Sulforaphane

How to grow broccoli sprouts

2026-09-15T00:00:00Z

Broccoli sprouts cost very little to grow and the process is genuinely simple. Most of what goes wrong comes down to drainage.

What you need

Seed sold specifically for sprouting, a wide-mouth jar, and a mesh lid. Muslin and a rubber band work as well as a purpose-made lid.

Garden seed is not a substitute. It is frequently treated with fungicide, which is fine for something you plant and not fine for something you eat whole, and it is not tested for the pathogens that sprouting conditions encourage.

The method

Put one to two tablespoons of seed in the jar and cover with cool water. Leave it overnight. In the morning, fit the lid and drain the water off completely.

From that point it is rinse and drain, twice a day. Fill with cool water, swirl, pour it all out, and rest the jar mouth-down at an angle so the last of the water keeps running out. Keep it out of direct sun.

By day three to five the sprouts will be one to two centimeters long with small seed leaves. Move the jar somewhere with indirect light for a few hours and the leaves will green up. Rinse once more, drain thoroughly, and refrigerate.

The two things that go wrong

Standing water. Every bad batch traces back to it. Seeds sitting in water ferment, the jar smells sour, and the same conditions favor bacteria you do not want. Drain completely, every time, and keep the jar angled.

Confusing root hairs with mould. Around day three, fine white fuzz appears on the roots and alarms people. Root hairs are fine, even, and attached to the root itself. Mould is gray or blue, appears in patches rather than evenly, and smells wrong. If in doubt, the smell is the reliable test.

On safety

Sprouts have a genuine food safety history, because the warm damp conditions that germinate a seed also suit bacteria. That risk is managed rather than eliminated: use sprouting seed, keep everything clean, drain properly, refrigerate promptly, and eat them within a few days.

Public health guidance generally advises that people who are pregnant, elderly, very young or immunocompromised eat sprouts cooked rather than raw. Cooking does reduce sulforaphane yield, which is a real trade-off rather than a detail to skip past.

Sulforaphane content by food

2026-09-15T00:00:00Z

Ask how much sulforaphane is in broccoli and you will get answers that differ by a factor of twenty. They are not all wrong. They are measuring different things.

Why this table exists

Sulforaphane figures circulate widely without the information needed to use them. The number depends on:

Cultivar. Glucoraphanin content varies several-fold between broccoli varieties.
Plant age. Young sprouts concentrate glucoraphanin far more densely than the mature vegetable. The 1997 study that established this reported three-day sprouts carrying on the order of twenty to fifty times the concentration found in mature broccoli by weight, with wide variation between seed lots.
Growing conditions and storage. Both sulfur availability in the soil and time since harvest move the result.
What was measured. Glucoraphanin content and sulforaphane yield are different quantities. Converting between them requires assumptions about hydrolysis that frequently go unstated.
The assay. HPLC after controlled enzymatic hydrolysis, cyclocondensation assay for total isothiocyanates, and estimation from total glucosinolates give different answers and are not interchangeable.

A figure without its method attached cannot be compared to anything. Every row here carries one.

The table

Table in preparation. Rows are added as each source is verified.

How to read a figure from this table

A value in milligrams per 100 grams fresh weight tells you what was in the sample the researchers measured. It does not tell you what you will absorb.

Between the two sit preparation and conversion. Boiling destroys myrosinase and much of the yield goes with it. Steaming briefly preserves more. Chopping and resting before cooking allows conversion to happen before heat arrives. Chewing does work that swallowing does not.

The table gives you the starting quantity. The dosage and cooking pages deal with what survives the journey.

Glucoraphanin

2026-09-15T00:00:00Z

Broccoli does not contain sulforaphane. It contains glucoraphanin, and the two are routinely confused, including on product labels.

What glucoraphanin is

Glucoraphanin belongs to a family of compounds called glucosinolates, which cruciferous plants produce and store in quantity. Structurally it carries a sugar group joined through a sulfur atom to a chain ending in a methylsulfinyl group, with a sulfated oxime in the middle. The sugar and the sulfate are both leaving groups, which is the whole point of the design.

In the intact plant it is stable and does nothing. It sits in the cell vacuole, chemically inert, waiting.

Why the plant keeps it separate

The enzyme that acts on glucoraphanin, myrosinase, is stored in different cells entirely. As long as the tissue is intact, the two never meet.

This is a defense system with a trigger. An insect chewing a leaf ruptures both compartments at once, myrosinase reaches glucoraphanin, and the plant produces a sharp, reactive isothiocyanate precisely where it is being eaten. Sulforaphane is a chemical weapon released on contact, and the fact that people find it interesting for other reasons is incidental to why it exists.

What this means for a label

Most products marketed for sulforaphane contain glucoraphanin from broccoli seed or sprout extract, because glucoraphanin survives manufacturing and storage while sulforaphane does not.

That leaves the conversion step to be solved somewhere else. Some products add myrosinase from a separate plant source. Others rely on the enzyme activity of gut bacteria, which varies enormously between individuals and is not something a label can promise. Two capsules stating the same glucoraphanin content can deliver very different amounts of sulforaphane to two different people, or to the same person on different days.

A label quoting a "sulforaphane equivalent" or "sulforaphane potential" is stating an upper bound assuming complete conversion. Complete conversion does not happen.

What is sulforaphane?

2026-09-15T00:00:00Z

Where it comes from

Cruciferous vegetables store a compound called glucoraphanin, a glucosinolate. They also produce an enzyme called myrosinase. In an undamaged plant the two are kept apart, in separate cellular compartments.

When the plant is cut, chewed, crushed or blended, those compartments break and the enzyme meets the precursor. Myrosinase strips the sugar off glucoraphanin, the remaining fragment loses a sulfate group and rearranges, and the result is sulforaphane.

This is a defense mechanism. The plant is not making a supplement ingredient; it is making something unpleasant for whatever is eating it, at the moment it is being eaten.

Why that matters in practice

Because the compound is made on demand rather than stored, how you handle the food changes how much you get. Heat destroys myrosinase. Chopping and waiting before cooking gives the enzyme time to work. Chewing thoroughly does more than swallowing quickly. These are not marginal effects.

It also explains the confusion around supplements. A product containing glucoraphanin has the precursor but may have no working enzyme, in which case conversion depends on gut bacteria, which vary widely between people.

Is it an essential nutrient?

No. There is no deficiency state, no recommended intake and no established requirement. Sulforaphane is a compound found in some foods that has been studied for possible effects, which is a different thing from a nutrient the body needs.

Sulforaphane side effects

2026-09-15T00:00:00Z

What the trials report

Most human studies of sulforaphane have been small, running from a few dozen to a few hundred participants over weeks rather than years. Within those limits, the commonly reported complaints are digestive: gas, bloating and loose stools. Some participants find the taste of sprout preparations difficult, which shows up in trials as poor compliance rather than as an adverse event.

The honest limitation is that a trial of forty people for eight weeks cannot detect an effect that appears in one person in a thousand, or after two years. Absence of reported harm at that scale is weak evidence of safety, not strong evidence.

Who has genuine reason for caution

Cruciferous vegetables contain compounds that can interfere with thyroid iodine uptake, which is relevant at supplement doses rather than normal food amounts. Anyone being treated for a thyroid condition should raise it with their doctor before taking a concentrated product.

Isothiocyanates have been reported to affect platelet function, so anyone on anticoagulant or antiplatelet medication should do the same. There is not enough data on pregnancy or breastfeeding at supplement doses to say anything useful, which is itself a reason for caution.

None of this applies to eating broccoli.