The Health Benefits of Cruciferous Vegetables and Sulforaphane

Cruciferous vegetables such as broccoli, Brussels sprouts, cabbage, cauliflower, and kale contain compounds called glucosinolates that can be converted into isothiocyanates, which have been shown to have anticancer and other health-promoting effects.

One particularly beneficial isothiocyanate is sulforaphane, which is found in high amounts in broccoli sprouts. This article summarizes the health benefits of cruciferous vegetables and sulforaphane based on a transcript discussing the latest research.

Cruciferous Vegetable Consumption and Mortality

Several large epidemiological studies have found that people who consume more cruciferous vegetables have lower mortality rates. One study divided people into quintiles based on vegetable intake. The top 20% who ate the most vegetables had a 16% lower risk of death from any cause compared to the bottom 20%. When looking specifically at cruciferous vegetable intake, the top 20% of consumers had a 22% lower mortality rate. This effect was primarily driven by a reduction in cardiovascular disease deaths.

These studies show a strong association between cruciferous vegetable consumption and longevity.

Sulforaphane and Cancer Prevention

Sulforaphane is one of the most studied isothiocyanates found in cruciferous vegetables, particularly broccoli sprouts. Multiple studies have shown sulforaphane has anti-cancer effects:

Men who ate 3-5 servings of cruciferous vegetables per week had a 40% lower risk of prostate cancer.
Men eating ?2 servings of broccoli per week had a 44% lower rate of bladder cancer.
Smokers eating ?4.5 servings of raw cruciferous vegetables per month had a 55% lower risk of lung cancer.
Women eating cruciferous vegetables ?1 time per week had a 17-50% lower risk of breast cancer.

Sulforaphane prevents cancer through several mechanisms:

It inhibits Phase 1 enzymes that activate pro-carcinogens into carcinogens that can damage DNA. This prevents formation of cancer-causing agents from sources like cigarette smoke.
It induces Phase 2 enzymes that promote excretion of carcinogens so they are eliminated from the body rather than causing DNA damage.
It reduces oxidative stress and inflammation, lowering DNA damage that can lead to cancer development.

Human trials have also shown positive effects of sulforaphane supplements in men with prostate cancer. Doses of 60 mg/day slowed prostate cancer progression by 86%.

Promoting Excretion of Carcinogens

Cruciferous vegetables can help rid the body of carcinogens like benzene and acrolein that are found in cigarette smoke, automobile exhaust, and other sources.

In one study, people drinking a broccoli sprout beverage excreted 61% more benzene over 12 weeks compared to the placebo group. The broccoli sprout drink also increased excretion of the air pollutant acrolein by 23-50% in other studies.

By enhancing excretion of carcinogens, cruciferous vegetables provide protection against DNA damage and cancer development. This may explain their strong link to reduced cancer rates.

Cardiovascular Disease Prevention

Higher intake of cruciferous vegetables is associated with lower cardiovascular disease incidence. This is likely due to anti-inflammatory and antioxidant effects mediated by sulforaphane.

Human trials using broccoli sprout supplements have shown improvements in cardiovascular disease risk markers:

40 mg/day sulforaphane reduced serum triglycerides 18.7% and LDL oxidation 13.5% in diabetics.
Similar doses reduced TNF-alpha (inflammatory marker) by 11% and CRP (cardiovascular risk marker) by 16%.
Doses providing ~60 mg/day sulforaphane lowered atherogenic index by over 50% in type 2 diabetics.

Through its antioxidant and anti-inflammatory activities, sulforaphane may help prevent atherosclerosis and lower heart disease risk.

Brain and Cognitive Health

Sulforaphane is able to cross the blood-brain barrier and stimulate antioxidant pathways in the brain. This may explain some of its neuroprotective properties:

Doses of 9-25 mg/day improved behavior and social interaction in young men with autism spectrum disorder.
30 mg/day improved cognition in schizophrenic patients.

Though not yet studied in humans, sulforaphane also shows promise for:

Alleviating depression and anxiety disorders by reducing inflammation that can impair neurotransmitter function.
Protecting against neurodegenerative diseases like Alzheimer’s and Parkinson’s by clearing abnormal protein aggregates.
Enhancing recovery from traumatic brain injury through antioxidant, anti-inflammatory, and neuroregenerative activities.

More research is needed, but sulforaphane has potential to support brain health and function through multiple mechanisms.

Effects on Aging

Oxidative stress and inflammation are major drivers of aging. By inducing antioxidant and anti-inflammatory genes, sulforaphane may help slow the aging process.

Animal studies show sulforaphane can extend lifespan, likely by activating similar genes involved in longevity pathways in humans (e.g. FOXO3).

In humans, sulforaphane from cruciferous vegetables:

Reduces DNA damage accumulation by lowering inflammation and oxidative stress.
Suppresses chronic inflammation through effects on NF-kB and inflammatory cytokines like IL-6.
Prevents age-related decline in immune function by reducing oxidative stress.

Though direct anti-aging trials are lacking, the downstream effects of sulforaphane on inflammation and antioxidant status provide a plausible mechanism for slowing aging.

Optimizing Sulforaphane Absorption

Broccoli sprouts are the richest dietary source of the sulforaphane. Sulforaphane is only formed when the enzyme converts glucoraphanin, which is highest in raw broccoli sprouts.

Cooking for more than 3-4 minutes at high temperatures inactivates enzymes and impairs sulforaphane formation. However, brief heating at mild temperatures (e.g. 70°C for 10 minutes) can increase sulforaphane yield. Mustard seeds can increase sulforaphane absorption from cooked cruciferous vegetables and supplements providing glucoraphanin.

Daily doses of 50-100 grams fresh broccoli sprouts may provide sulforaphane in amounts similar to those used in clinical trials demonstrating health benefits.

Sulforaphane Safety

Some older studies raised concerns that cruciferous vegetable consumption could impair thyroid function. However, this effect only seems to occur in cases of severe iodine deficiency, which is rare today.

Human trials using sulforaphane doses similar to those found in 70 grams of broccoli sprouts show no adverse effects on thyroid hormones or liver function. In healthy individuals, sulforaphane consumption appears to be safe and well tolerated.

Sulforaphane Offer A Variety Of Health Benefits

Research provides compelling evidence that cruciferous vegetables like broccoli and their bioactive isothiocyanates like sulforaphane offer a variety of health benefits. They show particular promise for cancer prevention, but also have positive effects on cardiovascular, brain, immune, and inflammatory disorders.

Consuming broccoli sprouts and other cruciferous vegetables is a simple way to potentially improve long-term health and longevity. More human research is still needed, but the current data is encouraging that optimizing intake of sulforaphane-rich foods may be protective against multiple age-related chronic diseases.