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What Are Prebiotics? A Detailed Look at Prebiotic Foods and Fiber
By Kimberly Yawitz
You may have heard of probiotics, but do you know about prebiotics?
Despite the similarity in names, there are some key differences.
While probiotics rightfully get a lot of praise from health experts, prebiotics are important as well.
So, what are prebiotics, and how can you get more of them?
Keep reading to learn more about the power of prebiotics.
What Are Prebiotics?
Prebiotics are a relatively new discovery in terms of medical science.
They're very different from probiotics, but they work closely with them.
Prebiotics vs. Probiotics
- Stronger immune system
- Healthier gut
- Symptom relief from depression and anxiety
- Lower body weight
- Improved heart health
- Cancer prevention
Prebiotics are compounds in foods that feed probiotic bacteria. In doing so, they help beneficial bacteria grow and to work more effectively.
Fibers resist digestion in the stomach and the small intestine. They reach the colon intact, where they're fermented by probiotic bacteria for fuel (3).
Some probiotic bacteria can feed off of these. However, these fatty acids are thought to have health benefits beyond feeding beneficial bacteria, including (4):
- improved gut health
- a stronger immune system
- enhanced glucose and dietary fat metabolism
- appetite control.
Bacteria in the colon feed off of prebiotic fiber to form short-chain fatty acids (24).
In short, both prebiotics and their digestive end-products are important to health.
Benefits of Prebiotics
Prebiotics are said to have several health benefits, including:
- A healthier ratio of beneficial to harmful bacteria
- Increased bone health
- Lower risk of allergies
- Reduced intestinal permeability
- A healthier immune system.
Most studies to date, though, show that these benefits aren't from the prebiotics themselves. So far, few studies have directly linked prebiotics to positive health outcomes. Rather, they play an important supporting role by helping probiotics be more effective (5).
Summary: Prebiotics are fibers that help feed probiotics. In doing so, they increase the population of healthy bacteria and help them work more effectively.
Though all prebiotics are fiber, not all dietary fibers are prebiotics.
The most common prebiotic fibers include:
- Guar gum
- Resistant Starch, including maltodextrin
Here are a few types of foods that can help nourish your gut bacteria.
Onions and garlic can be added to a variety of dishes to boost intake of prebiotics. Jerusalem artichokes and leeks are delicious roasted, while jicama is great raw in salads or baked like French fries.
Human and animal studies have shown that root vegetables can positively impact the gut biome.
One study found that after 40 days pigs fed inulin or Jerusalem artichoke had higher levels of short-chain fatty acids in the colon. The Jerusalem artichoke group also saw increases in beneficial Bifidobacterium spp. bacteria (6).
Also, in one small human study, volunteers who drank juice shots fortified with inulin from Jerusalem artichoke had significantly greater increases in probiotic bacteria than those who drank plain juice (7).
Eating fruit every day is recommended as part of a healthy and balanced diet.
Among many other health benefits, certain fruits have positive impacts on the gut biome.
Apples and bananas are particularly rich in prebiotic fibers. Apples are high in pectin, while ripe bananas contain inulin, and unripe bananas also have resistant starch.
In one small study, women who ate two medium bananas per day for 60 days saw modest increases in bifidobacteria (8).
Meanwhile, rodent studies have found that the pectin in apples increases levels of beneficial gut bacteria while decreasing harmful bacterial strains (9).
Examples include greens (especially dandelion greens), peas, corn, leeks and asparagus.
Greens can be used in salads, but soaking or sautéing dandelion greens can reduce their bitterness. Other spring vegetables are highly versatile and can be incorporated into a number of dishes.
Would it surprise you to know that chocolate can help promote a healthy gut biome?
Cocoa beans contain fibers that can be fermented by probiotics. They also contain antioxidants called polyphenols, which can help beneficial bacteria grow in the gut (12).
Just keep in mind that not all chocolate is created equal. Look for a dark chocolate with few additives, or stir pure cocoa powder into yogurt, smoothies, oats or baked goods.
Lentils are legumes, which means they grow in a pod.
Prebiotic fiber content varies depending on the type of lentil. Some types are rich in resistant starches, while others are higher in fructooligosaccharides or sugar alcohols (14).
Animal studies have found that lentil-based diets promote a favorable balance of healthy to unhealthy gut bacteria. However, limited data are available in humans (15).
Nonetheless, lentils have many health benefits, and it makes sense to include them in the diet as tolerated. They're great in soups, curries, salads or on their own.
Wheat is the most abundant source of prebiotics in the Western diet (16).
Wheat and other whole grains contain various types of prebiotic fiber. For example, barley and oats are high in beta-glucan. Others contain resistant starch or other fibers.
In one small human study, consumption of 48 grams of a whole grain breakfast per day for three weeks resulted in significant increases in bifidobacteria and lactobacilli (17).
Also, in one lab study, beta-glucan from oats showed greater prebiotic activity than other prebiotic foods, including corn and sugar beets (18).
You can maximize the prebiotic benefit by experimenting with a variety of whole grains. Whole wheat bread, rice and pasta are great, but don't overlook less popular grains like barley, rye, farro and quinoa.
Most nuts and seeds contain some prebiotic fiber, though walnuts are among the richest sources.
In one human study with 135 healthy adult volunteers, daily walnut consumption positively altered the gut biome by significantly increasing the abundance of Ruminococcaceae and Bifidobacteria, and significantly decreasing levels of Clostridium sp. bacteria.
Volunteers in this study ate 43 grams per day (a little over 1/3 cup chopped) of walnuts. Participants reduced calories from fat or carbohydrates due to the high calorie content of walnuts (19).
Summary: The best way to consume adequate prebiotic fibers is to eat a variety of plant foods. Aim for 5-9 servings of fruits and vegetables per day and round out your plate with whole grains, legumes and nuts. Feel free to indulge in pure cocoa for dessert.
There's a growing market for prebiotic supplements with sales expected to reach $7.5 billion by 2023 (5).
A large selection of prebiotic supplements are available online, many of which contain inulin as an active ingredient. Some popular ones include:
- Dr. Tobias GutMeiser Ultimate Prebiotic
- Prebio Thrive
- Biohm Super Greens
- Uplift Food Daily Uplifter.
Unfortunately, few studies have specifically examined prebiotic supplements. Most have focused on animals or human infants, while others have looked at synbiotic supplements, which include both prebiotics and probiotics (20).
These supplements are probably safe for most adults, but we don't know enough to say if they're effective (21).
Summary: Prebiotic supplements have been very popular, and many options are available online. The research hasn't caught up to the demand yet, at least in human adults. While they won't likely harm you, there's not enough evidence to say if they work.
Are Prebiotics Right for Everyone?
Prebiotics are safe for most people.
However, some people with irritable bowel syndrome or other digestive issues are intolerant to certain prebiotic fibers. This is because many prebiotics are high in FODMAPs.
FODMAPs are fibers that undergo fermentation in the colon, just like prebiotics. In fact, certain prebiotic foods are also high in FODMAPs.
Reaction to FODMAPs in the gut.
A diet that temporarily restricts foods high in FODMAPs may be helpful for people who frequently experience this type of discomfort (22).
That's not to say that you should give up prebiotics altogether, though. Doing so alters the composition of beneficial gut bacteria, many of which lower gastrointestinal distress.
Even on a FODMAP elimination diet, prebiotic foods that are high in FODMAPs should be reintroduced gradually as tolerated (23).
A free 7-day low-FODMAP starter plan is available here.
Summary: Some prebiotic fibers are high in FODMAPs, which can cause gastrointestinal issues in people who are sensitive. A diet that temporarily restricts then reintroduces high-FODMAP foods may be helpful. The reintroduction phase is important, because unnecessarily restricting prebiotic foods will limit the effectiveness of gut-friendly probiotics.
Some Final Thoughts on Prebiotics
No studies to date have directly linked prebiotics to positive health outcomes.
But that's not to diminish their importance. Prebiotics feed probiotics and allow them to work more effectively.
As such, they play a secondary role in many important bodily functions.
There are many supplements on the market, but research hasn't caught up to consumer demand.
For now, the best way to obtain prebiotics is to eat a diet with a wide variety of fibrous plant foods.
Do your best to incorporate whole grains, root vegetables, spring vegetables (when available), fruits, legumes and nuts.
A bit of high-quality dark chocolate won't hurt, either.
Reposted with permission from our media associate Diet vs Disease.
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Global Banks, Led by JPMorgan Chase, Invested $1.9 Trillion in Fossil Fuels Since Paris Climate Pact
By Sharon Kelly
A report published Wednesday names the banks that have played the biggest recent role in funding fossil fuel projects, finding that since 2016, immediately following the Paris agreement's adoption, 33 global banks have poured $1.9 trillion into financing climate-changing projects worldwide.
By Patti Lynn
2018 was a groundbreaking year in the public conversation about climate change. Last February, The New York Times reported that a record percentage of Americans now believe that climate change is caused by humans, and there was a 20 percentage point rise in "the number of Americans who say they worry 'a great deal' about climate change."
England faces an "existential threat" if it does not change how it manages its water, the head of the country's Environment Agency warned Tuesday.
By Jessica Corbett
A new analysis revealed Tuesday that over the past two decades heat records across the U.S. have been broken twice as often as cold ones—underscoring experts' warnings about the increasingly dangerous consequences of failing to dramatically curb planet-warming emissions.
By Madison Dapcevich
Ask any resident of San Francisco about the waterfront parrots, and they will surely tell you a story of red-faced conures squawking or dive-bombing between building peaks. Ask a team of researchers from the University of Georgia, however, and they will tell you of a mysterious string of neurological poisonings impacting the naturalized flock for decades.
The initial cause of the fire was not yet known, but it has been driven by the strong wind and jumped the North Santiam River, The Salem Statesman Journal reported. As of Tuesday night, it threatened around 35 homes and 30 buildings, and was 20 percent contained.
The unanimous verdict was announced Tuesday in San Francisco in the first federal case to be brought against Monsanto, now owned by Bayer, alleging that repeated use of the company's glyphosate-containing weedkiller caused the plaintiff's cancer. Seventy-year-old Edwin Hardeman of Santa Rosa, California said he used Roundup for almost 30 years on his properties before developing non-Hodgkin's lymphoma.
"Today's verdict reinforces what another jury found last year, and what scientists with the state of California and the World Health Organization have concluded: Glyphosate causes cancer in people," Environmental Working Group President Ken Cook said in a statement. "As similar lawsuits mount, the evidence will grow that Roundup is not safe, and that the company has tried to cover it up."
Judge Vince Chhabria has split Hardeman's trial into two phases. The first, decided Tuesday, focused exclusively on whether or not Roundup use caused the plaintiff's cancer. The second, to begin Wednesday, will assess if Bayer is liable for damages.
"We are disappointed with the jury's initial decision, but we continue to believe firmly that the science confirms glyphosate-based herbicides do not cause cancer," Bayer spokesman Dan Childs said in a statement reported by The Guardian. "We are confident the evidence in phase two will show that Monsanto's conduct has been appropriate and the company should not be liable for Mr. Hardeman's cancer."
Some legal experts said that Chhabria's decision to split the trial was beneficial to Bayer, Reuters reported. The company had complained that the jury in Johnson's case had been distracted by the lawyers' claims that Monsanto had sought to mislead scientists and the public about Roundup's safety.
However, a remark made by Chhabria during the trial and reported by The Guardian was blatantly critical of the company.
"Although the evidence that Roundup causes cancer is quite equivocal, there is strong evidence from which a jury could conclude that Monsanto does not particularly care whether its product is in fact giving people cancer, focusing instead on manipulating public opinion and undermining anyone who raises genuine and legitimate concerns about the issue," he said.
Many regulatory bodies, including the U.S. Environmental Protection Agency, have ruled that glyphosate is safe for humans, but the World Health Organization's International Agency for Research on Cancer found it was "probably carcinogenic to humans" in 2015. A university study earlier this year found that glyphosate use increased cancer risk by as much as 41 percent.
Hardeman's lawyers Jennifer Moore and Aimee Wagstaff said they would now reveal Monsanto's efforts to mislead the public about the safety of its product.
"Now we can focus on the evidence that Monsanto has not taken a responsible, objective approach to the safety of Roundup," they wrote in a statement reported by The Guardian.
Hardeman's case is considered a "bellwether" trial for the more than 760 glyphosate cases Chhabria is hearing. In total, there are around 11,200 such lawsuits pending in the U.S., according to Reuters.
University of Richmond law professor Carl Tobias told Reuters that Tuesday's decision showed that the verdict in Johnson's case was not "an aberration," and could possibly predict how future juries in the thousands of pending cases would respond.