The American Gut Project and the 30 Plants a Week Challenge

December 2, 2025 •

4 min read

Research from the American Gut Project, published in 2018, found that participants eating 30 or more different types of plants per week had significantly more diverse gut microbiomes compared to those who ate fewer than ten. This finding led to the popular '30 Plants a Week' challenge, a dietary strategy focused on variety over quantity to promote better gut health.

Quick Summary

This article explores the findings of the American Gut Project, detailing the evidence linking a diverse plant-rich diet to a healthier gut microbiome. It provides actionable advice on how to integrate 30 different plant types into your weekly meals, from fruits and vegetables to nuts, seeds, and herbs.

Key Points

Origin of the '30 Plants' Goal: The goal to eat 30 different plants a week came from a 2018 American Gut Project study, which found that participants eating this many plant types had the most diverse gut microbiomes.
Focus on Diversity, Not Quantity: The core principle is variety over volume, meaning the goal is to consume a wide range of different plant species throughout the week to feed different types of gut microbes.
What Counts as a Plant: The definition is broad, including fruits, vegetables, legumes, nuts, seeds, whole grains, and herbs and spices. Different colors of the same fruit or vegetable can also count as separate points.
Benefits for Gut Health: A more diverse gut microbiome, fostered by eating diverse plants, is linked to a stronger immune system, better digestion, reduced inflammation, and improved metabolic health.
Easy Ways to Increase Variety: Simple strategies like adding a mix of seeds to breakfast, using more herbs, and buying canned or frozen mixed vegetables can make reaching the goal manageable.
Fiber and Polyphenols are Key: Different plants provide unique fibers (prebiotics) and polyphenols, which nourish various beneficial gut bacteria and support a robust microbial ecosystem.

Unpacking the American Gut Project's Landmark Discovery

The American Gut Project was a crowdsourced, citizen-science initiative launched in 2012 by researchers including Rob Knight, Jeff Leach, and Jack Gilbert, with contributions from over 10,000 people across multiple countries. Its primary goal was to map the human gut microbiome and explore how diet, lifestyle, and other factors influence its composition. Unlike traditional lab studies, this project collected data from everyday individuals, creating the largest public reference database of the human gut microbiome to date.

A key finding from the 2018 analysis was the direct link between dietary diversity and the health of the gut microbiome. The study revealed that people who consumed a wider variety of plant foods had a significantly more diverse and robust gut microbiome. Specifically, those who consistently ate 30 or more different types of plants every week had a greater diversity of gut microbes compared to those who ate 10 or fewer. This groundbreaking research shifted the focus from simply eating more fruits and vegetables to emphasizing variety.

The Science Behind the '30 Plants' Recommendation

The gut microbiome is a complex ecosystem of trillions of bacteria, fungi, viruses, and other microorganisms living in our digestive tract. A diverse microbiome is linked to numerous health benefits, including better metabolic function, a stronger immune system, and even improved mental health. The reason a variety of plants is so crucial comes down to the different types of fiber and nutrients they contain. Plants provide beneficial nutrients like prebiotics, fiber, and polyphenols that fuel the beneficial bacteria in your gut.

Fiber: Different types of dietary fiber act as prebiotics, which are non-digestible compounds that feed specific strains of 'good' bacteria. Each plant contains a unique mix of fibers, so eating a wide variety ensures you are feeding a broader range of beneficial microbes.
Polyphenols: These are antioxidant and anti-inflammatory plant compounds responsible for the vibrant colors in fruits and vegetables. Different colors signify different types of polyphenols, each providing unique health benefits. Your gut microbes metabolize these compounds, converting them into beneficial byproducts that are crucial for your overall health.
Nutrients: Diverse plants offer a full spectrum of vitamins, minerals, and phytonutrients that support not only your gut but your entire body, from hormone regulation to immune function.

Practical Ways to Reach 30 Plants a Week

The '30 Plants a Week' goal might seem intimidating, but it is surprisingly achievable once you know what counts. This isn't about consuming massive quantities but rather adding small amounts of new plant foods throughout your week. The six main categories of plants to track are fruits, vegetables, legumes, whole grains, nuts and seeds, and herbs and spices. Even different colors of the same food, like a red apple and a green apple, can sometimes count as separate points. Here are some practical ways to get started:

Rethink your morning meal: Upgrade your breakfast. Instead of plain oatmeal, add walnuts, pumpkin seeds, mixed berries, and a sprinkle of cinnamon for five plants in one go.
Supercharge your salads: Add more than just lettuce. Toss in chopped fennel, cherry tomatoes, mixed seeds, and chickpeas to drastically increase your plant count.
Embrace frozen and tinned foods: Don't feel you have to buy everything fresh. Stock your freezer with mixed berries for smoothies and canned beans and chickpeas for quick additions to meals.
Make it saucy: When making a simple tomato sauce, add onion, garlic, celery, and carrots while it simmers to boost variety without extra effort.
Use herbs and spices generously: Remember that herbs and spices count, sometimes as a quarter of a point each. Sprinkle fresh parsley on your dinner or add dried oregano to your sauce to increase your tally.
Snack strategically: Swap processed snacks for mixed nuts, a variety of seeds, or veggie sticks with hummus.

The American Gut Project vs. Traditional '5-a-Day' Advice


Feature	American Gut Project (30 Plants a Week)	Traditional '5-a-Day' Guidance
Primary Goal	Focuses on dietary diversity to foster a varied gut microbiome.	Emphasizes quantity to ensure adequate nutrient intake from fruits and vegetables.
What Counts	Fruits, vegetables, legumes, whole grains, nuts, seeds, herbs, and spices all contribute.	Primarily focuses on fruits and vegetables.
Measurement	Counts unique plant types per week; variety is key.	Counts portions of fruits and vegetables consumed daily.
Key Benefit	Drives microbial diversity, which is linked to better immune, metabolic, and mental health.	Ensures a minimum level of fiber, vitamins, and minerals.
Inclusivity	Encourages adding more foods, making it approachable and less restrictive.	Can be less effective if people eat the same few plants regularly.

A Sustainable Approach to Lifelong Health

The American Gut Project's findings have provided a powerful, evidence-based motivation for changing our eating habits. The 30-plants-a-week goal is not about perfection but progress. It’s a positive message that encourages adding more variety, which often leads to naturally displacing less nutritious, ultra-processed choices. Even if you don't hit the 30-mark every single week, consistently striving for more diversity will yield significant gut and overall health benefits. By making small, sustainable changes and focusing on the abundance of plant foods available, you can cultivate a thriving internal ecosystem and build a foundation for lifelong wellness. The legacy of the American Gut Project is a simple, actionable blueprint for nourishing your body from the inside out.

Conclusion

The American Gut Project delivered a clear, data-backed message: a diverse diet is key to a diverse and healthy gut microbiome. By aiming for 30 different types of plants a week, you provide the wide array of nutrients and fiber that fuel a flourishing microbial ecosystem. This approach goes beyond traditional nutritional advice by emphasizing variety, making it a sustainable and enjoyable path to better digestion, stronger immunity, and overall vitality. Embracing this challenge is a proactive step toward building a more resilient and health-promoting body. For further insights into the gut microbiome, explore resources like ZOE, co-founded by Professor Tim Spector, a key researcher in the British arm of the project.

Frequently Asked Questions

The recommendation originated from the American Gut Project, a large-scale citizen science study conducted in 2018. Researchers found that individuals who consumed 30 or more different plant foods per week had a more diverse and healthier gut microbiome.

A plant is defined broadly and includes fruits, vegetables, whole grains, legumes (beans, chickpeas, lentils), nuts, seeds, herbs, and spices. Some foods, like dark chocolate (over 70% cocoa), coffee, and different colors of the same food (e.g., red and green apples), also count.

While quantity is still important, variety is emphasized because different plants contain different types of fiber, prebiotics, and polyphenols that feed a wider array of beneficial gut microbes. This diversity in food leads to greater microbial diversity, which is a key marker of gut health.

No, the 30 plants a week approach is not strictly vegan or vegetarian. The focus is on increasing plant diversity, not eliminating animal products. Omnivores can still participate by incorporating more plants into their regular meals alongside meat or dairy.

You can keep a simple running list on your phone or use an app designed for this purpose. Many find it helpful to focus on adding one or two new plant items to each meal, such as a sprinkle of seeds on yogurt, extra herbs in a sauce, or a handful of nuts as a snack.

The goal is progress, not perfection. Even increasing your plant variety to 15 or 20 types per week will provide significant health benefits. The key is to aim for a little more diversity each week, making it a sustainable and positive habit.

Highly refined plant products, such as fruit juices or white bread, generally do not count. The focus is on whole or minimally processed plant foods that contain the fiber and nutrients that benefit gut microbes.