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Quiz: Nutrition Science — What Food Does for Your Body

Test your understanding of macronutrients, digestion, micronutrients, and the gut microbiome with these questions.

1. Which macronutrient provides the MOST calories per gram?

  1. Carbohydrates (4 Cal/g)
  2. Protein (4 Cal/g)
  3. Fat (9 Cal/g)
  4. Dietary fiber (0 Cal/g)
Show Answer

The correct answer is C. Fat provides 9 Calories per gram — more than twice the energy density of carbohydrates or protein (both 4 Cal/g). This high energy density makes fat an efficient long-term energy storage molecule. Dietary fiber is a carbohydrate that humans cannot fully digest, so it contributes essentially no usable calories.

Concept Tested: Caloric Density of Foods

2. Where in the digestive system does the majority of nutrient absorption occur?

  1. Stomach
  2. Large intestine (colon)
  3. Small intestine
  4. Liver
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The correct answer is C. The small intestine is the primary site of both digestion and absorption. It is lined with finger-like projections called villi (covered by microvilli) that provide an enormous absorptive surface area of approximately 250 square meters. The stomach primarily digests proteins with acid and enzymes. The large intestine absorbs water and electrolytes. The liver processes absorbed nutrients but is not an absorption organ itself.

Concept Tested: Nutrient Absorption

3. A food with a high glycemic index (GI) value will

  1. Cause blood glucose to rise slowly and steadily over several hours
  2. Be digested slowly because it contains large amounts of dietary fiber
  3. Cause blood glucose to rise quickly, often followed by a rapid drop
  4. Provide more total calories than a low-GI food of the same serving size
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The correct answer is C. High-GI foods (GI above 70) are rapidly digested and absorbed, causing a quick spike in blood glucose. The pancreas releases a surge of insulin to lower blood glucose, often resulting in a rapid drop that can cause energy crashes and renewed hunger. Option A describes low-GI foods. Option B describes foods high in fiber (which lower GI). Option D is incorrect — GI measures speed of glucose response, not total caloric content.

Concept Tested: Glycemic Index

4. Dietary fiber is beneficial primarily because it

  1. Provides 9 Calories per gram of concentrated energy for cells
  2. Slows glucose absorption, feeds gut bacteria, and promotes satiety
  3. Is a complete protein containing all nine essential amino acids
  4. Dissolves all fat-soluble vitamins so they can be absorbed in the small intestine
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The correct answer is B. Dietary fiber slows glucose absorption by forming a gel in the digestive tract, feeds beneficial gut microbiome bacteria (which ferment it into short-chain fatty acids), and promotes satiety by expanding in the stomach. Option A is incorrect — fiber is indigestible and provides essentially no usable calories. Option C describes animal proteins, not fiber. Option D describes bile salts, not fiber.

Concept Tested: Dietary Fiber Function

5. Which vitamin deficiency causes scurvy — a disease characterized by bleeding gums and slow wound healing?

  1. Vitamin D deficiency
  2. Vitamin A deficiency
  3. Vitamin K deficiency
  4. Vitamin C deficiency
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The correct answer is D. Vitamin C (ascorbic acid) is essential for collagen synthesis. Without it, collagen structures in blood vessels, skin, and connective tissue weaken, causing bleeding gums, impaired wound healing, and eventually severe scurvy. Vitamin D deficiency causes rickets/osteomalacia. Vitamin A deficiency causes night blindness. Vitamin K deficiency impairs blood clotting.

Concept Tested: Vitamins in Food

6. The gut microbiome is primarily located in the

  1. Stomach, where acid conditions select for beneficial bacteria
  2. Small intestine, where nutrient absorption occurs alongside microbial activity
  3. Large intestine (colon), where bacteria ferment dietary fiber
  4. Liver, where microbial metabolites are processed
Show Answer

The correct answer is C. The gut microbiome — approximately 38 trillion bacteria — is primarily located in the large intestine (colon). The colon is where dietary fiber that escaped digestion in the small intestine is fermented by bacteria into short-chain fatty acids (SCFAs) like butyrate. The stomach's very low pH (1.5–3.5) kills most bacteria. The small intestine has fewer bacteria due to rapid transit time and digestive enzymes.

Concept Tested: Gut Microbiome Basics

7. Fat-soluble vitamins (A, D, E, K) differ from water-soluble vitamins (B vitamins, C) because fat-soluble vitamins

  1. Provide calories that the body can use for energy production
  2. Are stored in body fat and liver, and can accumulate to toxic levels if over-consumed
  3. Must be consumed daily because they are excreted in urine within hours
  4. Are only found in animal products like meat and dairy, not in plants
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The correct answer is B. Fat-soluble vitamins (A, D, E, K) are stored in the liver and fatty tissues and can accumulate to harmful levels with excessive supplementation. Water-soluble vitamins (B vitamins and C) are not stored long-term; excess is excreted in urine, which is why they need to be consumed regularly — this is what option C describes, but it applies to water-soluble, not fat-soluble, vitamins. Option A is incorrect — vitamins don't provide calories. Option D is false — many fat-soluble vitamins are found in plant foods (vitamin K in leafy greens, beta-carotene in orange vegetables).

Concept Tested: Vitamins in Food

8. A person consumes 2,500 Calories per day but expends only 2,000 Calories. According to the principle of energy balance, this person will

  1. Lose weight because metabolism will slow to compensate for the extra food
  2. Maintain their current weight because the body automatically adjusts caloric output
  3. Gain weight over time as the excess 500 Calories are stored as fat
  4. Experience nutrient deficiencies because the extra calories dilute essential micronutrients
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The correct answer is C. Energy balance states that when caloric intake exceeds caloric expenditure, the excess energy is stored — primarily as fat in adipose tissue. A surplus of 500 Calories per day would result in approximately 1 pound of fat gain per week (since 1 pound of fat ≈ 3,500 Calories). The body does not automatically compensate for caloric surpluses. Options A and B incorrectly describe automatic metabolic adjustment. Option D is not caused by caloric surplus.

Concept Tested: Energy Balance

9. On a Nutrition Facts label, a food showing 25% Daily Value (DV) for sodium should be considered

  1. A low-sodium food because 25% is less than half of the daily recommended amount
  2. A high-sodium food — 20% DV or more is considered high
  3. A moderate-sodium food because 25% is exactly average for packaged foods
  4. The ideal sodium content because the Dietary Guidelines recommend 25% DV per meal
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The correct answer is B. On the Nutrition Facts label, 5% DV or less is considered low and 20% DV or more is considered high. At 25% DV, this food is high in sodium — consuming it contributes significantly to the daily sodium limit of 2,300 mg. Option A incorrectly interprets 25% as low. Option C is not a nutritional standard. Option D invents a guideline that does not exist.

Concept Tested: Nutrition Facts Label

10. Table salt is iodized (iodine is added to it) primarily to prevent

  1. Scurvy caused by vitamin C deficiency in populations with low fruit intake
  2. Iron-deficiency anemia in individuals who do not consume red meat
  3. Goiter and thyroid dysfunction caused by iodine deficiency
  4. Pellagra caused by niacin deficiency in corn-based diets
Show Answer

The correct answer is C. Iodine is an essential mineral required to produce thyroid hormones. Iodine deficiency causes the thyroid gland to enlarge (goiter) and impairs thyroid function, leading to hypothyroidism. Salt iodization is one of the most successful public health interventions in history, essentially eliminating endemic iodine deficiency in countries that adopted it. Options A, B, and D describe other deficiency diseases prevented by different fortification strategies (vitamin C in foods, iron in cereals, niacin in enriched flour).

Concept Tested: Malnutrition and Deficiency Diseases