How much sulforaphane per day

Sulforaphane is not an essential nutrient. Nobody becomes deficient in it, so no agency has set a daily intake or an upper limit. Anyone quoting a "recommended" amount is quoting a trial dose, a supplement label, or a guess. This page covers the first of those, with the method behind every figure. For what the compound is and how it forms, start with the sulforaphane overview.

Is there a recommended daily amount of sulforaphane?

No. Official intake values exist for vitamins and minerals, and sulforaphane is neither. What you can find is the dose a given trial chose to test, in a given group, for a set number of weeks.

Those doses are useful for scale. They tell you what amount researchers thought worth giving to people, and what happened. They do not show that the amount is right for anyone else.

What doses have human trials used?

Trials report doses in micromoles (µmol), because the chemistry works per molecule. The milligram figures below are our arithmetic from the molar masses. The trials did not report them.

Both trials measured specific outcomes and neither was designed to find a best dose. The Qidong trial measured how much people excreted of the breakdown products of benzene and acrolein, two air pollutants. The autism trial measured behavior on rating scales completed by parents, carers and physicians. Neither result tells you what a healthy adult should take.

Why does a glucoraphanin dose deliver so much less?

Most products and many food figures give glucoraphanin, the stable precursor, instead of sulforaphane. Glucoraphanin has to be split by the enzyme myrosinase before any sulforaphane exists, and that step is where most of the dose goes missing.

The formal phase I study puts the clearest figure on the size of that loss, because it dosed the two forms separately. Nine treated volunteers took 21 doses over seven days as in-patients on a crucifer-free diet. On sprout extract containing the precursor, cumulative urinary excretion was 17.8 ± 8.6 percent of the dose at 25 µmol and 19.6 ± 11.7 percent at 100 µmol. On 25 µmol of isothiocyanate that had already been formed, it was 70.6 ± 2.0 percent, and far more consistent between people. Roughly four fifths of a precursor dose does not arrive.

A 2015 Johns Hopkins study put numbers on it in a small group, five volunteers for most comparisons. Given glucoraphanin with no active plant enzyme, they excreted about 10 percent of the dose as sulforaphane metabolites. When broccoli sprouts or seeds with their own myrosinase still active were given, recovery rose to almost 40 percent. The doses were measured by HPLC and the urinary metabolites by cyclocondensation assay.

The Qidong trial found a similar pattern at scale. Median excretion among people drinking the beverage was 8.4 to 9.7 percent of the daily dose as metabolites across the 12 weeks, measured by isotope-dilution mass spectrometry. An earlier study from the same Hopkins group found that chewing fresh sprouts thoroughly gave higher excretion than swallowing them whole, because chewing brings the plant's enzyme into contact with glucoraphanin.

The figures differ between studies, but they point the same way: 100 µmol of glucoraphanin on a label and 100 µmol of sulforaphane in a capsule are very different doses.

The largest daily amounts anyone has given deliberately are higher again, and they came from a drug rather than a food. A phase 1 trial of stabilized sulforaphane dosed 18 healthy men at 46.2 or 92.4 mg of sulforaphane a day for a week, which by the same arithmetic is about 260 or 520 µmol. Peak blood concentrations of sulforaphane plus metabolites reached 0.43 to 2.12 µmol/L at 3 to 6 hours, measured by validated LC-MS/MS, and urinary recovery ran from under 1 percent to 41 percent without tracking the dose. Those blood concentrations overlap the ones four people reached from a single sprout dose of about 200 µmol, described below. Two different preparations at broadly similar doses, measured by two different assays, put a broadly similar amount in the blood.

How long does sulforaphane stay in the body?

Hours, not days. In a Johns Hopkins study, four volunteers took a single dose of about 200 µmol of broccoli sprout isothiocyanates, mostly sulforaphane with smaller amounts of iberin and erucin. Concentrations in plasma, serum and red blood cells peaked one hour after the dose, between 0.943 and 2.27 µmol/l, then fell with first-order kinetics and a half-life of 1.77 ± 0.13 hours. By eight hours the volunteers had excreted 58.3 ± 2.8 percent of the dose. Everything was measured by cyclocondensation assay, which counts total isothiocyanates and their dithiocarbamate metabolites rather than sulforaphane on its own.

Four people and a single dose is a small study. A Dutch crossover trial in eight men put the excretion half-life in the same range, 2.6 hours after raw broccoli and 2.4 hours after cooked. Nothing in the human data suggests sulforaphane accumulates. A daily amount is a few hours of exposure repeated, not a reservoir that fills up.

When should you take sulforaphane?

No human trial has compared morning with evening, or with food against on an empty stomach. There is no evidence-based time of day, and anyone who names one is going beyond what has been tested. What researchers have compared is the preparation, and that changes absorption by roughly a factor of ten.

The three point at one variable, and it is the myrosinase question again. Heat destroys the plant enzyme, so cooked broccoli delivered about a tenth of what the same weight of raw broccoli delivered. A supplement made from sprouts with no active enzyme behaved much like the cooked broccoli, slower and far lower, even though it carried a similar glucoraphanin dose. The same split has been measured in dried material: a glucoraphanin-rich sulforaphane powder returned 19 and 24 percent of its dose in two studies of four men, against 74 percent for an air-dried sprout powder whose enzyme survived the drying.

The Oregon State trial is worth reading closely if you take capsules. Its subjects were given six pills. The label serving for that product was one. The authors set out the implication themselves: someone taking the recommended serving and believing it supplies an equivalent dose of isothiocyanates is not getting one. What separates one product from another is covered on the sulforaphane supplements page.

On whether to take it with food, the honest answer is that nobody has run the experiment. The Dutch subjects ate their broccoli with a warm meal. The Oregon State subjects fasted each morning before their dose. The two trials differ in preparation, dose, sampling and population, so the gap between them cannot be pinned on food. For fresh sprouts, the step that has been shown to matter is chewing, because that is what brings the plant's enzyme into contact with glucoraphanin. See broccoli sprouts for how much of the precursor they carry.

How do you convert micromoles to milligrams?

Multiply micromoles by the molar mass, then divide by 1,000. Sulforaphane has a molar mass of 177.3 g/mol, so 1 µmol is 0.177 mg. Glucoraphanin has a molar mass of 437.5 g/mol, so 1 µmol is 0.4375 mg.

This is why a glucoraphanin label can look large. A capsule with 30 mg of glucoraphanin holds about 69 µmol. Even if all of it converted, that would make about 12 mg of sulforaphane, and the studies above show that most of it does not convert.

How much sulforaphane do broccoli sprouts provide?

Broccoli sprouts are the richest common food source of glucoraphanin, and they carry their own active myrosinase when eaten raw. That is why the 2015 study saw higher recovery from sprouts than from glucoraphanin alone. The broccoli sprouts section covers them in detail, including how to grow broccoli sprouts at home.

A per-gram figure is harder. Published glucoraphanin content for sprouts varies widely between seed lots and growing conditions, and this site does not quote one without its assay. Measured values, each with its method, are going into the sulforaphane content by food table as they are verified. For the gram amounts of fresh sprouts that trials have fed people, see how much broccoli sprouts per day.

Is there a maximum safe dose?

No upper limit has been set, and no trial has run long enough or large enough to find one. The evidence on safety is thin and short-term.

A 2006 phase I study kept 12 healthy volunteers on a research ward, nine taking broccoli sprout extract and three placebo, with doses every eight hours for seven days. The researchers ran 32 types of blood test, including liver and thyroid function, and saw no toxic effects. Nine people for one week cannot reveal a rare or slow-developing problem.

The 18-week autism trial recorded vomiting, abdominal pain, flatulence, constipation, diarrhea, irritability and several other complaints in 12 to 19 percent of participants on sulforaphane. The authors report the same incidence in the placebo group. Two participants each had a single seizure, one after three weeks on sulforaphane and one three weeks after stopping, and both had a history of seizures. The authors wrote that they could not rule out seizures as an adverse effect in autism. The sulforaphane side effects page covers what trials have reported and who has reason for caution.