Nutrition Chapter 9 (Exam 3)

What are vitamins?

• Tasteless, organic compounds

• Required in small amounts

Functions:

-Regulate metabolism

-Help convert energy in fat, carbohydrate, and protein into A T P

-Preserve tissues

-Promote growth and reproduction

-Act as antioxidants

• Deficiencies can result in potentially serious symptoms

Criteria for designating vitamins

1.Cannot be synthesized in ample amounts in the body, but essential to human health

2.Chronic deficiency is likely to cause physical symptoms

–Symptoms will disappear once the vitamin level in the body is restored unless the deficiency has caused permanent damage.

History of Vitamins (Discovered 100 years ago)

• Diseases caused by vitamin deficiency and the foods that helped cure them were recognized long before the vitamin was discovered

• In the eighteenth century, acid in citrus fruit was noted to cure the symptoms of scurvy (vitamin C deficiency) in British sailors

• In the early 1900s, scientists discovered that thiamin cured beriberi and vitamin D cured rickets

• Scientists have shifted their vitamin research focus from curing disease to prevention of disease

• Vital + Amine = Vitamin

• Each new vitamin was given a temporary name when it was discovered

• The naming of vitamins follows the letters of the alphabet, starting with A; we are now at the letter K

  • A, B, C, D, E, and K

  • Vitamins F, G, and H were dropped

• The nomenclature changed when vitamin B was found to have several functions

  • Subscripts were added for each new isolated role

  • Vitamin B Complex

Criteria for classifying vitamins

• Vitamins are classified based on solubility

  • Nine water-soluble:

    • B vitamin complex

    • Vitamin C

  • Four fat-soluble:

    • Vitamin A

    • Vitamin D

    • Vitamin E

    • Vitamin K

• Solubility influences a vitamin’s:

–Digestion

–Absorption

–Transportation

–Storage

-Excretion

All Vitamins are Organic, but Differ in Structure and Function

• All vitamins contain carbon (organic), hydrogen, and oxygen

  • Some vitamins contain nitrogen, cobalt, or sulfur

• The chemical structure of each vitamin is unique

• There are no bonds for the body to hydrolyze during digestion

  • vitamins are absorbed into the enterocytes intact

• Vitamins perform numerous essential functions

• Some vitamins have more than one role in metabolism

Provitamins

• Substances found in foods that are not directly usable by the body

• Vitamin precursor converted to an active form once absorbed in the body

• Example: beta-carotene (provitamin)→ vitamin A

(can be converted to active vitamins by the body)

Preformed vitamins

• Vitamins found in foods in their active form

• Do not need to be converted

• Example: vitamin A

Vitamin toxicity (hypervitaminosis)

• Rare

• Results from ingesting excess vitamins, which leads to tissue saturation

• Can damage cells, sometimes permanently

• Results from supplementing with megadoses of vitamins; does not occur from eating foods

•Vitamin C and most other water-soluble vitamins do not cause toxicity because the excess is excreted in the urine

•Vitamin B6 is sometimes linked to toxicity, and the fat-soluble vitamins A, D, and E, which are stored in the body’s tissues, can be toxic in mega doses

•To prevent toxicity, the Dietary Reference Intakes (DRI) include a tolerable upper intake level (UL) for most vitamins

How Do Vitamins differ in their Absorption and Storage

Where does absorption take place in the body?

• All absorption takes place in the small intestine

• fat soluble and water soluble differ in

  • absorption

  • bioavailability

Vitamins differ in Bioavailability

• Degree to which a nutrient is absorbed from foods and used in the body

____ varies based on:

-Amount in food

-Preparation

-Efficiency of digestion and absorption of food

-Individual nutritional status

-Natural or synthetic

• Fat-soluble vitamins are generally less bioavailable than water-soluble vitamins

• Vitamins from plant foods are generally less bioavailable than those in animal foods

Fat-soluble Vitamins Absorption

• Attached to proteins in foods, released in the stomach with the help of pepsin and HCL

• Are absorbed in the duodenum

• Packaged in micelles that transport them close to the intestinal mucosa

• Packaged in chylomicrons → lymph system → bloodstream

• Lack of fatty acid and bile can lead to deficiency

Fat soluble Vitamin Storage

• The liver is the main storage site for vitamin A; to a lesser extent for vitamins K and E

• Vitamin D is mainly stored in the fat and muscle tissue

• Can build up in the body to the point of toxicity, particularly vitamin A

___-soluble vitamins are stored after they are absorbed

Water-soluble Vitamins Absorption

• Absorbed with water and enter directly into the bloodstream

• Most absorbed in the duodenum and jejunum, and B12 is absorbed in the ileum

Water-soluble Vitamins Excretion

• Not stored in the body

• Excess intake excreted through the urine

• Important to consume adequate amounts daily

• Dietary excesses (megadosing) can be harmful

___-soluble vitamins are not stored after absorption

What are Antioxidants?

• Group of compounds that neutralize free radicals, helping to counteract the oxidation that takes place in cells

• Includes:

  • Vitamin E

  • Vitamin C

  • Selenium (mineral)

  • Flavonoids (phytochemical)

  • Carotenoids (phytochemical)

• Free radicals

  • By-products of the body’s metabolic reactions

  • Molecules with an unpaired electron, which makes them unstable

  • Factors that increase free radical production include:

    • U V light

    • Exposure to toxins from smoking

    • Exposure to environmental pollutants

What are Antioxidants/Free radicals?

• ____are molecules with an unpaired electron

• Oxidative stress occurs when free radicals accumulate faster than the body can metabolize them

  • Damages D N A and body proteins, and alters cell structure

  • Excess free radicals contribute to chronic diseases:

    • Heart disease

    • Cancer

    • Aging

    • Diabetes

    • Parkinson’s disease

    • Alzheimer’s disease

Phytochemicals

• Antioxidant-rich foods also contain other protective compounds

• ____are naturally occurring plant compounds that give plant food their vibrant colors; also act as antioxidants.

  • Carotenoids

  • Flavonoids

Antioxidant Supplements

• Studies are underway exploring the role of antioxidant supplements in fighting disease

• Currently, supplements are not recommended; instead, phytochemical- and antioxidant-rich foods should be part of a balanced diet

What’s the Best Food Sources of Vitamins

• Whole foods

  • Fruits, vegetables, and whole grains

  • Rich in vitamins, phytochemicals, antioxidants, and fiber

• Dietary Guidelines for Americans recommends:

  • Eat a wide variety of foods from each food group, with ample amounts of vitamin-rich fruits, vegetables, whole grains, and dairy foods.

  • Most people do not need supplements if they consume a balanced diet.

How can vitamins be destroyed?

• Exposure to oxygen

  • Water-soluble vitamins

  • Vitamins A, E, and K

• Exposure to ultraviolet light

  • Riboflavin

  • Beta-carotene and vitamin C

• Water

  • Most water-soluble vitamins will leach out of foods when soaked or cooked in liquids, so cooking foods in as little water as possible is recommended to retain those vitamins

  • Adding vegetables to water that is already boiling can inactivate food enzymes that oxidize the vitamins

• Changes in pH

  • Most vitamins are stable in acid, but adding ingredients such as baking soda to foods increases the pH and destroys certain vitamins

  • Thiamin and vitamin C

• Heat

  • Especially prolonged heat from cooking, will also destroy water-soluble vitamins, especially vitamin C

  • Microwaving, steaming, or stir-frying are better than boiling

  • Refrigeration preserves vitamins in food

• Vegetables and fruits begin to lose their vitamins almost immediately after being harvested, and some preparation and storage methods can accelerate vitamin loss

• Fat-soluble vitamins tend to be more stable than water-soluble vitamins

____can be destroyed during cooking or storage

How you prepare and store fresh foods can affect their nutritional content

How to preserve your vitamins

• Cook vegetables in a small amount of already boiling water—not cold water brought to a boil. Use any leftover cooking liquid as a soup or gravy base

• Don’t rinse rice before cooking it or pasta after cooking it. You’ll wash away water-soluble vitamins. Boiling rice in excess water (6 parts water to 1 part rice) is more effective at reducing its arsenic content and will preserve more of the vitamins

• Microwave or stir-fry vegetables instead of boiling or frying them. These methods reduce the amount of time vegetables are exposed to heat and therefore the loss of vitamins

• Store produce in a refrigerator and eat it soon after purchasing

• Cut vegetables and fruits in larger pieces to reduce the surface area exposed to oxygen. Prepare vegetables close to the time that they are going to be cooked and/or served

Fortified foods with vitamins

____-voluntary addition of nutrients by manufacturers to:

-Vitamins and minerals are the most commonly used nutrients, but fiber, amino acids, essential fatty acids, and other bioactive ingredients are also sometimes added

-Enhance the nutrient quality of food

-Prevent or correct dietary deficiencies

-Ensure adequate intake for some individuals

• Enriched foods are a type of fortified food that have had nutrients added back to them to make up for nutrients that were lost during processing

• Fortified foods can help those with deficient diets achieve adequate intake of nutrients

• Fortification can contribute to health risks:

–Lead to vitamin excess

–Displace nutrient-rich foods

▪Such as an orange-flavored drink fortified with vitamin C displacing pure orange juice

What is Vitamin A?

• A family of fat-soluble retinoids (retinol, retinal, retinoic acid)

• Retinol is the most usable to the body

• Preformed vitamin A (retinol or retinyl ester) is found primarily in animal foods.

• Body stores vitamin A as a retinyl ester in the liver

• Some plants contain provitamin A carotenoids, which are precursors to retinol in your body

  • Beta-carotene is split into two molecules of retinal

  • Carotenoids:

    • beta-carotene

    • beta-cryptoxanthin

    • alpha-carotene

Vitamin A Absorption and Transport

• All forms of vitamin __ are absorbed by active transport in the small intestine with bile salts and micelles

• Beta-carotene is absorbed by passive diffusion

  • Reduced with high fiber intake

  • Improved in cooked foods

• Most forms of vitamin ___are packaged into chylomicrons and enter lymph

• Retinoic acid is attached to albumin and transported to the liver via the portal vein

• Vitamin __ is stored in the liver and difficult to excrete, leading to possibility of vitamin toxicity

  • Excretion through bile helps to prevent toxicity

Metabolic Functions of Vitamin A

• Participates in:

  • Vision (figure 9.7—Retinal and its role in vision)

  • Epithelial tissue maintenance

    • Protein synthesis

    • Cell division and differentiation

    • Epithelial tissues line body cavities or cover body surfaces

  • Growth

  • Reproduction

  • A healthy immune system

  • Bone health

  • Too much vitamin __ can break down bone

  • May help fight cancer

  • Carotenoids are antioxidants

    • Lycopene, lutein, and zeaxanthin (nonprovitamin __ compounds)

      • Body does not convert them to vitamin __

Daily needs of Vitamin A

• Vitamin needs for adults (RDA)

  • Males: 900 micrograms (μ g) retinol activity equivalents (R A E)

  • Females: 700 μ grams R A E

  • Upper limit: 3,000 μ g as performed vitamin A onlyramsas pas saaasp

• Beta-carotene (no RDA): 3 to 6 milligrams daily

• Strict vegans need to meet vitamin __ intake through carotenoids and beta-carotene–rich foods

Food sources:

• Beef liver

• Fortified dairy producs and cereal

• Egg carrots, spinach, sweet potatoes

Vitamin A Toxicity

• Excessive amounts of preformed vitamin __ can accumulate to toxic levels

  • Toxic levels occur by taking supplements, not with food intake

  • >15,000 μ grams can cause symptoms of toxicity

  • Hypervitaminosis __ can lead to liver damage and even death

• Overconsumption:

  • During pregnancy can cause birth defects in the face, skull, and C N S of the child

  • Can potentially result in osteoporosis and bone fractures in adults

• Carotenoids in foods are not toxic

  • Do not pose serious health problems

  • Excess carotenoids can cause carotenodermia

• Overconsuming beta-carotene supplements

  • May increase a smoker’s lung cancer risk

Vitamin A Deficiency

• Chronic vitamin __ deficiency causes night blindness.

• Prolonged vitamin __ deficiency leads to xerophthalmia

  • Leading cause of preventable blindness in children, mostly in developing countries

• Deficiency can lead to keratinization of epithelial tissues

  • Epithelial cells don’t secrete mucus

  • Cells are unable to function properly, promoting infection

What is Vitamin D

• Called the “sunshine vitamin”

• Derived from a reaction between ultraviolet rays and a form of cholesterol in the skin

  • Exposure to sunlight can synthesize all of the body’s vitamin __ needs.

    • Considered a conditionally essential nutrient

• Considered a prohormone

  • Physically inactive precursor to a hormone

• Found in two forms

  • Cholecalciferol (vitamin __ 3): Produced in the skin and found in animal foods

  • Ergocalciferol (vitamin __2): Found in plants and dietary supplements

Vitamin D3 or D2

• Vitamin D3 may be more effective at increasing levels of vitamin D in the blood. Although, scientists debate vitamin D3 vs D2

• Pick whichever form of D is easier to find, but be sure to get enough.

Absorption of Vitamin D2 or Vitamin D3

• Vitamin D2 and Vitamin D3 consumed in the diet are absorbed into the small intestine as part of a micelle along with other dietary lipids

• Repackaged into chylomicrons and circulates through the lymph system before arriving at the liver for storage

Metabolic functions of Vitamin D

• Bone growth

  • Calcitriol stimulates intestinal calcium and phosphorus absorption

  • Maintains healthy ratio of calcium and phosphorus in the blood

  • Controls interaction between osteoblasts (new bone formation) and osteoclasts (bone degradation)

• May prevent some cancers

  • Incidence of breast, colon, and prostate cancer is higher in individuals living in sun-poor areas of the world.

How Calcium levels Decreases in the Blood

• PTH stimulates the kidney to increase the amount of active vitamin D (calcitriol)

• How does calcitriol increase calcium blood levels?

  • Increases calcium absorption from digested food in the small intestine

  • Stimulates the reabsorption of calcium through the kidneys

  • Releases calcium from the bone

    • Stimulates osteoclast and inhibits osteoblast

Metabolic Functions of Vitamin D

• Potentially helps reduce risk of some autoimmune disorders

• May prevent diabetes

  • May reduce type 1 diabetes risk by 50 percent in adults

  • Type 2 diabetes is associated with low blood vitamin D levels.

• May regulate blood pressure

Daily needs of Vitamin D

• Sun exposure cannot meet everyone’s vitamin __ needs

  • The skin pigment melanin and use of suncreens reduce vitamin __ production

  • Sunlight intensity during winter in some locations is not sufficient to make enough vitamin __

• Vitamin __ needs based on dietary sources

• Adults:

  • 15 to 20 μ grams (600 to 800 I U) per day, depending on age

  • U L: 100 μ grams (4,000 I U)

• Children:

  • 15 μ grams per day

  • UL: 50 μgrams (2,000 IU)

Food sources:

• Fatty fish such as salmon, tuna, sardines

• Fortified foods such as dairy products, orange juice, cereals

Vitamin D Toxicity

• A high intake can cause loss of appetite, nausea, vomiting, and constipation

• Overuse of supplements may lead to hypervitaminosis __

• Hypercalcemia

  • Can cause damaging calcium deposits in kidneys, lungs, blood vessels, and heart

  • Can affect the nervous system and cause severe depression

• Too-high levels are rarely caused by food intake or overexposure to the sun

Vitamin D Deficiency

• Rickets: Vitamin __ deficiency disease in children

  • Bones aren’t adequately mineralized with calcium and phosphorus, causing them to weaken, leading to bowed legs

  • On the rise in the United States due to decreased milk consumption, fear of skin cancer from sun exposure, and air pollution

• Other vitamin __ deficiency disorders

  • Osteomalacia: Adult equivalent of rickets

  • Osteoporosis: Condition where bones don't mineralize properly

  • Muscle and bone weakness and pain

What is Vitamin E?

• Alpha-tocopherol is the most active form in the body

• The synthetic form in supplements is only half as active as the natural form

Vitamin E Absorption and Transport

• Absorbed with bile salts and micelles into the enterocytes

• Packaged in chylomicrons → lymph → circulation → liver

• Ninety percent of vitamin __ is stored in adipose tissue

• Excess vitamin __ is excreted through the bile, urine, feces, and the pores of the skin

Metabolic Functions of Vitamin E

• Acts as a powerful antioxidant

  • Protects cell membranes; prevents oxidation of L D L cholesterol

• Acts as an anticoagulant, inhibiting formation of harmful clots inside bloodstream

• No evidence supporting a role in prevention of cancer or other diseases has been conclusively identified

Daily Needs of Vitamin E

• Adults need 15 milligrams of alpha-tocopherol equivalents.

• UL is 1,000 milligrams/day

  • Current suspicion that the upper limit may be too high

Food sources:

•vegetable and seed oils

•Avocados

•Wheat germ

•Nuts and seeds

•Fortified cereals

•Green leafy vegetables

Vitamin E Toxicity

• Toxicity

  • No known risk of consuming too much vitamin __ from natural food sources

    • Overconsumption of synthetic form in dietary supplements and fortified foods can increase risk of a hemorrhage

Vitamin E Deficiency

• Deficiency

  • Rare

  • Chronic deficiency of vitamin __ can cause nerve problems, muscle weakness, and free radical damage to cell membranes

What is Vitamin K

• Three forms of vitamin __

  • Phylloquinone is found in green plants (primary source in diet)

  • Menaquinone is synthesized by intestinal bacteria

  • Menadione is the synthetic form

Vitamin K Absorption and Transport

• Most vitamin __ is absorbed in the jejunum

• Ten percent of vitamin __ is produced by bacteria in the colon

• Vitamin __ is incorporated into chylomicrons and transported to the liver where they are stored

• When a diet is deficient in vitamin __:

  • Storage forms are transported by VLDL, LDL, and HDL

• Excess vitamin __ is excreted, mostly bound to bile

Role of Vitamin K in Blood Clotting

• Regulates blood clotting via coagulation (process of blood clotting)

  • Involved in synthesizing four blood-clotting factors

    • II (prothrombin), VII, IX, X

Low Blood levels of Vitamin K

• Anticoagulation medications such as coumadin or warfarin and severe liver disease can result in low blood-levels of vitamin __, increasing the risk of hemorrhage

• Difficult for blood clots because there are low levels of vitamin __ in the blood

Anticoagulation- Inhibit clotting of the blood

Coumadin or Warfarin (Vitamin K)

• Blood thinner prescription medication used to treat and prevent blood clots

• Patients need to be consistent with their vitamin K intake

• Sudden changes in vitamin __ in the diet:

  • Increase of vitamin

    • Vitamin overriding the effect of the drug; enabling the blood to clot too quickly

  • Decrease of vitamin

    • Vitamin can enhance the effectiveness of the drug and increase the risk of bleeding

Metabolic Functions of Vitamin K

• Promotes strong bones

  • Assists with the carboxylation of other proteins

  • Interacts with proteins osteocalcin and matrix Gla protein, which is essential for the formation of a strong bone matrix

Daily needs of Vitamin K

• Adults:

  • Men: 120 μ grams/day

  • Women: 90 μ grams/day

• Recommendations are based on current consumption, as the amount contributed by intestinal synthesis is unknown.

Food sources:

• Green leafy vegetables

• Soybeans

• Vegetable oil and margarine

Vitamin K Toxicity

• Toxicity

  • No known adverse effects

  • Individuals taking anticoagulant medications should keep vitamin K intake consistent

    • Changes in intake can increase or decrease drug effectiveness

Vitamin K Deficiency

• Deficiency

  • Infants are born with too little vitamin __

  • Deficiency severe enough to affect blood clotting is extremely rare

  • May cause hip fracture in older men and women

Are Vitamin Supplements necessary for Good Health?

• No evidence supports the use of supplements and preventing chronic diseases or cognitive decline

• Not a substitute for healthy eating

• Can cause adverse side effects

• Are not regulated like drugs and do not require F D A approval to be put on the market

  • Supplements can’t be removed unless they have been shown to be unsafe or cause harm

• How to choose a supplement

  • Choose supplements with the United States Pharmacopeial Convention seal (U S P)

  • Read the label carefully

Who might benefit from supplements?

• May be helpful for some individuals

  • Pregnant and lactating women

  • Older individuals who need vitamin B₁₂

  • Individuals who lack dietary vitamin D or sun exposure

  • Individuals on low-kilocalorie diets

  • Strict vegetarians

  • Individuals with food allergies or lactose intolerance

  • Individuals who abuse alcohol

  • Individuals who are food insecure

  • Breast-fed infants