Nutrition and Vitamin Deficiencies Practice Questions
21 free Nutrition and Vitamin Deficiencies practice questions for the USMLE Step 1. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
A 4-year-old child from a low-income region presents with night blindness and develops Bitot’s spots on conjunctiva. Which vitamin deficiency is most likely responsible?
- A Vitamin D
- B Vitamin A
- C Vitamin C
- D Vitamin K
Correct answer: Vitamin A
Vitamin A deficiency classically causes night blindness and Bitot’s spots due to impaired maintenance of retinal photoreceptors and conjunctival epithelium.
Which of the following is a fat-soluble vitamin that tends to accumulate in body fat and liver, and deficiencies take months to develop if intake is inadequate?
- A Vitamin C
- B Vitamin B6
- C Vitamin A
- D Vitamin B9
Correct answer: Vitamin A
Vitamin A is fat-soluble, stored in adipose tissues and liver, so deficiency develops slowly over time when intake is inadequate.
An adult strict vegetarian presents with macrocytic anemia and hypersegmented neutrophils. Serum methylmalonic acid is normal but homocysteine is elevated. Which vitamin deficiency is most likely?
- A Vitamin B12 (cobalamin)
- B Vitamin B9 (folate)
- C Vitamin B6 (pyridoxine)
- D Vitamin C (ascorbic acid)
Correct answer: Vitamin B9 (folate)
Folate (vitamin B9) deficiency causes megaloblastic anemia with elevated homocysteine but normal methylmalonic acid, distinguishing it from B12 deficiency.
Deficiency of which vitamin leads to pellagra, characterized by the “3 Ds”: dermatitis, diarrhea, and dementia?
- A Vitamin B2 (riboflavin)
- B Vitamin B3 (niacin)
- C Vitamin B1 (thiamine)
- D Vitamin B6 (pyridoxine)
Correct answer: Vitamin B3 (niacin)
Niacin (vitamin B3) deficiency causes pellagra with the clinical triad of dermatitis, diarrhea and dementia due to impaired NAD/NADP-dependent redox reactions.
Chronic deficiency of which vitamin impairs calcium absorption, predisposing to osteomalacia in adults or rickets in children?
- A Vitamin A
- B Vitamin D
- C Vitamin C
- D Vitamin K
Correct answer: Vitamin D
Vitamin D deficiency reduces intestinal absorption of calcium and phosphorus, leading to hypocalcemia, bone demineralization, and osteomalacia in adults or rickets in children.
A patient with chronic alcohol use presents with confusion, ophthalmoplegia and ataxia. Which vitamin deficiency should be suspected?
- A Vitamin B1 (thiamine)
- B Vitamin B2 (riboflavin)
- C Vitamin B3 (niacin)
- D Vitamin B6 (pyridoxine)
Correct answer: Vitamin B1 (thiamine)
Thiamine (vitamin B1) deficiency in chronic alcohol use can precipitate Wernicke encephalopathy (confusion, ophthalmoplegia, ataxia) due to impaired carbohydrate metabolism in neurons.
Deficiency of which vitamin leads to cheilosis, angular stomatitis, and corneal vascularization due to impaired maintenance of mucous membranes?
- A Vitamin B2 (riboflavin)
- B Vitamin B12 (cobalamin)
- C Vitamin B6 (pyridoxine)
- D Vitamin C (ascorbic acid)
Correct answer: Vitamin B2 (riboflavin)
Riboflavin (vitamin B2) deficiency affects carbohydrate and protein metabolism and mucous-membrane integrity, leading to cheilosis, angular stomatitis, and corneal vascularization.
A 28-year-old woman reports easy bruising and prolonged bleeding after minor cuts. Laboratory shows prolonged prothrombin time. Which vitamin deficiency is most consistent with this presentation?
- A Vitamin K
- B Vitamin E
- C Vitamin A
- D Vitamin C
Correct answer: Vitamin K
Vitamin K is essential for gamma-carboxylation of clotting factors II, VII, IX and X; its deficiency impairs clotting and causes bleeding tendency, bruising, and prolonged PT.
Which vitamin deficiency would most likely manifest with scurvy: poor wound healing, bleeding gums, and joint pain?
- A Vitamin E
- B Vitamin C
- C Vitamin B1
- D Vitamin B3
Correct answer: Vitamin C
Vitamin C deficiency (ascorbic acid) impairs collagen hydroxylation, compromising connective tissue integrity and leading to scurvy with bleeding gums, poor wound healing, and joint pain.
Which statement correctly contrasts fat-soluble versus water-soluble vitamins in terms of storage and deficiency development?
- A Fat-soluble vitamins are not stored anywhere in the body, so their deficiencies appear within days
- B Water-soluble vitamins accumulate in adipose tissue and cause toxicity before any deficiency
- C Fat-soluble vitamins are stored in liver/fat, so deficiencies develop slowly
- D Only water-soluble vitamins are required for normal human metabolism and cell function
Correct answer: Fat-soluble vitamins are stored in liver/fat, so deficiencies develop slowly
Fat-soluble vitamins (A, D, E, K) are stored in liver and adipose tissue; therefore, deficiency develops gradually if intake is inadequate. Water-soluble vitamins (B and C) are not stored and need regular replenishment.
Which population group is at highest risk of developing deficiency of fat-soluble vitamins due to impaired fat absorption?
- A Individuals with well-controlled chronic kidney disease on dialysis
- B People with fat malabsorption such as cystic fibrosis or cholestasis
- C Endurance athletes maintaining a high daily calorie intake
- D Healthy young adults consuming a varied, balanced daily diet
Correct answer: People with fat malabsorption such as cystic fibrosis or cholestasis
Patients with fat malabsorption (e.g., cystic fibrosis, cholestasis, intestinal disease) cannot adequately absorb dietary fats, compromising absorption of fat-soluble vitamins and predisposing to deficiency.
An adult vegetarian who has not consumed dairy or eggs for several years presents with fatigue and paresthesias in lower limbs. Which vitamin deficiency is most likely?
- A Vitamin B12 (cobalamin)
- B Vitamin B2 (riboflavin)
- C Vitamin C (ascorbic acid)
- D Vitamin B6 (pyridoxine)
Correct answer: Vitamin B12 (cobalamin)
Vitamin B12 is primarily found in animal products; long-term vegetarian diet without supplementation can lead to B12 deficiency causing anemia and neurologic symptoms.
Deficiency of which vitamin during pregnancy increases risk of neural tube defects in the fetus?
- A Vitamin B1 (thiamine)
- B Vitamin B9 (folate)
- C Vitamin B2 (riboflavin)
- D Vitamin B6 (pyridoxine)
Correct answer: Vitamin B9 (folate)
Folate (vitamin B9) is essential for nucleic acid synthesis and methylation reactions; maternal folate deficiency impairs DNA synthesis in the developing neural tube, increasing neural tube defect risk.
Which vitamin deficiency may present with seborrheic dermatitis-like rash, glossitis, and cheilitis especially in severe malnutrition or chronic disease?
- A Vitamin B6 (pyridoxine)
- B Vitamin B3 (niacin)
- C Vitamin A (retinol)
- D Vitamin D (calciferol)
Correct answer: Vitamin B6 (pyridoxine)
Vitamin B6 deficiency can cause dermatologic manifestations including seborrheic dermatitis–like rash, glossitis and cheilitis due to its role in amino acid and lipid metabolism affecting skin and mucosal integrity.
Which vitamin plays a critical coenzyme role in redox reactions of carbohydrate and protein metabolism and whose deficiency leads to mucocutaneous lesions and corneal changes?
- A Vitamin B2 (riboflavin)
- B Vitamin B12 (cobalamin)
- C Vitamin B6 (pyridoxine)
- D Vitamin C (ascorbic acid)
Correct answer: Vitamin B2 (riboflavin)
Riboflavin (vitamin B2) serves as coenzyme in numerous redox reactions; deficiency impairs metabolic pathways and leads to mucocutaneous lesions, cheilosis, stomatitis and corneal vascularization.
An adult with chronic pancreatitis (causing fat malabsorption) is at risk of deficiency of which vitamin leading to bleeding tendency and poor bone mineralization?
- A Vitamin B12
- B Vitamin C
- C Vitamin D
- D Vitamin B6
Correct answer: Vitamin D
Chronic pancreatitis impairs fat absorption, compromising absorption of fat-soluble vitamins; deficiency of vitamin D reduces calcium and phosphorus absorption, leading to poor bone mineralization and risk of bleeding via bone fragility.
Deficiency of which vitamin can impair immune function and integrity of epithelial barriers, increasing susceptibility to infections?
- A Vitamin A
- B Vitamin B1
- C Vitamin C
- D Vitamin B3
Correct answer: Vitamin A
Vitamin A is essential for maintenance of epithelial tissues and mucous membranes; deficiency compromises barrier integrity and impairs immune defenses, increasing infection risk.
Which vitamin deficiency in newborns (especially if not given prophylaxis) leads to increased risk of bleeding and hemorrhagic disease?
- A Vitamin A
- B Vitamin C
- C Vitamin K
- D Vitamin D
Correct answer: Vitamin K
Vitamin K deficiency in neonates impairs gamma-carboxylation of clotting factors, leading to bleeding disorders and hemorrhagic disease of the newborn.
Which vitamin deficiency is most likely responsible when a patient has slow wound healing, easy bruising, and frequent gum bleeding in a context of poor diet low in fresh fruits and vegetables?
- A Vitamin E (tocopherol)
- B Vitamin C (ascorbic acid)
- C Vitamin B1 (thiamine)
- D Vitamin B2 (riboflavin)
Correct answer: Vitamin C (ascorbic acid)
Vitamin C deficiency impairs collagen synthesis, leading to weak connective tissue, poor wound healing, gum bleeding, and bruising typical of scurvy.
Which vitamin deficiency can result in megaloblastic anemia with neurological symptoms due to impaired DNA synthesis and methylation reactions?
- A Vitamin B2 (riboflavin)
- B Vitamin B9 (folate)
- C Vitamin B6 (pyridoxine)
- D Vitamin C (ascorbic acid)
Correct answer: Vitamin B9 (folate)
Folate (vitamin B9) is necessary for synthesis of purines and thymidylate; its deficiency impairs DNA synthesis leading to megaloblastic anemia, and also affects methylation reactions important for neurologic function.
In populations with limited sun exposure and low dietary intake of fatty-fish or fortified dairy, deficiency of which vitamin is a common global problem leading to muscle weakness and bone pain?
- A Vitamin A
- B Vitamin B6
- C Vitamin D
- D Vitamin C
Correct answer: Vitamin D
Vitamin D deficiency is common worldwide when sun exposure or dietary intake is inadequate; this leads to impaired calcium absorption, muscle weakness, bone pain and increased risk of osteomalacia and fractures.