Introduction to Nutrition

What are “DRIs?”

• dietary reference intakes

• specifically developed reference values for nutrients

• Used to:

  • develop nutrition labels

  • developing dietary guidelines and food guides

  • ensuring foods and supplements contain safe levels of nutrients

  • creating patient and consumer counseling and educational programs

  • assessing nutrient intakes

  • monitoring the nutritional health of the population

EER

Energy/calorie need

EAR

Meets needs of 50%

RDA

Meets needs of 97-98%

AI

Best estimate when RDA is unavailable

UL

Maximum safe intake

CDRR

Reduce chronic diseases risk

AMDR

Recommended % calories from macronutrients

Macronutrients

• Nutrients required in large amounts

• Provides energy (in forms of calories)

• Carbohydrates, proteins, and Lipids

Micronutrients

• Nutrients required in small amounts

• Found in trace amounts in food

• Do NOT provide calories or energy

• Vitamins, minerals, phytochemicals/phytonutrients

Carbohydrates

• Primary function is to provide energy

• Spares protein from being used as energy and prevents ketoacidosis

• Provides 4 kcalories/gram

• Biomolecular terms: Saccharides

• Classifications:

  • Simplex: monosaccharides and disaccharides

  • Complex: oligosaccharides and polysaccharides

Monosaccharides

• Glucose (most abundant): plant based food

• Fructose: fruits and vegetables plant-based

• Galactose: milk and cheese

Disaccharides

• Maltose: grains and malt

• Sucrose: fruits, nectar, honey, and table sugar

• Lactose: dairy, whey products

Polysaccharides

• Starch

• Glycogen

• Fiber

Glycemic Index

A scale that ranks foods from 0 to 100 based on how quickly the food raises blood glucose levels

• Pure sugar has a score of 100

• High GI foods:

  • Soda

  • White bread

  • White rice

• Low GI foods:

  • Beans

  • Oats

  • Whole Grains

  • Most vegetables

Simple Carbohydrates

• Digest quickly and cause blood glucose levels to spike

• Can occur naturally in foods or added

“Added Sugars”

• Sugar added during processing or preparation

• Lack vitamins, minerals, and fiber

• Limit added sugars to “less than 10% of calories per day” starting at the age of 2

Sugar Alcohol

• Example: xyitol, sorbitol, mannitol

• few calories than sugar

• less sweet than sugar

• Found in sugar-free gum, candy, or protein bars

• May cause bloating, gas, or diarrhea

Sugar Substitutes

• Example: stevia, sucralose, aspartame

• Little or no calories

• Much sweeter than sugar

• Found in diet sodas, flavored drinks, protein powders

• Generally well tolerated

Pros of Sugar Sweeteners

• Do not significantly raise blood glucose levels

• Helpful for DM management

• Lower calorie intake

• Reduce added sugar intake

Cons of Artificial Sugar Sweeteners

• Sugar alcohol may cause GI upset

• Possible effects on appetite and gut microbiome

• May maintain preferance for sweet foods

• Weight-loss benefits may be modest

Complex Carbohydrates

• Digest more slowly and supply a slower release of glucose into the bloodstream

• Most often rich in vitamins, minerals, and fiber

Fiber

• Nondigestable constituent of plants

• Two forms:

  • Soluble fiber:

    • Dissolve in water

    • Sources include oats, nuts, seeds, legumes, and most fruits

  • Insoluble fiber:

    • Does not dissolve in water

    • Sources include whole wheat, brown rice, other whole grains, and most vegetables

What counts as “High Fiber?”

• High source: >5grams per serving

• Good source: 2.5-4.9 grams per serving

Whole Grains

• Contains bran, germ, and endosperm

• Higher in fiber, vitamins, and mineral

• Slower digestion

• Lower glycemic response

• Examples: oatmeal, brown rice, quinoa, and whole wheat bread

Refined Grains

• Bran and germ removed during processing

• Lower in fiber and micronutrients

• Faster digestion

• Higher glycemic response

• Examples: white bread, white rice, “some wheat breads,” crackers, pastas, or pastries

Lipids

• Function

  • Provides energy

  • Regulates metabolism

  • Forms cell membranes

  • Supports the hormonal function of fat-soluble vitamins: A, D, E, and K

• Provides: 9 kcalories/gram

• Classification:

  • Fatty acids and Triglycerides

  • Cholesterol and Sterols

• Use for energy sources

• Becomes a source of energy during times of fasting when glycogen stores are reduced

Saturated Fats

• No double bonds

• Usually solid

• Raises LDL cholesterol

• Sources: meat, butter, cheese, full fat dairy products, lard, palm oil, and coconut oil

Unsaturated Fat

• One or more double bonds

• Usually lipid

• Improves lipid profile

• Sources: Oils, nuts, seeds, avocados, nut butters, fish

Vitamins

• Water soluble: easily absorbed into body and cells; easily excreted; low chance of toxicity!

  • B vitamins (thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folate, B-12)

  • Vitamins C

• Fat Soluble: can have icidence of toxicity (usually with supplements) incidencethe

  • Vitamin A

  • Vitamin D

  • Vitamin E

  • Vitamin K

Minerals

• Major Minerals (needed in gram amounts)

  • Sodium, potassium, chloride, calcium, magnesium, sulfur, and phosphorus

• Trace minerals (needed in amounts less than 100 mg)

  • Iron, zinc, copper, selenium, chromium, iodine, fluoride, manganese, and molybdenum

Enrichment

• Adding nutrients back that were lost during processing

• Examples: White flour enriched with thiamine, niacin, iron

• Returns nutrients that were originally present

Fortification

• Adding nutrients that were not originally present (or adding extra amts)

• Examples:

  • Milf fortified with Vitamin D

  • Breakfast cereals fortified with iron and B vitamins

  • Grain products fortified with Folic acid

• Adds nutrients to improve public health

Hypovitaminosis

• Deficiency

• Low levels of one or more vitamins

  • Primary deficiency: inadequate dietary intake

  • Secondary deficiency: result of an underlying disorder

Hypervitaminosis

• Toxicity

• Abnormally high storage levels of vitamins

• Can lead to toxic symptoms and diverse health effects

• Primarily caused by fat-soluble vitamins (D and A)

  • Stored by the body longer

  • Not as easily excreted in the urine

Thiamine (Vit B1)

Primary role for the body:

• Energy prduction: help you convert carbohydrates, fats, and proteins into usable cellular energy production

• Nerve signaling and brain health: participates in initiaition of nerve impulse propogation

Food Source:

• Yeast, legumes, brown rice, whole grains, pork

• Thiamine low in white or milled rice and cereals because processing removes thiamine

Absorption:

• Proximal small intestine

Toxicity: None (water soluble vitamin)

Thiamine Deficiency

• Beriberi

• High-risk populations:

  • Diets based on polished rice

  • Refugee or famine settings

  • Severe malnutrition

  • Alcohol abuse disorder

  • Bariatric surgery: less absorption

Dry Beriberi

• Nerves dry out

• Ataxia

• Decreased tendon reflexes

• Nystagmus

• Peripheral neuropathy

Wet Beriberi

• Heart (fluid overload and heart failure)

• Dilated cardiomyopathy

• Heart failure

  • Edema

  • DOE

  • Elevated JVP

  • Tachycardia

Infantile Beriberi

Breastfed infants of thiamine-deficient mothers

Wernicke-Korsakoff Syndromes

Form of Dry Beriberi

Wernicke Encephalopathy (WE)

• The acute neurological syndrome

  • Classic symptom triad:

    • Encephalopathy

    • Oculomotor dysfunction (nystagmus)

    • Gait ataxia

Korsakoff Syndrome

Chronic neurologic condition, sequelae of WE

At risk population for Wernicke-Korsakoff Syndrome

Alcohol abuse disorder or prior bariatric surgery

Diagnosis of Wernicke Encephalopathy

• Primarily a clinical diagnosis

  • Caine Criteria (2 out of 4 for Dx)

    • Dietary deficiency

    • Oculomotor abnormalities

    • Cerebellar dysfunction

    • AMS or mild memory impairment

  • High index of suspicion esp for patients with alcohol abuse disorder

    • If left untreated, most patients progress to coma or death

  • Response to treatment may be diagnostic

  • Serum thiamine level: limited sensitivity and specificity

Treatment of Wernicke Encephalopathy

• Immediate IV replacement x 5 days

  • Often with other B vitamins

• Daily oral supplements thereafter

Prognosis of Wernicke Encephalopathy

With prompt treatment:

• Ocular improvement: hours to days

• Vestibular improvement: within 2 weeks

• Confusion subsides: days to weeks

Niacin

Primary Role for the Body:

• Energy production: involved in the synthesis and metabolism of carbohydrates, fatty acids, and proteins

Food sources

• Widely distributed in plant and animal foods

• Good sources: yeast, organ meats, chx breast, salmon, PB, brown rice

Absorption

• Primarily jejunum

Toxicity: None

• Flushing can occur with pharmacologic doses of 1000-3000mg/day; no serious sequelae from flushing

Niacin Deficiency

• Pellagra: “Raw Skin”

• Characteristics: 4 D’s

  • Photosensitive pigmented dermatitis

  • Diarrhea

  • Disorientation

  • May progress to death

• Diagnosis: clinical

• At-risk populations:

  • Most common in the developing world

  • Alcohol use disorder

  • Crohn’s disease

  • Significant small bowel surgeries

  • Carcinoid syndrome

Vitamin B12 (Cobalamin)

Primary Role for the Body

• DNA and RNA synthesis

• RBC production in the bone marrow

• Development, myelination, and function of the central nervous system

Food sources

• Meats, dairy products, and eggs

• Some seafoods

• Fortified breakfast cereals

Absorption: Terminal ileum

Toxicity: none

Vit B12 absorption

1. B12 released from food by stomach acid and pepsin

2. B12 binds R-protein in stomach

3. Gastric parietal cells in the stomach secrete intrinsic factor

4. B12 binds IF in duodenum

5. B12/IF complex absorbed in distal ileum

Vit B12 Deficiency Etiologies

• Decreased intake: vegan diet

• Stomach problems:

  • Pernicious anemia: autoimmune condition that prevents the formation of IF

  • Gastric bypass

  • Chronic gastritis

• Medication Related:

  • PPIs: reduce gastric acid

  • Metformin: decreases absorption in the ileum

• Illeal Disease:

  • Crohn’s Disease

  • Illeocectomy

Prevalence of Vit B12 Deficiency

• 1.6-7.6% general population, 5-14% older adults

• 3% hospitalized patients

Clinical Manifestations of Vit B12 Deficiency

• Blood

  • Macrocytic Megaloblastic Anemia

    • Fatigue

  • Cytopenias

• Nervous System

  • Parathesias

  • Ataxia

  • Cognitive changes/slowing

• Other

  • Glossitis

  • Mild jaundice

Diagnosis of Vit B12 Deficiency

• CBC: Macrocytic anemia (low hgb, high MCV)

• Serum Vit B12

  • 200 to 300pg/mL: borderline

  • Below 200 pg/mL —> low; consistent with deficiency

• Metabolite testing(for selective pts)

  • Serum methylmalonic acid (MMA)

    • High in vit B12 deficiency

    • Normal in folate deficiency

  • Homocysteine

    • High in Vit B12 deficiency

    • High in folate deficiency

Treatment for Vit B12 Deficiency

• Severe formulations

  • PO

  • SL

  • IM

  • Deep SQ

• Route/duration dependent on underlying etiology

  • PR/SL: dietary deficiency

  • Parental (IM, deep SQ): pernicious anemia, altered GI anatomy

Folate (B9)

Critical role in:

• DNA and RNA synthesis

• RBC production in the bone marrow

• Embryonic development: helps close the neural tube in the first few weeks of pregnancy, preventing severe birth defects like spina bifida and ancephaly

Food sources:

• Vegetables

• Fruits and fruit juice

• Nuts, beans, peas

• Fortified grains

• Seafood, meat, poultry

• Eggs, dairy products

Absorption: Jejunum

Folate Deficiency Etiologies

• Increased requirement

  • Pregancy

  • Hemolytic anemia

  • Hemodialysis

• Decreased intake (very rare due to fortification)

  • Alcohol abuse disorder

  • Use of goat milk as main source of food in infants and toddlers

  • Residence in a country where routine folic acid fortification does not occur

• Decreased absorption

  • Prior bowel surgery

• Medications:

  • Methotrexate: interferes with metabolism

Dietary Guidelines for Americans (DGA)

• Established by: HHS and USDA

• History: first edition 1980, and a new edition is published every 5 years

• Purpose:

  • Provide evidence-based nutrition recommendations

  • Used to guide: nutrition counseling, school lunch programs, SNAP/WIC, public health initiatives

  • Includes DRIs for macronutrients and micronutrients

• Audience: Professionals (healthcare providers, nutrition educators, federal nutrition program, policy makers)

What changed in the DGA 2025-2030?

• Greater focus on Whole Foods and reducing highly processed foods

• More emphasis on high-quality protein

• Less emphasis on low-fat dairy

• Stronger messaging on reducing sugar-sweetened beverages

• Increased discussion on chronic disease prevention

What stayed the same in the DGA 2025-2030?

• eat more fruits and vegetables

• choose whole grains

• limit added sugars

• maintain healthy dietary patterns across lifespan

Additional emphasis on the 2025-2030 DGA

• whole foods and minimally processed foods

• reducing highly processed foods

Why the new emphasis on Whole Foods?

• all cause mortality

• overall cancer

• cardiovascular disease

• liver: all diseases

• non-alcoholic fatty liver disease

• obesity

• type 2 diabetes

• depression

• dementia

What prevalence is on the rise?

Obesity

Life expectancy in the US

has gone up, but is still lower compared to other countries

What is 66% of the US diet?

Highly processed food

How do you identify highly processed foods?

• refined grains and/or added sugars

• refined fats and oils

• long, complicated ingredient lists including chemical additives (i.e., artificial sweeteners, flavor enhancers, artificial colors and emulsifiers)

Examples of High Quality Protein

• fish

• poultry

• eggs

• dairy

• lean meats

• soy products

• beans and lentils

What is adequate protein intake important for?

• Muscle maintenance

• Healthy aging

• Prevention of sarcopenia

What does DGA 2025-2030 recognize?

• Full fat may within healthy dietary patterns

• Less emphasis on choosing only low-fat products

What recommendations of added sugar remain the same?

• <10% of daily calories should come from simple sugars

  • equates to 50gm/day for a 2,000-calories/day diet

What is the new focus on added sugars?

• sugar sweetened beverages identified as a major concern

• water encouraged as the primary beverage

Protein serving goals

1.2-1.6gm/kg/day

Dairy serving goals

3 servings a day

vegetables serving goals

3 servings a day

Fruit serving goals

2 servings a day

Whole grain serving goals

2-4 servings a day

DGA 2025-2030 takeaways

• build meals around whole food

• eat plenty of fruits and vegetables

• prioritize high-quality foods

• drink water instead of sugary beverages

• focus on long-term dietary patterns, not individual foods

Vitamin C (Ascorbic Acid)

• biological roles

  • builds and repairs tissues

  • supports immune systems

  • acts as an antioxidant

  • improves absorption of iron

• food source:

  • citrus fruits and tomatoes

  • bell peppers, brussels sprouts, cauliflower, broccoli, cabbage, and spinach

• toxicity: rare and often self-limited (water-soluble vitamin)

Vitamin C Deficiency:

• Scurvy

• Characteristics:

  • petechiae

  • perifollicular hemorrhage

  • bruising

  • gingivitis

  • arthralgias

  • impaired wound healing

• Diagnosis: clinical

• At-risk population:

  • rare

  • severely malnourished

  • alcohol use disorders

  • Prior bariatric surgery

Vitamin A

• Biological role:

  • Eye integrity

  • Phototransduction

• Food source:

  • Provitamin A carotenoids

    • Plant foods: green leafy vegetables, sweet potatoes, and carrots

  • Preformed Vitamin A (retinol, retinal, retinoic acid, and retinyl esters)

    • Animal products: liver, kidney, egg yolk, and butter

Vitamin A Deficiency:

• Rare: patients with a history of bariatric surgery

• Clinical manifestations:

  • Xerophthalmia: dryness of the conjunctiva and cornea manifested by Bitot spots

  • Nyctolopia: night blindness

• Diagnosis: serum retinol levels

• Treatment:

  • Oral supplementation

  • Encourage increasing consumption of food sources high in vitamin A

Vitamin A Toxicity:

• Most often due to chronic ingestion of synthetic vitamin A

• Acute toxicity:

  • single dose of >660,000 IU

  • symptoms include n/v, vertigo, and blurry vision

• Chronic toxicity:

  • long-term ingestion of >10x the RDA (33,000 IU)

  • symptoms include ataxia, alopecia, hepatotoxicity, and visual impairment

• Can be teratogenic in the first trimester in doses only several times the RDA

• Diagnosis: clinical

  • Serum Vit A is not reliable because most of Vit A is stored in the liver

• Treatment: stop vitamin A supplements and restrict vitamin A-rich foods (especially sources of preformed vitamin A, such as liver, kidney, and egg yolk)

Vitamin D

• biological role:

  • promotes calcium absorption

  • needed for bone growth and bone remodeling by osteoblasts and osteoclasts

• sources:

  • dietary: fatty fish, fish liver oils, beef liver, egg yolks, cheese, mushrooms, fortified milk

  • sun exposure: UV rays

    • cutaneous 7-dehydrocholesteral —> previtamin D3 (which in turn becomes vitamin D3

Vitamin D Deficiency:

• Prevalence:

  • Borderline: 5.5%

  • Deficiency: 15.6%

• Clinical manifestations:

  • Mild deficiency: asymptomatic

  • Severe deficiency: bone pain and tenderness, muscle weakness, fracture, difficulty walking

    • Adults: osteomalacia

    • Children: Rickets

• At-risk populations:

  • Elderly confined to indoors

  • Those institutionalized

  • Those with osteoporosis, hyperparathyroidism

  • Malabsorption:

    • Bariatric surgery

    • Crohn’s disease

    • Celiac disease

• Diagnosis: Serum 25-Hydroxyvitamin D

  • 20 ng/mL: adequate

  • 12-20 ng/mL: insufficient

  • <12ng/mL: deficient

• Treatment: Vitamin D3 (cholecalciferol) and Vitamin D2 (ergocalciferol)

• Prevention: AAP recommends vitamin D supplements for exclusively and partially breastfed infants starting shortly after birth

Vitamin D Toxicity

• Rare

• Causes: inappropriate use of vitamin D preperations or inadvertent overfortification

• Prolonged exposure of the skin to sunlight does not produce toxic amounts of vitamin D

• Symptoms:

  • Confusion

  • Polyuria

  • Polydipsia

  • Anorexia, vomiting

  • Muscle weakness

Iron

• Biologic role: necessary component of hemoglobin and myoglobin

• Sources: 2 forms of dietary iron

  • Heme: derived from animal food sources such as meat, poultry, and fish

    • More easily absorbed than non-heme iron

  • Non-heme: derived from plant sources, such as cereal, legumes, fruits, and vegetables

    • Vitamin C enhances absorption of non-heme iron

• Absorption: duodenum and jejunum

  • Rates of absorption are indirectly proportional to the body’s iron stores

Iron Deficiency:

• Causes:

  • Inadeqaute intake (esp intake in vegan/strict vegetarian diet)

  • Chronic blood loss

  • Malabsorption: bariatric surgery, celiac disease

  • CKD, chronic liver disease

• Clinical manifestations:

  • Microcytic anemia: fatigue or exercise weakness

  • Pica

  • Severe cases: tachycardia, dyspnea, cognitive impairment

• Physical finding:

  • pallor

  • dry skin

  • alopecia

  • atrophic glossitis

  • angular cheilitis

  • koilophyia (spoon nails)

• Diagnosis: CBC

  • Decreased hemoglobin and decreased MCV

  • Iron studies: Ferritin (most useful)

    • serum iron

    • transferrin/TIBC

    • transferrin saturation

Treatment of Iron Deficiency

• Oral:

  • Ferrous gluconate: 324 mg tablet (contains 38 mg elemental iron)

  • Ferrous sulfate

    • 325 mg tablets (65 mg elemental iron)

    • 220 mg/5mL oral elixer (44 mg elemental iron)

    • 75 mg/mL oral solution (15 mg elemental)

  • IV:

    • ferric carboxymaltose (FCM), ferric gluconate (FG), ferumoxytol, iron sucrose (IS), ferric derisomaltose (also called iron isomaltoside), and low molecular weight iron dextran

Iron Overload:

• Cause:

  • Over-supplementation or chronic transfusions

  • Hereditary Hemochromatosis

    • Can result in liver damage

• Treatment: phelbotomy

Calcium:

• Biologic role: provides strength and structure to bones and teeth

  • Essential for muscle contraction, nerve transmission, and blood vessel function

• Tightly regulated: Controlled by PTH, vitamin D, and calcitonin to maintain normal blood calcium levels

• Food source: milk, yogurt, cheese, calcium-set tofu, calcium-fortified orange juice, chinese cabbage, kale, and broccoli

What does an inadequate dietary intake of calcium lead to?

• osteoporosis

• fractures

• rickets

• osteomalacia

What can excess intake of calcium be associated with?

• Nephrolithiasis

• Vascular and soft tissue calcification

• Reduced iron and zinc

• Constipation

• Most calcium excess comes from supplements, not food

Sodium

• Function

  • maintain fluid balance

  • Regulates blood pressure

  • Supports nerve and muscle function

• Food source:

  • Table salt: 1 tsp of salt is equal to 2,300 mg

  • Restaurant foods

• Recommendation: <2,300 mg of sodium per day

What can excess sodium intake do?

• Fluid retention/edema

  • Major concern for patient with CHF, CKD, Cirrhosis

• Long-term effects

  • HTN

  • Cardiovascular disease

  • Stroke

  • Research shows positive linear association with sodium intake with increased blood pressure and CVD risk

Potassium

• Biological role:

  • major intracellular electrolyte

  • maintains fluid balance

  • essential for nerve conduction and muscle contraction

  • critical for normal cardiac rhythm

• Food source:

  • bananas

  • potatoes

  • leafy green vegetables

  • beans and legumes

  • avacodos

• Most potassium abnormalities are caused by disease or medication, not dietary intake

Low potassium (hypokalemia)

• muscle weakness

• fatigue

• cardiac arrhythmias

High potassium (hyperkalemia)

• muscle weakness

• cardiac arrhythmias

  • can be life-threatening