Showing papers in "Nutrition Reviews in 2006"

Long-Lasting Neural and Behavioral Effects of Iron Deficiency in Infancy

Abstract: Infants are at high risk for iron deficiency and iron-deficiency anemia. This review summarizes evidence of long-term effects of iron deficiency in infancy. Follow-up studies from preschool age to adolescence report poorer cognitive, motor, and social-emotional function, as well as persisting neurophysiologic differences. Research in animal models points to mechanisms for such long-lasting effects. Potential mechanisms relate to effects of iron deficiency during brain development on neurometabolism, myelination, and neurotransmitter function.

Scientific Evidence of Interventions Using the Mediterranean Diet: a Systematic Review

Abstract: The Mediterranean Diet has been associated with greater longevity and quality of life in epidemiological studies, the majority being observational. The application of evidence-based medicine to the area of public health nutrition involves the necessity of developing clinical trials and systematic reviews to develop sound recommendations. The purpose of this study was to analyze and review the experimental studies on Mediterranean diet and disease prevention. A systematic review was made and a total of 43 articles corresponding to 35 different experimental studies were selected. Results were analyzed for the effects of the Mediterranean diet on lipoproteins, endothelial resistance, diabetes and antioxidative capacity, cardiovascular diseases, arthritis, cancer, body composition, and psychological function. The Mediterranean diet showed favorable effects on lipoprotein levels, endothelium vasodilatation, insulin resistance, metabolic syndrome, antioxidant capacity, myocardial and cardiovascular mortality, and cancer incidence in obese patients and in those with previous myocardial infarction. Results disclose the mechanisms of the Mediterranean diet in disease prevention, particularly in cardiovascular disease secondary prevention, but also emphasize the need to undertake experimental research and systematic reviews in the areas of primary prevention of cardiovascular disease, hypertension, diabetes, obesity, infectious diseases, age-related cognitive impairment, and cancer, among others. Interventions should use food scores or patterns to ascertain adherence to the Mediterranean diet. Further experimental research is needed to corroborate the benefits of the Mediterranean diet and the underlying mechanisms, and in this sense the methodology of the ongoing PREDIMED study is explained.

Nutrition in Brain Development and Aging: Role of Essential Fatty Acids

Abstract: The essential fatty acids (EFAs), particularly the n-3 long-chain polyunsaturated fatty acids (LCPs), are important for brain development during both the fetal and postnatal period. They are also increasingly seen to be of value in limiting the cognitive decline during aging. EFA deficiency was first shown over 75 years ago, but the more subtle effects of the n-3 fatty acids in terms of skin changes, a poor response to linoleic acid supplementation, abnormal visual function, and peripheral neuropathy were only discovered later. Both n-3 and n-6 LCPs play important roles in neuronal growth, development of synaptic processing of neural cell interaction, and expression of genes regulating cell differentiation and growth. The fetus and placenta are dependent on maternal EFA supply for their growth and development, with docosahexaenomic acid (DHA)-supplemented infants showing significantly greater mental and psychomotor development scores (breast-fed children do even better). Dietary DHA is needed for the optimum functional maturation of the retina and visual cortex, with visual acuity and mental development seemingly improved by extra DHA. Aging is also associated with decreased brain levels of DHA: fish consumption is associated with decreased risk of dementia and Alzheimer's disease, and the reported daily use of fish-oil supplements has been linked to improved cognitive function scores, but confirmation of these effects is needed.

Bitter Gourd (Momordica charantia): a Dietary Approach to Hyperglycemia

Abstract: Bitter gourd (Momordica charantia) is a vegetable with pantropical distribution. It contains substances with antidiabetic properties such as charantin, vicine, and polypeptide-p, as well as other unspecific bioactive components such as antioxidants. Metabolic and hypoglycemic effects of bitter gourd extracts have been demonstrated in cell culture, animal, and human studies. The mechanism of action, whether it is via regulation of insulin release or altered glucose metabolism and its insulin-like effect, is still under debate. Adverse effects are also known. Nevertheless, bitter gourd has the potential to become a component of the diet or a dietary supplement for diabetic and prediabetic patients. Well-designed interdisciplinary research by nutritionists, medical doctors, and agronomists is needed before a dietary recommendation can be given and a product brought to the market.

Minor Components of Olive Oil: Evidence to Date of Health Benefits in Humans

Abstract: Olive oil is a functional food, which in addition to a high level of monounsaturated fatty acids also contains multiple minor components with biological properties. A large number of studies, mainly experimental, have been carried out on some of these components. However, the precepts of evidence-based medicine require adequate scientific evidence (level I or II) to be provided before nutritional recommendations for the general public can be formulated. In this review, we summarize the state of the art of the body of knowledge and discuss the extent to which there exists evidence for the health benefits of the minor components of olive oil.

The psychosocial and behavioral characteristics related to energy misreporting.

Abstract: Energy underreporting occurs in 2% to 85% and overreporting in 1% to 39% of various populations. Efforts are needed to understand the psychosocial and behavioral characteristics associated with misreporting to help improve the accuracy of dietary self-reporting. Past research suggests that higher social desirability and greater eating restraint are key factors influencing misreporting, while a history of dieting and being overweight are more moderately associated. Eating disinhibition, body image, depression, anxiety, and fear of negative evaluation may be related to energy misreporting, but evidence is insufficient. This review will provide a detailed discussion of the published associations among psychosocial and behavioral characteristics and energy misreporting.

Probiotics and Their Potential Health Claims

Abstract: Many studies have attempted to identify specific positive health effects of probiotics. One of the challenges in generalizing health effects of probiotics is that different strains exert disparate effects on human health. As a result, the efficacy of one strain or species cannot necessarily be inferred from another. The objective of this review is to examine the current scientific literature that could be used as the basis for potential health claims. More specifically, this paper will review existing evidence of different probiotic strains to prevent and treat diarrhea, treat irritable bowel syndrome (IBS), treat inflammatory bowel disease, and prevent colon cancer. The strongest evidence is related to the use of Lactobacillus rhamnosus GG in the prevention and treatment of rotavirus-associated diarrhea. Further examination of the literature also shows promise in the treatment of some forms of IBS with probiotics. Future studies that use consistent supplementation regimes will allow more definitive conclusions to be drawn on the effects of probiotics on IBS, inflammatory bowel disease, and colon cancer.

Is there an association between sweetened beverages and adiposity

Abstract: Four mechanisms were reviewed to explain the possible association between sweetened beverages and increased overweight or obesity: excess caloric intake, glycemic index and glycemic load, lack of effect of liquid calories on satiety, and displacement of milk. The findings were inconsistent across studies. The strongest support was for the excess caloric intake hypothesis, but the findings were not conclusive. Assigning possible links between sweetened beverage consumption and adiposity requires research that compares and contrasts specific mechanisms, especially in populations at risk for obesity, while controlling for likely confounding variables.

Vitamin D status and the metabolic syndrome.

Abstract: The identification of vitamin D receptor expression in different tissues suggests a widespread role for vitamin D action beyond its classical function in bone and mineral metabolism. Recently, the importance of vitamin D status as a risk factor in the development of metabolic syndrome has been the focus of several studies.

Bioavailability of selenium from foods.

Abstract: Selenium (Se), an essential nutrient, is needed for activity of several important proteins. Additionally, the consumption of Se in amounts that exceed the Recommended Dietary Allowance (RDA) may protect against prostate and colorectal cancer. Supplemental Se may be acquired through the diet, but Se bioavailability depends on the source. Therefore, dietary advice concerning improvement of Se intake depends on characterization of Se bioavailability from Se-containing food sources.

Effectiveness of monetary incentives in modifying dietary behavior: a review of randomized, controlled trials

Abstract: To review research evidence on the effectiveness of monetary incentives in modifying dietary behavior, we conducted a systematic review of randomized, controlled trials (RCTs) identified from electronic bibliographic databases and reference lists of retrieved relevant articles. Studies eligible for inclusion met the following criteria: RCT comparing a form of monetary incentive with a comparative intervention or control; incentives were a central component of the study intervention and their effect was able to be disaggregated from other intervention components; study participants were community-based; and outcome variables included anthropometric or dietary assessment measures. Data were extracted on study populations, setting, interventions, outcome variables, trial duration, and follow-up. Appraisal of trial methodological quality was undertaken based on comparability of baseline characteristics, randomization method, allocation concealment, blinding, follow-up, and use of intention-to-treat analysis. Four RCTs were identified as meeting the inclusion criteria. All four trials demonstrated a positive effect of monetary incentives on food purchases, food consumption, or weight loss. However, the trials had some methodological limitations including small sample sizes and short durations. In addition, no studies to date have assessed effects according to socioeconomic or ethnic group or measured the cost-effectiveness of such schemes. Monetary incentives are a promising strategy to modify dietary behavior, but more research is needed to address the gaps in evidence. In particular, larger, long-term RCTs are needed with population groups at high risk of nutrition-related diseases.

The Emerging Role of Flavonoid‐Rich Cocoa and Chocolate in Cardiovascular Health and Disease

Abstract: Cocoa and chocolate have recently been found to be rich plant-derived sources of antioxidant flavonoids with beneficial cardiovascular properties. These favorable physiological effects include: antioxidant activity, vasodilation and blood pressure reduction, inhibition of platelet activity, and decreased inflammation. Increasing evidence from experimental and clinical studies using cocoa-derived products and chocolate suggest an important role for these high-flavanol-containing foods in heart and vascular protection.

Perinatal choline influences brain structure and function.

Abstract: Choline is derived not only from the diet, but also from de novo synthesis. It is important for methyl-group metabolism, the formation of membranes, kidney function, and neurotransmission. When deprived of dietary choline, most adult men and postmenopausal women develop signs of organ dysfunction (fatty liver or muscle damage) and have a decreased capacity to convert homocysteine to methionine. Choline is critical during fetal development, when it influences stem cell proliferation and apoptosis, thereby altering brain structure and function (memory is permanently enhanced in rodents exposed to choline during the latter part of gestation).

Hydration and Cognitive Function in Children

Abstract: Adequate fluid intake is critical for survival. While adults are at liberty to drink fluids as wanted, children and infants are dependent upon caregivers for food and fluid. Children are at greater risk for dehydration than adults due to their higher surface-to-mass ratio. Additionally, children have different thirst sensitivities and body cooling mechanisms than adults. Children differ from adults in total body water content, and boys and girls differ in body water content with maturation. Research in young adults shows that mild dehydration corresponding to only 1% to 2% of body weight loss can lead to significant impairment in cognitive function. Dehydration in infants is associated with confusion, irritability, and lethargy; in children, it may produce decrements in cognitive performance.

A Potential Role for Vitamin D on Hiv Infection

Abstract: Despite advances in the knowledge of vitamin D's potent immunomodulatory activity, its role on HIV disease progression is unknown. Decreased concentrations of 1α,25-hydroxyvitamin D3, or 1,25(OH)2D, the active form of vitamin D, have been reported among HIV-infected people and attributed to defects in renal hydroxylation and increased utilization. A few studies also described low levels of 25-hydroxyvitamin D3, 25(OH)D, the vitamin obtained from solar synthesis and diet. An inverse association between 1,25(OH)2D concentrations and mortality has been reported from a small cohort of HIV-infected adults, and some cross-sectional studies have indicated positive correlations between 1,25(OH)2D and CD4+ cell counts. Additional observational studies are needed to confirm the associations between vitamin D status and HIV disease progression. These investigations would provide useful insights on the potential role of vitamin D supplementation to HIV-infected persons and the planning of intervention trials.

Vegetarian Diets and Weight Status

Abstract: The increasing global health problems of overweight and obesity are associated with coronary heart disease, hypertension, diabetes, osteoarthritis, and certain cancers, among other health concerns. Vegetarian diets are associated with reduced body weight, lower incidence of certain chronic disease, and lower medical costs compared with non-vegetarian diets. We reviewed the literature to ascertain the extent to which and by what mechanism(s) a plant-based diet may mediate body weight.

Treatment and prevention of obesity: what is the role of exercise?

Abstract: The increasing prevalence of overweight and obesity highlight the need for improved intervention strategies to counteract this significant public health problem. To this end, it appears that increases in energy expenditure through exercise and other forms of physical activity may be an important component of effective interventions to enhance initial weight loss and the prevention of weight regain. However, to achieve these outcomes, adequate levels of exercise and physical activity appear to be necessary, with 60 to 90 min/d currently being recommended. While this appears to be a significant amount of activity, overweight and obese adults should be counseled to progressively increase to these levels of exercise and physical activity. Moreover, there is significant evidence that even if an overweight or obese adult is unable to achieve this level of activity, that significant health benefits can be realized by participating in at least 30 minutes of daily activity that is at least moderate in intensity. Therefore, it is important to have interventions that target these levels of physical activity to improve health-related outcomes and to facilitate long-term weight control.

Plasma Concentrations of Plant Sterols: Physiology and Relationship with Coronary Heart Disease

Abstract: Recently, it has been questioned whether elevated levels of circulating plant sterols increase the risk of coronary heart disease (CHD). To date, no definitive conclusions regarding such a relationship have been reached, nor have there been any studies summarizing the factors that contribute to the observed elevations in plant sterol concentrations in plasma. Thus, the purpose of this review is to systematically compare the plant sterol levels of subjects from the general population and to describe factors that contribute to the variations observed. The question of whether elevated plasma concentrations of plant sterols are associated with an increased risk of CHD was also assessed. Results indicate that the key factors accounting for variations in circulating plant sterol concentrations include: apolipoprotein E phenotypes, ATP-binding cassette transporter polymorphisms, use of statin drugs, presence of metabolic syndrome, dietary intake of plant sterols, gender, and analytical techniques used in the measurement of plant sterols in the plasma. An analysis of the studies examining the relationship between circulating levels of plant sterols and CHD risk in non-sitosterolemic populations revealed no clear associations. Furthermore, it was shown that the above-mentioned factors play an important role in determining the levels of plant sterols in plasma. Since these factors may act as potential confounders, they must be controlled for before more solid conclusions can be reached.

Does a high folate intake increase the risk of breast cancer

Abstract: Although not uniformly consistent, epidemiologic studies generally suggest an inverse association between dietary intake and blood measurements of folate and breast cancer risk. However, the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening trial has recently reported for the first time a potential harmful effect of high folate intake on breast cancer risk. In this study, the risk of developing breast cancer was significantly increased by 20% in women reporting supplemental folic acid intake > or = 400 microg/d compared with those reporting no supplemental intake. Furthermore, although food folate intake was not significantly related to breast cancer risk, total folate intake, mainly from folic acid supplementation, significantly increased breast cancer risk by 32%. The data from the PLCO trial support prior observations made in epidemiologic, clinical, and animal studies suggesting that folate possesses dual modulatory effects on the development and progression of cancer depending on the timing and dose of folate intervention. Based on the lack of compelling supportive evidence, routine folic acid supplementation should not be recommended as a chemopreventive measure against breast cancer at present.

Is 9-cis-retinoic acid the endogenous ligand for the retinoic acid-X receptor?

Abstract: Specific proteins in the nucleus act as transcription factors upon activation through binding of small molecules (all-trans-retinoic acid, thyroid hormone, vitamin D, and others). The activated (liganded) receptors bind to specific DNA elements as heterodimers, each in combination with the retinoic acid-X receptor (RXR). 9-Cis-retinoic acid binds to RXR with high affinity and activates it. Though 9-cis-retinoic acid was initially found in animal tissues, in later work 9-cis-retinoic acid could not be detected. A search for a ligand for RXR in tissues showed that unsaturated fatty acids, particularly linoleic, linolenic, and docosahexaenoic acids, bound to and activated RXR as specific ligands, although with low affinity. A critical experiment demonstrated that, at least in developing mouse skin, 9-cis-retinoic acid is not the ligand for RXR.

Zinc Deficiency in Pregnancy and Fetal Outcome

Abstract: Maternal zinc deficiency during pregnancy has been related to adverse effects on progeny, and there are data showing that mild to moderate zinc deficiency (as assessed by available indicators) is quite common in the developing world. Observational data relating zinc deficiency to adverse fetal outcome have produced conflicting results, mainly because of the lack of a valid indicator of zinc deficiency in pregnancy. Studies of human pregnancy and zinc supplementation, including those from developing countries, have failed to document a consistent beneficial effect on fetal growth, duration of gestation, and early neonatal survival. Preliminary results from unpublished studies in developing countries have also proven to be discouraging. However, recent data and some preliminary findings indicate a beneficial effect of maternal zinc supplementation on neonatal immune status and infant morbidity from infectious diseases, and there is also preliminary evidence that zinc supplementation may prevent congenital malformations (cleft lip/palate). With respect to neurobehavioral development, the evidence is conflicting, with only one study reporting a positive outcome. More research is required to assess the benefits of the large-scale introduction of zinc supplementation during pregnancy on congenital malformations, immune functions, neurobehavior, and overall neonatal survival in countries where zinc deficiency is a problem. Currently available information does not support the routine use of zinc supplementation to improve pregnancy outcome.

Probiotics: Immunomodulation and Evaluation of Safety and Efficacy

Abstract: The intake of probiotics has been associated with beneficial effects on the immune system, such as improved disease resistance and diminished risk of allergies. This review gives an overview of the immunomodulatory effects of probiotics investigated with in vitro assays, experimental animal models, and clinical trials, and explores possible mechanisms underlying the immunomodulatory effects. Immunomodulation, however, is not always beneficial and might induce detrimental effects; therefore, a scheme is proposed for benefit-risk assessment of immunomodulation by probiotics. Within this scheme, expert judgment based on data derived from a panel of in vitro assays, animal models, and clinical trials should lead to conclusions on efficacy and safety aspects of probiotics.

Trans Fatty Acids, Insulin Resistance, and Type 2 Diabetes

Abstract: Type 2 diabetes, a growing global health problem, has a complex etiology involving many interactions between genetic and environmental factors. Essential to the development of the disease is insulin resistance of the peripheral tissues. Insulin resistance may be partly modified by the specific types of dietary fatty acids. Trans fatty acids (TFAs), created through the transformation of polyunsaturated fatty acids from their natural cis form to the trans form, are abundant in the Western diet. TFAs take on similar properties as saturated fats, and appear to be more atherogenic. High intakes of saturated fats may promote insulin resistance. It is therefore reasonable to hypothesize that high intakes of TFAs would have similar, or stronger, effects. In this review, all current evidence on the topic of TFAs, insulin resistance, and type 2 diabetes is summarized and interpreted. Although there is some support from observational and experimental studies for the hypothesis that high intakes of TFAs may increase the risk for type 2 diabetes, inconsistencies across studies and methodological problems make it premature to draw definitive conclusions at this time. More experimental research in humans is needed to further address this question.

Calorie restriction increases life span: a molecular mechanism.

Abstract: Calorie restriction increases the life span of many organisms, from yeast to mammals. In yeast, the life span gene affected by calorie restriction is Sir2 (silent information regulator 2). In mammals, Sirt1, an ortholog of Sir2, controls the metabolism of white adipose tissue. Calorie restriction activates Sirt1, and the expressed Sirt1 protein inhibits the action of peroxysome proliferator-activator receptor gamma (PPARgamma), the nuclear receptor that promotes adipogenesis. The effect is lipolysis and loss of fat. Lowering of adiposity appears to be one mechanism whereby calorie restriction affects life span.

Early Nutrition and Long-Term Cardiovascular Health

Abstract: Evidence that early nutrition can influence (program) later cardiovascular health was first obtained for the long-term effects of overfeeding in animals. This concept is now supported in humans by evidence for a beneficial effect of breast-feeding on the major components of the metabolic syndrome (obesity, blood pressure, cholesterol metabolism, and insulin resistance) that affect cardiovascular risk. The size of this effect is large and relevant for public health. The potential mechanisms involved include a benefit of slower weight gain in breast-fed compared with formula-fed babies.

Nutrition recommendations for the treatment and prevention of type 2 diabetes and the metabolic syndrome: an evidenced-based review.

Abstract: Nutritional recommendations for the prevention and management of diabetes and other diseases were in the past based principally upon the opinion of “expert” committees. Leading clinicians and researchers who served on such committees were expected to base their advice on their own clinical experience or research, or on that of others known to them. More recently, in parallel with the development of evidence-based medicine, nutritional management is required to be based on evidence-based nutrition. This involves a prescribed method for searching the relevant literature using an agreed set of descriptors and relevant data banks (e.g., Medline, Embase). Individual studies are evaluated according to specified criteria and assigned to one of five evidence classes according to the type and quality of the study (Table 1). Recommendations themselves are graded according to the strength of the evidence. Grade A recommendations are based on evidence of class Ia or Ib, which require meta-analyses of randomized, controlled clinical trials, or at least one appropriately conducted randomized, controlled trial. Ideally, evidence-based guidelines are based upon trials with fatal or nonfatal clinical endpoints. Given the complexities of large-scale nutritional intervention studies, which are required to produce such clinical endpoints, it is often necessary to base recommendations on surrogate endpoints. Surrogate endpoints relevant to the management of diabetes are shown in Table 2. In the past 4 years, there have been several randomized, controlled trials that have examined the role of lifestyle modification in the prevention of diabetes among persons at high risk who have already developed impaired glucose tolerance. It has thus been possible to generate evidence-based recommendations for the prevention and the management of type 2 diabetes. Randomized, controlled trials that have examined potential agents for the prevention of type 1 diabetes have not confirmed the potential of any of the agents tested to reduce risk. The Diabetes and Nutrition Study Group (DNSG) of the European Association for the Study of Diabetes (EASD) has recently published its guidelines derived from evidence-based nutritional approaches to the treatment and prevention of diabetes mellitus, upon which this review is largely based.

How an increased intake of alpha-tocopherol can suppress the bioavailability of gamma-tocopherol.

Abstract: α-Tocopherol is the only form of vitamin E in vitamin supplements, whereas γ-tocopherol is the predominant form of vitamin E in the US diet. γ-Tocopherol has beneficial properties as an anti-inflammatory and possibly anti-atherogenic and anticancer agent. Excess α-tocopherol taken in supplements causes a reduction of γ-tocopherol concentration in plasma. The biochemical mechanism of this effect, which is important to human nutrition, has recently been elucidated.

Measurement of Food Availability in the Home

Abstract: The importance of environment on food choices has recently received increased attention. One environment likely to be influential is the home food environment. This review examines 23 studies that used either researcher-conducted open inventories or self-report checklists to assess food availability in the home. Only three were open inventories (this technique is rarely used, most likely because of low feasibility). Self-report checklists varied in length and the items included. Two checklists, validated using observation, showed high sensitivity and specificity (87% or above). We provide recommendations to develop and validate population-specific tools that measure home food availability.

The elimination of trans fats from spreads: how science helped to turn an industry around.

Abstract: Mensink and Katan showed in 1990 that trans fats reduce high- and increase low-density lipoprotein cholesterol. Unilever aided this study because the company considered knowledge on trans fats incomplete in spite of their long history of safe use. The decision in 1994 to remove trans fats from Unilever's retail spreads was triggered by media events, but it was built on a solid understanding of the nutritional and technological aspects of trans fats. Over the next 14 years, manufacturers worldwide followed suit. This experience illustrates that food companies need to know about the health effects of their products and how to apply that knowledge.

Dietary therapy in idiopathic nephrolithiasis.

Abstract: Like other diseases striking predominantly the affluent societies, idiopathic nephrolithiasis is increasing in rich countries and appears to be closely related to dietary habits In this review we summarize the latest evidence about the efficacy of dietary treatment for idiopathic calcium and uric acid stones, dealing especially with its effect on the urinary stone risk factors, stone recurrences, and clinical limitations After a short introduction on epidemiology and pathogene-sis, we review the role of the most important foods and nutrients in stone formation and protection: water and other fluids, proteins, carbohydrates, fats, salt, milk and dairy products, fruits and vegetables, and vitamins The final part of the paper will provide practical guidelines for pursuing an anti-lithogenic diet in idiopathic calcium and uric acid stones