Clinical Nutrition Midterm #1

Essential Nutrients

Compounds that the human body cannot make. They must be absorbed from consumption of food.

What is emulsification and how does it work?

*Digestions and Absorption of lipids

• As stomach contents enter the small intestine, the digestive system sets out to combine the separated fats with its own watery fluids.

• Bile is an emulsifier (contains bile salts, lecithin and substances derived from cholesterol)

• Emulsification: separates the hydrophobic fat globules from sticking to each other (to break fat into smaller pieces for absorption)

• Emulsification increases the surface area of lipids over a thousand-fold, making them more accessible to the digestive enzymes

• Once the stomach contents have been emulsified, fat-breaking enzymes work on the triacylglycerols and diglycerides to sever fatty acids from their glycerol foundations.

What is bile? What does it do? What happens to it after it is used?

Bile: A fluid made by the liver and stored in the gallbladder that breaks down fats into fatty acids.

What does it do?

• The gallbladder secretes a much smaller amount of bile, A fluid made by the liver and stored in the gallbladder that breaks down fats into fatty acids. to help digest fats, also through a duct that leads to the duodenum.

• Bile is made in the liver and stored in the gallbladder.

• Bile’s components act like detergents by surrounding fats similar to the way dish soap removes grease from a frying pan. This allows for the movement of fats in the watery environment of the small intestine.

• Bile is an emulsifier

What happens to it after it is used?

• Peristalsis and segmentation move and mix the food to propel food forward. Segmentation sloshes food back and forth in both directions

• All the components of food are completely broken down into their absorbable units (to get absorbed into the small intestine)

• Bascially: (reabsorbed in the lower small intestine and recycled back to the liver, while a small portion leaves the body through waste)

DRIs

• Estimated Average Requirements (EAR)

• Recommended Dietary Allowances (RDA)

• Adequate Intakes (AI)

• Tolerable Upper Intake Levels (UL)

• Acceptable Macronutrient Distribution Ranges (AMDR)

Estimated Average Requirements (EARs)

Average daily intake levels for nutrients estimated to meet the needs of 50 percent of the target group. Used in nutrition research and policy-making. EARs form the basis for which RDA values are set.

Recommended Dietary Allowances (RDAs)

Based upon the EARs, these are nutrient-intake goals designed to meet the requirements of 97 to 98 percent of the target group for a given nutrient.

Adequate Intakes (AIs)

If scientific data is insufficient to establish an EAR value, an AI is established based on the scientific data that is available. As with the RDA, the AI serves a nutrient-intake goal.

Tolerable Upper Intake Levels (ULs)

The highest average daily nutrient intake level at which a nutrient can be consumed safely by 97.5 percent of a target group. Above that level, it can pose a risk of toxicity.

Acceptable Macronutrient Distribution Ranges (AMDRs)

The value of the energy-yielding nutrients carbohydrates, protein, and fat, expressed as percentages of total daily calorie intake, sufficient to provide total adequate energy needs; staying within the AMDR is associated with reducing the risks for developing chronic disease.

What is Fiber and what does it do?

Is a carbohydrate!

Dietary fiber is an indigestible plant carbohydrate that moves through your body to support digestion, control blood sugar, and lower cholesterol

• Dietary Fiber

  • Insoluble Fiber

  • Soluble fiber

• Functional Fiber

Dietary Fiber

Polysaccharides that are highly branched and cross-linked and only found in plant-based foods, with the exception of chitin (which forms the exoskeletons of some animals).

• Humans do not produce the enzymes that can break down dietary fiber (however, bacteria in the large intestine (colon) do)

• Dietary fiber= good for health

• Soluble fibers yield more energy than insoluble fibers

• Dietary fiber is digested much less in the GI tract than other carbohydrates; the rise in blood glucose after eating them is less and slower.

Ex) Pectin, gums, cellulose, and Lignin

Dietary Fiber:

• Soluble

• Insoluble

Soluble Fiber

Ex) Insulin, pectin, and guar gum, they are found in peas, beans oats, barley, and rye.

* More accessible to bacterial enzymes in the large intesine so they can be broken down to a greater extent than insoluble fibers can

Insoluble fiber

Ex) Cellulose and lignin, they are found in peas, beans, whole-grain foods, flax, cauliflower, and avocados.

*Cellulose is the most abundant fiber in plants, making up the cell walls and providing structure.

Functional Fiber

• Prvides health benefits to humans

• can be extracted from plants and purified or synthetically made

Ex) Psyllium-seed husk

*science shows that consuming Psyllium-seed husk reduces blood cholesterol levels

Total dietary fiber intake

Dietary fiber + functional fiber = Total dietary fiber intake

Average American Diet

• The average diet falls short of achieving the recommended dietary intakes of calcium

• Contains too many processed foods with added sugars and saturated fats

• Not enough fruits, vegetables and whole grains

• Consumes more kilocalories each day than ever before

Case study:

• One group on an average American control diet, another group put on a diet rich in fruits, vegetables and third group on a combination diet rich in fruits, vegetables and low-fat dairy produces with reduced saturated and total fat intake.

  • The combination diet significantly lowered blood pressure

Lipids

are a family of molecules composed of carbon, hydrogen, and oxygen, but unlike carbohydrates, they are insoluble in water

• Found in butter, oils, meats, dairy products, nuts and seeds, and in many processed foods.

• Three main types of lipids:

  • Triglycerides

  • Phospholipids

  • sterols

• Lipids provide more energy per gram than carbohydrates (nine kilocalories per gram of lipid)

• Main job: store energy

• Other functions: important component of cell membranes, surround and protect organs, aid in temperature regulation and regulate many other functions in the body

Function of lipids

1. Serve as structural components of cell membranes

2. Function as energy storehouses

3. Act as important signaling molecules

4. Insulating and protecting

Serve as structural components of cell membranes

• Phospholipids are crucial for building the protective barrier, or membrane, around your body’s cells.

Function as energy storehouses

• The excess energy from food is incorporated into adipose tissue (fat)

• Fats are packed together tightly without water and store far greater amounts of energy in a reduced space

• Energy is needed to power the muscles for all the physical work and play an average person engages in.

Act as important signaling molecules

• Triglycerides control the body’s internal climate, maintaining constant temperature.

• Triglycerides help the body produce and regulate hormones

• Lipids help form nerve cell membranes, insulate neurons, and facilitate the signaling of electrical impulses throughout the brain.

Ex) Adipose tissue secretes the hormone leptin, which helps regulate appetite.

Insulating and protecting

• Visceral fat or adipose tissue surrounds delicate organs.

• Vital organs such as the heart, kidneys, and liver are protected by visceral fat.

• Subcutaneous fat (fat underneath the skin) insulates the body from extreme temperatures and helps keep the internal climate under control

The absorbable units for Macromolecules

The macronutrients you ear, lipids, carbohydrates, and proteins, are broken down into the absorbable units (free fatty acids, monosaccharides and amino acids) and absorbed into the enterocytes of the small intestine

• Lipids: free fatty acids

• Carbs: monosaccharides

• Proteins: amino acids

Read food label

The first part of the nutritional facts panel gives you information on the serving size and how many servings are in the container.

• See the percent daily value on the far right-hand side= helps determine if the food is a good source of a particular nutrient or not

• The Daily value (DV): represents the recommended amount of a given nutrient based on the RDI of that nutrient in a 2,000-kilocalorie diet

• The percentage of Daily Value (percent DV): The percentage of the amount of the nutrient in relationship to the DV. They are applicable only for a 2,000-calorie daily diet (not 2,500 calories). represents the proportion of the total daily recommended amount that you will get from one serving of the food.

Ex)

For example, in the food label in Figure 2.10, the percent DV of calcium for one serving of is 20 percent, which means that one serving provides 20 percent of the daily recommended calcium intake. Since the DV for calcium is 1,000 milligrams, the food producer determined the percent DV for calcium by taking the calcium content in milligrams in each serving, and dividing it by 1,000 milligrams, and then multiplying it by 100 to get it into percentage format.

What is an essential fatty acid and food sources

Essential fatty acid: A fatty acid that the body cannot synthesize and must be supplied through the diet.

Food sources:

• Omega-3

• Omega-6

3 and 6 refer to the position of the first carbon-carbon double bond, and omega refers to the methyl end of the chain.

*The human body cannot make double bonds before the ninth carbon.

• Omega 3 and omega 6 are precusros to important compounds called eicosanoids

Omega-3

• Fatty fish and certain plant seeds (salmon, sardines, anchovies, flax seeds, chia seeds, walnuts)

eicosanoids derived from omega-3 fatty acids are known to have anti-inflammatory effects.

Omega-6

• Vegetable oils, hemp seeds, processed foods, fried items

Eicosanoids derived from omega-6 fatty acids are known to increase blood pressure, immune response, and inflammation.

Eiconsanoids

Compounds derived from polyunsaturated fatty acids that control several body functions.

Eicosanoids are powerful hormones that control many other hormones and important body functions, such as the central nervous system and the immune system.

The goal of dietary reference intakes

• Basically: to provide science-based nutrient standards that promote health, prevent nutritional deficiencies, and reduce the risk of chronic diseases.

• DRIs are important not only to help the average person determine whether their intake of a particular nutrient is adequate; they are also used by health-care professionals and policymakers to determine nutritional recommendations for special groups of people who may need help reaching nutritional goals. This includes people who are participating in programs such as the Special Supplemental Food Program for Women, Infants, and Children.

• DRI is not appropriate for people who are ill or malnourished.

HDL and its functions

High-density lipoproteins are also known as “good cholesterol.” They contain the maximum percentage of protein and a lower percentage of cholesterol and collect and transport excess cholesterol, returning it to the liver for reuse or excretion.

• “Good cholesterol”

• Responsible for carrying cholesterol out of the bloodstream and tissues and into the liver (reused or removed from the body with bile)

• High HDL values indicate a reduced risk of heart disease

• A way to increase HDL levels it to exercise.

What happens if we eat too much Macronutrients? What does it turn into?

leads to a calorie surplus that causes weight gain

• Excess macronutrients turn into adipose tissue (fat)

Stages of the Digestive tract

• Ingestion(thinking about food, involuntary release of saliva): eating or drinking and swallowing at the beginning of the digestive tract

• Digestion (mouth): Chemical breakdown of food involves enzymes, mechanical breakdown (chewing) (and peristalsis and segmentation)

• Absorption(small intestine): has microvilli for increasing SA:V ratio (small intestine → large intestine)

• Elimination: elimination of indigestible food as feces (stored in the rectum until it is expelled through the anus)

Digestive tract in order (From mouth to anus)

• Mouth: Food enters, gets chewed by teeth, and mixes with saliva containing enzymes that start breaking down carbohydrates.

• Esophagus: A muscular tube that pushes the chewed food (bolus) down to the stomach using wave-like muscle contractions called peristalsis.

• Stomach: A muscular sac that churns food and mixes it with strong acids and digestive enzymes to break down proteins into a liquid mixture called chyme.

• Small Intestine: The main site for chemical digestion and nutrient absorption, aided by digestive juices from the liver, pancreas, and gallbladder. It has three parts:

  • Duodenum

  • Jejunum

  • Ileum

• Large Intestine (Colon): Absorbs water and minerals from the remaining waste, turning liquid residue into solid stool. [1, 2]

• Rectum: Stores the stool until it is ready to be pushed out of the body.

• Anus: The final opening where waste (feces) leaves the body. [1]

Where does chemical digestion stop and start for each macronutrient?

Carbohydrates

• Starts: Mouth (Salivary amylase breaks down starches into smaller sugars).

• Stops: Small intestine (Pancreatic amylase and brush border enzymes like maltase, sucrase, and lactase finish breakdown into monosaccharides).

Proteins

• Starts: Stomach (Hydrochloric acid and pepsin break proteins into smaller polypeptides).

• Stops: Small intestine (Pancreatic proteases like trypsin and brush border aminopeptidases reduce them to free amino acids).

Lipids (Fats)

• Starts: Mouth / Stomach (Lingual and gastric lipases begin minor initial breakdown of triglycerides).

• Stops: Small intestine (Bile emulsifies fats and pancreatic lipase completes digestion into free fatty acids and monoglycerides).

4 accessory organs

1. Salivary Glands

• Located in and around the mouth.

• Produce saliva to moisten food.

• Contain the enzyme amylase to begin breaking down starches.

2. Liver

• Located in the upper right abdomen.

• Produces bile to break down and emulsify fats.

• Processes and filters nutrient-rich blood coming from the digestive tract.

3. Gallbladder

• Located just beneath the liver.

• Stores and concentrates excess bile produced by the liver.

• Releases bile into the small intestine when you eat fatty foods.

4. Pancreas

• Located behind the stomach.

• Produces digestive enzymes that break down proteins, fats, and carbohydrates.

• Secretes bicarbonate to neutralize harsh stomach acid as food enters the small intestine.

Lipid case study

Type 1 Diabetes VS Type 2 Diabetes

Type 1 diabetes: an autoimmune disease in which insulin secreting cells in the pancreas are killed by an abnormal reponse of the immune system, causing a lack of insulin in the body.

• It is an autoimmune disease

• Treatment: Insulin injections

• Symptoms: hunger, excessive thirst, urination and rapid weight loss

• If type 1 diabetes goes untreated: Ketoacidosis

Type 2 diabetes: A metabolic disease of insulin insufficiency; also caused by muscle, liver, and fat cells, no longer responding to the insulin in the body.

• is an metabolic disease

• Treatment: medication and lifestyle changes

• Symptoms: more gradual and less noticeable than type 1 diabetes: thirst and urination, unexplained weight loss and hunger

• Cells in the body have become resistant to insulin and no longer receive the full physiological message of insulin to take up glucose form the blood.

• no longer responding to the insulin in the body

What are the required things on the food label? (8 required items) / mandatory inclusion

1. Name and address of the manufacturer, packager, or distributor

2. Statement of identity, what the product actually is

3. Country of origin

4. Net contents of the package: weight, measure, or numerical count

5. Ingredients, listed in descending order by weight

6. Nutrient information of serving size based on what people are actually eating and percentage daily values

The 6 classes of nutrients

Macronutrients:

• Carbohydrates

  • Ex) Glucose, fructose, galactose…etc

• Lipids

  • Ex) Phospholipids, triglycerides, glycerol, and cholesterol

• Proteins

  • Ex) keratin (structure of hair and nails) , and collagen(makes bones strong but flexible)

• Water

Micronutrients:

• Vitamins

  • Ex) Vitamin A(supports vision and skin) ,C(supports immunity and healing) ,D (aids in calcium absorption)

• Minerals

  • Ex) Calcium, Potassium, Magnesium

Macronutrients food sources

Carbohydrates: Starchy foods, grains, fruits, and legumes, packaged blueberry muffin

Lipids: Vegetable oils, butter, animal fats and nuts

Proteins: meat, chicken breasts, salmon(omega 3), fish, eggs and dairy products

Water: water (H2O)

Classification of fatty acids

All have the -COOH group on one end of a carbon chain and a methyl (CH3) group on the other end

• Different chain lengths

• Different degree of saturation (number of double bonds)

• State of fatty acid (soild or liquid at room temp)
  
  *Carbon chain length shorter= lower melting point = becomes more liquid

• Saturated fatty acid: no double bonds- soild at room temp

• Unsaturated fatty acid: contains one or more double bonds - liquid at room temp

  • Monounsaturated fatty acid: has one double bond - help regulate blood cholesterol levels

  • Polyunsaturated fatty acid- fatty acid with two or more double bonds between carbons

Type of monosaccharides

• Glucose

• Fructose

• Galactose

DNA/RNA

• Ribose

• Deoxyribose

Types of disaccharides

-Sucrose(table sugar): Glucose + Fructose
-Lactose(sugar in milk): Glucose + Galactose
-Maltose(sugar in malt): Glucose+ Glucose

Carbohydrate function

1. Energy production

Primary role: Supply energy to all cells in the body

2. Energy storage

If the body already has enough energy, the excess glucose is stored as glycogen

3. Building Macromolecules

Some glucose is converted to ribose and deoxyribose (building blocks for DNA and RNA)

4. Sparing Protein

Not enough energy from glucose; glucose is synthesized from noncarbohydrate sources like amino acids (gluconeogenesis). Adequate glucose= spares proteins from being broken down to make glucose for energy needed by the body

5. Lipid metabolism

As blood glucose rise, the use of lipids as an energy source is inhibited. Glucose has a “fat-sparing” effect!

Molecular difference between carbs/fat and protein

Carbs: CH2O (Carbon, oxygen, and hydrogen) 1:2:1 ratio

Fat: made up of carbon, hydrogen, and oxygen

Protein: made up of carbon, hydrogen, and oxygen oxygen and NITROGEN

Protein structure

1. Primary structure

The linear sequence of amino acids in a polypeptide chain.

Ex) Insulin

1. Secondary structure

Folding into alpha helices and beta-pleated sheets

Ex) alpha-keratin (found in hair and nails)

1. Tertiary structure

Further folding into a 3D shape (the side chains/r group determine the shape)
Ex) Myoglobin

1. Quaternary structure

The arrangement of multiple folded protein chains (subunits) working together as a single functional complex.

Ex) Hemoglobin

Essential Vs Nonessential fatty acids

Essential fatty acids: A fatty acid that the body cannot synthesize and must be supplied through the diet

Nonessential fatty acids: A fatty acid that can be synthesized by the body

Complete vs incomplete protein sources

Complete protein source: Foods that contain all nine of the essential amino acids in the proportions needed by the human body

Ex) animal-dervied foods such as milk, cheese, eggs fish, and meat , soy, seafood, and seafood

Incomplete protein source: Foods that contain some, but not all the essential amino acids

Ex) Legumes and corn

Kwashiorkor vs. Marasmus

Kwashiorkor: A syndrome of severe protein and micronutrient deficiency, characterized by swelling (edema) of the feet and abdomen, poor skin health, growth retardation, low muscle mass, and liver malfunction.

*Mostly effects only children (SWELLING)

Marasmus: A syndrome of severe protein and energy deficiency, characterized by emaciation, poor skin health, and growth retardation.

*Effects children and adults

What classes of macromolecules give you energy VS not

Gives energy: Carbohydrates, fats, and proteins

No energy: vitamins, minerals

Calorie/kilocalorie

A kilocalorie is the amount of heat generated needed to raise the temperature of 1 kilogram of water 1 degree Celsius (this is what is denoted on the Nutrition Facts panel).

Nutrient dense food vs calorie dense food

Nutrient dense food: Foods that contain many nutrients per calorie

• Nutrient-dense foods are the opposite of “empty-calorie” foods, such as sugary carbonated beverages, which are also called “nutrient-poor.
  Ex) fruits and vegetables, lean meats, poultry, fish, low-fat dairy products, and whole grains

Calorie dense food: Calorie-dense foods pack a high number of calories into a small portion of food.

Ex) nuts, avocado, oils

How are amino acids classified? (how do they differ)

1. Side chain (r group) (polar, nonpolar, acidic, basic)

2. Essentiality (essential or nonessential, conditionally essental amino acid)

Polar amino acid

Hydrophilic amino acids that are not charged.

Nonpolar amino acid

Hydrophobic amino acids with side groups that are long or bulky.

Acidic amino acid

Hydrophilic amino acids that are negatively charged.

Basic amino acid

Hydrophilic amino acids that are positively charged.

Nonessential amino acid

Amino acids that are made in the human body in sufficient amounts to meet our needs.

Essential amino acid

Amino acids that are not made by the human body (or are not made in sufficient amounts to meet our needs) and must be obtained from the diet.

Conditionally essential amino acid

Amino acids that become essential during certain times in life, such as child growth.

What is protein turn over?

The process of continually breaking down proteins and building new ones.

• Every day over 250 grams of protein in your body are dismantled and 250 grams of new protein are built. To form these new proteins, amino acids from food and from protein destruction are available in the body.

Chemical digestion in the stomach (proteins)

• The stomach releases gastric juices containing hydrochloric acidSecreted by stomach cells; aids in the chemical breakdown of proteins. and the enzyme pepsinAn enzyme secreted by stomach cells. It breaks the peptide bonds between amino acids, producing much shorter protein fragments., which initiate the breakdown of the protein. The acidity of the stomach facilitates the unfolding of the proteins that still retain part of their three-dimensional structure after cooking and helps break down the protein aggregates formed during cooking.

• Pepsin, which is secreted by the cells that line the stomach, dismantles the protein chains into smaller and smaller fragments by breaking the peptide bonds between amino acids.

*protein digestion takes a longer time than carb digestion! (high protein foods remain in the stomach longer, making you feel full)