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Quiz: Food and Mood

Test your understanding of Chapter 15. Choose the best answer, then click Show Answer to check.

Question 1

What is a dietary pattern?

  1. A single nutrient that researchers measure in the blood
  2. The overall combination of foods and drinks a person usually eats over time, studied as a whole
  3. A strict meal plan that a doctor prescribes
  4. The order in which foods are eaten during one meal
Show Answer

The correct answer is B. Researchers study whole patterns because foods come in bundles, and people who eat more of one food often eat differently in other ways too. Option A describes studying one nutrient at a time, which is exactly what pattern research tries to move beyond.

Concept Tested: Dietary Pattern Bloom's Level: Remember

Question 2

What made the SMILES trial a randomized controlled trial?

  1. Participants chose whether they wanted diet support or social support.
  2. It included more than 10,000 people.
  3. Chance decided whether each participant got dietitian support or social support.
  4. Nobody, including the participants, knew which group they were in.
Show Answer

The correct answer is C. Random assignment is what makes a trial randomized, and it balances hidden factors between groups on average. Option D is wrong: participants knew their group; only the people rating depression were blinded. Option B is wrong too, since SMILES enrolled just 67 people.

Concept Tested: SMILES Trial Bloom's Level: Remember

Question 3

About how much fiber does the average person in the US eat each day, according to the national survey data in this chapter?

  1. About 16 grams
  2. About 31 grams
  3. About 50 grams
  4. About 5 grams
Show Answer

The correct answer is A. Average intake was 16.2 grams a day in the 2009 to 2010 national survey, while the 2020 to 2025 Dietary Guidelines suggested about 25 grams for girls and 31 grams for boys aged 14 to 18. Option B is the suggested amount for teen boys, not what people actually eat; that difference is the dietary fiber gap.

Concept Tested: Dietary Fiber Gap Bloom's Level: Remember

Question 4

Why can people who take daily vitamins look healthier in observational studies, even if the vitamins themselves do little?

  1. Because vitamins always improve mood within a week
  2. Because people who choose one health behavior often have other healthy habits and advantages
  3. Because observational studies randomly assign who takes vitamins
  4. Because vitamins are ultra-processed foods
Show Answer

The correct answer is B. This is healthy user bias: people who follow one piece of health advice often also sleep more, exercise more, and see doctors regularly, which makes the behavior look more helpful than it is. Option C is wrong because observational studies don't assign anything; that's what makes them vulnerable to this bias.

Concept Tested: Healthy User Bias Bloom's Level: Understand

Question 5

A 2024 umbrella review rated the link between ultra-processed food and anxiety as "convincing" evidence of an association, but "low" quality. What does that combination mean?

  1. The link is probably a statistical fluke.
  2. Ultra-processed food has been proven to cause anxiety.
  3. The studies were randomized trials with many dropouts.
  4. The link is consistent and unlikely to be chance, but the mostly observational designs can't show what causes it.
Show Answer

The correct answer is D. "Convincing" describes how statistically solid and consistent the association is (not how big the effect is); "low quality" reflects that the studies were mostly observational snapshots that can't rule out confounding or reverse causation. Option B is the common misreading that turns a strong link into a proven cause.

Concept Tested: Ultra-Processed Food Bloom's Level: Understand

Question 6

Researchers suggest fiber might improve mood because gut microbes turn fiber into short-chain fatty acids that could affect the brain. In this pathway, what role do the gut microbes play?

  1. A mediator variable, because they lie on the path between fiber and mood
  2. A confounder, because they affect both fiber intake and mood from outside the path
  3. A placebo, because they have no effect
  4. A control group
Show Answer

The correct answer is A. A mediator carries the effect along the causal path and explains how a cause works. Option B describes a confounder, which sits outside the path and affects both ends (like family income), creating a link without being part of the mechanism.

Concept Tested: Mediator Variable Bloom's Level: Understand

Question 7

A student uses the Diet Pattern Explorer with the true effect set to none and all hidden factors on. In observational mode she sees a correlation of about -0.6. What should she conclude?

  1. Diet strongly improves mood in this simulated world.
  2. The simulation is broken, because there should be no correlation at all.
  3. The hidden factors created the link, so the correlation does not show that diet affects mood.
  4. Randomized trials would show the same -0.6 link.
Show Answer

The correct answer is C. She set the true effect to zero, so the entire link comes from food access, sleep, and low mood changing eating. Option D is wrong because a coin flip balances those hidden factors, so the trial shows only a small chance difference.

Concept Tested: Observational Study Bloom's Level: Apply

Question 8

Maya, a fictional 16-year-old, reads that a Mediterranean diet helps depression and decides to cut out every food not on a list she found online, even though she feels anxious about eating. Based on the chapter, what is the biggest concern?

  1. She won't get enough olive oil.
  2. Strict, self-imposed food rules can raise eating disorder risk, and the trials added diet support rather than cutting food groups.
  3. Mediterranean diets are proven to make depression worse.
  4. Online lists are always more accurate than dietitians.
Show Answer

The correct answer is B. Restrictive eating and anxiety about food can be warning signs for an eating disorder, and none of the trials in this chapter tested cutting out food groups for mood. Maya would do better talking with a doctor or registered dietitian. Option C is wrong because the small trials found possible benefits, not harm, when diet support was added to care.

Concept Tested: Eating Disorder Risk Bloom's Level: Apply

Question 9

The SMILES trial found remission in 32.3% of the diet group versus 8.0% of the social support group, while the much larger PREDIMED trial found no significant overall effect of a Mediterranean diet on new depression. Which analysis best explains how both can be true?

  1. PREDIMED must have measured depression the wrong way.
  2. SMILES proves diet cures depression, so PREDIMED can be ignored.
  3. Both trials studied the same people in the same way, so they should agree exactly.
  4. They asked different questions in different people: SMILES treated adults already depressed for 12 weeks, while PREDIMED tried to prevent new depression in older adults at high heart risk.
Show Answer

The correct answer is D. SMILES tested treatment as an add-on in 67 adults with depression; PREDIMED tested prevention in 3,923 adults aged 55 to 80. Different questions, groups, and outcomes can give different answers, and SMILES was also small and not fully blinded. Option B overstates a single small trial.

Concept Tested: Mediterranean Diet Bloom's Level: Analyze

Question 10

An observational study finds that teens from families with less money eat fewer fresh vegetables and report more low mood. Which analysis best explains why this doesn't show that vegetables improve mood?

  1. Food insecurity and money stress could affect both diet and mood, acting as confounders.
  2. Vegetables are never linked to mood in any study.
  3. Teens can't report their mood accurately.
  4. The study should have used mice instead.
Show Answer

The correct answer is A. Families with limited money may have less access to fresh food and also more financial stress, which affects mood, so the link could appear even if vegetables did nothing. In 2024, 13.7% of US households were food insecure at some point. Option D is wrong because a mouse study couldn't capture income or human mood in the same way.

Concept Tested: Food Insecurity Bloom's Level: Analyze