Vitamin A Nutritional Guidelines Quiz

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Questions and Answers

What is the Recommended Dietary Allowance (RDA) of vitamin A for males?

800 μg RAE

900 μg RAE (correct)

1000 μg RAE

700 μg RAE

Which of the following foods is NOT a good source of vitamin A?

Pumpkin, canned

Carrots, cooked

Broccoli, cooked

White rice, cooked (correct)

What is the upper limit (UL) for vitamin A intake in μg RAE?

3000 μg RAE

6000 μg RAE

4000 μg RAE

5000 μg RAE (correct)

Which food provides the highest carotenoid content among the listed options?

Sweet potato, canned Signup and view all the answers

How should one consider their total vitamin A intake?

Combined dietary and supplement sources Signup and view all the answers

What is a potential effect of high Vitamin A intake on bone health?

Decreased bone mineral density Signup and view all the answers

Which of the following symptoms is NOT associated with excessive Vitamin A intake?

Increased appetite Signup and view all the answers

What is a known teratogenic effect of high Vitamin A intake during pregnancy?

Birth defects Signup and view all the answers

What daily intake level of Vitamin A defines the upper limit (UL) for adults?

12,000 μg/day Signup and view all the answers

In the study by Dudas in 1992, what was the daily Vitamin A dose compared among subjects?

1,800 μg/day Signup and view all the answers

What is the primary acute sign of vitamin A poisoning in dogs?

Vomiting Signup and view all the answers

Which of the following is a chronic sign of vitamin A poisoning in dogs?

Constipation Signup and view all the answers

What bioavailability can be expected when consuming cooked forms of carotenoids?

30-50% Signup and view all the answers

Which carotenoid converts to vitamin A at the highest efficiency?

β-carotene Signup and view all the answers

How many servings of fruits and vegetables are recommended per day for optimal carotenoid intake?

5+ servings Signup and view all the answers

What do β-apocarotenoids derive from during the synthesis of vitamin A?

Non-central cleavage Signup and view all the answers

What is the ratio of β-carotene to retinol equivalency?

12:1 Signup and view all the answers

Which sign is NOT typically associated with vitamin A poisoning in dogs?

Lean muscle gain Signup and view all the answers

What was the primary endpoint of the clinical trials evaluating β-carotene supplementation?

Lung cancer incidence Signup and view all the answers

What was the average age of participants in the CARET study?

57 years Signup and view all the answers

What was the increase in lung cancer risk observed in the β-carotene group of the CARET study?

28% Signup and view all the answers

How many participants were enrolled in the ATBC study?

29,133 Signup and view all the answers

What was the treatment dose of β-carotene in the CARET study?

30 mg/day Signup and view all the answers

Which group showed an 18% increase in lung cancer risk according to the ATBC study?

β-Carotene group Signup and view all the answers

What was the treatment compliance assessed by in both studies?

Serum β-carotene levels Signup and view all the answers

What was the primary population at risk in these β-carotene trials?

Heavy smokers and asbestos exposed individuals Signup and view all the answers

What effect does β-apo-14′-carotenal have on RXR?

It functions as a transcriptional repressor of RXR. Signup and view all the answers

What is a potential consequence of high intakes of β-carotene?

Development of hypercarotenemia. Signup and view all the answers

What was the finding related to intakes of Vitamin A over 3,000 μg/d in the studies mentioned?

Increased risk of CNC defects Signup and view all the answers

Which transcription factors are repressed by β-apo-13-carotenone?

RXR and CYP26A1. Signup and view all the answers

Which case report demonstrated severe hepatotoxicity from a Vitamin A dose of 7,600 μg/d?

Hatoff 1982 Signup and view all the answers

Among the studies listed, which reported no increased risk of CNC defects?

Khoury, 1996 Signup and view all the answers

Which of the following is true regarding the function of β-carotene?

It inhibits cell proliferation. Signup and view all the answers

What relationship exists between retinol levels and CYP expression?

High levels of retinol decrease CYP expression. Signup and view all the answers

What is the established tolerable upper intake level (UL) of Vitamin A for adults?

3,000 μg/d Signup and view all the answers

What is implied by the modest inhibition of nuclear receptors by various β-apocarotenoids?

They can influence a range of transcription factors. Signup and view all the answers

What condition was observed in multiple cases where the Vitamin A intake was notably high?

Severe fibrosis Signup and view all the answers

In observational studies, higher carotenoid intakes are associated with what outcome?

Decreased risk of cancer. Signup and view all the answers

At what intake level did the study by Mills, 1997, identify cranial neural crest defects?

≥ 4,500 μg/d Signup and view all the answers

How does β-carotene circulate in the blood?

In VLDL/LDL particles. Signup and view all the answers

What was the lowest intake range examined in the cohort studies related to cranial neural crest defects?

< 1,500 μg/d Signup and view all the answers

What condition was reported to occur from Vitamin A ingestion through fish liver curry?

Hypervitaminosis A Signup and view all the answers

Which study reported the highest dose with adverse outcomes of 30,000 μg/d?

Farrell 1977 Signup and view all the answers

For what population was the tolerable upper intake level of 600-900 μg/d established?

Infants and children Signup and view all the answers

Study Notes

Vitamin A Adverse Effects

Vitamin A's Tolerable Upper Intake Level (UL) is not a recommended intake level, but rather the highest daily intake likely causing no adverse effects in most.
Risk of adverse effects increases with intakes above the UL.
UL is based on total intake from foods, fortified foods and supplements.
The Therapeutic Index (TI) is the margin of safety between the Recommended Dietary Allowance (RDA) and the UL.
Vitamin A has a narrow TI compared to other nutrients.
High Vitamin A intakes can easily lead to adverse effects.
High intakes may lead to bone mineral density loss, progressive liver toxicity, skin disorders, alopecia (hair loss), nausea, vomiting, and teratogenesis (birth defects).

Vitamin A DRI Table

The DRI table provides Recommended Dietary Allowances (RDA/AI) and Tolerable Upper Intake Levels (UL) for various age groups (infants, children, adult males, adult females, pregnancy, lactation).
Retinol Activity Equivalents (RAE) are used to measure Vitamin A intake.
Values vary according to age and sex.
The table presents Daily Allowances for Vitamin A in µg/day (RAE) for different age groups categorized as infants, children, adult males, adult females, pregnancy and lactation.

Dietary Sources of Vitamin A

Dietary sources of vitamin A include beef liver, pumpkin, carrots, sweet potatoes, raisins bran cereal, oatmeal, cheese, ricotta, whole milk, broccoli, asparagus.
High in carotenoids (provitamin A) such as pumpkin, sweet potato, carrots, and cantaloupe.

Birth Defect Data for Vitamin A UL

Studies examined the relationship between vitamin A intake and birth defects.
Several studies analyzed cases of birth defects in relation to vitamin A intake levels.
Birth defects, especially craniofacial malformations (cleft palate and cleft lip), are linked to high vitamin A intake during pregnancy.
Increased risk of birth defects with intakes over 3000 µg/day for women of childbearing age

Liver Abnormalities and Vitamin A UL

High intake of Vitamin A can cause liver abnormalities such as fibrosis, marked cirrhosis, and liver cell hypertrophy.
Several case reports indicated liver abnormalities in subjects with unusually high vitamin A intake levels.
The case studies show a dose-response relationship.
The values reflect the relationship between intake of Vitamin A and liver abnormalities.

Adverse Effects: Hypervitaminosis A

Ingesting large amounts of fish liver curry can lead to acute vitamin A toxicity.
Symptoms include nausea, vomiting, blurred vision, superficial peeling of skin, and symptoms lasting several days.
Chronic intake of high amounts of Vitamin A can cause damage to the liver, skin, and other organ systems.
Liver fibrosis and lipid accumulation in stellate cells are frequent side effects of excessive vitamin A intake over many years.

Canine Hypervitaminosis A

All dietary sources of vitamin A should be carefully considered for dogs.
Dehydrated Liver is a common source of Vitamin A.
Acute symptoms include vomiting, drowsiness, irritability, and skin peeling.
Chronic signs include poor hair coat, skin issues, weakness, weight loss, constipation, excessive bone growth, and impaired movement.
Other signs include appetite loss, lethargy, joint and bone pain, jaundice, excessive thirst and urination, and eye irritation.

Carotenoids (Provitamin A)

Carotenoids are red, orange, and yellow pigments found in plants that can be converted into vitamin A.
5 or more servings of fruits and vegetables are recommended for obtaining 3–6 mg of β-carotene daily.
Cooked and heat processed forms of carotenoids are more bioavailable than raw versions.
Supplements of carotenoids are typically more bioavailable than dietary sources.
β-carotene plays an important role as an antioxidant.

β-carotene

β-carotene circulates in blood within VLDL/LDL particles.
High intakes can lead to hypercarotenemia (orange/yellowing of the skin).
Evidence suggests protective, antioxidant functions.
β-carotene can inhibit cell proliferation, showing potential anti-cancer effects.

β-Carotene and Cancer

Observational studies suggest a lower risk of lung cancer with higher β-carotene intake.
However, randomized controlled trials showed an increased risk of lung cancer and mortality among participants taking supplemental β-carotene.
Timing of β-carotene intake might play a role in its effect on lung cancer development.
β-carotene metabolites can have cytotoxic and genotoxic effects in animal models.
Supplemental β-carotene can induce lung CYP1A1 and CYP1A2, leading to increased activation of carcinogens from cigarette smoke.

The Research Pyramid for B-Carotene in Lung Cancer

The Research Pyramid illustrates the hierarchy of scientific evidence regarding health topics.
Randomized controlled trials are the gold standard for determining cause-and-effect relationships, as opposed to observational studies.

Adverse Effects of Beta-Carotene: CARET & ATBC studies detailed

CARET and ATBC trials examined the effect of beta-carotene supplementation on lung cancer risk.
Significant findings in both RCTs showed an unexpected increase in lung cancer risk and mortality in beta-carotene supplementation groups compared to placebo.
The increased risk was more significant than risk reduction found in previous observational studies.

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Test your knowledge of vitamin A dietary recommendations and food sources with this quiz. Explore questions on the Recommended Dietary Allowance (RDA), upper intake limits, and effects of vitamin A on health. Ideal for students and nutrition enthusiasts alike.