Rebekah S. Marsh, PhD.Kaplan University

Objectives What will we be learning about tonight?

Vitamin A Vitamin E Vitamin D Vitamin K

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Vitamin A: Dietary Recommendations

Diet recommendations Recommended Dietary Allowance (RDA):

Adult males 1000 ug Retinyl Equivalents (RE)/dAdult females, 800 ug RE/d

Deficiency of Vitamin A

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Deficiency of Vitamin A (cont.)

How much vitamin A do you think is currently given to children in developing countries in a single dose?

Toxicity of Vitamin A Acute intake of extremely high doses of

vitamin A (>200 mg RE in adult humans) Can cause nausea, vomiting, headache, and

increased cerebrospinal pressure. Symptoms are generally transient.

Chronic high intakes (e.g., >10x RDA) can cause hair loss, bone and muscle pain, headache, liver damage, and increased blood lipid concentrations. A particular danger in pregnant women is

teratogenesis (birth defects). On the other hand, carotenoids as a source of

vitamin A are not toxic, even with very high intakes.

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There are over 600 carotenoids in nature. Carotenoids generally contain a conjugated

polyene structure which is efficient at absorbing light, and are the major yellow and red pigments in many fruits and vegetables.

Beta-carotene and alpha-carotene are responsible for the orange color of carrots, and lycopene for the red color of tomatoes; astaxanthin imparts a red or pink color to lobsters and salmon.

Major storage sites:

Because the carotenoids are fat-soluble, they are found in fatty tissues in the body and are transported in blood by lipoproteins.

The predominant carotenoids found in human tissues are beta-carotene, alpha-carotene, lycopene, lutein, zeaxanthin, and beta-cryptoxanthin; their relative abundance depends on dietary intake.

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Functions:

In animals some carotenoids serve as dietary precursors to vitamin A, and many of them may function as fat-soluble antioxidants.

In plants they serve as antioxidants to protect the highly reactive photosystems and also act as accessory photopigments.

Increased consumption of foods rich in carotenoids is associated with decreased risk of some degenerative diseases, and there is some evidence also for their role in improving immune function.

What foods contain Carotenoids?

Diet recommendations:

No formal diet recommendation for carotenoids has yet been established but some experts suggest intakes of 5 to 6 mg daily (about twice the average daily American intake).

CarotenoidsDeficiency

One study has found that carotenoid deficiency is associated with skin changes (including acne and dermatitis).

o These changes were detrimental but not life-threatening.

This effect should be confirmed by additional studies before making dietary recommendations.

ToxicityThe carotenoids are remarkably devoid of toxicity, and serve as good nontoxic sources of vitamin A. Massive overconsumption of carotenoids can result in yellowing of the skin, especially of the hand and ears , but has no adverse health effects. The color disappears within a week or so after reducing intake of carotene-rich foods.

Vitamin E: Dietary RecommendationsThe Recommended Dietary Allowance (RDA) for vitamin E is based primarily on customary intakes from US food sources.

The current RDA for males is 10 mg and 8 mg for females.

However, the requirement for vitamin E increases with higher intakes of polyunsaturated fatty acids (PUFA). The recommended ratio of E/PUFA is 0.4 mg d--tocopherol per gram of PUFA.

In defining the ideal intake, factors to consider are intake of other antioxidants, age, environmental pollutants, and physical activity

Deficiency of Vitamin E The main signs of severe deficiency in

animals are reproductive failure, nutritional "muscular dystrophy," hemolytic anemia, and neurological and immunological abnormalities.

The last three processes also have been identified in humans. However, vitamin E deficiency occurs

rarely in humans, having been reported in only two situations: premature infants with very low birth weight and patients who fail to absorb fat.

Toxicity of Vitamin E Vitamin E is relatively safe compared to

the fat-soluble vitamins. Few side effects from high intakes of

this vitamin have been reported, even at doses as high as 3200 mg daily.

However, high vitamin E supplementation may be contraindicated when a coagulation defect is present due to vitamin K deficiency or in individuals receiving anticoagulant drugs.

Synthesis of Vitamin D

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1. 7-dehydrocholesterol is absorbed through the skin generating vitamin D3 (cholecalciferol).

2. Within the liver, cholecalciferal is hydroxylated to 25-hydroxycholecalciferol

by the enzyme 25-hydroxyvitamin D3-1-hydroxylase enzyme

3. Within the kidney, 25-hydroxyvitamin D serves as a substrate for 1--hydroxylase, yielding 1,25-dihydroxyvitamin D (calcitriol, 1alpha,25-dihydroxyvitamin D]—the most potent form of vitamin D.

4. The active form of vitamin D can then aid in bone formation/breakdown

Vitamin D: Dietary RecommendationsThe IOM concluded that it was not possible to determine a recommended dietary allowance (RDA) for vitamin D from the literature but rather to recommend an adequate intake (AI).

Based on the available literature and assuming some exposure to sunlight:

Ages 0 - 50 years was set at 200 IU (5 mg)/day.Adults 51 - 70 years as 400 IU (10 mg)/dayAdults > 71 years, 600 IU (15 mg)/day.

No increase for pregnancy or lactation. A Tolerable Upper Limit level for vitamin D for ages 0 - 12 months was set at a limit of 1,000 IU (25 mg)/day. For older children and adults, including pregnant and lactating women, the UL was set at 2,000 IU (50 mmg)/day.

Deficiency of Vitamin D In children leading problem is

rickets In adults leading problem is

osteomalacia What is the difference between

the two? Who is at risk for deficiency? Other deficiency symptoms

muscle weakness, bony deformities, neuromuscular irritability causing muscle spasms of the larynx and hands, generalized convulsions and tetany

Toxicity of Vitamin D Excessive quantities of vitamin D (in

excess of 5,000-10,000 IU/day) can cause: Hypercalcemia Hypercalciuria kidney stones soft tissue calcifications

Vitamin K Vitamin K is a coenzyme for a microsomal enzyme that

catalyzes the conversion of specific glutamyl residues to gamma-carboxyglutamyl (Gla) residues in a small number of proteins.

Several of the Gla-proteins are essential for blood clotting and its regulation.

Others have a role in the regulation of tissue mineralization and cell proliferation.

Phylloquinone from plants and a series of bacterial menaquinones are natural forms of the vitamin.

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Four main steps:1. Vasoconstriction- limiting

blood flow to the injured area2. Platelet

activation/adhesion/ aggregation- forms a platelet plug

3. Fibrin meshwork (clot)- binds blood cells together; forms hemostatic plug

4. Fibrinolysis (clot dissolution)- removes clots during wound healing

Blood Clotting

RDAs (µg/day) are: 5 at age 0-6 months, 10 for 6-12 months, 15 for 1-3 years, 20 for 4-6 years, 30 for 7-10 years 45 for 11-14 years 55 for females 15-18 years, 60 for females 19-24 years, 65 for

females 25 years and older, pregnant and lactating women and males 15-18; 70 for males 19-24 years

80 for males 25 years and older.

Most Americans obtain almost no menaquinones with their diet, but it is likely that some vitamin K (menaquinones) from bacterial production in the lower intestines is absorbed, the amounts appear to be much less than what is usually available from dietary sources.

Vitamin K: Dietary Recommended Daily Allowances

Deficiency of Vitamin K Historically, vitamin K deficiency has been defined as a

disruption of blood clotting Infants are at risk for severe cerebral hemorrhage during the

first 3-4 months impaired fat absorption in conjunction with a low vitamin intake from

breastfeeding. (Human milk contains much less vitamin K than infant formulas).

In the US and many other countries newborn infants routinely receive vitamin K.

Bleeding due to the lack of vitamin K is very rare in older children and adults

Oral antibiotic treatment, in conjunction with low vitamin K intake, can induce bleeding.

Less than a few days' intake of vitamin K is stored, most of it in liver and bone symptoms appear rapidly.

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Deficiency of Vitamin K Suboptimal vitamin K status (Vs.

deficiency) may contribute to the progression of osteoporosis and atherosclerosis

4-hydroxy coumarins are vitamin K antagonists that interfere with reactivation of the vitamin and suppress production of mature Gla-proteins needed for coagulation. Some 4-hydroxy coumarins are

medically important anticoagulants What age group may be

deficient in Vitamin K, thus requiring an injection?

Toxicity of Vitamin K Large amounts of phylloquinone or

menaquinones can be consumed over extended periods with no toxic effects

Menadione is currently used in animal feeds, but not in foods for human consumption, because it causes hemolytic anemia, hyperbilirubinemia, and kernicterus in infants.

References Nutrient Information (2010). American

Society for Nutrition. Retrieved on May 18, 2010 from http://jn.nutrition.org/nutinfo/