Nutrition & Health Terms: Key Definitions in Medicine

What are the major components that regulate digestion?

- Hormones (chemical messengers)

- Enzymes (catalysts for cellular reactions)

- Acid (turns bolus of food into chyme in the stomach and activates enzymes)

- Bile (digests fat, made in liver and stored in GB)

- Saliva (moistens food and facilitates taste)

- Bicarb (buffer to acid in the small intestine, released from pancreas)

What are the 3 phases of digestion?

1. Cephalic phase (occurs in the mouth)

2. Gastric phase (begins when food enters your stomach)

3. Intestinal phase (food entering small intestine)

Describe the cephalic phase of digestion.

- Voluntary phase: consciously moving the bolus of food to the back of your tongue

- Involuntary phase: epiglottis moves over the pharynx to move the food from the esophagus to the stomach

Describe the gastric phase of digestion.

- Bolus of food goes down the esophagus and encounters the GE sphincter, which opens so the bolus can enter the stomach

- Stomach is lined with gastric pits (contains mucus, chief, parietal, and G cells that release hormones)

- Food becomes chyme once it is chemically and physically broken down

- When chyme is ready to leave the stomach, it hits the pyloric sphincter and enters the small intestine (duodenum)

Describe the intestinal phase of digestion.

- Food passes through the small intestine

- The majority of digestion happens in this phase (as well as absorption of nutrients)

- Ileocecal sphincter regulates flow of material from ileum to cecum

- Liver and pancreas synthesize bile and enzymes that are secreted into the small intestine for digestion/absorption (gastrin, secretin, CCK, ghrelin)

What are the main 3 functions of the large intestine?

- Absorption of fluids and electrolytes

- Storage and elimination of waste (food residue from small intestine)

- Protects against pathogenic bacteria (microbiota also breaks down some undigested food and synthesizes some vitamins (Vitamin K and some B vitamins))

What are some common digestive problems?

- GERD

- Peptic ulcer disease

- Diverticulosis

What is gastroesophageal reflux disease?

Mechanical problem in the LES (lower esophageal sphincter), causes decreased pressure and thus allows for reversal of gastric secretions

What are risk factors for GERD?

- Certain foods (coffee, alcohol)

- Medications (CCBs, nitrates, beta blockers)

- Hormones (low levels of progesterone)

- Smoking

- Obesity

What are some complications of GERD?

- Esophagitis

- Pre-cancerous Barrett's esophagus

- Adenocarcinoma

What are some symptoms of GERD?

- Heartburn

- Regurgitation

- Dysphagia

- Coughing, hoarseness

What is peptic ulcer disease?

Defect in gastric or duodenal wall that extends through muscularis mucosa into deeper layers

Balance of gastric acid secretion and mucosal defense is disrupted

What are risk factors for peptic ulcer disease?

- NSAIDs

- H. pylori infection

- Alcohol use

- Physiologic stress

What are symptoms of peptic ulcer disease?

- Epigastric pain (gnawing or burning sensation)

- Dyspepsia

- Belching/bloating

- Distention

- Heartburn

- Chest discomfort

- Hematemesis

- Melena

What is diverticulosis?

Small pouches or sacs that form and push outward through weak spots in the colon wall

What are risk factors for diverticulosis?

- Low fiber diet

- Overweight/obesity

- Physical inactivity

- Genetics

What are symptoms of diverticulosis?

- May be asymptomatic

- LLQ abdominal discomfort/pain

- Changes in BM

- Rectal bleeding

What are complications of diverticulosis?

Diverticulitis (an infection of one or more diverticula, caused by obstruction by fecalith causing swelling in the colon) --> needs abx

What is a positive energy balance?

Energy intake > energy expenditure --> weight gain

What is a negative energy balance?

Energy intake < energy expenditure --> weight loss

What comprises our total energy expenditure (TEE)?

- Thermic effect of food (energy required to process food, 10% TEE)

- Physical activity (energy required for movement, 30% TEE)

- Basal metabolism (energy required for basic life function while resting, 50-70% TEE)

What are factors which influence basal metabolism?

- Body temperature (ex. fevers)

- Thyroid hormones

- Nervous system activity (ex. fight/flight response)

- Age (basal metabolism decline begins at 30 y/o)

- Nutritional state

- Pregnancy (fetal development, lactation)

- Caffeine, nicotine

What is nutrition?

The science of food, the nutrients, and other substances within food --> their action, interaction, and balance in relation to health and disease

And the processes by which the organism ingests, absorbs, transports, uses and excretes food substances

What is an essential nutrient?

Chemicals contained in food that our bodies cannot manufacture at all OR cannot manufacture in sufficient quantities

What are the 6 essential nutrients?

- Water

- Carbohydrates

- Lipids (fatty acids, made up of CHO)

- Proteins (20 amino acids, made up of NCHO)

- Minerals (macro and micro/trace minerals)

- Vitamins (water soluble and fat soluble)

Which amino acids are essential?

9 out of 20

Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

What are macro minerals?

Required in >100 mg/day

Include calcium, phosphorus, magnesium, sodium

What are micro, or trace, minerals?

Required in <100 mg/day

Include nickel, iron, zinc, copper, manganese

What is the recommended dietary allowance (RDA) for vitamins and minerals?

Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97-98%) healthy people

What are the acceptable macronutrient distribution ranges?

- Carbohydrates: 45-65% of total caloric intake

- Proteins: 10-35%

- Fats: 20-35%

What is the total caloric value of protein, carbs, fats and alcohol?

- Proteins = 4 kcal/g

- Carbs = 4 kcal/g

- Fat = 9 kcal/g

- Alcohol = 7 kcal/g

What is the primary source of energy in our diet?

Carbohydrates (glucose is main energy source for CNS and RBC)

What are simple carbohydrates?

- Monosaccharides (fructose, glucose, galactose)

- Disaccharides (lactose, maltose, sucrose)

What are complex carbohydrates and what foods are they found in?

- Oligosaccharides (ralfinose, stachyose -- dried beans, soy beans, peas, lentils)

- Polysaccharides (dietary fiber, starch, glycogen)

What is the RDA for carbohydrates?

130 grams/day

How do glucose stores change if energy is needed or not needed by the body?

If energy is needed: glucose is transported in blood to cells

If energy is not needed: glucose is converted to a storage form (glycogen) and stored in the liver

If energy is not needed and there is enough glycogen in the liver: glucose is converted to fat for energy storage

What are low CHO diets (low carb)?

- Atkins

- Paleo

- Ketogenic

Low CHO diets can be seen used as treatment for:

Epilepsy

1/2 of children on this diet experience 50% reduction in their # of seizures, 10-15% of children become seizure free

Can also be used for diabetes tx

What is glycogenolysis, gluconeogenesis, and ketogenesis?

- Glycogenolysis: glucose released from glycogen stores

- Gluconeogenesis: protein used as energy

- Ketogenesis: liver metabolism of fats

Where do we get high quality vs low quality essential amino acids from?

- High quality (complete proteins): animal foods

- Low quality (incomplete proteins): plant foods

We need more protein if we are:

- Undergoing surgery

- Have open wounds

- Burns

- Pregnant

- Elite athletes

- Cancer

What is the RDA for proteins?

0.8-1 g/kg of healthy body weight per day

What is the function of proteins in the human body?

- Structure (bone matrix made up of collagen)

- Catalysts (enzymes that speed up reactions)

- Movement (actin and myosin protein fibers)

- Transport (one cell to another, move molecules across cell membranes)

- Communication (hormones such as insulin, glucagon, gastrin, CCK)

- Protection (antibodies protect against environmental antigens, mucosal cells lining of GI tract, proteins in skin)

- Fluid balance regulation (albumin in blood)

- Energy source

What are risk factors for protein energy malnutrition (PEM) in the US?

- Poverty

- Elderly

- Anorexic

- Chronic malabsorption

- Chronic renal failure

- Neuromuscular disease

What is marasmus?

Negative energy balance

Inadequate intake of protein and overall calories (occurs during weaning) --> adaptive response to starvation

Body draws from own stores resulting in emaciation (loss of subcutaneous fat, muscle wasting)

What is Kwashiorkor?

Occurs in older children aged 1-5 y/o

Inadequate protein intake with reasonable caloric intake

Edema is characteristic

What is the function of fats?

- Satiety value (feeling full and satisfied)

- Carrier of fat-soluble vitamins

- Palatability of food

- Important component of cell membranes (made up of phospholipids -- 2 FA + glycerol head attached to a phosphate group)

- Insulates our body, protects enzymes

What are the two essential fatty acids?

- Alpha linolenic (omega 3, precursor to EPA/DHA found in canola oil, soy oil, walnuts, flaxseeds, fatty fish)

- Alpha linoleic (omega 6, precursor to arachidonic acid found in safflower oil, vegetable oils)

What is the role of essential fatty acids in the body?

- Immunity

- Vision

- Cell membranes

- Produce eicosanoids (signaling molecules important for maintaining and regulating BP)

- Reproduction

- Pain response

- Fever

- Blood clotting

How are fatty acids stored in adipose cells?

As triglycerides

How are triglycerides and cholesterol transported around the body?

Liver synthesizes lipoproteins (chylomicrons, VLDL, IDL, LDL, and HDL) to transport them

What is the AMDR of fats?

20-35% of total kcal

What are some features of water-soluble vitamins?

- Bound to proteins (must be cleaved prior to absorption)

- Digested in the small intestine and stomach

- Absorbed via simple diffusion when intake is high

- Absorbed via active transport when intake is low

- Minimal toxicity

What is the function of thiamine (vitamin B1)?

- Utilized in the citric acid cycle for DNA and RNA synthesis, NADPH and hydrogen ion synthesis

- Allows body to convert carbohydrates to energy

- Important in nerve signaling and development of neurotransmitters

Thiamine (vitamin B1) is found in what food sources?

- Enriched in pasta, rice, flour, breads

- Pork

- Fish

What are causes of thiamine (B1) deficiency?

- Most due to alcoholism

- Malabsorption

- Dialysis

How does thiamine (B1) deficiency present?

- Early: anorexia, muscle cramps, paresthesias, irritability

- Advanced: Beri Beri

What are the two subtypes of Beri Beri disease?

- Dry (PNS and CNS affected)

- Wet (CV system affected)

How does dry Beri Beri disease present?

Peripheral:

- Paresthesias, loss of reflexes

- Sensory and motor neuropathy with pain

Central:

- Wernicke-Korsakoff syndrome (nystagmus progressing to ophthalmoplegia, truncal ataxia, confusion)

- Amnesia, confabulation, impaired learning

How does wet Beri Beri disease present?

- Peripheral vasodilation resulting in high-output HF

- Dyspnea, tachycardia

- Cardiomegaly (dilated cardiomyopathy)

- Pulmonary and peripheral edema

What are the different functions of riboflavin (vitamin B2)?

- Energy metabolism (oxidation/reduction reactions)

- Activates vitamin A, folic acid, pyridoxine, vitamin K

- Fat synthesis and lipolysis

- Important in RBC production

- Needed for tryptophan (AA) conversion to niacin (B3)

Riboflavin (vitamin B2) is found in what food sources?

- Eggs

- Organ meats (liver, kidneys)

- Lean meat

- Milk/milk products

- Green vegetables

- Grains and cereals are fortified

How does riboflavin (B2) deficiency (ariboflavinosis) present?

- Inflammation of the tongue and mouth

- Cracking corners of mouth

- Eye disorders

- Light sensitivity

- Red/sore tongue

- Confusion

- Seborrheic dermatitis

What is the function of niacin (vitamin B3)?

- Oxidation/reduction reactions (energy)

- Synthesis of hormones, cholesterol and DNA

- Repair of DNA

- Can be synthesized in the body by tryptophan

What is a common adverse effect of prescription niacin? How do we prevent it?

Rx niacin often used in patients to help lower cholesterol

Can cause flushing --> use baby ASA prior to intake to help prevent (does not always work)

Niacin (vitamin B3) is found in what food sources?

- Turkey, chicken, liver, tuna, grass-fed beef

- Peanuts

- Mushrooms

- Green peas

- Avocado

How does niacin toxicity present?

Vascular dilation causing flushing, burning, itching

How does niacin deficiency (pellagra) present?

- 4 D's: dermatitis, diarrhea, dementia, death

- Can cause liver damage

What is the function of pantothenic acid (vitamin B5)?

Energy production and synthesis of fatty acids, adrenal hormones, neurotransmitters and heme

Pantothenic acid (vitamin B5) is found in what food sources?

- Animal liver and kidney, fish, shellfish, pork, chicken, egg yolk

- Milk, yogurt

- Legumes, mushrooms

- Avocados

- Broccoli, sweet potatoes, whole grains

How does pantothenic acid (B5) deficiency present?

- Rare, associated with severe malnutrition

- Numbness and burning of the hands and feet

- Headache, irritability, restlessness

What is the function of pyridoxine (vitamin B6)?

- Transamination synthesis of non-essential amino acids

- Neurotransmitter synthesis

- Glycogen breakdown and gluconeogenesis

- Production of neurotransmitter serotonin

Pyridoxine (vitamin B6) is found in what food sources?

- Breakfast cereals are fortified

- Seafood, lean meats, poultry, eggs

- Legumes, nuts, seeds, soy products

Which patients are at risk of having a pyridoxine (vitamin B6) deficiency?

- Oral contraceptive users (depletes B6 stores)

- Elderly

- Alcoholics (small intestine does not absorb B6)

- Adolescents

How does vitamin B6 deficiency present?

- Microcytic hypochromic anemia

- Dermatitis

- Glossitis

- Depression, confusion

- Convulsion

What is the function of biotin (vitamin B7)?

- Carboxylation reactions (involved in the digestion of carbohydrates, synthesis of fatty acids, and gluconeogenesis)

- Energy production and FA synthesis

Why are high levels of biotin troublesome?

High levels of biotin (>10,000 mcg) may interfere with diagnostic assays:

- Thyroid hormone

- Vitamin D25-OH

- BNP

- Troponin

May produce falsely normal or abnormal resulting in inappropriate dx/management

Biotin (vitamin B7) is found in what food sources?

- Turkey, chicken, liver, tuna, grass-fed beef

- Peanuts

- Mushrooms

- Green peas

- Avocado

How does a biotin deficiency present?

- Hair loss (alopecia)

- Depression

- Fatigue

- Numbness/tingling

- Ataxia

- Seizures

What is a risk factor for biotin deficiency?

Excess raw egg white intake (Avidin protein binds to biotin)

What are the functions of folic acid (vitamin B9)?

- Synthesis of amino acids

- Formation of heme (ring molecule in Hgb, needed to make RBCs)

- Synthesis of DNA

- Helps with conversion of homocystiene to methionine (AAs)

High levels of homocysteine is an indicator for:

Cardiovascular disease

How does folic acid deficiency present?

- Glossitis

- Mouth sores

- Fatigue

- Weakness and neurological issues

- Depression

- Memory loss

No paresthesias with this deficiency

Folic acid (vitamin B9) is found in what food sources?

- Cereals, breads, flours, pastas, rice (enriched/fortified)

- Citrus fruits

- Beans

- Leafy green vegetables

What are risk factors for developing folic acid deficiency?

- Alcoholics

- Pregnant women

- Elderly

What are complications associated with folic acid deficiency?

- Megaloblastic anemia (RBCs large and immature)

- Neural tube defects (increased risk of spina bifida and other defects)

- Elevated risk of heart disease (due to homocysteine levels)

- Infertility

- Certain cancers

- Cardiovascular disease

- Depression

- Dementia

- Decreased cognitive function

- Alzheimer's disease

What is the function of cobalamin (vitamin B12)?

- DNA synthesis

- Myelin sheath of nerve fibers

- Involved in single-carbon transfers with folate

What do we need in order to properly absorb vitamin B12?

Intrinsic factor

Vitamin B12 is found in what food sources?

Synthesized by microorganisms, only found in animals

What are risk factors for vitamin B12 deficiency?

- Vegans/strict vegetarian diet

- Alcoholics

- Gastrectomy patients

- Atrophic gastritis

- Elderly

- Infants of vegan mothers

- Gastric bypass

- PPI use

- Metformin use

- +/- beta blockers

How does vitamin B12 deficiency present?

Megaloblastic anemia (absorption failure) OR pernicious anemia (deficiency of intrinsic factor

- Often irreversible neurological defects

- Paresthesias

- Dizziness

- Malaise/fatigue

- Glossitis

- Dyspnea

- Balance problems

- Weakness

- Memory impairment, depression

How do we treat vitamin B12 deficiency?

- Take B12 under the tongue (absorbs directly into the blood, no need for intrinsic factor)

- Can also do IM injections, nasal gel/spray

What are the two types of B12 we can use?

- Methylcobalamin (helps with nerve-related sx, memory)

- Hydroxycobalamin (helps with inflammation)

What is the function of ascorbic acid (vitamin C)?

- Free radical scavenger (neutralizes them, why we use it for anti-inflammation)

- Collagen formation (connective tissue/skin, muscle, bone)

- Metabolism of phenylalanine to tyrosine

- Neurotransmitter synthesis

- Hormone synthesis

- Improves absorption of iron

Vitamin C is found in what food sources?

- Broccoli, kale, brussel sprouts, cauliflower

- Papaya, strawberries, grapefruit, orange, limes, lemons

- Squash, tomatoes, potatoes

- Spinach, cabbage, turnip greens

How does vitamin C toxicity present?

- Kidney stones

- Cramps

- Diarrhea

- Nausea

How does vitamin C deficiency present?

Scurvy

- Connective tissue affected

- Pinpoint hemorrhages

- Bleeding gums/loose teeth

- Unhealed wounds, ulcers

- Bone pain, brittle bones

- Hair loss -- cork screw hair

- Low immunity and hemolysis

What are the fat soluble vitamins?

A, D, E, and K

What are some features of fat soluble vitamins?

- Found in fatty foods

- Deficiencies associated with fat malabsorption

- Easily destroyed by heat and/or light

- Stored in the liver and fatty tissues, eliminated slowly

- Requires micelles (transport poorly soluble FA to enterocyte surface where vitamins can be absorbed)

- Also requires action of bile for digestion/absorption

- Once transported into the intestinal cell, vitamins are packaged with other lipids into chylomicrons

- Toxicities dangerous and sometimes fatal!!

What are the two types of Vitamin A?

- Retinoids (preformed vitamin A, animals)

- Carotenoids (provitamin A, beta-carotene, plants)