Are 30+ plants a week essential for good gut health?

If you've spent anytime online and have even a vague interest in gut health then you've probably come across the recommendation to consume at least 30 different types of plant foods per week. The advice to eat 30+ plants a week has been promoted everywhere. The team at Zoe bang on about all the time as well as other high profile figures, namely Dr Megan Rossi AKA The Gut Health Doctor and Hugh Fearnley-Whittingstall who's recently published a book on the topic. Heck, even we've promoted it in the past.

But, as time has gone on and we see it touted more and more as indisputable advice for those wanting to improve gut health, we now think it deserves a bit more scrutiny than most give it. Which is exactly what we're doing with this latest blog: we're aiming to answer the question 'do we need to eat 30+ plants per week for good gut health?'.

Where did '30+ plant points' come from?

So we're actually going to start with the crux of the problem with plant points. As of writing this recommendation comes from one single study. Now, this was a very cool study done by the The Microsetta Initiative (formerly known as the American Gut Project) which is a monster citizen-science project which aims to crowd source science about the gut microbiota and further our knowledge in this area. They want to catalogue the diversity of the microbes in our gut and do so by collecting poop, oral or skin samples and lifestyle information from individuals all over the world.

What they found in this study, which was published in a peer-reviewed journal, is that the variety of plants in the diet was more predictive of microbial diversity than dietary tags like vegan or vegetarian. Since it's very difficult to look at total diversity they used the diversity of microbes which produce a short chain fatty acid called butyrate as a surrogate marker for diversity as a whole. Butyrate provides around 70% of the energy requirements of enterocytes (epithelial cells that line the gut) and is considered to be anti-inflammatory, helping to protect against colorectal cancer.

Limitations of this study

So there are a few reasons why we shouldn't take this study as the definitive proof that eating 30+ different plants a week betters gut health. Firstly, subjective self-reporting was used to measure the plant diversity of people's diets, meaning they were asked to recall what they eat on a typical week. If you're anything like me I struggle to remember everything I ate yesterday, let alone guess what I eat on a 'typical week', which for most of us doesn't exist, in detail. That's a lot to ask and means that figures given are not liekly to be entirely accurate! Social desirability is also a factor, people want to be seen as 'good' eaters and so are much more likely to over-report than under-report.

It's also pushing it to say that the surrogate measure used in this study (the measure of the diversity of butyrate producers) definitely acts as a surrogate for good gut health. The participants actual gut health wasn't looked at. So we think this is stretching things, to put it lightly. Gut health and our gut microbiota is vastly complicated. Butyrate producers make up only around 20% of the total bacteria community in our gut, so 80% of the actual diversity of our gut isn't being looked at at all, neither is the diversity of other microbes, such as fungi, parasites and viruses.

Diversity of the microbiome is also a bit of a 'loose' term in general. What's a 'good' level of diversity for me and helps my body, might look different for you or say, anyone else! We don't have a blueprint for what this means, although if you ask the team at Zoe I'm sure they'll give you a different answer. Lots of companies claim to be able to give you huge insight into your microbiota, however even Zoe - which claims to have the "World's most advanced home gut health test" - only gives you information on about 30 different microbes. Which is absolutely nothing when you consider the thousands of species we all carry inside us. This area is really, really new and we just don't know that much yet about how our gut microbes effect our health and vice versa. In addition, poop tests can only tell us about those microbes which leave our body, the gold standard of gut microbiota measurements is a biopsy of the microbes actually residing in your colon, which is much more invasive but would give us much better insight into our resident gut microbiota.

In addition, and I think this is a big one, this study compared extremes of plant intake. They looked at individuals who consumed <10 different plants a week and compared them with those who ate 30+ different plants, finding significant differences between these two groups. Therefore, we have no idea if eating say 15 or 20 different plants a week was just as good as 30. This means the number 30 is potentially totally arbitrary and might even be far too high a number to strive for, we just don't know as there has been nothing to test this.

This study was also purely observational and no clinical trials (to date) have been conducted to actually see what happens if we get individuals who aren't eating a wide range of plant foods to eat 30+ different plants per week. Would the diversity of their gut microbes change? And would this lead to improvements in gut health? We don't know! Randomised controlled trials are the gold standard way to test results that we find in observational studies and there just aren't any for 30+ plants.

Who might '30+ plants' harm?

There are health conditions and individuals who also really wouldn't benefit from increasing intake of plant foods, which is where we get our source of fibre. Those suffering from inflammatory bowel disease IBD (especially when in active flare-ups), irritable bowel syndrome (IBS) or those with gut symptoms like constipation, bloating and pain may actually make their symptoms and condition worse by trying to get more plant foods into their diet.

Numbers around food is also a really easy way to get obsessive with your diet. We get messages from everywhere telling us we have to keep an eye on calories and macronutrients, but now we have to track our intake of plants too? Rates of eating disorders is on the rise in the UK, which should be taken seriously by all of us they are the most deadly psychological conditions. Anything which places targets or rigid figures on our diet can easily push us into disordered eating practices which are the gateway for eating disorders.

What do we think is a better approach?

When it comes to public health recommendations one single study is never used to inform advice. As we've shown, individual studies have their limitations and only give us a tiny snapshot of data which is often not applicable to the billions of humans in this world and all their individual differences and lives. Health recommendations have to have a sufficient and convincing body of evidence to support their use. For example, the 5 a day campaign has been around for more than two decades and is based on hundreds of research articles, clinical trials and analysis of public health campaigns. This advice is promoted by massive health promotion bodies such as the WHO and most countries around the World. We have heaps of evidence which shows that eating 5 or more fruits and vegetables a day tangibly improves health in different ways, we just don't have this for '30+ plants'.

There's a lot of focus nowadays on eating just the right thing to 'optimise' your gut health, blood sugars, weight or anything else we think we need to control in order to be healthy. But, we argue that health is made up of so much more than these individual factors and pieces of us to measure. Our overall health is determined by our stress management, quality of sleep, work-life balance, personal relationships, finances, emotional wellbeing, physical environment and exposure to pollutants, genetics, community safety, access to healthcare and so much more.

Although there's no doubt that diet can effect our health there is no one perfect diet which will remove all gut symptoms or leave you skipping down the street with energy every day. Life is more complex than that, but our diets really don't have to be. It can be so tempting to think that we need fancy supplements, or exact quantities and numbers of particular foods and macronutrients in order to be healthy, but honestly, people were healthy and happy before we started to obsess over our diets and can be without it now. The basics of nutrition have been shown time and time again to be plenty good enough to support our health, even our gut health. What this means in a nutshell is a diet which includes a range of foods from all the food groups, with plenty of fruits, vegetables, pulses, wholegrains and water.

So, we think that a better approach is, well, one that works for you and preserves your relationship with food. As mentioned above, putting numbers around food and setting do's and don'ts can be harmful, particularly to those struggling with disordered eating and eating perfectionism. It is likely that if you eat less than 30 different plants a week you can still have good gut and general health. Therefore, we believe there's no need to stress if you keep seeing this number and don't consume anywhere near it. If more solid research comes to light in the future underscoring this advice them sure, we'll re-think but for now we're not going to worry too much and just try to eat as wider range of foods as is within our control.

If you're looking to include more living fermented foods in your diet please have a look at our online shop and our range of in-person workshops and online courses!