Vegan diet

What are the main motives for adopting a vegan diet?

Ethical (animal welfare), ecological (environment), health, religious/spiritual, hygienic, aesthetic, economic, political. Kerschke-Risch (2015): ethical motives ranked #1 among German vegans.

What is the difference between a vegan, a flexitarian, and a pudding vegetarian?

Vegan: excludes all animal products. Flexitarian: mostly plant-based but occasionally eats animal products. Pudding vegetarian: avoids meat but eats low-quality processed plant foods. Distinction matters because misclassification biases health research results.

List the types of vegetarian diets covered in the course.

Lacto-ovo-vegetarian, lacto-vegetarian, ovo-vegetarian, vegan, pesco-vegetarian, semi-vegetarian, flexitarian, fruitarian, raw food, pudding-vegetarian.

Why can a vegan diet NOT be automatically considered healthy?

A vegan diet excludes animal products but says nothing about food quality. A "pudding vegan" relying on processed/junk plant foods can be severely micronutrient-deficient.

What trend was observed in Swiss vegan/vegetarian prevalence between 2015 and 2022?

Dietary intake data rely on self-reporting and may not reflect actual absorption. Serum B12 is insensitive — it stays normal even with functional deficiency because it includes inactive analogues. Holo-transcobalamin (holoTC) is the bioactive fraction and falls early in depletion. Methylmalonic acid (MMA) rises when B12-dependent enzymatic reactions are impaired — it is the most functionally relevant marker. The gold standard assessment combines holoTC + MMA.

According to the Adventist Health Study II (Rizzo 2013), how do vegans differ nutritionally from omnivores?

Vegans have: lower protein, lower saturated/trans fat, lower DHA, higher fibre, higher carbohydrates. Also lower vitamin B12, iodine, and calcium (confirmed in Swiss cohort, Schüpbach 2017).

What are the clinical consequences of low DHA intake in vegans?

DHA (omega-3) is critical for brain function, retinal health, and anti-inflammatory processes. Low intake may impair cognition, increase triglycerides, and raise cardiovascular risk. Algae-derived DHA supplements are recommended.

What does the Swiss cohort (Schüpbach 2017) show about blood nutrient levels in vegans?

Significant proportions of vegans had blood values below reference levels for vitamin B12, iodine, calcium, selenium, and vitamin D — more so than vegetarians or omnivores.

What does Kwok et al. (2014) conclude about vegetarianism and cardiovascular risk?

Vegetarianism is associated with ~25–29% lower risk of ischaemic heart disease mortality. Results were weaker for cerebrovascular disease. SDA studies were analysed separately due to additional lifestyle confounders (no alcohol, no tobacco).

What is the "healthy user bias" in vegan health studies?

Vegans tend to exercise more, smoke less, have lower BMI, and be more health-conscious. These lifestyle factors independently reduce disease risk, making it difficult to attribute benefits solely to the diet.

What did the EPIC-Oxford study (Appleby 2007) find about fracture risk in vegans?

Vegans had 30% higher fracture risk (RR 1.30). This excess risk disappeared when calcium intake was ≥525 mg/day, highlighting calcium adequacy as the key protective factor.

What does Dinu et al. (2017) conclude about vegan diets and chronic disease risk?

Vegans show lower risk of ischaemic heart disease, hypertension, type 2 diabetes, and lower BMI. However, residual confounding from healthy lifestyle factors limits causal interpretation.

What does Key et al. (2014) find about cancer risk in vegetarians/vegans?

Overall cancer risk ~12% lower in vegetarians. Colorectal cancer shows the most consistent reduction (high fibre, no haem iron, no processed meat). Effects on hormone-sensitive cancers (breast, prostate) are less clear.

List all potentially critical nutrients in a vegan diet (DGE, Richter 2016).

Vitamin B12, omega-3 FA, iron, iodine, vitamin D, zinc, calcium, high-quality protein, vitamin B2, selenium. B12 and calcium are specifically critical for vegans (vs. lacto-ovo-vegetarians who cover these via dairy/eggs).

What is the prevalence of vitamin B12 deficiency in vegans/vegetarians (Pawlak 2013)?

62% of pregnant women, 25–86% of children, 21–41% of adolescents, 11–90% of elderly show biochemical B12 deficiency. Prevalence is higher in vegans than vegetarians.

Why is spirulina NOT a reliable B12 source for vegans?

Spirulina contains pseudovitamin B12 — inactive analogues that compete with true B12 for absorption but cannot be used by human enzymes. Active B12 is found in Chlorella, Porphyra (nori), and Enteromorpha, but amounts are unstandardised.

Why are vegans at risk of iodine deficiency even in countries with iodisation programmes?

Main iodine sources are seafood and dairy (dairy iodine comes from iodophor disinfectants in farming). Plant milks are rarely iodine-fortified in Europe. Health-conscious vegans often use sea/Himalayan salt, which contains negligible iodine.

Which plant foods provide the most bioavailable calcium?

Calcium-set tofu (~31% absorption), kale and bok choy (~40–64%, low oxalate), fortified plant milks (~30–32%). Spinach is NOT reliable despite high calcium content — oxalates reduce absorption to ~5%.

What is DIAAS and why do plant proteins score lower than animal proteins?

DIAAS measures digestibility of each indispensable amino acid at the end of the small intestine. Plant proteins score lower due to antinutritional factors (phytates, trypsin inhibitors) and amino acid gaps — cereals lack lysine, legumes lack methionine. Soy scores highest (~0.9–1.0).

Which amino acid is most limiting in vegan diets and what are the consequences?

Lysine, scarce in cereals. Consequences: impaired collagen synthesis, reduced calcium absorption, impaired immune function, reduced carnitine synthesis. Solution: increase legume intake (lentils, beans, soy = high lysine).

Should vegans target the same protein intake (0.8 g/kg/day) as omnivores?

No. Lower plant protein digestibility means effective IAA delivery is reduced. Most guidelines recommend 0.9–1.1 g/kg/day for vegans. Elderly vegans need even more (1.0–1.2 g/kg/day) due to anabolic resistance.

What is the position of the AND (2025) on vegan diets?

Appropriately planned vegan diets can be nutritionally adequate for adults and offer long-term cardiometabolic health benefits. RDNs play a key role in personalised guidance.

What is the DGE (2024) position on veganism for vulnerable groups?

DGE does NOT make a clear recommendation for children, adolescents, pregnant/breastfeeding women, or elderly due to limited evidence and risk of irreversible harm. Specialist nutritional counselling is urgently recommended for these groups.

What does the Swiss FCN (2018) recommend regarding veganism?

Not recommended for pregnant women, breastfeeding mothers, infants, toddlers, adolescents, frail elderly, or individuals with eating disorders. Acceptable for healthy, well-informed adults.

What is the minimum mandatory supplementation for all vegans?

Vitamin B12 (cyanocobalamin or methylcobalamin), via daily low dose (~50–100 µg) or weekly high dose (~2000 µg). Additionally recommended: vitamin D, iodine, algae-derived DHA/EPA, and calcium if dietary intake is insufficient.