The 9 Diets Explained: What Each Allows, Avoids, and Who They Suit

In everyday talk, "diet" often means a temporary restriction for weight loss. This article is about the other meaning — a sustained way of eating. Vnutri tags every food in the catalog against 9 diets: vegan, vegetarian, pescatarian, gluten-free, dairy-free, keto, paleo, Mediterranean, and low-FODMAP. They aren't ranked "best" to "worst" — each solves a different problem.

Below: a short breakdown of what each diet excludes, why, who it's for, and where the traps are. Every section links to the catalog page listing the foods compatible with that diet.

Vegan

Excludes: meat, fish, dairy, eggs, honey, gelatin, any animal-derived product.

Includes: plants. Legumes, whole grains, vegetables, fruit, nuts, seeds. Fortified products — plant milk, nutritional yeast, meat substitutes.

Evidence: lower risk of coronary heart disease (−25 %, Tonstad 2013), type 2 diabetes (−30 %), some cancers. Highest fiber intake of any pattern (median 41 g/day vs 18 g for omnivores).

Why people choose it: ethics, environmental footprint, health, weight management.

Traps:

• B12 — not present in plants. Supplements or fortified foods only. See B12 for vegans.
• Iron — non-heme, lower absorption. Sunflower seeds, lentils, spinach + vitamin C. See iron without meat.
• Zinc, calcium, iodine, omega-3 EPA/DHA — need attention and a thought-out diet.

Suits: motivated people willing to learn. Not for those wanting minimum effort.

Full list — vegan-compatible foods.

Vegetarian (lacto-ovo)

Excludes: meat, fish, seafood, gelatin.

Includes: eggs, dairy, plus everything a vegan eats. Cheese, yogurt, kefir, omelets.

Evidence: similar cardiometabolic benefits to vegan, softer. Easier on B12 (dairy and eggs supply it). EPI 2024 — −13 % cardiovascular mortality vs omnivores.

Why people choose it: balance between ethics and convenience. Keeps dairy and eggs as solid sources of B12, calcium, and protein.

Traps: iron and zinc are still non-heme. B12 is covered with a varied diet.

Suits: most people willing to drop meat. An easy step from omnivore.

Full list — vegetarian-compatible foods.

Pescatarian

Excludes: poultry and red meat.

Includes: fish, seafood, eggs, dairy, plus plants.

Evidence: close to the Mediterranean pattern. The strongest of the "hybrid" patterns at reducing coronary disease (−24 %, Adventist Health Study 2). Omega-3 EPA/DHA covered through fatty fish.

Why people choose it: want out of meat-eating but keep full-spectrum protein and omega-3. Often a transition step toward vegetarianism.

Traps: mercury in large predator fish (tuna, swordfish). Better to lean on small fatty fish — sardines, mackerel, herring.

Suits: anyone for whom "more fish, less meat" is a sustainable rule.

Full list — pescatarian-compatible foods.

Gluten-free

Excludes: wheat, rye, barley, spelt, triticale, bulgur, couscous, semolina, seitan, any product made with them.

Includes: rice, corn, quinoa, buckwheat, oats (certified gluten-free), millet, amaranth. Meat, fish, vegetables, fruit, dairy by default.

Evidence: required in celiac disease (~1 % of the population) and non-celiac gluten sensitivity (3–6 %). For healthy people — no proven benefit. The Lebwohl 2017 cohort found that in non-celiacs, low gluten intake did not lower cardiovascular risk and may raise it (fewer whole grains, less fiber). See gluten-free without celiac.

Why people choose it: medical necessity (celiac), sensitivity, trend.

Traps:

• Gluten-free packaged foods are often worse nutritionally — more sugar, more fat, less fiber.
• Cost is 2–3× higher.
• Whole gluten-free grains (quinoa, buckwheat, oats) are great; processed "gluten-free" analogs of bread or cookies aren't.

Suits: anyone with a medical indication. Without one, there's no clear benefit.

Full list — gluten-free-compatible foods.

Dairy-free

Excludes: milk, cheese, yogurt, butter, cream, ice cream, anything made from milk. Also (often) whey protein, casein, and lactose.

Includes: plant milks (oat, almond, soy), nut-based cheeses, vegan yogurt. Meat, fish, vegetables, fruit, grains.

Evidence: needed for lactase non-persistence (~70 % of East Asian adults, 30 % of Europeans), cow's milk protein allergy, or for some patients during IBD flares.

Why people choose it: intolerance, medical indication, vegan, elimination diet.

Traps:

• Calcium. Dairy covers ~50 % of daily calcium in a standard diet. Replacements: sardines with bones, calcium-set tofu, fortified plant milk, sesame seeds. See calcium without dairy.
• Vitamin D in fortified milk — replaced by a supplement.

Suits: lactose intolerance or milk protein allergy. Without a diagnosis it's a lifestyle choice, not a medical need.

Full list — dairy-free-compatible foods.

Keto

Excludes: sugar, all grains, legumes, most fruit, starchy vegetables in any quantity. Bread, pasta, rice, sweets.

Includes: meat, fish, eggs, nuts, cheese, butter and olive oil, avocado, leafy greens, berries in moderation.

Parameters: 70–80 % of calories from fat, 20–25 % protein, < 5–10 % carbohydrate. In practice — 20–50 g of net carbs per day. See keto basics.

Evidence: established for drug-resistant epilepsy in children (a 100-year standard) and for short-term weight loss. Long-term data are mixed: cholesterol response varies, cardiovascular effect depends on fat quality.

Why people choose it: fast short-term weight loss, hunger control, epilepsy, insulin resistance.

Traps:

• "Keto flu" in the first 1–2 weeks: fatigue, headache, irritability. Driven by sodium and water loss.
• Fiber is low by default; covered through broccoli, avocado, seeds.
• Long-term adherence is low — most people don't last a year.

Suits: those willing to plan and tolerate the first week.

Full list — keto-compatible foods.

Paleo

Excludes: legumes, grains, dairy, refined sugar, processed oils (sunflower, soy).

Includes: meat, fish, eggs, vegetables, fruit, nuts, seeds, root vegetables. Olive and coconut oil, avocado.

Evidence: Manheimer 2015 meta-analysis found modest short-term improvements in waist circumference and LDL. Long-term data are scarce. The "what hunter-gatherers ate" framing is a simplification — actual hunter-gatherer diets vary widely.

Why people choose it: want to drop ultra-processed foods but less strict than keto. Some autoimmune patients use it to reduce inflammation.

Traps:

• Calcium — no dairy means leaning on leafy greens and sardines.
• Fiber — without legumes or grains, lower than Mediterranean.
• Cost — meat, nuts, and fish make it expensive.

Suits: anyone willing to drop grains and legumes for whole foods. Mixed long-term evidence.

More — paleo vs keto. Full list — paleo-compatible foods.

Mediterranean

Excludes: nothing strictly. Minimizes red meat, ultra-processed foods, added sugars.

Includes: olive oil as the main fat, vegetables, fruit, legumes, whole grains, nuts, seeds, fish and seafood several times a week, fermented dairy (yogurt, feta) in moderation, red wine optional.

Evidence: the strongest of any diet. The PREDIMED trial (Estruch 2018) — a randomized study, 7,447 participants, 5 years — cut major cardiovascular events by 30 % vs control. Lower type 2 diabetes, depression, and cognitive decline.

Why people choose it: proven benefit, flexibility, nothing strictly banned. The most "normal" diet on the list.

Traps: needs access to quality products (extra-virgin olive oil, fresh fish, vegetables). Harder to maintain outside the Mediterranean basin.

Suits: almost everyone. The American Heart Association's default recommendation.

Full list — Mediterranean-compatible foods. See a Mediterranean week.

Low-FODMAP

Excludes (for 4–6 weeks): specific carbohydrate types that ferment in the gut. Onion, garlic, wheat, beans, apples, pears, mango, honey, lactose, sorbitol.

Includes: meat, fish, eggs, rice, potato, carrot, spinach, banana, orange, lactose-free dairy, hard cheeses, oats.

Evidence: developed at Monash University for irritable bowel syndrome (IBS). Cuts symptoms in 70–80 % of patients (Halmos 2014). Not a lifestyle diet — a therapeutic protocol with elimination (6 weeks) and reintroduction (8–12 weeks) phases.

Why people choose it: IBS diagnosis or chronic functional GI symptoms. See low-FODMAP for IBS.

Traps:

• Not for healthy people. Long-term low-FODMAP eating harms the microbiota.
• Needs a dietitian or the Monash FODMAP app.
• Reintroduction phase is critical — without it, the diet is wasted.

Suits: only with a medical indication.

Full list — low-FODMAP-compatible foods.

Comparison table

Diet	Protein sources	Main nutrient risks	Evidence base
Vegan	Legumes, tofu, nuts	B12, iron, zinc, omega-3, iodine	Strong (meta-analyses)
Vegetarian	+ eggs, dairy	Iron, B12 (softer)	Strong
Pescatarian	+ fish	Mercury in big predators	Strong
Gluten-free	Anything gluten-free	Fiber, B vitamins	Celiac only
Dairy-free	Anything dairy-free	Calcium, vitamin D	Intolerance only
Keto	Meat, fish, cheese, eggs	Fiber, electrolytes	Epilepsy, short-term weight
Paleo	Meat, fish, eggs	Calcium, fiber	Short-term waist reduction
Mediterranean	Fish, legumes, nuts	Minimal	Strongest (PREDIMED)
Low-FODMAP	Anything	Fiber, diversity	IBS (therapeutic)

Which diet suits you

There's no "best" diet. There's the one you'll stick with.

• Standard CVD risk, want a healthy pattern — Mediterranean.
• Ethical reasons — vegan or vegetarian.
• Celiac — gluten-free.
• IBS — low-FODMAP under clinical guidance.
• Type 2 diabetes or fast short-term weight loss — keto or low-carb.
• Want to drop ultra-processed but not too strict — paleo or Mediterranean.

See also the glycemic index — how carbs behave under different diets, and macros vs micros — how to track both classes of nutrients.

How Vnutri shows diets

The Vnutri catalog tags 845+ foods against all 9 diets. For the first six (vegan, vegetarian, pescatarian, gluten-free, dairy-free, keto) — deterministic rules: category and token absence, net carbs for keto. For the last three (paleo, Mediterranean, low-FODMAP) — Claude Sonnet expert classification with review.

Filtering: each diet page lists the compatible foods with nutrition data. Category and nutrient filters combine — "vegan and high protein", "keto and high fiber".

Frequently asked questions

Can you combine multiple diets?

Yes, and often it's sensible. Vegan + gluten-free (for a vegan celiac). Mediterranean + dairy-free. Keto + low-FODMAP (rarely). Vnutri shows the intersection in its filters.

Which diet is best for long-term health?

By volume of evidence — Mediterranean. PREDIMED is the only RCT of a diet of that scale to show a drop in hard endpoints (heart attack, stroke). Other diets are effective for specific goals but lack that breadth of evidence.

Is keto sustainable for life?

Long-term data over 10+ years are limited. Adherence is low — most people don't last a year. For epilepsy (where medical keto is the standard) it's used for years under clinical care. For others — better as a short or cyclic protocol.

Can you be healthy on a vegan diet?

Yes — with B12 supplementation and a planned diet. Adventist Health Study 2 showed the lowest cardiovascular mortality in vegans. Without B12, no.

What does FODMAP stand for?

Fermentable Oligo-, Di-, Monosaccharides And Polyols. A group of carbs poorly absorbed in the small intestine and fermented in the large. They cause gas and pain in IBS patients. Not harmful for healthy people.

Why such a complicated diet classification?

Each one solves a different problem: ethics (vegan), medicine (gluten-free, low-FODMAP, dairy-free), long-term health (Mediterranean), short-term weight loss or epilepsy (keto). Vnutri doesn't rank diets — it lets you filter by your context.

References

• Tonstad S, et al. Vegetarian diets and incidence of diabetes in the Adventist Health Study-2. Nutr Metab Cardiovasc Dis. 2013;23(4):292–299.
• Estruch R, et al. Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts (PREDIMED). N Engl J Med. 2018;378(25):e34.
• Halmos EP, et al. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology. 2014;146(1):67–75.
• Lebwohl B, et al. Long-term gluten consumption in adults without celiac disease and risk of coronary heart disease. BMJ. 2017;357:j1892.
• Manheimer EW, et al. Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis. Am J Clin Nutr. 2015;102(4):922–932.