By Dr. Mercola
Cruciferous vegetables like broccoli, cabbage and cauliflower are prized for their cancer-fighting powers, which come, in part, from the organosulfur compound sulforaphane. This beneficial compound is an immune stimulant, antioxidant and anti-inflammatory, and now researchers believe it may also prove useful for fighting Alzheimer’s disease, by altering the production of amyloid beta and tau, two main factors known to contribute to Alzheimer’s disease.
In Alzheimer’s patients, levels of amyloid beta protein may become abnormally high, clumping together to form plaques that disrupt neuron function. Abnormal accumulations of the protein tau may also collect inside neurons, forming threads, or neurofibrillary tangles, that disrupt communication between neurons.1
In a mouse model of Alzheimer’s disease, sulforaphane not only cleared the accumulation of amyloid beta and tau but also improved memory deficits in the mice, hinting at a potential treatment that could also be useful in humans.2
Sulforaphane Stands Out as Potential Alzheimer’s Treatment
Research into sulforaphane for Alzheimer’s disease continues to show exciting potential for this broccoli compound. In another study, mice with Alzheimer’s were treated with sulforaphane for four months, which significantly inhibited both the generation and accumulation of amyloid-beta. What’s more, it also alleviated several pathological changes associated with Alzheimer’s, including oxidative stress and neuroinflammation.3
As in the featured study, the Alzheimer’s mice also demonstrated cognitive benefits, remaining normal, cognitively speaking, compared to wild-type mice at 10 months of age, which is when dementia typically begins in Alzheimer’s mice. In tests of neurons themselves, pretreating cortical neurons with sulforaphane protected them against injury caused by amyloid beta.
Yet another study, this one published in 2009, revealed that antioxidants including sulforaphane protect cells from oxidative damage, facilitate removal of the amyloid-beta peptide and reduce abnormal protein-related causes of disease.4
In studying how sulforaphane interacts with amyloid beta to prevent various neurodegenerative processes, researchers used liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) to reveal that amyloid beta is less likely to aggregate in the presence of sulforaphane.5
Further, in mice with Alzheimer’s-like lesions induced, in part, by administration of aluminum, researchers believe suforaphane reduced reduced neurobehavioral deficits by promoting the growth of new neurons (neurogenesis) as well as reducing the aluminum load.6
What Else Is Sulforaphane Good For?
Eating more cruciferous veggies in an attempt to boost your sulforaphane intake, or taking it via high-quality supplement, is useful for far more than brain health. For instance, sulforaphane may be helpful in the treatment of diabetes as well as lowering blood glucose levels and improving gene expression in your liver.
In fact, sulforaphane was found to inhibit glucose production in cultured cells and improve glucose tolerance in rodents on high-fat or high-fructose diets. Sulforaphane-containing broccoli sprout extract also improved fasting glucose in adults with obesity and Type 2 diabetes.7
This sulfur compound also normalizes DNA methylation, which plays a role in a number of diseases, including hypertension, kidney function, gut health and cancer. Sulforaphane also increases enzymes in your liver that help destroy cancer-causing chemicals you may consume or be exposed to in your environment and is also known to block inflammation and damage to joint cartilage.8 In addition, studies have shown sulforaphane:
- Causes apoptosis (programmed cell death) in colon,9 prostate, breast and tobacco-induced lung cancer cells;10 three servings of broccoli per week may reduce your risk of prostate cancer by more than 60 percent11
- Activates nuclear factor-like 2 (Nrf2), a transcription factor that regulates cellular oxidation and reduction and aids in detoxification,12 as well as other phase 2 detoxification enzymes. In one study, sulforaphane was found to increase excretion of airborne pollutants by 61 percent13
- Reduces damaging reactive oxygen species (ROS) by as much as 73 percent, thereby lowering your risk of inflammation,14 which is a hallmark of cancer. It also lowers C-reactive protein, a marker of inflammation15
- Reduces the expression of long noncoding RNA in prostate cancer cells, thereby influencing the micro RNA and reducing the cancer cells’ ability to form colonies by as much as 400 percent16
The Best Sources of Sulforaphane
It’s possible to get meaningful amounts of sulforaphane from eating cruciferous vegetables like broccoli, but there are some caveats. Sulforaphane is formed when you chop or chew broccoli (this combines its precursor glucoraphanin and the enzyme myrosinase). Once swallowed, your gut bacteria may then help to release some of broccoli’s sulforaphane so your body can benefit, but it’s a tricky proposition because sulforaphane is attached to a sugar molecule with a sulfur bond.
Researchers have found that one of the best ways to maximize sulforaphane your body can use is to heat the broccoli for 10 minutes at 140 degrees Fahrenheit (or steam it lightly for three to four minutes until it’s tough-tender).17 This was just enough heat to kill the epithiospecifier protein, which was “grabbing the sulfur” and “greatly depleting the amount of sulforaphane in a serving of broccoli.”
Unfortunately, frozen broccoli has diminished ability to produce sulforaphane because the enzyme myrosinase,18 which converts glucoraphanin to sulforaphane, is quickly destroyed during the blanching process.19 Further, the sulforaphane content of broccoli can be further optimized by adding a myrosinase-containing food to it, such as mustard seed, wasabi, arugula, coleslaw or daikon radishes.20 Another alternative is to eat broccoli sprouts, which have more concentrated nutrients.
For example, tests have revealed that 3-day-old broccoli sprouts consistently contain anywhere from 10 to 100 times the amount of glucoraphanin — the precursor to sulforaphane — found in mature broccoli.21
In addition, broccoli sprouts enhanced the absorption of sulforaphane when consumed along with a broccoli powder, and broccoli sprouts alone had the highest absorption rate of all (74 percent).22 Juice from broccoli sprouts, in particular, has been shown to protect against the negative effects of beta amyloid and be effective in activating the Nrf2 signaling pathway.23
Increased Vegetable Intake Reduces Your Dementia Risk
People who eat more vegetables and fruits have a reduced risk of cognitive impairment and dementia,24 and sulforaphane is likely just one beneficial compound responsible for this protective effect. Folate is another vegetable compound known to lower the risk of Alzheimer’s disease, in this case by reducing homocysteine. High levels of the amino acid homocysteine are linked to brain shrinkage and an increased risk of Alzheimer’s, but B vitamins such as folate are known to suppress homocysteine.
Dark leafy greens are one of the best sources of folate, although it’s also found in broccoli, asparagus, avocado and more. Carotenoids are another important compound for brain health. Most often associated with orange produce like sweet potatoes and carrots, some carotenoids, namely lutein and zeaxanthin, are also found in dark green vegetables like kale and spinach.
Lutein and zeaxanthin, in turn, are most known for the role they play in vision health, such as reducing the risk of age-related macular degeneration. However, accumulating evidence suggests they play a powerful role in cognitive health as well. One study, the first of its kind, found lutein and zeaxanthin may promote cognitive function in old age by enhancing neural efficiency.25
In the study of 43 older adults, participants were asked to learn pairs of unrelated words while undergoing functional magnetic resonance imaging (fMRI). Higher levels of the two carotenoids were associated with lower brain activity during memory tasks, which suggests they did not have to work as hard to complete them.
Dietary Changes May Be Key for Preventing Alzheimer’s
Alzheimer’s disease has grown to be one of the most pressing and tragic public health issues facing the U.S. With the number of people affected expected to triple by 2050, the Alzheimer’s Association estimates that by midcentury someone in the U.S will develop Alzheimer’s disease every 33 seconds.26 It’s often said that Alzheimer’s cannot be prevented, but in addition to sulforaphane and other veggie compounds, key dietary changes may represent a crucial avenue of prevention when it comes to this disease.
For instance, a study of 60 Alzheimer’s patients looked into the effect of probiotic supplements on cognitive function, with promising results.27 Those who drank milk containing probiotics experienced significant improvements in cognitive function. To prevent Alzheimer’s, however, you need to focus on a diet that powers your brain and body with healthy fats, not net carbs (total carbohydrates minus fiber), i.e., a ketogenic diet.
A ketogenic diet calls for minimizing carbohydrates and replacing them with healthy fats and adequate amounts of high-quality protein. I recommend a cyclical or targeted ketogenic diet for everyone, where you increase carbs and protein once you are able to burn fat for fuel on the two to three days a week you are strength training. I believe this is healthy for most individuals, whether they have a chronic health problem or not.
I say that because the ketogenic diet will help you optimize your health by converting from burning carbohydrates for energy to burning fat as your primary source of fuel. You can learn more about this approach to improving your mitochondrial function, which is also at the heart of Alzheimer’s disease, in my book, “Fat for Fuel.”
One of the most common side effects of being a sugar-burner is that you end up with insulin and leptin resistance, which it at the root of most chronic disease. Keep in mind that adopting the ketogenic diet along with intermittent fasting may further boost your results.
Another excellent resource is Dr. Dale Bredesen’s “The End of Alzheimer’s: The First Program to Prevent and Reverse Cognitive Decline,” which evaluates 150 factors, including biochemistry, genetics and historical imaging, known to contribute to Alzheimer’s disease. This identifies your disease subtype or combination of subtypes so an effective treatment protocol can be devised.
Additional important nutrients include animal-based omega-3 fats, magnesium, vitamin D and fiber, along with exercise to increase brain-derived neurotrophic factor (BDNF), stress reduction and optimized sleep. As mentioned, the research on sulforaphane is also exciting, so consuming plenty of it, especially in combination with myrosinase to maximize absorption, is an excellent strategy and one of the many factors you can control to cut your Alzheimer’s risk considerably.