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Eur J Cancer ; Association of antioxidants with memory in a multiethnic elderly sample using the Third National Health and Nutrition Examination Survey. Int J Obes Lond. B For good health, carbohydrate intake from vegetables, fruits, whole grains, legumes, and dairy products should be advised over intake from other carbohydrate sources, especially those that contain added fats, sugars, or sodium. Predicting adult obesity from childhood obesity: Lancet ;
Table of Contents
Grapes also contain a fair amount of fiber. These are a few example forms of fiber that have been sold as supplements or food additives. These may be marketed to consumers for nutritional purposes, treatment of various gastrointestinal disorders , and for such possible health benefits as lowering cholesterol levels, reducing risk of colon cancer , and losing weight. Soluble fiber supplements may be beneficial for alleviating symptoms of irritable bowel syndrome , such as diarrhea or constipation and abdominal discomfort.
One insoluble fiber, resistant starch from high-amylose corn, has been used as a supplement and may contribute to improving insulin sensitivity and glycemic management    as well as promoting regularity  and possibly relief of diarrhea. Chemically defined as oligosaccharides occurring naturally in most plants, inulins have nutritional value as carbohydrates , or more specifically as fructans , a polymer of the natural plant sugar, fructose.
Inulin is typically extracted by manufacturers from enriched plant sources such as chicory roots or Jerusalem artichokes for use in prepared foods. As a prebiotic fermentable fiber, its metabolism by gut flora yields short-chain fatty acids see below which increase absorption of calcium ,  magnesium ,  and iron ,  resulting from upregulation of mineral-transporting genes and their membrane transport proteins within the colon wall.
Among other potential beneficial effects noted above, inulin promotes an increase in the mass and health of intestinal Lactobacillus and Bifidobacterium populations. Inulin's primary disadvantage is its tolerance. Vegetable gum fiber supplements are relatively new to the market. Often sold as a powder, vegetable gum fibers dissolve easily with no aftertaste. In preliminary clinical trials, they have proven effective for the treatment of irritable bowel syndrome.
Many molecules that are considered to be "dietary fiber" are so because humans lack the necessary enzymes to split the glycosidic bond and they reach the large intestine.
Many foods contain varying types of dietary fibers, all of which contribute to health in different ways. Dietary fibers make three primary contributions: Some fibers contribute through one primary mechanism. For instance, cellulose and wheat bran provide excellent bulking effects, but are minimally fermented. Alternatively, many dietary fibers can contribute to health through more than one of these mechanisms.
For instance, psyllium provides bulking as well as viscosity. Bulking fibers can be soluble i. They absorb water and can significantly increase stool weight and regularity. Most bulking fibers are not fermented or are minimally fermented throughout the intestinal tract. Viscous fibers thicken the contents of the intestinal tract and may attenuate the absorption of sugar, reduce sugar response after eating, and reduce lipid absorption notably shown with cholesterol absorption.
Their use in food formulations is often limited to low levels, due to their viscosity and thickening effects. Some viscous fibers may also be partially or fully fermented within the intestinal tract guar gum, beta-glucan, glucomannan and pectins , but some viscous fibers are minimally or not fermented modified cellulose such as methylcellulose and psyllium.
Fermentable fibers are consumed by the microbiota within the large intestines, mildly increasing fecal bulk and producing short-chain fatty acids as byproducts with wide-ranging physiological activities discussion below. Resistant starch , inulin , fructooligosaccharide and galactooligosaccharide are dietary fibers which are fully fermented. These include insoluble as well as soluble fibers. This fermentation influences the expression of many genes within the large intestine,  which affect digestive function and lipid and glucose metabolism, as well as the immune system, inflammation and more.
Dietary fibers can change the nature of the contents of the gastrointestinal tract and can change how other nutrients and chemicals are absorbed through bulking and viscosity. Insoluble fiber is associated with reduced risk of diabetes, but the mechanism by which this is achieved is unknown.
Not yet formally proposed as an essential macronutrient , dietary fiber has importance in the diet, with regulatory authorities in many developed countries recommending increases in fiber intake. Dietary fiber has distinct physicochemical properties. Most semi-solid foods, fiber and fat are a combination of gel matrices which are hydrated or collapsed with microstructural elements, globules, solutions or encapsulating walls. Fresh fruit and vegetables are cellular materials.
Micelles are colloid-sized clusters of molecules which form in conditions as those above, similar to the critical micelle concentration of detergents. The multiple physical phases in the intestinal tract slow the rate of absorption compared to that of the suspension solvent alone. Adding viscous polysaccharides to carbohydrate meals can reduce post-prandial blood glucose concentrations.
Wheat and maize but not oats modify glucose absorption, the rate being dependent upon the particle size. The reduction in absorption rate with guar gum may be due to the increased resistance by viscous solutions to the convective flows created by intestinal contractions. Dietary fiber interacts with pancreatic and enteric enzymes and their substrates. Human pancreatic enzyme activity is reduced when incubated with most fiber sources. Fiber may affect amylase activity and hence the rate of hydrolysis of starch.
The more viscous polysaccharides extend the mouth-to- cecum transit time; guar, tragacanth and pectin being slower than wheat bran. The substrates utilized by the cecum have either passed along the entire intestine or are biliary excretion products. The effects of dietary fiber in the colon are on. Enlargement of the cecum is a common finding when some dietary fibers are fed and this is now believed to be normal physiological adjustment. Such an increase may be due to a number of factors, prolonged cecal residence of the fiber, increased bacterial mass, or increased bacterial end-products.
Some non-absorbed carbohydrates, e. Almost all of these short-chain fatty acids will be absorbed from the colon. This means that fecal short-chain fatty acid estimations do not reflect cecal and colonic fermentation, only the efficiency of absorption, the ability of the fiber residue to sequestrate short-chain fatty acids, and the continued fermentation of fiber around the colon, which presumably will continue until the substrate is exhausted.
The production of short-chain fatty acids has several possible actions on the gut mucosa. All of the short-chain fatty acids are readily absorbed by the colonic mucosa, but only acetic acid reaches the systemic circulation in appreciable amounts. Butyric acid appears to be used as a fuel by the colonic mucosa as the preferred energy source for colonic cells.
Dietary fiber may act on each phase of ingestion, digestion, absorption and excretion to affect cholesterol metabolism,  such as the following:. An important action of some fibers is to reduce the reabsorption of bile acids in the ileum and hence the amount and type of bile acid and fats reaching the colon.
A reduction in the reabsorption of bile acid from the ileum has several direct effects. The fibers that are most effective in influencing sterol metabolism e. It is therefore unlikely that the reduction in body cholesterol is due to adsorption to this fermented fiber in the colon.
Feces consist of a plasticine-like material, made up of water, bacteria, lipids, sterols, mucus and fiber. Wheat bran is minimally fermented and binds water and when added to the diet increases fecal weight in a predictable linear manner and decreases intestinal transit time.
The particle size of the fiber is all-important, coarse wheat bran being more effective than fine wheat bran. The greater the water-holding capacity of the bran, the greater the effect on fecal weight. The fermentation of some fibers results in an increase in the bacterial content and possibly fecal weight. Research has shown that fiber may benefit health in several different ways. Lignin and probably related materials that are resistant to enzymatic degradation, diminish the nutritional value of foods.
Fiber does not bind to minerals and vitamins and therefore does not restrict their absorption, but rather evidence exists that fermentable fiber sources improve absorption of minerals, especially calcium. The analytic cohort consisted of , men and , women aged 50—71 years. Diet was assessed with a self-administered food-frequency questionnaire at baseline in —; 2, incident colorectal cancer cases were identified during five years of follow-up.
The result was that total fiber intake was not associated with colorectal cancer. Although many researchers believe that dietary fiber intake reduces risk of colon cancer, one study conducted by researchers at the Harvard School of Medicine of over 88, women did not show a statistically significant relationship between higher fiber consumption and lower rates of colorectal cancer or adenomas.
Dietary fiber has many functions in diet, one of which may be to aid in energy intake control and reduced risk for development of obesity. The role of dietary fiber in energy intake regulation and obesity development is related to its unique physical and chemical properties that aid in early signals of satiation and enhanced or prolonged signals of satiety.
Early signals of satiation may be induced through cephalic- and gastric-phase responses related to the bulking effects of dietary fiber on energy density and palatability, whereas the viscosity-producing effects of certain fibers may enhance satiety through intestinal-phase events related to modified gastrointestinal function and subsequent delay in fat absorption.
In general, fiber-rich diets, whether achieved through fiber supplementation or incorporation of high fiber foods into meals, have a reduced energy density compared with high fat diets. There are also indications that women may be more sensitive to dietary manipulation with fiber than men.
The relationship of body weight status and fiber effect on energy intake suggests that obese individuals may be more likely to reduce food intake with dietary fiber inclusion. Current recommendations from the United States National Academy of Sciences , Institute of Medicine , state that for Adequate Intake, adult men ages 14—50 consume 38 grams of dietary fiber per day, men 51 and older 30 grams, women ages 19—50 to consume 25 grams per day, women 51 and older 21 grams.
No guidelines have yet been established for the elderly or very ill. Patients with current constipation , vomiting , and abdominal pain should see a physician. Certain bulking agents are not commonly recommended with the prescription of opioids because the slow transit time mixed with larger stools may lead to severe constipation, pain, or obstruction. Observational studies have found an association between lower selenium concentrations in people with HIV and an increased risk of cardiomyopathy, death, and, in pregnant women, HIV transmission to offspring and early death of offspring [ ].
Some randomized clinical trials of selenium supplementation in adults with HIV have found that selenium supplementation can reduce the risk of hospitalization and prevent increases of HIV-1 viral load; preventing HIV-1 viral load progression can lead to increases in numbers of CD4 cells, a type of white blood cell that fights infection [ 30 , 31 ].
However, one trial showed that selenium supplementation in pregnant women can prevent early death in infants but has no effects on maternal viral load or CD4 counts [ 32 , 33 ]. This section focuses on four diseases and disorders in which selenium might play a role: Because of its effects on DNA repair, apoptosis, and the endocrine and immune systems as well as other mechanisms, including its antioxidant properties, selenium might play a role in the prevention of cancer [ 2 , 9 , 34 , 35 ].
Epidemiological studies have suggested an inverse association between selenium status and the risk of colorectal, prostate, lung, bladder, skin, esophageal, and gastric cancers [ 36 ]. The authors found no association between selenium intake and risk of breast cancer. A meta-analysis of 20 epidemiologic studies showed a potential inverse association between toenail, serum, and plasma selenium levels and prostate cancer risk [ 37 ].
Randomized controlled trials of selenium supplementation for cancer prevention have yielded conflicting results. The authors of a Cochrane review concluded, based on nine randomized clinical trials, that selenium might help prevent gastrointestinal cancers but noted that these results need to be confirmed in more appropriately designed randomized clinical trials [ 38 ].
A secondary analysis of the double-blind, randomized, controlled Nutritional Prevention of Cancer Trial in 1, U. In , the FDA allowed a qualified health claim on foods and dietary supplements containing selenium to state that while "some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer FDA has determined that this evidence is limited and not conclusive" [ 42 ].
More research is needed to confirm the relationship between selenium concentrations and cancer risk and to determine whether selenium supplements can help prevent any form of cancer. Selenoproteins help prevent the oxidative modification of lipids, reducing inflammation and preventing platelets from aggregating [ 9 ]. For these reasons, experts have suggested that selenium supplements could reduce the risk of cardiovascular disease or deaths associated with cardiovascular disease.
The epidemiological data on the role of selenium in cardiovascular disease have yielded conflicting conclusions. Some observational studies have found an inverse association between serum selenium concentrations and risk of hypertension or coronary heart disease.
A meta-analysis of 25 observational studies found that people with lower selenium concentrations had a higher risk of coronary heart disease [ 43 ]. However, other observational studies failed to find statistically significant links between selenium concentrations and risk of heart disease or cardiac death, or they found that higher selenium concentrations are associated with an increased risk of cardiovascular disease [ ].
Several clinical trials have examined whether selenium supplementation reduces the risk of cardiovascular disease. In one randomized, placebo-controlled study, for example, healthy adults aged 60 to 74 years with a mean baseline plasma selenium concentration of 9. A review of trials of selenium-only supplementation for the primary prevention of cardiovascular disease found no statistically significant effects of selenium on fatal and nonfatal cardiovascular events [ 51 ]. Almost all of the subjects in these clinical trials were well-nourished male adults in the United States.
The limited clinical-trial evidence to date does not support the use of selenium supplements for preventing heart disease, particularly in healthy people who already obtain sufficient selenium from food. Additional clinical trials are needed to better understand the contributions of selenium from food and dietary supplements to cardiovascular health. Serum selenium concentrations decline with age.
The results of observational studies are mixed [ 54 ]. In two large studies, participants with lower plasma selenium levels at baseline were more likely to experience cognitive decline over time, although whether the participants in these studies were selenium deficient is not clear [ 52 , 55 , 56 ]. An analysis of NHANES data on 4, elderly people in the United States found no association between serum selenium levels which ranged from lower than Researchers have evaluated whether taking an antioxidant supplement containing selenium reduces the risk of cognitive impairment in elderly people.
MAX study on 4, participants aged 45 to 60 years in France found that, compared with placebo, daily supplementation with mg ascorbic acid, 30 mg vitamin E, 6 mg beta-carotene, mcg selenium, and 20 mg zinc for 8 years was associated with higher episodic memory and semantic fluency test scores 6 years after the study ended [ 58 ].
More evidence is required to determine whether selenium supplements might help prevent or treat cognitive decline in elderly people. Selenium concentration is higher in the thyroid gland than in any other organ in the body, and, like iodine, selenium has important functions in thyroid hormone synthesis and metabolism. Epidemiological evidence supporting a relationship between selenium levels and thyroid gland function includes an analysis of data on 1, participants in the SU.
MAX study indicating an inverse relationship between serum selenium concentrations and thyroid volume, risk of goiter, and risk of thyroid tissue damage in people with mild iodine deficiency [ 59 ]. However, these results were statistically significant only in women. A cross-sectional study in adults with mild iodine deficiency in Denmark also found a significant inverse association between serum selenium concentration and thyroid volume in women [ 60 ].
Randomized, controlled trials of selenium supplementation in patients with thyroid disease have had varied results.
Compared with patients treated with placebo, those treated with selenium but not pentoxifylline reported a higher quality of life. Women with thyroid peroxidase antibodies tend to develop hypothyroxinemia while they are pregnant and thyroid dysfunction and hypothyroidism after giving birth [ 9 ]. The authors of a Cochrane review of hypothyroidism interventions during pregnancy concluded, based on a trial that administered supplements containing mcg selenium as selenomethionine daily to pregnant women with thyroid peroxidase antibodies [ 63 ], that selenomethionine supplementation in this population is a promising strategy, especially for reducing postpartum thyroiditis [ 64 ].
However, the authors called for large randomized clinical trials to provide high-quality evidence of this effect. Additional research is needed to determine whether selenium supplements can help prevent or treat thyroid disease. Chronically high intakes of the organic and inorganic forms of selenium have similar effects [ 6 ]. Early indicators of excess intake are a garlic odor in the breath and a metallic taste in the mouth. The most common clinical signs of chronically high selenium intakes, or selenosis, are hair and nail loss or brittleness.
Other symptoms include lesions of the skin and nervous system, nausea, diarrhea, skin rashes, mottled teeth, fatigue, irritability, and nervous system abnormalities. As discussed earlier, Brazil nuts contain very high amounts of selenium 68—91 mcg per nut and could cause selenium toxicity if consumed regularly. Acute selenium toxicity has resulted from the ingestion of misformulated over-the-counter products containing very large amounts of selenium [ 2 , 5 ].
In , for example, people experienced severe adverse reactions from taking a liquid dietary supplement containing times the labeled amount [ 65 ].
Acute selenium toxicity can cause severe gastrointestinal and neurological symptoms, acute respiratory distress syndrome, myocardial infarction, hair loss, muscle tenderness, tremors, lightheadedness, facial flushing, kidney failure, cardiac failure, and, in rare cases, death [ 2 , 6 ].
The FNB has established ULs for selenium from food and supplements based on the amounts of selenium that are associated with hair and nail brittleness and loss see Table 3 [ 6 ]. Selenium can interact with certain medications, and some medications can have an adverse effect on selenium levels. One example is provided below.
Individuals taking this and other medications on a regular basis should discuss their selenium status with their healthcare providers. Cisplatin, an inorganic platinum chemotherapy agent, is used to treat ovarian, bladder, lung, and other cancers. Cisplatin can reduce selenium levels in hair and serum but whether these reductions have a clinically significant impact is not known [ 66 , 67 ]. The federal government's Dietary Guidelines for Americans notes that "Nutritional needs should be met primarily from foods.
Foods in nutrient-dense forms contain essential vitamins and minerals and also dietary fiber and other naturally occurring substances that may have positive health effects. In some cases, fortified foods and dietary supplements may be useful in providing one or more nutrients that otherwise may be consumed in less-than-recommended amounts. For more information about building a healthy diet, refer to the Dietary Guidelines for Americans and the U.
Department of Agriculture's MyPlate. This fact sheet by the Office of Dietary Supplements ODS provides information that should not take the place of medical advice. We encourage you to talk to your healthcare providers doctor, registered dietitian, pharmacist, etc. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice.
March 2, History of changes to this fact sheet. Strengthening Knowledge and Understanding of Dietary Supplements. Selenium Fact Sheet for Health Professionals.
Modern Nutrition in Health and Disease. Bowman B, Russell R, eds. Present Knowledge in Nutrition. International Life Sciences Institute; Moderation is advised with regard to consuming alcohol and using some drugs. Alcohol inhibits glycogenesis in the liver and some drugs inhibit hunger symptoms. This, with impaired judgment, memory and concentration caused by some drugs can lead to hypoglycemia. People with diabetes who take insulin or tablets such as sulphonylureas should not, therefore, consume alcohol on an empty stomach but take some starchy food such as bread or potato crisps at the same time as consumption of alcohol.
The Pritikin Diet consists of fruit, vegetables, whole grains, and so on, and is high in carbohydrates and roughage. The diet is accompanied by exercise. It instead favors multi-grain and sourdough breads, legumes and whole grains that are converted more slowly to glucose in the bloodstream.
It has been suggested that the removal of carbohydrates from the diet and replacement with fatty foods such as nuts, seeds, meats, fish, oils, eggs, avocados, olives, and vegetables may help reverse diabetes. Fats would become the primary calorie source for the body, and complications due to insulin resistance would be minimized. It has been shown that a high fiber diet works better than the diet recommended by the American Diabetes Association in controlling diabetes and may control blood sugar levels with the same efficacy as oral diabetes drugs.
The Paleolithic diet has been shown to improve glucose tolerance in people with diabetes type 2 ,  ischemic heart disease and glucose intolerance ,  and in healthy pigs. A low-fat vegan diet improves glycemic control similar to the ADA diet. From Wikipedia, the free encyclopedia. This article needs more medical references for verification or relies too heavily on primary sources. Please review the contents of the article and add the appropriate references if you can.
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