Showing papers in "Nutrition Reviews in 2009"

Polyphenols: Chemistry, Dietary Sources, Metabolism, and Nutritional Significance

Abstract: Polyphenols constitute one of the most numerous and ubiquitous groups of plant metabolites and are an integral part of both human and animal diets. Ranging from simple phenolic molecules to highly polymerized compounds with molecular weights of greater than 30,000 Da, the occurrence of this complex group of substances in plant foods is extremely variable. Polyphenols traditionally have been considered antinutrients by animal nutritionists, because of the adverse effect of tannins, one type of polyphenol, on protein digestibility. However, recent interest in food phenolics has increased greatly, owing to their antioxidant capacity (free radical scavenging and metal chelating activities) and their possible beneficial implications in human health, such as in the treatment and prevention of cancer, cardiovascular disease, and other pathologies. Much of the literature refers to a single group of plant phenolics, the flavonoids. This review offers an overview of the nutritional effects of the main groups of polyphenolic compounds, including their metabolism, effects on nutrient bioavailability, and antioxidant activity, as well as a brief description of the chemistry of polyphenols and their occurrence in plant foods.

Health benefits of dietary fiber

Abstract: Dietary fiber intake provides many health benefits. However, average fiber intakes for US children and adults are less than half of the recommended levels. Individuals with high intakes of dietary fiber appear to be at significantly lower risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases. Increasing fiber intake lowers blood pressure and serum cholesterol levels. Increased intake of soluble fiber improves glycemia and insulin sensitivity in non-diabetic and diabetic individuals. Fiber supplementation in obese individuals significantly enhances weight loss. Increased fiber intake benefits a number of gastrointestinal disorders including the following: gastroesophageal reflux disease, duodenal ulcer, diverticulitis, constipation, and hemorrhoids. Prebiotic fibers appear to enhance immune function. Dietary fiber intake provides similar benefits for children as for adults. The recommended dietary fiber intakes for children and adults are 14 g/1000 kcal. More effective communication and consumer education is required to enhance fiber consumption from foods or supplements.

Selenium: Biochemical Role as a Component of Glutathione Peroxidase

Abstract: When hemolyzates from erythrocytes of selenium-deficient rats were incubated in vitro in the presence of ascorbate or H(2)O(2), added glutathione failed to protect the hemoglobin from oxidative damage. This occurred because the erythrocytes were practically devoid of glutathione-peroxidase activity. Extensively purified preparations of glutathione peroxidase contained a large part of the (75)Se of erythrocytes labeled in vivo. Many of the nutritional effects of selenium can be explained by its role in glutathione peroxidase.

The Nutrition Transition: New Trends in the Global Diet

Abstract: Analyses of economic and food availability data for 1962–1994 reveal a major shift in the structure of the global diet marked by an uncoupling of the classic relationship between incomes and fat intakes. Global availability of cheap vegetable oils and fats has resulted in greatly increased fat consumption among low-income nations. Consequently, the nutrition transition now occurs at lower levels of the gross national product than previously, and is accelerated further by high urbanization rates. Data from Asian nations, where diet structure is rapidly changing, suggest that diets higher in fats and sweeteners are also more diverse and more varied. Given that preferences for palatable diets are a universal human trait, fat consumption may be governed not by physiological mechanisms but by the amount of fat available in the food supply. Whereas economic development has led to improved food security and better health, adverse health effects of the nutrition transition include growing rates of childhood obesity. The implications of these trends are explored.

Free radicals and antioxidants: a personal view.

Abstract: Free radicals and other oxygen-derived species are constantly generated in vivo, both by “accidents of chemistry” and for specific metabolic purposes. The reactivity of different free radicals varies, but some can cause severe damage to biological molecules, especially to DNA, lipids, and proteins. Antioxidant defense systems scavenge and minimize the formation of oxygen-derived species, but they are not 100% effective. Hence, diet-derived antioxidants may be particularly important in diminishing cumulative oxidative damage and helping us to stay healthier for longer. Repair systems exist to deal with molecules that have been oxidatively damaged. Damage to DNA by hydroxyl radicals appears to occur in all aerobic cells, and might be a significant contributor to the age-dependent development of cancer. Lipid peroxidation probably contributes significantly to the development of atherosclerosis.

Dietary Fiber and Weight Regulation

Abstract: The influence of dietary fiber on energy regulation remains controversial. This review summarizes published studies on the effects of dietary fiber on hunger, satiety, energy intake, and body composition in healthy individuals. Under conditions of fixed energy intake, the majority of studies indicate that an increase in either soluble or insoluble fiber intake increases postmeal satiety and decreases subsequent hunger. When energy intake is ad libitum, mean values for published studies indicate that consumption of an additional 14 g/day fiber for >2 days is associated with a 10% decrease in energy intake and body weight loss of 1.9 kg over 3.8 months. Furthermore, obese individuals may exhibit a greater suppression of energy intake and body weight loss (mean energy intake in all studies was reduced to 82% by higher fiber intake in overweight/obese people versus 94% in lean people; body weight loss was 2.4 kg versus 0.8 kg). These amounts are very similar to the mean changes in energy intake and body weight changes observed when dietary fat content is lowered from 38% to 24% of energy intake in controlled studies of nonobese and obese subjects. The observed changes in energy intake and body weight occur both when the fiber is from naturally high-fiber foods and when it is from a fiber supplement. In view of the fact that mean dietary fiber intake in the United States is currently only 15 g/day (i.e., approximately half the American Heart Association recommendation of 25-30 g/day), efforts to increase dietary fiber in individuals consuming <25 g/day may help to decrease the currently high national prevalence of obesity.

The Nutrition Transition in Low-Income Countries: An Emerging Crisis

Abstract: Scientists have long recognized the importance of the demographics and epidemiologic transitions in higher income countries. Only recently has it become understood that similar sets of broadly based changes are occurring in lower income countries. What has not been recognized is that concurrent changes in nutrition are also occurring, with equally important implications for resource allocation in many low-income countries. Several major changes seem to be emerging, leading to a marked shift in the structure of diet and the distribution of body composition in many regions of the world: a rapid reduction in fertility and aging of the population, rapid urbanization, the epidemiologic transition, and economic changes affecting populations in different and uneven ways. These changes vary significantly over time. In general, we find that problems of under- and overnutrition often coexist, reflecting the trend in which an increasing proportion of people consume the types of diets associated with a number of chronic diseases. This is occurring more rapidly than previously seen in higher income countries, or even in Japan and Korea. Examples from Thailand, China, and Brazil provide evidence of the changes and trends in dietary intake, physical activity, and body composition patterns.

Lycopene: Chemistry, Biology, and Implications for Human Health and Disease

Abstract: A diet rich in carotenoid-containing foods is associated with a number of health benefits. Lycopene provides the familiar red color to tomato products and is one of the major carotenoids in the diet of North Americans and Europeans. Interest in lycopene is growing rapidly following the recent publication of epidemiologic studies implicating lycopene in the prevention of cardiovascular disease and cancers of the prostate or gastrointestinal tract. Lycopene has unique structural and chemical features that may contribute to specific biological properties. Data concerning lycopene bioavailability, tissue distribution, metabolism, excretion, and biological actions in experimental animals and humans are beginning to accumulate although much additional research is necessary. This review will summarize our knowledge in these areas as well as the associations between lycopene consumption and human health.

The Obesity Epidemic Is a Worldwide Phenomenon

Abstract: Obesity is not just a disease of developed nations. Obesity levels in some lower-income and transitional countries are as high as or higher than those reported for the United States and other developed countries, and those levels are increasing rapidly. Shifts in diet and activity are consistent with these changes, but little systematic work has been done to understand all the factors contributing to these high levels. The goal of this review is to provide an understanding of the patterns and trends of obesity arounnd the world and some of the major forces affecting these trends. Several nationally representative and nationwide surveys are discussed.

Thromboxanes: a new group of biologically active compounds derived from prostaglandin endoperoxides

Abstract: An unstable [t1/2 at 37 degrees = 32 +/- 2 (SD) sec] intermediate, thromboxane A2, was detected in the conversion of prostaglandin G2 into 8-(1-hydroxy-3-oxopropyl)-9,12L-dihydroxy-5,10-heptadecadienoic acid (thromboxane B2) in platelets. The intermediate was trapped by addition of methanol, ethanol, or sodium azide to suspensions of washed human platelets incubated for 30 sec with arachidonic acid or prostaglandin G2. The structures of the resulting derivatives demonstrated that the intermediate possessed an oxane ring as in thromboxane B2 but lacked its hemiacetal hydroxyl group. Additional experiments using 18O2 or [2H8]arachidonic acid in the formation of thromboxane B2 and CH3O2H for the trapping of thromboxane A2, together with information on the t1/2 of the intermediate, indicated the presence of an oxetane structure in thromboxane A2. Incubation of arachidonic acid or prostaglandin G2 with washed platelets led to formation of an unstable factor that induced irreversible platelet aggregation and caused release of [14C]serotonin from platelets that had been incubated with [14C]serotonin. The properties and the mode of formation of this factor indicated that it was identical with thromboxane A2. Furthermore, evidence is presented that the more unstable and major component of rabbit aorta contracting substance (RCS) formed in platelets and guinea pig lung is also thromboxane A2.

Is Glutamine a Conditionally Essential Amino Acid

Abstract: The nonessential amino acid glutamine has recently been the focus of extensive scientific interest because of its importance in cell and tissue cultures and its physiologic role in animals and humans Glutamine appears to be a unique amino acid, serving as a preferred respiratory fuel for rapidly proliferating cells, such as enterocytes and lymphocytes; a regulator of acid-base balance through the production of urinary ammonia; a carrier of nitrogen between tissues; and an important precursor of nucleic acids, nucleotides, amino sugars, and proteins Abundant evidence suggests that glutamine may become a “conditionally essential” amino acid in the critically ill During stress the body's requirements for glutamine appear to exceed the individual's ability to produce sufficient amounts of this amino acid Provision of supplemental glutamine in specialized enteral or parenteral feeding may enhance nutritional management and augment recovery of the seriously ill while minimizing hospital stay

Choline: an essential nutrient for public health

Abstract: Choline was officially recognized as an essential nutrient by the Institute of Medicine (IOM) in 1998. There is significant variation in the dietary requirement for choline that can be explained by common genetic polymorphisms. Because of its wide-ranging roles in human metabolism, from cell structure to neurotransmitter synthesis, choline-deficiency is now thought to have an impact on diseases such as liver disease, atherosclerosis, and, possibly, neurological disorders. Choline is found in a wide variety of foods. Eggs and meats are rich sources of choline in the North American diet, providing up to 430 milligrams per 100 grams. Mean choline intakes for older children, men, women, and pregnant women are far below the adequate intake level established by the IOM. Given the importance of choline in a wide range of critical functions in the human body, coupled with less-than-optimal intakes among the population, dietary guidance should be developed to encourage the intake of choline-rich foods.

Environmental and societal factors affect food choice and physical activity: rationale, influences, and leverage points.

Abstract: Sarah L. Booth, Ph.D., Vitamin K Laboratory, Jean Mayer USDAHuman Nutrition Research Center on Aging at Tufts University, Boston, MA; James F. Sallis, Ph.D., F.A.C.S.M., Department ofPsychology, San Diego State University, San Diego, CA; Cheryl Ritenbaugh, Ph.D., M.P.H., Kaiser Permanente Center for Health Research, Portland, O R James 0. Hill, Ph.D., Center for Human Nutrition, University of Colorado Health Sciences Center, Denver, CO; Leann L. Birch, Ph.D., Department ofHuman Development and Family Studies, Pennsylvania State University, University Park, PA; Lawrence D. Frank, Ph.D., College OfArchitecture, Georgia Institute of Technology, Atlanta, GA; Karen Glanz, Ph.D., M.P.H., Cancer Research Center of Hawaii, University of Hawaii, Honolulu, HI; David A. Himmelgreen, Ph.D., Department ofAnthropology, University of South Florida, Tampa, FL; Michael Mudd, Corporate Affairs, Kraft Foods, Inc., Northfield, IL; Barry M. Popkin, Ph.D., Department ofNutrition, Carolina Population Center, University of North Carolina, Chapel Hill, NC; Karyl A. Rickard, Ph.D., R.D., C.S.P., F.A.D.A., Nutrition and Dietetics Program, School ofAllied Health Sciences, Indiana University School of Medicine, Indianapolis, IN; Sachiko St. Jeor, Ph.D., R.D., Nutrition Education and Research Program, University of Nevada School of Medicine, Reno, W, Nicholas P. Hays, M.S., Energy Metabolism Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA.

Uptake and Metabolism of Plasma Glutamine by the Small Intestine

Abstract: An isolated, vascularly perfused preparation of rat intestine extracted large amounts of glutamine (75 µmoles per hour), but no other amino acid, from a recirculated blood perfusate. With l-[U-14C]glutamine, the carbon was partly incorporated into tissue acid-insoluble material (14%) and the rest reappeared with little delay in intestinal venous blood in CO2 (57%), citrulline (6%), proline (5%), and organic acids (18%), predominantly citric acid and lactic acid. Perfusate glutamine was the source of 32% of the CO2 produced by the preparation, although the perfusate contained 10 to 15 mm glucose. Most glutamine uptake and metabolism occurred in the small intestinal mucosal cells and, from analyses of labeled tissue metabolites, appeared to proceed via glutamic acid. The rapid flow of glutamine carbon through mucosa may be explained in part by the small glutamine pool, only 0.2 µmole per g of tissue. Glutamine nitrogen taken up by intestine could be approximately accounted for by the quantities of citrulline (34%), alanine (33%), ammonia (23%), and proline (10%) released back into the perfusate. Glutamine uptake comparable to that found in the isolated organ was observed in vivo, from arteriovenous concentration measurements across intestine in fasted dogs, cats, hamsters, monkeys, and conventional and germ-free rats. Twenty-five to 33% of plasma glutamine was extracted in each pass through the tissue. Glutamine uptake persisted in rats during transport of large amounts of glutamic acid from the intestinal lumen into the blood and in rats injected with 6-diazo-5-oxo-l-norleucine. The results of these studies suggest that glutamine derived from blood is an important respiratory substrate for cells in the small intestinal mucosa and that intestine is a major site for metabolism of glutamine released into the circulation by other tissues.

Enzyme Secretion and the Incorporation of P32 into Phospholipides of Pancreas Slices

Abstract: 1. When enzyme secretion was stimulated by carbamylcholine or acetylcholine (with eserine) in slices of pigeon pancreas, the incorporation of P32 into the phospholipide fraction of the stimulated slices was, after 2 hours, 4.8 to 8.7 (average, 7.0) times greater than the incorporation of P32 into the phospholipides of control slices. Neither respiration nor the incorporation of P32 into acid-soluble phosphate esters was increased. 2. Pilocarpine, which on a weight for weight basis was much less effective than carbamylcholine or acetylcholine in stimulating enzyme secretion in pancreas slices, was also much less effective in stimulating the uptake of P32 into phospholipides. 3. The stimulatory effects of carbamylcholine on both enzyme secretion and the incorporation of P32 into phospholipides were abolished by atropine. 4. The specific activity of the phospholipides from slices incubated anaerobically was less than 5 per cent of that observed aerobically. Anaerobically, carbamylcholine did not stimulate the incorporation of P32 into phospholipides to any significant extent. The specific activity of the acid-soluble phosphate esters after anaerobic incubation was 34 per cent of that found aerobically. 5. Cholinergic drugs had little or no effect on the incorporation of P32 into the phospholipides of the following tissue slices: pigeon and guinea pig liver, guinea pig heart ventricle, pigeon gizzard (smooth muscle), and guinea pig kidney cortex. A relatively slight stimulation of P32 uptake into phospholipides was observed in slices of pigeon brain (65 per cent) and guinea pig brain cortex (40 per cent). 6. Stimulation of amylase synthesis in slices of pigeon pancreas by the addition of a mixture of amino acids had no effect on the incorporation of P32 into phospholipides.

Philosophical Transactions of the Royal Society of London. for the Year Mdcccxxvii. Part I. Volume Cxvii:355–388, 1827

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How Accurate Is Self-Reported Dietary Energy Intake?

Abstract: The measurement of dietary intake by self-report has played a central role in nutritional science for decades. Despite its important role, however, little is known about the accuracy of self-reported intake. Recently, the doubly-labeled water method has been validated for the measurement of total energy expenditure in free-living subjects, and this method can serve as a reference for validating the accuracy of self-reported energy intake. Such comparisons have been made in nine recent studies, and considerable inaccuracy in self-reports of energy intake has been documented. Reported intakes tend to be lower than expenditure and thus are often underestimates of true habitual energy intake. Because the degree of underreporting increases with intake, it is speculated that individuals tend to report intakes that are closer to perceived norms than to actual intake.

Obesity, diets, and social inequalities

Abstract: Obesity and type 2 diabetes follow a socioeconomic gradient. Highest rates are observed among groups with the lowest levels of education and income and in the most deprived areas. Inequitable access to healthy foods is one mechanism by which socioeconomic factors influence the diet and health of a population. As incomes drop, energy-dense foods that are nutrient poor become the best way to provide daily calories at an affordable cost. By contrast, nutrient-rich foods and high-quality diets not only cost more but are consumed by more affluent groups. This article discusses obesity as an economic phenomenon. Obesity is the toxic consequence of economic insecurity and a failing economic environment.

Healthy Traditional Mediterranean Diet: an Expression of Culture, History, and Lifestyle

Abstract: The term Mediterranean diet refers to dietary patterns found in olive-growing areas of the Mediterranean region and described in the 1960s and beyond. There are several variants of the Mediterranean diet, but some common components can be identified: high monounsaturated/saturated fat ratio; ethanol consumption at moderate levels and mainly in the form of wine; high consumption of vegetables, fruits, legumes, and grains; moderate consumption of milk and dairy products, mostly in the form of cheese; and low consumption of meat and meat products. Growing evidence demonstrates that the Mediterranean diet is beneficial to health; the evidence is stronger for coronary heart disease, but it also applies to some forms of cancer. Results from recent investigations provide a strong biomedical foundation for the beneficial effects of the Mediterranean diet.

Tissue changes following deprivation of fat‐soluble a vitamin.

Abstract: The specific tissue changes which follow the deprivation of fat-soluble vitamin A in albino white rats and in the human concerns epithelial tissues. This effect is the substitution of stratified keratinizing epithelium for normal epithelium in various parts of the respiratory tract, alimentary tract, eyes, and paraocular glands and the genitourinary tract. We have described the morphological sequences which clearly show that the replacement of epithelium arises from focal proliferation of cells arising from the original epithelium and not by differentiation or change of preexisting cells. Young rats respond to the deficiency more promptly than adults. Growth activity of epithelium is not diminished. On the contrary, there is convincing evidence that it is greatly augmented. In a few of our animals the behavior of the replacing epithelium in respect to numbers of mitotic figures and response on the part of connective tissue and blood vessels suggests the acquisition of neoplastic properties. While the epitheliums which are the seats of these changes are largely of covering types, glandular epithelium is involved, specifically in the paraocular glands and salivary glands. It is highly probable also that the epithelium of gland ducts, respiratory mucosa, and genitourinary tract have secretory functions so that we conclude that the deficiency results in loss of specific (chemical) functions of the epitheliums concerned, while the power of growth becomes augmented. Explanation for the substitution of a chemically inactive (nonsecretory) epithelium, common in type for all locations, remains a matter of speculation. We can only speculate also in regard to the absence of change in the epithelium of such organ as the liver, parenchyma of the kidney, stomach, and intestines. The significance of the order or sequence in which different organs exhibit this change has not been determined. In general the respiratory mucosa in nares, trachea, and bronchi respond first, then the salivary glands, eye, genitourinary tract, then paraocular glands and pancreas, although as has been noted there are exceptions to this order. Our studies show that the mitochondrial apparatus is not primarily affected. Study of individual cells indicates that the first morphological evidence of avitaminosis will be found in the nucleus. We have not devoted sufficient study to be certain, but an increase of chromatin and in some instances in size of nucleoli are early morphological manifestations. Other important effects of fat-soluble A deficiency are atrophy of glandular organs, emaciation, localized edema of testes, submaxillary gland, and connective tissue structures of the lungs and focal myocardial lesions. From our own limited experience with rats fed on a water-soluble B deficient diet and from work by Cramer, Drew, and Mottram, the loss of fat in water-soluble B deficiency is as great, if not greater than in vitamin A deuciency, so that tor tne present we assume that this is not a specific manifestation of any one avitaminosis. The same applies to glandular atrophy. Both of these effects probably concern the nutrition as a whole and may be ascribed to inanition. The occurrence of transient edema in testes and salivary gland coinciding with a period of maximum atrophic change, suggests the hypothesis that this edema is the result of failure of epithelium to utilize transported material, which leads further to the hypothesis that the capillaries of these organs are differentiated in regard to permeability to the respective materials utilized by the cells. It would seem that in the case of the testis we have a unique instance of complete atrophy producible at will without impairment of circulation and supporting tissues. This phenomenon may possibly be followed with advantage in the study of the mechanism of edema. Vascularization of the cornea, as we have shown it to be independent of infection, must be a physiological response to the increased demands of the rapidly growing epithelium which has replaced the corneal epithelium. We have assumed throughout this work that the diet on which we kept our animals was deficient in respect to a single substance or group of substances having similar physiological properties, designated by the term fat-soluble vitamin A. Whether or not more than one so called vitamin or accessory substance was missing in the diet we employed does not affect the theoretical importance of the morphological results. Work by Evans and Bishop would indicate that other factors affecting fertility in addition to the so called antixerophthalmic or vitamin A factor may have been missing. Our own experience leads us to believe the specific effects we have described upon epithelial tissues were in all probability due to withdrawal of a single factor. We have shown how these effects, that is the replacement of uterine epithelium by keratinizing epithelium can account for sterility in the female. Whether or not the atrophy of the testis is due to the same factor remains to be proved, but presumptive evidence is strong that this is the case. The study of the reverse changes that follow in the rapid amelioration when the rats are restored to an adequate diet has been begun and will be reported later. We have shown that the substitution of keratinizing epithelium in all locations is not secondary to infections, and presumably is a primary effect of the withdrawal of factors essential for the chemical activities or maintenance of differentiation of the epitheliums concerned. It is, of course, possible that the phenomenon is produced in a roundabout way in that it may be secondary to the effects of the avitaminosis upon the metabolism of tissue-sustaining substances. This possibility is supported by the cessation of growth of the skeleton and teeth, although we know that other avitaminoses produce retardation of growth.

Nutrition classics. The Journal of Laboratory and Clinical Medicine, Volume 92, 1978: Menopausal changes in calcium balance performance.

Abstract: Editor's Note: This paper is one of the first suggesting that idiapathic osteoporosis may be n disorder of calcium metabolism for which increased intakes calcium mas be preventative.

Fish Consumption and Risk of Sudden Cardiac Death

Abstract: Studies show conflicting results regarding the protective effect of dietary fish and fish oil on certain types of cardiovascular disease. A recent epidemiologic study supports the hypothesis that moderate consumption (1–2 meals/week) of fish lowers the risk of sudden cardiac death in humans.

Sensory-specific Satiety

Abstract: ll animals, but especially omnivores such as rats and humans, face the seemingly daunting task of selecting a diet that supplies all of the essential nutrients. The complexity of factors that can affect food selection was out­lined in a recent review which listed the follow­ing influences on the appetite for specific foods: metabolic influences (eg, caloric requirements, neurotransmitter levels, hor­mones); specific appetites (eg, NaCI when salt-deficient); disease states (eg, diabetes, cancer); pharmacological influences (eg, ano­rectic drugs); environmental influences (eg, temperature); social influences (eg, culture, re­ligion); learned preferences and aversions; and hedonic factors (eg, palatability, taste, tex­ture, odor).