Nutrition is the science that studies food and how food nourishes our bodies and influences our health. It identifies the processes by which we consume, digest, metabolize, and store nutrients in foods, and how these nutrients affect our bodies.Organic nutrients contain oxygen: carbohydrates, lipids/fats, proteins, and vitaminsInorganic nutrients do not contain carbon: water and mineralsMacronutrients are nutrients that the body requires in relatively large amounts to support normal function and healthCarbohydrates, lipids/fats, and proteinsMicronutrients are nutrients that are needed in relatively small amounts to support normal health and body functionsVitamins and mineralsFat soluble vitamins are vitamins that are soluble in fat and stored in the human body. Toxicity can result from consuming excess amounts that accumulate in the bodyA, D, E, and KWater soluble vitamins are soluble in water and are not stored in the body. Excess is excreted in urine. Toxicity can occur as a result of vitamin supplementationC, B-vitaminsCarbohydrates (4kcal/g) are the primary source of fuel for the body, particularly neurologic functioning and exerciseLipids/Fats (9kcal/g) include triglycerides, phospholipids, and sterols. They are an important source of energy during low-intensity exerciseProteins (4kcal/g) supports tissue growth, repair, and maintenance. NOT a primary energy sourceDRI (Dietary Reference Intake) is a set of reference values aimed at preventing and reducing the risk of chronic disease and promoting optimal health. For HEALTHY PEOPLE ONLYThe U.S. Food and Drug Administration (FDA) regulates food labelsThe Dietary Guidelines for Americans are a set of principles developed by the USDA to help design a healthful diet and lifestyle. Guidelines include:Adequate nutrients within calorie needs:Consume a variety of nutrient-dense foods and beverages within and among the basic food groups while choosing foods that are limited in saturated and trans fats, cholesterol, and added sugars.Weight Management:Being overweight or obese increases risk for chronic diseases. Maintain body weight by balancing calories from food and beverages with calories expended.Physical activity:Engage in regular physical activity and reduce sedentary activities to promote health, psychological well-being, and a healthful body weight. Includes cardio, stretching, and resistance exercises at least 30 minutes a dayFood groups to encourage:Eat a variety of fruits and vegetables, 3 or more ounces of whole grain foods, and 3 cups per day of low-fat milk (or the equivalent)CarbohydratesChoose fiber-rich fruits, vegetables, and whole grains, & beverages with little added sugar; 45-65% of total energyFatsConsume less than 10% calories from saturated fats and less than 300mg/day of cholesterol; trans fat intake should be as low as possible; 20-35% of total energy intake with most fats coming from fish (omega 3 & 6), nuts, and vegetable oilProteinsChoose lean meats and poultry. When cooking: bake, broil, or grill, and vary protein routine; 10-35% energy intakeSodium and PotassiumExcessive potassium consumption linked to healthy blood pressure & excess sodium intake is linked to high blood pressureConsume less than 2,300 mg of sodium, choose foods with little salt, and consume potassium-rich foods such as fruits and vegetablesAlcoholDoes not provide any nutrients; no more than 1 drink per women and 2 for menMyPyramid and MyPlate are intended to help Americans:Eat in moderation, eat a variety of foods, consume the right proportion of each recommended food group, personalize eating plan, increase physical activity, and set goals for gradual lifestyle improvementHunger is the physiological drive for food & is nonspecificAppetite is a psychological desire to consume specific foods; it is aroused by environmental cues that stimulate our sensesGastric juice is composed of hydrochloric acid, gastric lipase, and intrinsic factorHydrochloric acid (HCL) denatures proteins and activates pepsin. It also converts pepsinogen to pepsin for further breakdown of proteinsGastric lipase is an enzyme that digests fat (lipid digestion)Intrinsic factor is a protein that is critical to the absorption of vitamin B12. It is secreted by parietal cellsChyme is a semifluid mass consisting of partially digested food, water, and gastric juices. It helps facilitate chemical digestion in the stomachMucus is the layer in the stomach lining that protects the stomach from the acid in gastric juicesBicarbonate also assists in protecting stomach lining, and neutralizes acid near the surface of the stomach’s liningDigestive enzymes and hormones:Salivary amylase mouth; digests carbohydratesLingual lipase mouth and activated in the stomach; digests lipidsPancreatic lipase & co-lipase small intestine; digests lipidsGastrin produced in stomachStimulates secretion of HCL and pepsinogenStimulates gastric motilityPromotes proliferation of gastric mucosal cellsCholecystokinin (CCK) small intestinePancreas – Stimulates secretion of pancreatic digestive enzymesStomach – Slows gastric emptyingGallbladder – Stimulates gallbladder contraction to release bileGhrelin – hormone that regulates hunger and appetite; also YY or PYY, and beta endorphinsLeptin – hormone that regulates satiety; also serotonin and CCKThree accessory organs are:Gallbladder – stores that bile produced by the liver CCK signals the release of the bile bile emulsifies the lipidsPancreas - manufactures, holds, and secretes digestive enzymes; stores enzymes in the inactive form; located behind the stomachLiver – synthesizes chemicals like bile for metabolism, receives the products of digestion via the portal vein, releases glucose from glycogen stores, stores vitamins, manufactures blood proteins, and filters the bloodGlycogen is stored in the liver and musclesMuscle glycogen – storage of 120g; provides energy to the muscles especially during intense exerciseLiver glycogen – storage of 70g; between meals our bodies draw on liver glycogen to maintain blood glucose levels and support the needs of our cellsHormones involved in blood glucose regulation:Insulin (beta cells) decrease blood glucose which increases glycogenesisGlucagon (alpha cells) increase blood glucose; catabolicEpinephrine increases glycogenolysis & glycolysisNorepinephrine increases blood glucoseCortisol increases gluconeogenesis (production of glucose from amino acids); catabolicGrowth hormone
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