a diet quality score, it is questionable whether a dietary score can be obtained that is a much better predictor of health outcome.     

Perspectives of Dietary Assessment in Human Health and Disease

Diet and human health have a complex set of relationships, so it is crucial to identify the cause-effects paths and their management. Diet is crucial for maintaining health (prevention) and unhealthy diets or diet components can cause disease in the long term (non-communicable disease) but also in the short term (foodborne diseases). The present paper aims to provide a synthesis of current research in the field of dietary assessment in health and disease as an introduction to the special issue on “Dietary Assessment and Human Health and Disease”. Dietary assessment, continuously evolving in terms of methodology and tools, provides the core information basis for all the studies where it is necessary to disentangle the relationship between diet and human health and disease. Estimating dietary patterns allows for assessing dietary quality, adequacy, exposure, and environmental impact in nutritional surveillance so on the one hand, providing information for further clinical studies and on another hand, helping the policy to design tailored interventions considering individual and planetary health, considering that planetary health is crucial for individual health too, as the SARS-CoV-2 (COVID-19) pandemic has taught. Overall, dietary assessment should be a core component in One-Health-based initiatives to tackle public health nutrition issues.     

Effects of maternal dietary intake on human milk composition

The composition of human milk can be affected by the diet consumed by the lactating woman. The influence of the maternal diet on milk composition varies in magnitude between nutrients; for some nutrients no effect at all has yet been documented. Concentrations of fatty acids, fat-soluble and water-soluble vitamins in milk are, in general, significantly affected by the levels of these nutrients in the diet. Protein concentration may be affected under some conditions, although the magnitude of this change appears relatively limited. Lactose, mineral, trace element and electrolyte concentrations seem comparatively resistant to varying maternal intakes. Although there has been significant progress in this research area in the past decade, many early studies are difficult to interpret due to limitations in the study design and analytical methods. This review demonstrates a distinct need for carefully controlled studies on the effects of both nutrient deficiencies and supplements on milk composition. Interactions among nutrients, homeostatic mechanisms and energy balance (weight loss) are factors that need to be studied further. Information from such research will suggest strategies for nutrition intervention in areas of poor nutrition and provide dietary guidelines for lactating women.     

Influences of Dietary and Other Factors on Xenobiotic Metabolism and Carcinogenesis—A Review Article in Memory of Dr. Allan H. Conney (1930–2013)

This article reviews our current understanding on how xenobiotic metabolism and carcinogenesis are influenced by dietary and other factors. A major contributor to this research area was Dr. Allan Conney, and his contributions are highlighted. His studies on the induction of microsomal xenobiotic-metabolizing enzymes led to the characterization of the cytochrome P450 enzymes, which catalyze the metabolism of drugs, endogenous substrates, carcinogens and many other xenobiotics. These processes are influenced by drugs, diet, and other environmental factors. These studies provided the molecular basis for drug–drug, diet–drug, and herb–drug interactions. The elucidation of the metabolic activation of chemicals to their ultimate carcinogenic forms enables us to understand the molecular basis of chemical carcinogenesis. These studies led to many subsequent investigations on dietary approaches for cancer chemoprevention, including blocking of carcinogen activation, enhancing carcinogen detoxification, and influencing oncogenic pathways, which were carried out by Dr. Conney and others. The strengths and potential for practical application of these approaches are assessed herein.     

Position of the Academy of Nutrition and Dietetics: Functional Foods

It is the position of the Academy of Nutrition and Dietetics to recognize that although all foods provide some level of physiological function, the term functional foods is defined as whole foods along with fortified, enriched, or enhanced foods that have a potentially beneficial effect on health when consumed as part of a varied diet on a regular basis at effective levels based on significant standards of evidence. The Academy supports Food and Drug Administration?approved health claims on food labels when based on rigorous scientific substantiation. All food is essentially functional at some level as it provides energy and nutrients needed to sustain life. However, there is growing evidence that some food components, not considered nutrients in the traditional sense, may provide positive health benefits. Foods containing these food components are called functional foods. Functional food research holds many promises for improving the quality of life for consumers; however, to achieve such outcomes, scientific research must effectively establish the bioavailability and efficacy of these compounds at levels that are physiologically achievable under typical dietary patterns. This Position Paper reviews the complexities of defining functional foods; categories of foods marketed as functional; regulation of functional foods; the scientific substantiation of and advancement of functional food research; as well as a message to registered dietitians and dietetic technicians, registered, on how to remain current in their knowledge of functional food research and the translation of this information to consumers.