Are tomatoes or spinach cruciferous vegetables?

No. Tomatoes belong to the Solanaceae family and spinach to the Amaranthaceae family. Cruciferous vegetables are exclusively plants from the Brassicaceae family. Their defining characteristic is their glucosinolate content, which is not present in tomatoes or spinach.

Which cruciferous vegetable has the most glucoraphanin?

Broccoli and its microgreens are the sources with the highest documented concentration of glucoraphanin. Within broccoli, there is considerable variability among varieties: an analysis of 50 commercial accessions found differences of up to 27 times between the poorest and the richest (Kushad et al., 1999).

Can you eat cruciferous vegetables every day?

Yes, in most healthy people. Dietary guidelines include them among the vegetables to prioritize. People with untreated hypothyroidism or severe iodine deficiency may want to moderate their consumption of large quantities of raw cruciferous vegetables, although the available evidence shows that the actual risk is low with adequate iodine intake.

Does frozen broccoli retain glucosinolates?

The blanching process prior to industrial freezing inactivates myrosinase. Frozen broccoli contains glucoraphanin, but its conversion to sulforaphane depends on the gut microbiota as there is no active enzyme. There is a loss of glucosinolates, but frozen broccoli is still a nutritious vegetable in general terms.

Is there any cruciferous vegetable without a bitter taste?

Cauliflower and pak choi are generally the mildest. Romanesco cabbage also has a less intense flavor than kale or Brussels sprouts. Gentle cooking reduces bitterness by inactivating myrosinase and modifies the volatile compounds responsible for the flavor.

Cruciferous Vegetables: What They Are, Complete List, and How to Prepare Them

💡 Key Takeaways

Cruciferous vegetables are not a food group defined by nutritional marketing, but by botany: they belong to the Brassicaceae family and share a biochemistry based on glucosinolates that distinguishes them from any other plant family.

Cruciferous vegetables belong to the Brassicaceae family and are distinguished by their glucosinolate content.
Broccoli, cauliflower, kale, radish, watercress, and Brussels sprouts are commonly consumed cruciferous vegetables.
Each cruciferous vegetable has a distinct glucosinolate profile; broccoli is notable for its glucoraphanin.
Cooking reduces both glucosinolates and gas: there is a balance between palatability and content.
Including something raw in the same meal restores the myrosinase activity that cooking destroys.

This article includes a comprehensive table of 13 edible cruciferous vegetables with their main glucosinolate, active isothiocyanate, and consumed part, based on data from Agagündüz et al. (2022) and Kushad et al. (1999).

Table of Contents

Broccoli, kale, cauliflower, watercress, radish, Brussels sprouts. They all appear on healthy food lists, sometimes for different reasons and sometimes without much explanation. What they have in common is that they belong to the same botanical family and share a particular chemistry that differentiates them from other vegetables.

This article explains what defines a cruciferous vegetable, which vegetables fall into that category, and how preparation affects what the body can absorb.

What defines a cruciferous vegetable

Cruciferous vegetables are plants of the Brassicaceae family. The name comes from the shape of their flowers: four petals arranged in a cross. What makes them interesting from a nutritional point of view is that they contain glucosinolates, sulfur compounds that do not exist in the same concentration or with the same variety in other plant families.

Glucosinolates are secondary metabolites. The plant produces them as a defense against herbivores and insects. When plant tissue is damaged — by biting, cutting, or chewing — glucosinolates come into contact with the myrosinase enzyme and are hydrolyzed into isothiocyanates. Some of these isothiocyanates, such as sulforaphane (from broccoli) or allyl-isothiocyanate (from mustard and radish), have been studied for their effects on the Nrf2 pathway and endogenous antioxidant systems.

Each cruciferous vegetable has a different glucosinolate profile. Broccoli stands out for its glucoraphanin; watercress, for gluconasturtiin; kale, for its variety of indole and aliphatic glucosinolates. This diversity is a reason not to reduce cruciferous vegetables to a single species.

List of edible cruciferous vegetables

Vegetable	Main glucosinolate	Active isothiocyanate	Part consumed
Broccoli (Brassica oleracea var. italica)	Glucoraphanin	Sulforaphane	Inflorescence, stem
Cauliflower (B. oleracea var. botrytis)	Glucoraphanin (less than broccoli)	Sulforaphane	Inflorescence
Kale (B. oleracea var. sabellica)	Gluconapin, glucobrassicin	Various isothiocyanates and indoles	Leaves
Brussels sprouts (B. oleracea var. gemmifera)	Glucoraphanin, sinigrin	Sulforaphane, allyl-ITC	Lateral buds
White cabbage (B. oleracea var. capitata)	Glucoraphanin, glucoiberin	Sulforaphane, iberin	Leaves
Red cabbage (B. oleracea var. capitata rubra)	Glucoraphanin + anthocyanins	Sulforaphane	Leaves
Radish (Raphanus sativus)	Glucoraphanin (root), glucoiberin	Sulforaphane, 4-methylthio-3-butenyl-ITC	Root, leaves, sprouts
Watercress (Nasturtium officinale)	Gluconasturtiin	PEITC (phenylethyl-ITC)	Leaves and stems
Mustard (Sinapis alba, Brassica juncea)	Sinigrin, gluconapin	Allyl-ITC (pungent)	Seeds, leaves
Arugula (Eruca vesicaria)	Glucoerucin	Erucin (sulforaphane analog)	Leaves
Turnip (Brassica rapa var. rapa)	Gluconapin	But-3-enyl-ITC	Root, leaves
Pak choi (B. rapa var. chinensis)	Gluconasturtiin, glucoiberin	Various isothiocyanates	Leaves, stems
Broccoli sprouts/microgreens	Glucoraphanin (highly concentrated)	Sulforaphane	Entire seedling

→ Why sprouts concentrate more glucoraphanin: Broccoli sprouts: glucoraphanin, myrosinase, and why form matters

Why cruciferous vegetables have a more intense flavor

The bitter, pungent, or slightly sulfurous taste of broccoli, kale, or Brussels sprouts comes directly from their glucosinolates. When chewed, myrosinase hydrolyzes the glucosinolates and releases the isothiocyanates, which are responsible for the characteristic flavor. Heat reduces this conversion — because it inactivates myrosinase — which explains why boiled broccoli tastes different from raw broccoli.

The intensity of the flavor varies by species and variety. Brussels sprouts and kale tend to be more bitter; cauliflower and pak choi, milder. Within the same species, variety, cultivation, and harvest time influence the glucosinolate content and, therefore, the flavor.

How to prepare them: the cooking-glucosinolate balance

Cooking affects glucosinolates in two ways. First: heat inactivates myrosinase, reducing the conversion of glucosinolates to isothiocyanates in the vegetable. Second: glucosinolates are water-soluble and are partially lost in the cooking water.

Brief steaming (3–5 minutes). Reduces leaching losses compared to boiling, and retains more myrosinase activity than long cooking.
Boiling in abundant water. Reduces total glucosinolates but also compounds that produce gas. May be preferable for people with sensitive digestion.
Raw or fermented (sauerkraut, kimchi). Preserves glucosinolates and myrosinase. Fermentation also improves digestibility.
Mixed strategy. Adding a small amount of raw cruciferous vegetable — sprouts, arugula, ground mustard seeds — to the cooked dish provides active myrosinase that can improve the conversion of glucoraphanin from the cooked vegetable.

There is no "optimal" preparation that maximizes all parameters at once. Palatability and digestive tolerance matter as much as chemistry, because they determine whether the habit is maintained.

How many cruciferous vegetables should be consumed?

Dietary guidelines do not establish a specific recommendation for cruciferous vegetables as a group. General vegetable recommendations — 400–600 g/day in most European guidelines — include cruciferous vegetables among the options to prioritize for their nutritional density.

Observational studies on cruciferous vegetable consumption and health markers have used quantities ranging from 1 to 5 weekly servings (one serving ≈ 80–100 g). Regularity seems more determining than the exact quantity.

→ Cruciferous vegetables and hypothyroidism: Cruciferous vegetables and hypothyroidism: myth or evidence
→ Why cruciferous vegetables cause gas and how to reduce it: Why do cruciferous vegetables cause gas and how to eat them without bloating?

Conclusion

What unites broccoli, kale, cauliflower, radish, and watercress is not just that they appear on the same lists of recommended foods. It is that they share a particular biochemistry — glucosinolates — that is not present in the same way in other plant families. Each cruciferous vegetable has its own profile, which justifies varying among them instead of concentrating on just one.

Preparation influences how much of that chemistry is utilized: raw preserves more myrosinase; cooked reduces gas. Combining both forms in the usual diet is the most reasonable strategy.

→ Why broccoli is one of the most studied cruciferous vegetables: Broccoli: why it is one of the most studied vegetables

→ What is glucoraphanin and how the mechanism works: What is glucoraphanin? The precursor to sulforaphane explained
→ Which cruciferous vegetables concentrate the most glucoraphanin: Where is glucoraphanin concentrated? The best dietary sources