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AlternativeMed

Explore Functional Foods

A directory of functional foods with a sourced guide, grouped by type: fermented foods, fiber-rich foods, nuts and seeds, fruits and vegetables, fish and soy, tea and coffee, fortified foods.

Content last updated . This page has not been medically reviewed.

Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.

Each food below has a guide about the food as eaten: what research exists, what kind it is, and cautions. Foods without a link have no guide yet. Some foods have their own guides in other sections.

Directory

FoodTypeKey caution
YogurtFermentedAdded sugar; dairy allergy
KefirFermentedEvidence low quality
KimchiFermentedSodium; MAOI
SauerkrautFermentedSodium; MAOI
KombuchaFermentedProper evidence not found
MisoFermentedSodium; soy allergy
TempehFermentedProper evidence not found
NattoFermentedVitamin K; warfarin
OatsFiberAdded sugar in flavored products
BarleyFiberContains gluten
LegumesFiberGas; potassium
FlaxseedSeedSeed versus oil
Chia seedsSeedClaims outrun evidence
WalnutsNutTree nut allergy
AlmondsNutTree nut allergy
PistachiosNutSalt; allergy
Pumpkin seedsSeedProper evidence not found
AvocadoFruitVitamin K; potassium
BlueberriesFruitStudies often use powder
PomegranateFruitJuice sugar
Citrus fruitsFruitGrapefruit and medicines
TomatoesVegetableObservational only
Broccoli and cruciferousVegetableVitamin K
Leafy greensVegetableWarfarin
BeetrootVegetableLow-certainty evidence
Oily fishFishMercury advice
Soy foodsLegumeAllergy
Black teaDrinkCaffeine
CoffeeDrinkPregnancy
Fortified foodsFortifiedStacking with supplements

Foods with a guide in another section

FoodWhere
Olive oilNatural Ingredients
Cacao and cocoaNatural Ingredients
Colloidal oatmeal (skin)Natural Ingredients
SeaweedNatural Ingredients
HoneyNatural Ingredients
Apple cider vinegarNatural Ingredients
Green teaHerbs & Botanicals
GarlicHerbs & Botanicals
Ginger, turmericHerbs & Botanicals, Turmeric

Names are in standard scientific form and were checked against NCBI Taxonomy and the GBIF checklist on October 22, 2026. Plain names show as links when a guide has been published, and as dashed labels when a guide is in preparation. Each mushroom has one guide, even when it appears in more than one group.

Fermented Foods & Drinks

Foods made through microbial growth. Live cultures depend on the product; fermented does not mean probiotic.

  • Yogurt

    Yogurt as a functional food: what a 108-study review and cohort meta-analyses say, what live cultures mean, lactose, added sugar and safety in pregnancy.

  • Kefir

    Kefir as a functional food: a systematic review of 16 human studies, the limited evidence on cholesterol and blood pressure, and why high-quality trials are still needed.

  • Kimchi

    Kimchi as a functional food: what small randomized trials show for body weight, blood sugar and cholesterol, why a kimchi-derived probiotic is not kimchi, and sodium.

  • Sauerkraut

    Sauerkraut as a functional food: an 87-person crossover trial of fresh and pasteurized sauerkraut, why pasteurized worked as well, and sodium and tyramine cautions.

  • Kombucha

    Kombucha as a functional food: what reviews cover (production and microbiology), why proper evidence for health effects was not found, and cautions.

  • Miso

    Miso as a functional food: fermented soybean paste, what we could and could not find in clinical research, sodium, and tyramine cautions.

  • Tempeh

    Tempeh as a functional food: fermented soybean cake, why proper evidence for health effects was not found, and allergy and safety notes.

  • Natto

    Natto as a functional food: fermented soybeans, very high vitamin K and the warfarin caution, and why proper evidence for health effects was not found.

Fiber-Rich & Prebiotic Foods

Whole grains, legumes and seeds. The best-supported effects are for beta-glucan and cholesterol.

  • Oats

    Oats as a functional food: meta-analysis of oat beta-glucan and LDL cholesterol, the FDA-authorized 3 g beta-glucan claim, and what is not shown.

  • Barley

    Barley as a functional food: beta-glucan, a 5-week trial on bile acids and cholesterol, the FDA claim for oats or barley, and what is not shown.

  • Legumes: Beans, Lentils & Chickpeas

    Legumes (beans, lentils, chickpeas) as functional foods: dose-response meta-analysis of heart disease, a chickpea trial review on blood sugar, and cautions.

  • Flaxseed

    Flaxseed as a functional food: meta-analysis on apolipoproteins, why flaxseed oil is different from seed, and evidence gaps on ground versus whole.

  • Chia Seeds

    Chia seeds as a functional food: a 4-trial meta-analysis on inflammation markers, an umbrella review of other outcomes, and where claims outrun evidence.

Nuts, Seeds & Unsaturated Fats

Energy-dense foods. Studied by swapping them for other foods, not adding them on top.

  • Walnuts

    Walnuts as a functional food: a 26-trial meta-analysis on LDL cholesterol and triglycerides, blood pressure findings, calories and allergy.

  • Almonds

    Almonds as a functional food: meta-analyses on body weight, fat mass, C-reactive protein and interleukin-6, and what the effects mean.

  • Pistachios

    Pistachios as a functional food: meta-analyses of cardiometabolic markers and blood sugar in people at risk of heart disease, with limits.

  • Pumpkin Seeds

    Pumpkin seeds as a functional food: why proper evidence for the seeds as food was not found, and what the pumpkin seed oil trial does and does not show.

  • Avocado

    Avocado as a functional food: small trials on macular pigment and after-meal markers, and the limits of what they show.

Fruits & Vegetables

Whole produce and juices. Most disease evidence is observational.

  • Blueberries

    Blueberries as a functional food: a randomized trial of wild blueberry powder in older adults, a pregnancy trial combined with fiber, and limits.

  • Pomegranate

    Pomegranate as a functional food: meta-analyses of blood pressure, the mostly animal evidence on cognition, and cautions.

  • Citrus Fruits & Orange Juice

    Citrus fruits and orange juice as functional foods: hesperidin trials, blood orange juice and blood vessel function, grapefruit and medicines.

  • Tomatoes

    Tomatoes as a functional food: a meta-analysis linking tomato intake to prostate cancer risk, why case-control and cohort studies disagree, and limits.

  • Broccoli & Cruciferous Vegetables

    Broccoli and cruciferous vegetables as functional foods: observational meta-analyses on cancer and prostate cancer, and why they are not proof.

  • Leafy Greens

    Leafy greens as functional foods: observational meta-analyses on cardiovascular disease and lutein, and the warfarin vitamin K caution.

  • Beetroot & Beet Juice

    Beetroot and beet juice as functional foods: dietary nitrate and blood pressure, a meta-analysis in hypertension with low certainty, and conflicting reviews.

Fish & Soy Foods

Protein foods. Fish as food is kept apart from fish-oil supplements.

  • Oily Fish

    Oily fish as a functional food: observational studies on heart disease and mortality, FDA mercury advice, and how fish as food differs from fish-oil supplements.

  • Soy Foods

    Soy foods as functional foods: meta-analysis of soy protein and LDL cholesterol, the FDA 25 g claim, isoflavones for menopause, and soy versus supplements.

Tea & Coffee

Common drinks with large evidence bases. Cocoa has its own guide in Natural Ingredients; green tea in Herbs & Botanicals.

  • Black Tea

    Black tea as a functional food: a meta-analysis on LDL cholesterol, a review on blood pressure with green tea, and caffeine. Green tea is in Herbs & Botanicals.

  • Coffee

    Coffee as a functional food: two umbrella reviews, why most evidence is observational, and cautions in pregnancy and for fracture risk.

Fortified Foods

Foods with nutrients added. Different from supplements and from naturally rich foods.

  • Fortified Foods

    Fortified foods: what fortification is, the FDA fortification policy, plant sterol-enriched foods and the FDA claim, and where proper evidence was not found.

About the PubMed counts: they come from a text search of PubMed (NCBI E-utilities) for the scientific and common names plus the "randomized controlled trial" publication type. They include studies of extracts, blends and non-health uses, and a trial can find no effect. A count shows how much human research has been indexed, not whether something works.

Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.