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Nutrition Exam 2
Lecture Notes
Chapter 4 Notes: The Carbohydrates: Sugar, Starch, Glycogen, and Fiber
Carbohydrates
❖ Ideal nutrients ➢ Meet body’s energy needs ➢ Feed brain and nervous system ➢ Keep digestive system fit ➢ Keep your body lean ❖ Digestible and indigestible carbohydrates ❖ Complex vs. simple carbohydrates
A Close Look at Carbohydrates
❖ Contain the sun’s radiant energy ❖ Green plants ➢ Photosynthesis ■ Glucose ➢ Plants do not use all of the energy stored in their sugars ❖ Carbohydrate-rich foods ➢ Plants ➢ Milk
Sugars
❖ Six sugar molecules ❖ Chemical names end in -ose ➢ Monosaccharides ■ Glucose, fructose, and galactose ➢ Disaccharides ■ Lactose, maltose, and sucrose
How Monosaccharides Join to Form Disaccharides
❖ Three types of monosaccharides join together to make three types of disaccharides ➢ Fructose ■ Sucrose (fructose-glucose) ➢ Glucose ■ Sucrose (fructose-glucose) ■ Maltose (glucose-glucose) ➢ Galactose ■ Lactose (glucose-galactose)
Starch, Glycogen, and Fibers
❖ Starch ➢ Glucose units are linked in long, occasionally branched chains to make starch. Human digestive enzymes can digest these bonds, retrieving glucose. Real glucose units are so tiny that you can’t see them, even with the highest-power light microscope. ➢ Packed in granules in plant’s seeds ❖ Glycogen ➢ ➢ Glycogen resembles starch in that the bonds between its glucose units can be broken by human enzymes, but the chains of glycogen are more highly branched. ❖ Fibers (Cellulose) ➢ Supporting structures ➢ Digestion involves bacterial fermentation ➢ The bonds that link glucose units together in cellulose are different from the bonds in starch or glycogen. Human enzymes cannot digest them.
How Glucose Molecules Join to Form Polysaccharides
❖ Starch is the storage form of glucose in plants and also yields glucose for the body’s use
The Need for Carbohydrates
❖ They are essential
transit of food through upper GI tract; delay nutrient absorption, Hold moisture in stools, softening them (less fermentable soluble fibers), Nourish beneficial bacterial colonies in the colon, yield small fat molecules after fermentation that the colon can use for energy, increase satiety
And receive these probable health benefits
❖ Alleviate constipation (less fermentable soluble fibers), lower risk of heart disease, lower risk of diabetes, lower risk of colon and rectal cancer, increase satiety (improve weight management)
Characteristics, Sources, and Health Effects of Fibers: Insoluble
People who eat these foods:
Brown rice, fruits, legumes, seeds, vegetables (cabbage, carrots, brussels sprouts), wheat bran, whole grains, extracted fibers are used as food additives
Obtain these types of fibers:
❖ Cellulose, lignins, resistant starch, hemicellulose
With these actions in the body:
❖ Stimulate colon lining, increase fecal weight, and speed fecal passage through the colon. Provide bulk and feelings of fullness, alleviate constipation, lower risk of hemorrhoids and appendicitis, reduce complications from diverticulosis, lower risk of colon and rectal cancer
Why do Nutrition Experts Recommend Fiber-Rich Foods?
❖ Consumption of more than just fiber ➢ Complex carbohydrates ❖ Blood Cholesterol control ➢ Soluble fiber ❖ Blood glucose control ➢ Soluble fiber ❖ Health benefits ➢ Reduces risk of heart disease and stroke ➢ Reduces risk of diabetes ➢ Risk of colon and rectum cancers lower with higher fiber intakes
Cholesterol is only found in foods that come from animals, there is no cholesterol in foods that come from plants. So, there is no cholesterol in fruit, vegetables, grains, seeds, nuts, beans, peas and lentils.
❖ Also ➢ Improves digestive tract health ➢ Promotes growth of healthy gut microbiota
❖ Digestive Tract Health ➢ Soluble and insoluble fibers ➢ Ample fluid intake ➢ Benefits of fiber ■ Protects against constipation, hemorrhoids, appendicitis, and diverticulosis ❖ Fiber intakes and excesses ➢ Few people in the U.S. meet recommendations ■ 14 grams total fiber per 1,000 calories ■ Adding fiber to diet ■ Where should you get your fiber? ● Supplements? ■ Too much fiber?
❖ Refined grains remove ➢ Germ ➢ Bran
Enrichment of Refined Grains
❖ U.S. Enrichment Act of 1942 ➢ Iron, thiamin, riboflavin, and niacin ➢ Folate added in 1996 ❖ Whole-grain foods superior to enriched grain foods ➢ Vitamin B 6 , magnesium, zinc, fiber, and phytochemicals
Finding the real whole-grain foods
❖ Not every choice must be 100% whole grain ❖ Food labels ➢ High fiber ➢ Brown color ❖ Cereals
From Carbohydrates to Glucose
❖ Digestion and absorption ➢ Starch and disaccharides are broken down into monosaccharides for absorption ❖ Starch digestion ➢ Begins in the mouth ■ Splits starch into shorter units ➢ Ceases in the stomach ■ Resumes in the small intestine ➢ Resistant starch
Digesting Sugars and Fiber
❖ Sugars ➢ Split to yield free monosaccharides ■ Enzymes on the small intestine lining ➢ Travel to the liver ❖ Soluble Fiber ➢ Not digested Fermented by bacteria in the colon ➢ The bacteria can also use the simple sugars – the healthiest bacteria
do better with the fiber than the simple sugar – there's a battle going on between the good bacteria and bad bacteria in the gut
Why Do Some People Have Trouble Digesting Milk?
❖ Ability to digest milk carbohydrates varies ➢ Lactase enzyme ■ Made by the small intestine ■ High in infants but reduced in childhood ■ Lactase persistence = maintain lactase expression (through childhood and adulthood)If you don’t have this persistence = can become lactose intolerant Different all around the world ● Northern Europe, the area in middle east, etc. have it = high dairy concentration = they have adapted/evolved to use the sugar at an early age ● In east Asia = don’t consume a lot of dairy = nonpersistent ● We have evolved to be able to use the lactose that is in our milk = depending on where your heritage is = you could be persistent or not ➢ Symptoms of intolerance ■ Nausea, pain, diarrhea, and gas ➢ Nutritional consequences ➢ Milk tolerance and strategies
The body’s use of glucose
❖ Basic carbohydrate unit used for energy ❖ The body handles glucose judiciously ➢ Maintains internal supply
Splitting Glucose for Energy
❖ Glucose is broken down ➢ Multiple fates ■ Partially or fully broken down for energy ■ Precursor for nucleic acids ■ Converted to fat ■ Stored as glycogen
➢ Also muscle ❖ Weight maintenance ➢ Dietary importance and carbohydrate composition
The Glycemic Index of Food
❖ Measures degree of elevation of blood glucose and insulin ➢ Food score ➢ Based on glucose ❖ Nutrition concerns ❖ Glucose metabolism affects the body’s insulin response ❖ The glycemic index reflects the degree to which a food raises blood glucose.
Glycemic Index of Selected Foods
❖ Why High vs Low
Diabetes
❖ A disease of high glucose (hyperglycemia) ❖ A leading cause of death in the U.S. ❖ Prediabetes ➢ High insulin levels ➢ Fasting plasma glucose test ➢ HbA1C test ❖ Two common forms of diabetes ❖ Dangers of diabetes ➢ In the less common type 1 diabetes, the pancreas fails to produce insulin. The immune system attacks and destroys insulin-producing cells in the pancreas as if they were foreign cells. ➢ In the more common type 2 diabetes, the body cells fail to respond to insulin by taking up blood glucose. This condition tends to occur as a consequence of obesity, and the best preventive measure is often to maintain healthy body weight. ❖ T1D ➢ 5-10% percent of cases ➢ Commonage of occurrence ➢ Autoimmune disorder ■ Own immune system attacks the pancreas ■ Lose ability to produce insulin
➢ External sources of insulin ■ Fast-acting and long-acting forms
Discovery of Insulin - 1921
Experiment 1
Removed the pancreas from a dog which resulted in the following:
❖ Its blood sugar rose. ❖ It became thirsty, drank lots of water, and urinated more often ❖ It became weaker and weaker.
Experiment 2
Removed the pancreas from a dog;
❖ Chop it up with water and salts. ❖ Half froze the pieces, then ground them up and filtered. ❖ The extract was injected into the dog.
Type 2 Diabetes
❖ The most common form of diabetes ❖ Lose sensitivity to insulin ❖ Obesity underlies many cases ❖ Other factors ➢ Middle age and physical inactivity ➢ Body fat accumulation ➢ Genetic inheritance
Preventing type 2 diabetes
❖ Maintain healthy body weight ❖ Nutritious eating pattern ➢ Moderate in calories ➢ Low in saturated fat ➢ High in vegetables, legumes, fruit, fish, poultry, and whole grains ➢ Mediterranean style diet ❖ Regular physical activity
If I feel dizzy between meals, do I have hypoglycemia?
➢ Handled differently in the body ➢ Affects appetite differently ➢ Body fatness and blood lipids ■ Stimulates body fat-making pathway ➢ Fatty lipids ■ Nonalcoholic fatty liver disease (NAFLD)
Is Fructose Metabolism Different from Glucose Metabolism?
Key Points:
- Glucose can be stored as glycogen of fat
- Glucose metabolism has a control point
- Fructose has a direct path to fat storage
Sugar and Oral health
❖ Dietary starches fermented in the mouth contribute to dental caries ➢ Bread and crackers ❖ Dental caries ➢ Erosions on the surface of a tooth are caused by acids made by bacteria as they metabolize sugars ❖ Acids break down your teeth ❖ Have good dental health
Sugar and the brain
❖ Does high sugar intake affect the function of the brain? ❖ Where does insulin function in the brain? ❖ High sugar intake leads to insulin resistance ❖ Insulin resistance – also in the brain ➢ Insulin does not work at normal concentrations
High-Fructose Corn Syrup
❖ Made from corn ❖ 55% fructose/45% glucose ❖ Cornstarch mixed with acid and enzymes ❖ Starch is broken down into glucose ❖ Some glucose is converted to fructose ❖ Improved shelf-stability and food properties ❖ Average American consumes 40 lb a year
Alternative Sweeteners
Scientific research says yes for safety issues with
❖ acesulfame-K, aspartame, neotame, saccharin, and sucralose
How are fat useful in Food?
❖ Concentrated calorie source
➢ Lots of energy in small packages
❖ Fat-soluble nutrients
➢ Vitamins
➢ Essential fatty acids
❖ Sensory qualities
➢ Aromas
➢ Flavors
➢ Tenderness
Triglycerides: Fatty Acids and Glycerol
❖ Triglycerides
➢ Three fatty acids attached to the glycerol molecule
❖ Fatty acid differences
➢ Chain length
➢ Saturation
Saturated vs Unsaturated Fatty Acids
❖ Saturation
➢ Hydrogen atoms around the carbon atom
❖ Levels of saturation
➢ Saturated
➢ Unsaturated
■ Polyunsaturated
■ Monounsaturated
■ Saturation
■ Carbon bonds: single and double bonds
■ Three types of fatty acids
■ Essential fatty acids
❖ Our bodies can only make certain types of fatty acids
❖ A double bond after the 9th carbon front he omega end
❖ Therefore, omega-3 and omega-6 fatty acids are essential fatty acids
❖ Omega-3 fatty acid-alpha linolenic acid
❖ Omega- 6 fatty acid - linoleic acid
➢ 1st double bond is located on the 6th carbon from the omega
end
➢ Fats vs Oil
❖ Related to the melting point
❖ Oils
➢ More unsaturated
➢ Shorter carbon chain length
❖ Fats
➢ More saturation
➢ Longer carbon chain lengths
➢ Recap:
➢ Introduction to lipids
➢ Usefulness of lipids
➢ Triglyceride
➢ Fatty acids-types, saturation, omega-3/6, essential fatty acids
❖ The side of their molecule is how we determine fatty acids
Carbon lengths
❖ Short
➢ 5 or fewer carbons in the chain
❖ Medium
➢ 6 to 12 carbons in the chain
❖ Long
➢ 14 to 22 carbons in the chain
➢ Fat vs. Oil
❖ What type of fatty acid is this
❖ Is it oil or fat?
Plant vs animal saturated fat
❖ Coconut oil- health risk
❖ Coconut oil consumption vs corn, palm, soybean, and safflower oils
➢ Increased blood lipids that increase the risk for cardiovascular
disease
➢ Coconut oil consumption vs butter
❖ Decrease blood lipids that increase the risk for cardiovascular disease
❖ Olive oil
Is olive oil really a good option?
➢ Higher olive oil intake was associated with a lower risk of CHD,
total CVD, and total and cause-specific mortality in 2 large
prospective cohorts of U.S. men and women.
➢ The substitution of margarine, butter, mayonnaise, and dairy fat
with olive oil could lead to a lower risk of CHD, CVD, and
mortality.
➢ The evidence says yes
❖ Omega-6 Fatty Acid
❖ How much do you need
❖ Phospholipid
❖ Structurally similar triglyceride
❖ Except that a fatty acid has been removed and replaced by a
phosphate-containing group
❖ Lecithin - an emulsifier
❖ Produced in the liver >> gallbladder >> small intestine
❖ Phospholipid functions
❖ Forms part of the cell membrane
❖ Is a component of bile
❖ Important emulsifier of fats in cooking
➢ The source is egg yolk
➢ Found in wheat germ, peanuts, soybeans
➢ Is added to many foods - baking
❖ Key point: Phospholipids are made in all cells
❖ Recap
❖ Fat vs Oils - saturation vs chain length
❖ Extra virgin coconut oil vs extra virgin olive oil
❖ Omega-6 functions/ health effects
❖ Omega -3 functions/health effects
❖ Phospholipids
❖ Lipids in the body
❖ Absorption
❖ Fatty acids split from glycerol
➢ Fatty acids, phospholipids, and monoglycerides
❖ Bile shuttles lipids across the mucus layer
❖ The efficiency of absorption process n
➢ speed of digestion
➢ Slows more fat in the diet
Digestions of phospholipids & Cholesterol
❖ Enzymes released
➢ From pancreas from cells of the small intestine
❖ Broken down to
➢ Glycerol
➢ Fatty acids
❖ Some cholesterol is bound to fiber and excreted
❖ Cholesterol is absorbed
➢ Specific transport proteins
➢ Look at the diagram in the book
Transport of Fats
➢ Glycerol and shorter-chain fatty acids
❖ Pass through the intestinal lining to the bloodstream
Larger lipids
❖ Protein carriers - lipoproteins
❖ Released into lymph
❖ Chylomicrons
Storing and using the body’s fat
❖ The body conserves fat molecules
➢ Fat depots
❖ Call for energy
➢ Dismantle stored triglycerides
■ Release fatty acids into the blood
❖ Question
➢ Is a low fat or low-carb diet better for losing weight?
■ Neither is good for losing weight
■ Both are good for losing weight
■ I give up; it doesn't make any sense.
Recommendations for Lipid Intakes
❖ Some fat in the diet is essential
❖ Essential fatty acids
❖ The healthy range of lipid (fats + oils) intakes
➢ DRI
■ 20 to 35 percent of daily energy
➢ Fats to consume in low amounts U.S fat intakes
➢ Fats are not bad, you just need to limit them and consume
healthier fats.
➢ Transporting fats in a water environment
❖ Lipoproteins serve as transport vehicles for lipids
❖ From the small intestine to all cells of the body (dietary route)
Transporting fats in a water environment
❖ Four lasses of lipoproteins
➢ Chylomicrons
➢ VLDL - very low density
➢ LDL - low density
➢ HDL - high density
