Human Nutrition Quiz - Carbohydrates

Carbohydrates (CHO)

• Carbohydrates are composed of monosaccharides, disaccharides, and polysaccharides.
• Monosaccharides are single sugars like glucose, fructose, and galactose.
• Disaccharides are pairs of monosaccharides, including maltose, sucrose, and lactose.
• Polysaccharides are large chains of monosaccharides, primarily glucose, like starch and fiber.
• Glucose is the primary energy source; it's part of all disaccharides and a building block of polysaccharides.
• Fructose is the sweetest sugar found in fruits and honey.
• Galactose is found in dairy products and is part of lactose.
• All monosaccharides differ in arrangement, not atom composition (6 C, 12 H, 6 O).
• Glycogen is the storage form of glucose in animals, highly branched, a rapid reserve energy source.
• Starch is the storage form in plants, long chains of amylopectin and amylose.
• Resistant starches behave similarly to fiber, found in grains, legumes, root crops.
• Fiber is from plants, composed of nonstarch polysaccharides (cannot be digested).
• Fiber is insoluble or soluble; functional fibers are added to foods or supplements.
• Soluble fiber dissolves in water, forms gels, fermented by bacteria, promoting heart health and lowering cholesterol. Sources include oats, barley, legumes, and citrus.
• Insoluble fiber does not dissolve, does not form gels, promotes bowel movements, preventing diverticular disease. Found in whole grains and vegetables.

Digestion and Absorption of Carbohydrates

• Digestion begins in the mouth, with most occurring in the small intestine.
• Within 1-4 hours post-meal, all sugars and starches are digested, leaving fiber.
• Fiber in the colon attracts water, softening stools for easier movement.
• Bacteria ferment fiber, producing gas, water, and short-chain fatty acids (SCFA) for colon cell energy.
• Remaining fiber is eliminated.
• Monosaccharide absorption occurs primarily in the small intestine.
• Glucose and galactose are absorbed via active transport (or facilitated if high CHO).
• Fructose absorption is slower due to facilitated transport.
• Liver metabolizes galactose and fructose into glucose.

Irritable Bowel Syndrome (IBS)

• IBS is an abnormal digestive function without structural issues.
• Symptoms include pain, diarrhea/constipation, bloating, altered motility.
• About 20% of the population has IBS; women are affected more.
• Etiology is poorly understood, involving factors like physiology, psychology, genetics, and diet.
• Treatments include a low FODMAP diet, restricting high-fermentable carbohydrates.

Lactose Intolerance

• Lactase enzyme activity decreases after childhood in many.
• Large lactose intake causes difficulty absorbing due to water draw in the gut and bloating, leading to gas and abdominal discomfort.
• Secondary lactose intolerance can occur due to damaged villi.
• Managing lactose intolerance involves gradual dairy increases, spreading intake throughout the day, using lactose-free options, and possibly enzyme pills.

Glucose Metabolism

• Glucose is the preferred energy source for cells (especially brain).
• Excess glucose isn't immediately used—converted to glycogen and stored in liver, muscles, and brain.
• During fasting, glycogen breaks down to liberate glucose.
• Long-term storage of glucose excess is fat.
• Gluconeogenesis creates glucose from protein.
• Fats cannot be converted to glucose; ketones (acids) are created as alternative fuel during carbohydrate deficit.
• Minimum daily carbohydrate needs are 50-100g.

Blood Glucose Homeostasis

• Hormones regulate blood glucose levels, including:
• Insulin (beta cells of pancreas): Promotes glucose uptake by cells when levels are high.
• Glucagon (alpha cells of pancreas): Stimulates glycogen breakdown in liver when levels are low.

Diabetes

• Diabetes is characterized by ineffective insulin action.
• Type 2 diabetes is often related to obesity; type 1 is likely from infection or genetics.
• Management goals include stable blood glucose via regular meals and snacks with similar carbohydrate content. Weight management is crucial.

Hypoglycemia

• Hypoglycemia is low blood glucose, characterized by symptoms like weakness, rapid heartbeat, and sweating.
• Potential causes include excess insulin, excessive exercise, inadequate food intake, and illness.

Glycemic Response

• Glycemic response is the rate at which blood glucose rises and falls after consuming carbohydrates.
• High glycemic response includes rapid rise and fall, possibly dipping below normal; happens with refined carbohydrates consumed in isolation.
• Lower glycemic response includes slow rise and fall; happens with complex carbohydrates and fiber.

Recommended Carbohydrate Intakes

• DRIs suggest no Tolerable Upper Limit (TUL) for sugar, with no more than 25% of energy intake from sugar.
• WHO/FAO recommends less than 10% from sugar, preferably less than 5%. Canada's Food Guide recommends limiting highly processed foods high in sugar and saturated fat. .

Sugar- Added and Concentrated Sugars

• Increased use of added sugars in processed foods is associated with obesity, diabetes, cardiovascular disease, inflammation, hypertension, and cancer.
• Limit concentrated sugars (honey, maple syrup) to 10% of daily calories.

High Fructose Corn Syrup (HFCS)

• HFCS is a common sweetener in beverages; its liquid form leads to lower satiety than solids.
• 50:50 glucose-fructose ratio.
• Cheap, readily available in manufacturing.
• Fructose metabolism in the liver may promote fat production and limit fat clearing, potentially increasing obesity. It does not increase insulin release or appetite.

Identifying Added Sugars

• Common added sugars include brown sugar, raw sugar, corn sweeteners, corn syrup, dextrose, fructose, glucose, honey, lactose, malt syrup, molasses, sucrose, maltodextrin, and cane syrup.

Double Burden of Malnutrition

• Overnutrition (e.g., obesity) often co-exists with nutrient deficiencies, caused by energy-dense/nutrient-poor foods ("empty calories").
• Approximately 1500 kcal of carefully chosen food daily is needed to fulfill micronutrient needs.

Artificial Sweeteners

• Artificial sweeteners (non-nutritive) such as aspartame and high-intensity sweeteners are discussed but sugar alcohols, such as sorbitol, provide calories and are nutritive.
• Do not stimulate dental caries, but can have laxative effects in large quantities, hence limiting intake is crucial.

Other Carbohydrates

• Whole grains, legumes, and vegetables provide various benefits, including reduced inflammation, blood pressure, and blood lipids.

Recommended Intakes of Starch and Fiber

• The daily recommended intakes aren't explicitly provided, though fiber's role in gut health is discussed.

Soluble vs. Insoluble Fiber

• Soluble fiber dissolves in water (oats, barley), slowing digestion and absorption, leading to a lower glycemic response and increased satiety.
• Insoluble fiber (whole grains, bran) increases stool weight and strength, reduces transit time, and strengthens GI muscles.

Summary of Benefits from Carbohydrates (general concepts relating to types)

• Soluble fibers are essential for reducing inflammation, blood pressure, and for binding bile acids to then remove from the body and thus regulate cholesterol levels.
• Insoluble fibers are crucial for promoting bowel movements, reducing transit time.