Questions: Nutrition Across the Lifespan: Pregnancy, Infancy, Childhood, and Aging

Question 1

A woman learns she is 6 weeks pregnant and immediately begins taking folate supplements. A nutritionist expresses concern. Why?

• A. Folate is harmful in early pregnancy and should only be taken in the second trimester
• B. Neural tube closure occurs around day 28 of gestation, often before pregnancy is confirmed, so starting at 6 weeks is too late to prevent neural tube defects
• C. The concern is unfounded; starting folate at 6 weeks is perfectly adequate for neural tube development
• D. Folate supplements interfere with iron absorption, which is more critical in early pregnancy

Answer: (B)

The neural tube closes within the first 28 days of gestation — a window that frequently passes before a woman knows she is pregnant. This is why public health policy recommends periconceptional folate supplementation (before and immediately after conception) for all women of reproductive age. Starting at week 6 misses the critical window entirely.

Question 2

Which mechanism best explains why elderly adults often become vitamin B12-deficient despite consuming adequate amounts in their diet?

• A. The kidneys excrete B12 more rapidly with aging, raising daily requirements
• B. Older adults lose taste for meat and dairy, the main B12 sources
• C. Declining intrinsic factor secretion by gastric parietal cells impairs B12 absorption in the small intestine
• D. B12 competes with calcium for absorption, and calcium intake increases with age

Answer: (C)

Vitamin B12 absorption requires intrinsic factor, a glycoprotein secreted by gastric parietal cells. With aging, atrophic gastritis and reduced parietal cell function decrease intrinsic factor production, so dietary B12 — even if adequate — cannot be efficiently absorbed. This distinguishes B12 deficiency in the elderly from the dietary insufficiency more common in vegans, and is why B12 injections or high-dose oral supplements (which allow passive absorption) may be needed.

Question 3

Pregnant women need approximately twice their normal caloric intake to support fetal growth.

• T. True
• F. False

Answer: False

This is a common misconception. Energy requirements during pregnancy increase by only about 340 kcal/day in the second trimester and 450 kcal/day in the third — a modest increment, not a doubling. 'Eating for two' overstates the caloric increase by a factor of roughly 4–5. Excessive gestational weight gain is associated with complications, making this misconception medically relevant.

Question 4

Breast milk provides immunological protection that infant formula cannot replicate, because it contains secretory IgA and other bioactive components that coat the infant's immature gut lining.

• T. True
• F. False

Answer: True

Breast milk contains secretory IgA, live immune cells, hormones, and bioactive compounds that actively protect the infant during the window before its own immune system is fully operational. Formula can match macronutrient composition reasonably well, but these immunological components cannot be replicated — they are produced by living mammary tissue and some are unstable. This is a functional gap, not merely a compositional one.

Question 5

Explain why older adults can develop sarcopenia (muscle loss) even if their protein intake meets standard recommendations. What physiological change makes protein less effective in aging muscle?

Model answer: Aging muscle develops 'anabolic resistance': it requires a larger protein stimulus (both quantity and leucine content) to achieve the same rate of muscle protein synthesis as young muscle. The same dietary protein dose that would stimulate robust muscle synthesis in a young adult produces a blunted response in an older adult. Standard recommendations based on younger populations may therefore underestimate protein needs in the elderly.

This is why some guidelines specifically recommend higher protein targets for older adults (1.0–1.2 g/kg/day or more) and emphasize protein distribution across meals rather than concentrating it in one sitting. Understanding that the physiological response to protein — not just the protein itself — changes with age is the key insight. Sarcopenia is partly a problem of impaired signaling, not just insufficient intake.