Have you ever wondered if there’s a natural way to lower your high blood pressure, guard against Alzheimer's, lose weight, and feel better? Well as it turns out there is. Michael Greger, M.D. FACLM, founder of NutritionFacts.org, and author of the instant New York Times bestseller “How Not to Die” celebrates evidence-based nutrition to add years to our life and life to our years.

NutritionFacts Grab Bag 28

The power of Ginkgo biloba, the best mouthwash for bad breath, and how to avoid cancerous hair dyes. This episode features audio from:

Visit the video pages for all sources and doctor’s notes related to this podcast.


Back by popular demand, it’s the NutritionFacts Grab Bag, where we look at the latest science on a whole variety of topics.

And, we start with Ginkgo Baloba. Turns out it doesn’t seem to have any effect in preventing cognitive decline or dementia. BUT, it may play a role in treating it.

More than a third of older Americans take some kind of “brain health supplement” to the tune of billions of dollars a year, and one of the most popular is Ginkgo biloba. U.S. household surveys suggest as many as 2 percent of Americans are taking gingko supplements. Ginkgo biloba is a tree with fan-shaped leaves, regarded as a living fossil, having persisted relatively unchanged for over a quarter billion years. Its resilience makes it a favorite of urban planners—hardy enough to survive even a nuclear blast (as one of the few survivors within a short radius of ground zero in Hiroshima).

Over the last 30 years or so, an extract of gingko leaves has become one of the most widely used herbal treatments for dementia. A 2009 Cochrane review of three dozen randomized, controlled trials involving more than 4,000 participants concluded that the “evidence that Ginkgo biloba has predictable and clinically significant benefit for people with dementia or cognitive impairment is inconsistent and unreliable.” One trial showed very large benefits, but others showed no effect at all. To put the subject to rest once and for all, two large randomized, double-blind, placebo-controlled trials were conducted; one in Europe, funded by a gingko supplement manufacturer, and the largest, longest study to date, funded by the NIH in the United States. More than 5,000 older men and women with either normal cognition or mild cognitive impairment were randomized to a gingko leaf extract or placebo for five or six years to see if it would prevent them from sliding into dementia. (Mild cognitive impairment (MCI) is the intermediate clinical state between normal cognition for one’s age and dementia.) The conversion rate of MCI to dementia is about 10 percent per year. The bottom line: neither trial showed any clear benefit, definitively demonstrating no preventative effect.

However, for those already suffering with dementia, gingko leaf extracts do appear to slow cognitive decline compared to placebo for those with Alzheimer’s, or dementia more broadly defined. Of course, that’s assuming there’s actually gingko in your gingko supplements. Investigations of gingko supplements off the shelves in both Europe and the U.S. found some that had no apparent gingko at all. As high as about one in six ginkgo supplements appeared to be all filler, without any detectable Ginkgo biloba DNA.

Side effects-wise, at typical doses, such as 120 mg twice a day, ginkgo extracts may cause mild stomach upset, headache, dizziness, constipation, and allergic skin reactions. Higher dosages can result in restlessness, diarrhea, nausea, vomiting, and weakness. There have been about a dozen published case reports of bleeding associated with gingko; but thankfully, this did not surface in systematic reviews of the dementia studies. Still, out of an abundance of caution, it has been recommended to stop taking gingko supplements at least two weeks before elective surgery.

The bottom line, according to a recent review of Alzheimer’s disease therapies, is that gingko is one of the few things that can beat out placebo for cognitive function.

In our next story, we look at the higher rate of bladder cancer among hairdressers. And we ask: is it due to exposure to hair dyes? And, what about at-home use of hair colorants?

Since there’s typically no way to reverse hair color loss, the use of hair colorants is a mainstay of management, a practice documented as far back as 1500 BCE. While gray hair may carry a distinguished look and limit women’s subjection to a sexualized gaze, hair color constitutes a multibillion-dollar market, with up to 60 percent of men and women in Western countries choosing to use coloring products, many of which to cover gray.

For over a century, aromatic amines have been the main chemicals used in commercial permanent, oxidative hair dyes. The primary problem with these compounds is that they can be potent contact allergens. Product labels often recommend a small 48-hour test application to the skin before use, but it can take up to a week for a skin allergy to flare up. They also may cause cancer.

Hair products contain more than 5,000 chemicals, and so it’s hard to narrow it down. But the aromatic amines, such as para-phenylenediamine, that are often used in hair dyes to prevent fading due to washing have been picked out as a “probable” carcinogen. Before industry reformulation in response to mandated cancer warning labels, nine out of ten permanent hair dye products were mutagenic, meaning capable of causing DNA mutations. This then appeared to translate into more than ten times the odds of DNA damage in breast cells obtained from the breast milk of women who had used hair dye in the last six months (compared to not using hair dyes at all). But does that translate into more cancer?

A meta-analysis of 42 studies found that hairdressers, particularly those who held their jobs ten or more years, were at significantly higher risk of developing bladder cancer later in life. Hairdressers, beauticians, and barbers may also suffer more lung cancer, voice box cancer, and multiple myeloma. There is some evidence that hairdressers may smoke more, but the researchers took this into account. They conclude that salons should be better ventilated, that gloves should be used. But how much is that going to help the person whose head has been soaked in it? Based on testing for radioactively-traced hair dye ingredients in the urine, experiments suggest the exposure to hair dye may be several hundredfold higher in hair dye users than the occupational risk to the hairdressers. But thankfully, there does not seem to be an excess risk of bladder cancer among those who just use hair dye personally. Furthermore, major changes took place in the 1980s to make hair dyes safer.

In 1979, the U.S. Food and Drug Administration started requiring cancer warning labels on hair dye products, leading the industry to start reformulating to eliminate the most carcinogenic ingredients. A turning point in bladder cancer risk isn’t apparent from the data, but this may be a function of the long latency time between exposure and malignancy for bladder cancer—which can be 30 or 40 years. If you look at faster-developing cancers, such as leukemia or follicular lymphoma, there does seem to be a drop-off in risk after 1980, though a 2019 meta-analysis looking at increased non-Hodgkin’s lymphoma risk without consideration of date range concluded, “exposure to hair colorants should be reduced as much as possible.” For prostate cancer, the doubling of odds associated with hair dye use seems limited to pre-1980 exposure, and there appears to be no link to brain tumors in either time frame.

As a tragically ironic aside, while the risk associated with hair products may have declined for white men and women, the opposite trend seems to have occurred for certain hair products targeted towards African Americans. The Black Women’s Health Study, which assessed exposure in the 1990s, found no association between breast cancer and the use of hair relaxers, chemical treatments used to straighten hair. But in the early 2000s, popular straighteners switched from noncarcinogenic compounds, like lye, to chemical cocktails containing formaldehyde. So now, frequent straightener use is associated with about a 30 percent higher breast cancer risk. Thankfully, there has been a shift towards embracing more natural hair styles in the African American community, resulting in the sales of hair relaxers falling by 40 percent in recent years.

Finally today, how do you treat the cause of bad breath?

Bad breath is an underestimated problem affecting a significant proportion of the global population. It seems most people regularly report encountering people with halitosis. Masking agents are frequently used to cover up bad breath, but studies have shown that the use of mouth rinses, sprays, or mints containing an agreeable masking odor only have a short-term effect, since you’re not treating the underlying cause. So, the exclusive usage of masking products can never be truly considered an effective solution to the problem.

The cause of bad breath is oral putrefaction, the degradation of certain amino acids mostly derived by bacterial breakdown of proteins in your mouth. Specifically, bacteria degrade the sulfur-containing amino acids, such as cysteine and methionine, into stinky compounds like the rotten egg gas hydrogen sulfide––so-called volatile sulfur compounds. If you measure these compounds spewing out of people’s mouths with machines with names like Breathtron, toothbrushing alone does not significantly reduce oral malodor. Brushing alone reduces sulfur breath compounds from more than 450 ppb down to about 300 ppb, which is still above the stinky breath threshold of 250 ppb. Add tongue cleaning, and you can drop that down to right around the threshold. But adding an antiseptic mouthwash—an antibacterial mouthwash—did even better. Okay, so what’s the best mouthwash to use?

To find out, researchers used the cysteine challenge test. Instead of giving people dairy products, which contain the protein casein (which is rich in the sulfur amino acid cysteine), they just had the participants swish directly with some cysteine, and then followed effectiveness using odorograms. For example, toothbrushing. When people swished with cysteine before brushing their teeth, here’s the spike in stinky sulfur compounds spewing out of their mouths. When they brushed their teeth with water and swished again at various times over the rest of the day, the spikes pretty much look the same––meaning toothbrushing with water didn’t remove many bad breath bacteria, since the subjects were spewing out similar spikes starting just 20 minutes later. Brushing with toothpaste works better. See how it knocks down the next spike of stinky compounds before the bacteria slowly grow back throughout the day.

What about using a tongue scraper? Here’s the odorogram. Tongue scraping knocks it down by about half before coming back over the next few hours.

What about chewing gum? There’s some effect that disappears over the subsequent few hours.

What about various mouthwashes? First of all, rinsing with water. Useless. It can be helpful for morning breath to rinse any stagnation that occurred overnight, but during the day, just rinsing with water isn’t clearing many bad breath bacteria. And swishing with Scope mouthwash? Just as useless as water. Scope is an anti-bacterial mouthwash, but it must not be good at killing the specific bacteria that cause bad breath. Peridex, though, cleaned house, killing off those bacteria even seven hours later. What is Peridex? That’s just a brand name for chlorhexidine. Uh oh, we know about that from this video. Chlorhexidine doesn’t just get rid of bad breath bacteria; it also kills off the good bacteria on your tongue that help you make nitric oxide, which protects your arteries. And so, chlorhexidine can raise your blood pressure. And that’s not all. Chlorhexidine can stain your teeth. That’s not what you want in a mouthwash. Adverse effects are not rare. Tooth staining, the build-up of tartar, taste disturbance, and damage to the lining of your mouth have all been reported with the use of chlorhexidine in about nine out of 10 people: 88 percent of people suffer various side effects.

But hey, chlorhexidine may be better than mouthwashes with hydrogen peroxide, which may be carcinogenic, potentially increasing your risk of mouth cancer. That’s not just based on studies on rodents, either. Cultures of human mouth lining cells show significant DNA damage. Triclosan was another common antibacterial ingredient in mouthwashes, now effectively banned in over-the-counter products.

Tongue scraping alone doesn’t always resolve the problem of halitosis. So, what can we use? If bad breath persists after improving tongue and dental hygiene, an active zinc-based mouth rinse can be introduced. Zinc binds directly to the volatile sulfur compounds and prevents them from gassing out of your mouth. Mouth rinses containing zinc chloride without alcohol have been found to instantly, though temporarily, effective for halitosis.

Researchers looked at eight mouth rinses, and the most effective was a zinc chloride one, and the least effective was Colgate Plax. In fact, both of the alcohol rinses were found to be the least effective. The thought is that they may exacerbate halitosis by drying up your mouth.

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