Know2eat

Collard greens

Brassica oleracea var. viridis

What collard greens has been studied for

3 associations assessed — 2 with at least some human evidence behind them. Strongest first.

  • 2 Limited
  • 1 Insufficient
3 things to know first — allergies, interactions and intake limits

About collard greens

A loose-leaved cabbage grown for its broad, flat, blue-green leaves, which stay firm through long cooking. It is the same species as kale, broccoli and cabbage, selected for leaf rather than head or flower.

Also known as Collards, Couve, Tree cabbage, Non-heading cabbage

Heart HealthEye HealthBone Health

The evidence in depth

Best supported: Limited

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how impressive the food is. How we rate evidence.

Blood lipid profile

Heart Health
Limited evidence

Steamed collards bind bile acids in laboratory conditions, and a small number of human trials of cruciferous vegetables report modest reductions in LDL cholesterol. Trials feeding collards specifically are almost non-existent, so this is inference from the wider brassica literature.

What may be going on: Bile acids bound in the gut are excreted rather than reabsorbed, which draws on hepatic cholesterol to replace them.

Limited evidence. Early human work, or mostly lab and animal research.

1 source

Deep research mode adds each paper’s own conclusion and stated limitations.

Macular health

Eye Health
Limited evidence

Collards are one of the densest dietary sources of lutein and zeaxanthin, and higher intake of those carotenoids is associated with denser macular pigment in observational work. The trials behind that association used supplements rather than the vegetable.

Limited evidence. Early human work, or mostly lab and animal research.

1 source

Deep research mode adds each paper’s own conclusion and stated limitations.

Bone mineral density

Bone Health
Insufficient evidence

Collards supply both calcium and vitamin K1, which is why they appear in bone-health advice. No trial has fed collards and measured bone density or fracture rate, so the link rests on nutrient content rather than on any tested outcome.

Insufficient evidence. Not enough human research to say anything useful yet.

No source is attached to this association yet, so it is rated insufficient by default. It is listed because people commonly ask about it — not because there is evidence for it.

Ask about Collard greens

Ask about Collard greens

Answers are written only from the entries on this page — the same nutrients, compounds, claims and citations you can read above. Nothing is added from outside the database, and every answer lists what it was built from.

AI explanations are not switched on for this site, so there is nothing to ask here. Everything above is read straight from the database and does not need them.

Key nutrients

Nutrient content per 100 grams
NutrientAmount% DV
Macronutrients
Calories32 kcal2%
Protein3.02 g6%
Total fat0.61 g1%
Carbohydrate5.42 g2%
Fibre4 g14%
Total sugars0.46 g—
Water89.6 g—
Fats
Saturated fat0.055 g0%
Monounsaturated fat0.03 g—
Polyunsaturated fat0.201 g—
Cholesterol0 mg0%
EPA (omega-3)0 g—
DHA (omega-3)0 g—
DPA (omega-3)0 g—
Linoleic acid (omega-6)0.082 g—
Vitamins
Vitamin A251 µg28%
Vitamin C35.3 mg39%
Vitamin D0 µg0%
Vitamin E2.26 mg15%
Vitamin K437 µg364%
Thiamin (B1)0.054 mg5%
Riboflavin (B2)0.13 mg10%
Niacin (B3)0.742 mg5%
Pantothenic acid (B5)0.267 mg5%
Vitamin B60.165 mg10%
Folate129 µg32%
Vitamin B120 µg0%
Choline23.2 mg4%
Minerals
Calcium232 mg18%
Iron0.47 mg3%
Magnesium27 mg6%
Phosphorus25 mg2%
Potassium213 mg5%
Sodium17 mg1%
Zinc0.21 mg2%
Copper0.046 mg5%
Manganese0.658 mg29%
Selenium1.3 µg2%
Other measured compounds
Beta-carotene2991 µg—
Alpha-carotene14 µg—
Lycopene0 µg—
Lutein + zeaxanthin4323 µg—
Caffeine0 mg—
Ash1.32 g—

Nutrient values are per 100 g of the USDA reference entry named on this page and vary with variety, growing conditions, storage and preparation.

Source record: Collards, raw (USDA FoodData Central, FDC ID 170406).

% DV uses the FDA Daily Values for adults and children aged 4 and over. A dash means no Daily Value has been established for that nutrient.

Bioactive compounds

Compounds present in meaningful amounts. Presence is banded rather than quantified, because whole-food levels vary enormously with variety, growing conditions, storage and preparation.

How preparation changes things

Only effects with real support are listed. If a preparation method is missing, it is because nothing dependable is documented — not because it makes no difference.

  • crushedIncreases isothiocyanate yield

    Chopping or shredding ruptures cells and lets myrosinase act on the glucosinolates. Waiting several minutes before applying heat allows more isothiocyanate to form before the enzyme is destroyed.

  • boiledReduces glucosinolates and myrosinase

    Long boiling, the traditional method, destroys myrosinase and leaches water-soluble glucosinolates into the pot liquor. Anyone drinking the liquor recovers some of what leached; anyone discarding it does not.

  • with fatIncreases carotenoid absorption

    Lutein and beta-carotene need dietary fat to be absorbed, which is one thing the traditional pairing with pork fat or olive oil happens to do.

Things to know

Allergies, interactions and intake concerns. Every food gets this section — a reference where everything is uniformly good is not a reference.

  • Interaction

    Vitamin K and warfarin

    Collards are among the densest food sources of vitamin K1, which directly opposes warfarin. The aim is a steady intake rather than avoidance, but adding or dropping a daily portion can move INR out of range, so tell whoever manages your anticoagulation first.

  • Worth knowing

    Goitrogens at high raw intake

    Raw brassicas release thiocyanates that compete with iodine for thyroid uptake. This matters mainly where iodine intake is low; the reported cases involve very large daily amounts of raw leaves or juice sustained for months, and cooking largely removes the concern.

  • Too much

    Fibre load when intake rises quickly

    The insoluble fibre and raffinose in collards are fermented in the colon. Wind and bloating are common when someone goes from eating none to eating them daily, and usually settle if the increase is gradual.