Plant-Based, Vegetarian, and Vegan Diets

Plant-based diets span a spectrum: flexitarian (mostly plants), lacto-ovo vegetarian (plants + dairy + eggs), pescatarian (plus fish), and vegan (no animal products). The Academy of Nutrition and Dietetics' current position (2025) is that, in adults, appropriately planned vegetarian and vegan dietary patterns can be nutritionally adequate and can offer long-term benefits, including improvements in several cardiometabolic health outcomes — plausibly helped by high fiber (see Dietary Fiber and Gut Health) and more unsaturated, less saturated fat. That paper covers non-pregnant, non-lactating adults only; children, teens, and pregnant or breastfeeding people need specific guidance. (Its 2016 predecessor had described well-planned vegetarian diets as appropriate for all stages of the life cycle.)

Completeness considerations (the trade-off for cutting animal foods):

• Vitamin B12: essentially absent from plants — vegans must use fortified foods or a supplement (see Vitamin B12).
• Protein quality: plant proteins are often lower in one or more EAAs and less digestible; eat a variety (legumes, soy, grains, nuts) across the day, and active vegans may aim slightly higher on total protein (see Protein — Functions, Quality, and Requirements).
• Iron and zinc: plant (non-heme) forms are less bioavailable; pair iron with vitamin C (see Iron, Minerals — Overview (Magnesium, Zinc, and the Remaining Trace Minerals)).
• Calcium and vitamin D: ensure fortified foods/sun or supplements (see Calcium, Vitamin D).
• Omega-3 (EPA/DHA): rely on ALA plus algae oil (see Omega-3 and Omega-6 Essential Fatty Acids).
• Iodine: the 2025–2030 Dietary Guidelines list it among the nutrients to monitor.

The 2025–2030 Dietary Guidelines add that vegetarian diets often fall short in vitamins D and E, choline and iron, while vegan diets show broader shortfalls (including B12, calcium, zinc, magnesium and protein). They advise targeted supplementation, diversifying plant proteins, using food preparation that improves mineral absorption, periodically monitoring iron, B12, vitamin D, calcium and iodine status, and significantly limiting highly processed vegetarian/vegan foods.

Pros: heart-healthy, high-fiber, environmentally lighter, often lower calorie density. Cons: requires planning to avoid the deficiencies above (see Who Is at Risk of Micronutrient Deficiency); poorly planned versions can lean on refined carbs and highly processed meat substitutes. Adherence and personal values often make it sustainable for those who choose it (see The Best Diet Is the One You Adhere To).

• Spectrum: flexitarian → vegetarian → pescatarian → vegan.
• AND (2025): in adults, well-planned vegetarian/vegan diets can be adequate and improve cardiometabolic outcomes; children/pregnancy/lactation need specific guidance.
• DGA 2025–2030: monitor iron, B12, vitamin D, calcium, iodine; limit highly processed vegan/vegetarian foods.
• Vegans must supplement B12 (or use fortified foods).
• Watch protein quality/variety, iron, zinc, calcium, vitamin D, EPA/DHA.
• Benefits: fiber, heart health; risks come from poor planning.