A 16-Week Vegan Diet Can Do Wonders for Your Gut Microbiome
By Dan Gray
- Research shows that 16 weeks of a vegan diet can boost the gut microbiome, helping with weight loss and overall health.
- A healthy microbiome is a diverse microbiome. A plant-based diet is the best way to achieve this.
- It isn't necessary to opt for a strictly vegan diet, but it's beneficial to limit meat intake.
New research shows that following a vegan diet for about 4 months can boost your gut microbiome. In turn, that can lead to improvements in body weight and blood sugar management.
But it doesn't mean you need to swear off the meat and dairy entirely.
It's significant, however, that moving toward a more plant-based diet is probably the healthiest choice.
The research, led by Dr. Hana Kahleova, MD, PhD, of the Physicians Committee for Responsible Medicine, was presented this week at the annual meeting of the European Association for the Study of Diabetes in Barcelona, Spain.
Researchers studied 147 participants, randomized into two groups. One followed a low-fat vegan diet. The other made no changes to their diet.
After the 16-week study was completed, researchers reported the vegan group saw their body weight, fat mass, and visceral fat levels go down.
"We expected to see changes in the gut microbiome on a plant-based diet," Kahleova told Healthline. "However, it was surprising to see how fast the changes occurred and how profound they were."
When asked what the biggest takeaway of the research is, Kahleova was unequivocal.
"Eat more plants," she said. "They contain fiber that boosts the gut microbiome and metabolic health."
What’s the Gut Microbiome?
Because this research deals with how a vegan diet boosts the gut microbiome, it's worth knowing what the gut microbiome actually is.
The microorganisms that live in the digestive tract, when properly balanced, promote a healthy digestive tract, along with the immune system, bowel movements, metabolism, and hormones that help with appetite regulation.
But when the microbiome is unbalanced, things can get out of whack.
"What's happened is we've moved to a more Western diet that includes such highly processed foods like bread, rice, pasta, and a lot of animal meat," explained Sharon Zarabi, RD, CDN, CPT, bariatric program director at Lenox Hill Hospital in New York.
"That has changed the harmony of the microbiome," Zarabi told Healthline. "A lot of the gut bacteria are imbalanced, and that can lead to exacerbated symptoms of irritable bowel syndrome, decreased immune system, and even proliferation of cancer cells."
Kristin Kirkpatrick, MS, RDN, manages wellness nutrition services at the Cleveland Clinic Wellness Institute in Ohio. She says the researchers' findings aren't surprising.
"Multiple studies show benefits to a plant-based diet. One of the greatest predictors of good gut health is a variety of antioxidant-, phytonutrient- and fiber-rich foods. Plants provide the bulk of these," Kirkpatrick told Healthline.
Plant-Based or Vegan: What’s Best?
While the study specifically looked at people who followed a vegan diet, dietitians say that while a plant-based diet is the healthy way to go, it isn't necessary to follow a strict vegan diet.
"When we're eating a more diverse plate of food that has different macronutrients, such as protein and fiber and complex carbs and healthy fat, we get to increase the diversity of the microbiome," Zarabi said.
"A vegan diet that promotes high-fiber foods that come from plants will improve the gut microbiome. But when we start to take out all animal protein, we tend to limit ourselves with where our protein is coming from. If you're [eating] from a vegan diet, it's mostly coming from beans and some vegetables. So it's really important to make sure you don't fall short on any nutrients," Zarabi said.
While it's hard to argue with some of the ethical reasons for embracing veganism — including animal welfare and reducing one's carbon footprint — it's still crucial to monitor one's nutrition.
"A vegan diet can be less advantageous if all your foods are frozen dinners and white grains," Kirkpatrick said. "Doing your research and meeting with your doctor or dietitian to help you get started is recommended."
You Are What You Eat
It might seem daunting to make the pivot from burgers and fries to lean protein and veggies. But it isn't impossible.
"I think the first step is familiarizing yourself with the different vegetables that are out there, specifically the vegetables that have the prebiotic fibers," Zarabi said. "These are the initial phase of what probiotics feed on: indigestible fibers that help encourage the growth and proliferation of the probiotics."
High-prebiotic foods include asparagus, onions, Jerusalem artichokes, cabbage, garlic, cashews, lentils, and chickpeas.
Zarabi cautions that when these foods are unfamiliar to the gut, initial side effects could include bloating and gas as the body learns to adapt.
"If you have those symptoms in the beginning, don't get turned off just yet," she said. "Give your body some time to adapt to the changes. If you're still feeling a lot of GI distress, you may want to work with a dietitian to figure out which vegetables or prebiotics are better for you."
When planning a meal, it's helpful to think in terms of thirds.
A third of the plate should be vegetables, a third should be lean protein sources, and a third should be complex carbs, such as sweet potatoes, beets, quinoa, bran, and oats.
There's also room for healthy fat, such as olive or avocado oil, because they help improve heart health.
Kirkpatrick recommends entirely cutting out red and processed meat, or at least limiting these products to twice a month.
"You are what you eat, so what goes into your body affects your health outcomes," Zarabi said.
"Eat as close to nature as possible," she said. "Think about what you're putting in your body. How many steps did it have to go through to get to you? Choose foods that are close to nature, the ones that include one ingredient. They're the best for you."
Reposted with permission from our media associate Healthline.
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When hurricanes and other extreme storms unleash downpours like Tropical Storm Beta has been doing in the South, the floodwater doesn't always stay within the government's flood risk zones.
New research suggests that nearly twice as many properties are at risk from a 100-year flood today than the Federal Emergency Management Agency's flood maps indicate.
Flooding Outside the Zones<p>About <a href="https://furmancenter.org/files/Floodplain_PopulationBrief_12DEC2017.pdf" target="_blank">15 million</a> Americans live in FEMA's current 100-year flood zones. The designation warns them that their properties face a 1% risk of flooding in any given year. They must obtain flood insurance if they want a federally ensured loan – insurance that helps them recover from flooding.</p><p>In Greater Houston, however, <a href="https://doi.org/10.1111/j.1539-6924.2012.01840.x" target="_blank">47% of claims</a> made to FEMA across three decades before Hurricane Harvey were outside of the 100-year flood zones. Harris County, recognizing that FEMA flood maps don't capture the full risk, now <a href="https://www.hcfcd.org/floodinsurance" target="_blank" rel="noopener noreferrer">recommends that every household</a> in Houston and the rest of the county have flood insurance.</p><p>New risk models point to a similar conclusion: Flood risk in these areas outstrips expectations in the current FEMA flood maps.</p><p>One of those models, from the <a href="https://firststreet.org/flood-lab/research/2020-national-flood-risk-assessment-highlights/" target="_blank">First Street Foundation</a>, estimates that the number of properties at risk in a 100-year storm is 1.7 times higher than the FEMA maps suggest. Other <a href="https://doi.org/10.1088/1748-9326/aaac65" target="_blank" rel="noopener noreferrer">researchers</a> find an even higher margin, with 2.6 to 3.1 times more people exposed to serious flooding in a 100-year storm than FEMA estimates.</p>
What FEMA’s Flood Maps Miss<p>Understanding why areas outside the 100-year flood zones are flooding more often than the FEMA maps suggest involves larger social and environmental issues. Three reasons stand out.</p><p>First, some places rely on relatively old FEMA maps that don't account for recent urbanization.</p><p>Urbanization matters because impervious surfaces – think pavement and buildings – are not effective sponges like natural landscapes can be. Moreover, the process for updating floodplain maps is locally variable and can take years to complete. Famously, New York City was updating its maps when Hurricane Sandy hit in 2012 but hadn't finished, meaning flood maps in effect <a href="https://projects.propublica.org/nyc-flood/" target="_blank">were from 1983</a>. FEMA is required to assess whether updates are needed every five years, but the <a href="https://www.fema.gov/cis/nation.html" target="_blank" rel="noopener noreferrer">majority of maps</a> <a href="https://www.oig.dhs.gov/sites/default/files/assets/2017/OIG-17-110-Sep17.pdf" target="_blank" rel="noopener noreferrer">are older</a>.</p><p>Second, binary thinking can lead people to an underaccounting of risk, and that can mean communities fail to take steps that could protect a neighborhood from flooding. The logic goes: if I'm not in the 100-year floodplain, then I'm not at risk. Risk perception <a href="https://doi.org/10.1088/1748-9326/ab195a" target="_blank" rel="noopener noreferrer">research</a> backs this up. FEMA-delineated flood zones are the major factor shaping flood mitigation behaviors.</p><p>Third, the era of climate change scuttles conventional assumptions.</p><p>As the planet warms, extreme storms are becoming <a href="https://nca2018.globalchange.gov/" target="_blank">more common and severe</a>. If greenhouse gas emissions continue to increase at a high rate, computer models suggest that the chances of a severe storm dropping 20 inches of rain on Texas in any given year will increase from about 1% at the end of the last century to 18% at the end of this one, a chance of <a href="https://doi.org/10.1073/pnas.1716222114" target="_blank" rel="noopener noreferrer">once every 5.5 years</a>. So far, <a href="https://www.rstreet.org/wp-content/uploads/2020/02/195.pdf" target="_blank" rel="noopener noreferrer">FEMA hasn't taken into account the impact climate change is having</a> on extreme weather and sea level rise.</p>
Racial Disparities in Flooding Outside the Zones<p>So, who is at risk?</p><p>Years of research and evidence from storms have highlighted social inequalities in areas with a high risk of flooding. But most local governments have less understanding of the social and demographic composition of communities that experience flood impacts outside of flood zones.</p><p>In analyzing the damage from Hurricane Harvey in the Houston area, I found that <a href="https://doi.org/10.1088/1748-9326/aba0fe" target="_blank">Black and Hispanic residents disproportionately experienced flooding</a> in areas beyond FEMA's 100-year flood zones.</p><p>With the majority of flooding from Hurricane Harvey occurring outside of 100-year flood zones, this meant that the overall impact of Harvey was racially unequal too.</p><p>Research into where flooding occurs in Baltimore, Chicago and Phoenix points to some of the potential causes. <a href="https://www.nap.edu/read/25381/chapter/4#16" target="_blank" rel="noopener noreferrer">In Baltimore and Chicago</a>, for example, aging storm and sewer infrastructure, poor construction and insufficient efforts to mitigate flooding are part of the flooding problem in some predominantly Black neighborhoods.</p>
What Can Be Done About It<p>Better accounting for those three reasons could substantively improve risk assessments and help cities prioritize infrastructure improvements and flood mitigation projects in these at-risk neighborhoods.</p><p>For example, First Street Foundation's risk maps account for <a href="https://firststreet.org/flood-lab/research/flood-model-methodology_overview/" target="_blank">climate change</a> and present <a href="https://floodfactor.com/" target="_blank" rel="noopener noreferrer">ratings</a> on a scale from 1 to 10. FEMA, which works with communities to update flood maps, is <a href="https://www.fema.gov/media-library-data/1521054297905-ca85d066dddb84c975b165db653c9049/TMAC_2017_Annual_Report_Final508(v8)_03-12-2018.pdf" target="_blank" rel="noopener noreferrer">exploring rating systems</a>. And the National Academies of Sciences, Engineering and Medicine recently <a href="https://www.nationalacademies.org/news/2019/03/new-report-calls-for-different-approaches-to-predict-and-understand-urban-flooding" target="_blank" rel="noopener noreferrer">called for a new generation of flood maps</a> that takes climate change into account.</p><p>Including recent urbanization in those assessments will matter too, especially in fast-growing cities like Houston, where <a href="https://authors.elsevier.com/a/1boBRyDvMFW6W" target="_blank" rel="noopener noreferrer">386 new square miles</a> of impervious surfaces were created in the last 20 years. That's greater than the land area of New York City. New construction in one area can also <a href="https://scalawagmagazine.org/2018/01/city-in-a-swamp-as-houston-booms-its-flood-problems-are-only-getting-worse/" target="_blank" rel="noopener noreferrer">impact older neighborhoods downhill</a> during a flood, as some Houston communities discovered in Hurricane Harvey.</p><p>Improving risk assessments is needed not just to better prepare communities for major flood events, but also to prevent racial inequalities – in housing and beyond – from <a href="https://www.npr.org/2019/03/05/688786177/how-federal-disaster-money-favors-the-rich" target="_blank" rel="noopener noreferrer">growing</a> after the unequal impacts of disasters.</p>
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