Interview

Go with your gut: scientist Tim Spector on why food is not just fuel

Linda Geddes

The scientist has spent years studying how gut health relates not just to nutrition, but to all aspects of our everyday wellbeing. He explains why it really is what’s inside that counts

Sun 15 May 2022 07.00 BST

Tim Spector’s kitchen fridge is swarming with life: kefir grains, sourdough mother, homemade kimchi and kombucha. Then there’s the vegetables: as varied and colourful as possible.

While many diets eschew certain food groups, Spector’s focuses on incorporating as much variety as possible: at least 30 different plants a week – including nuts, seeds, pulses, whole grains, fruits and vegetables – on top of starchy staples such as potatoes or rice. The reason? He believes that diversity is crucial to warding off infections, combating age-related diseases and maintaining a healthy weight.

Diversity cultivates a healthy microbiome – the micro-organisms living in our gut – which plays a vital role in digesting food, regulating our immune systems, and tweaking our brain chemistries through the chemicals they produce. “It’s that diversity of gut microbes that gives you a diversity of chemicals and, we believe, a healthier immune system and a better metabolism,” Spector says. “Once people start seeing that there is this link between the food we eat, our microbes and our immune systems, I think that changes the way we think about food. It’s not just fuel. It really is changing the way our body works.”

Spector’s diet today is a far cry from what he used to eat: typically, muesli, orange juice and tea for breakfast – sometimes with toast and marmalade – and a tuna mayonnaise sandwich, packet of crisps and carton of orange juice for lunch. “My breakfast now is a mixture of kefir and full-fat yoghurt with some berries and mixed nuts and seeds on top, plus one or two big cups of black coffee. For lunch, I might have a curry, or some other heavily plant-based meal. I am virtually vegetarian, and eat far fewer starchy foods than I used to.”

The event that prompted this change was suffering a mini stroke at the top of a mountain in his early 50s, after an energetic day of skiing in the Alps. “I went from being a sporty, fitter than average middle-aged man, to a pill-popping, depressed stroke victim with high blood pressure,” he recalls. It was a wake-up call that prompted him to reassess everything he thought he knew about healthy eating, including much of what he’d learned at medical school.

A professor of genetic epidemiology at King’s College London, Spector has spent much of his career researching how our life choices and events fuse with our genes. In 1993, he founded the UK Twins Registry at St Thomas’ Hospital in London, one of the richest collections of data about identical and non-identical twins in the world.

For years, Spector believed that genetics would explain much of why people are the way they are. And to some extent it does. For instance, Spector’s group was among the first to demonstrate that people’s weight distribution is largely influenced by their genes.

Trying to understand why one twin is sometimes overweight and the other skinny, one gets diabetes or cancer and the other doesn’t, has been a major theme for the past 20 years

The trouble is, although identical twins have many similarities, they can often be quite different – despite sharing the same genes. “Trying to understand why one twin is sometimes overweight and the other skinny; one gets diabetes or cancer and the other doesn’t, has been a major theme for the past 20 years,” Spector says.

The discovery, in 2014, that the composition of the microbes in people’s guts could influence their body weight, provided Spector’s first “Aha!” moment. But the blinkers really fell off when he and his colleagues measured twins’ and non-twins’ responses to identical meals, and discovered that they could vary hugely between individuals, influenced by both the microbiome and genetics.

“Up to that point, we didn’t really have enough belief that you could personalise nutrition, or that you could link the uniqueness of the microbiome to the uniqueness in the food response – but suddenly, you had those two elements together,” says Spector. “We’re all very different in how we respond to the same meal, and a lot of this is explained by the huge differences in our microbiomes.”

This doesn’t mean that other factors are irrelevant to people’s health: “How much you sleep at night, the quality of your food, the exercise you get, all these things are also important,” says Spector. “All we’re saying is that the microbiome is a major modifiable factor.”

Spector likens the bacteria, fungi, and viruses in our guts to a kind of inner chemical plant: “Our own bodies only produce 20-odd gut hormones or chemicals, but these microbes produce thousands, which not only break down food into small amounts and use the contents, but produce lots of signalling compounds that are sending constant messages to our immune systems,” he says. They also produce brain chemicals, such as serotonin, as well as additional molecules that control how our bodies change food into energy.

“We don’t know exactly how, but the state of your gut microbes will influence your blood sugar peaks, as well as how you digest fats and how quickly those fats are cleared by the body. Indirectly, both of those will lead to inflammation.”

This is important, Spector explains, because chronic inflammation may increase the risk of various diseases, including type 2 diabetes, heart disease and certain cancers. It may also steer people towards laying down more body fat, which in turn then produces more inflammation.

Our microbiome can also shape our responses to infection. Spector is probably best known for his work on the ZOE Covid symptom study, which has seen millions of users logging their daily symptoms via an app to help gain a better understanding of how Sars-CoV-2 spreads, and the nature of the illness it causes.

Tim Specter carrying giant asparagus

Photograph: Alicia Canter/The Guardian

One insight from the study is that people who consumed a greater diversity of plant-based foods pre-pandemic appear to be less susceptible to catching Covid-19, or becoming severely ill from it. While this doesn’t prove definitively that eating a diverse plant-based diet can ward off infections, Spector believes it could help: “Your immune system is compromised if you don’t have a good microbiome controlling it, and so it may either under- or overreact [to pathogens],” he says. “I don’t think eating for our microbiomes would stop pandemics, but I think it could make everyone less ill if they got infected.”

So, how do we eat for our microbiomes? In Spector’s view, this comes back to consuming a diverse and predominantly plant-based diet, which is free from highly processed foods. “These are foods that you recognise, and could make yourself from your kitchen ingredients,” says Spector. “It’s plants that are rich in defence chemicals called polyphenols – generally ones with strong tastes and colours, slight bitterness, thick skins – basically the opposite of an iceberg lettuce. It’s those grapes we used to have as kids that were a bit sour and bitter. It’s the purple carrot rather than the white carrot”

To up the polyphenol content even further, Spector recommends lashings of green tea, extra virgin olive oil, brightly coloured fruit and vegetables, herbs and spices – plus a dusting of dark chocolate. And don’t forget the four Ks: kefir, kombucha, kimchi and kraut (sauer) – as well as cheese and yoghurt – which act as fertiliser for our resident gut bacteria.

What this amounts to is very similar to a Mediterranean diet – one high in fruits, vegetables, and whole grains, and containing less meat and dairy products than a typical western diet. Spector says: “It doesn’t really matter if you have bits of meat and fish on top of that – I don’t believe they’re necessarily healthy, but as long as you’re getting enough plants on your plate, it’s fine.”

In his latest book, Spoon Fed, Spector also discusses how microbes can affect people’s mental health. Among scientists, there’s a growing consensus that depression may be linked to elevated levels of inflammation in at least a subset of patients; Spector argues that having the right gut microbes can counter this, because they secrete a range of chemicals that both keep inflammation in check, as well as altering our mood more directly. For instance, certain microbes help to produce serotonin – the same chemical that’s increased by some antidepressants. Studies have also suggested that people with depression have a less diverse set of microbes, on average, compared with healthy individuals. “A diverse Mediterranean-style diet with a range of fermented foods to keep your microbes happy is looking like the best present you can offer your brain,” Spector writes.

A diverse Mediterranean-style diet with a range of fermented foods to keep your microbes happy is looking like the best present you can offer your brain

Spector describes the changes he’s made to his diet as “an evolving process”. He only eats meat about once a month, while concerns about sustainability means he only has fish occasionally, at restaurants: “I wouldn’t say I suddenly had the answer when I discovered the microbiome, but I’ve slowly been changing the habits I had when I was a smug doctor thinking that I knew everything.”As well as a desire to nurture his “inner garden”, his dietary choices are motivated by the insights he’s gained from monitoring his personal responses to different foods. This is why he eschews large amounts of pasta, rice and potatoes – not because they are inherently unhealthy, but because using a continuous glucose monitor has revealed that they produce worryingly high spikes in his blood sugar levels.

He is highly dismissive of one-size-fits-all diets, and the notion that weight loss is all about calories in v calories out: “It is complete nonsense,” he says. “You and I can eat two identical muffins with the same calories in them, and you might have a mild sugar spike and no sugar dip, whereas I will have a big sugar spike and a sugar dip, and I will overeat by 200 calories in that day, and you won’t. That simple experiment, which we’ve now done on thousands of people, just blows out of the water the idea that it’s all about calories.”

In April, ZOE, the personalised nutrition company that Spector co-founded, began inviting about 180,000 individuals on its waiting list to buy an early access version of its “ZOE programme”, an attempt to bring personalised nutrition to the UK masses. It’s still a luxury lifestyle option at the moment – the £260 price tag puts it out of reach of the mass market – but early access members will start with an at-home test, the results of which provides them with personalised scores for thousands of foods in the ZOE app. Members also access daily lessons, recipes, live chat with ZOE coaches, and more. The programme consists of two parts: testing and ongoing membership. A testing kit consisting of three packets of standardised muffins (to test your biological responses and challenge your metabolism with high doses of fat and sugar), a continuous glucose monitor, plus stool and blood sampling kits; the idea is to test how people respond to various foods over a two-week period, and provide them with personalised scores for thousands of foods, and nutrition coaching, based on these results.

Spector’s ultimate goal is to change the way people think about food. “You’re eating hundreds of chemicals when you eat a carrot, it’s not just the orange colour – there’s all this other stuff that’s hidden,” he says. “All those things are lost when you stick food into a factory, ultra-process it, and put it into a vacuum pack.”

Review

Food for Life by Tim Spector review – the science of eating well

The epidemiologist and author of The Diet Myth returns with a comprehensive guide to foods that foster healthy microbiomes

Katy Guest

Katy Guest

Thu 3 Nov 2022 11.00 GMT

Tim Spector, an epidemiologist and co-founder of the ZOE nutrition study, wants to change the way people think about food. His 2015 book The Diet Myth popularised the idea that each of us has a unique and constantly changing gut microbiome that is crucial to our health. Spoon-Fed, in 2020, exposed diet misinformation. Food for Life, at over 500 pages, overlaps with these but offers more information than ever before. It aims to think about food for “our individual health, the health of our society and the health of our planet”. It’s complex, hard to digest and obviously good for us, like an enormous portion of fibrous vegetables, well balanced with spices.

Once you wrap your head around the microbes in our guts, which need a varied diet themselves in order to process the food that makes us healthy, much of it seems like common sense. Eating a wide range of plants keeps you well – 30 a week is ideal, including seeds, nuts, herbs and spices. “Ultra-processed foods” (UPFs) – a “heady, addictive mix” that makes us “fatter but less nourished”, are bad. Anything that claims to be a “superfood” is probably a con.

Two cups of Americano coffee provide more fibre than a banana

Other findings seem counterintuitive, but are often deliciously reassuring. Two cups of Americano coffee provide more fibre than a banana. You can reheat rice; unopened mussels won’t kill you; and eating meat doesn’t give you cancer (though “replacing 30% of traditional burger meat with mushrooms or fungi would be the equivalent of taking 2m cars off the road”). Some sources of nutrition are more beneficial together, like corn with beans, or “a glass of red wine daily with friends”. Replacing sugar, salt, fat and gluten with weird and untested chemicals is usually pointless and probably dangerous, and the 1980s advice to change butter and cream for margarines and vegetable oils was “one of the biggest health scandals ever”.

Appealingly, Spector writes as a food lover. He’s comically keen on kimchi, kombucha and sourdough bread – in fact, fermented foods are manna to our friendly microbes, including the cacao beans in good-quality chocolate. But he’s sometimes frustratingly understated when it comes to the politics – and finances – of food. Our choices are “a puzzle of availability, convenience, taste and education,” he admits, while cheerfully recommending that cheap UPFs and sugary children’s yoghurts “should be avoided”; that people should “choose organic, grass fed and whole milk” and “good honey from your local beekeeper”; and that “the tenfold increase in price” is the way to pick the right extra virgin olive oil.

However, his aim in this book is not to give advice. Our gut microbiomes are so different that, in human studies, there is an “eight- to tenfold variation in individual insulin, blood sugar and blood fat responses to the same meals”, and so every person’s ideal diet is different, and should be based on sensible choices from a position of knowledge.

Food for Life is a feast of that knowledge. It contains so much information that it’s impossible to process by reading it from start to finish, but bullet-pointed tips at the end of each chapter and an appendix of food tables make it a valuable reference book to keep on a kitchen shelf.

Food for Life by Tim Spector is published by Jonathan Cape (£20). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply.

This Diet Is Changing The Way We Think About Nutrition

Anna Haines

Contributor

I cover wellness and beauty.

0

Listen to article9 minutes

A woman looks at the ZOE app on her iPhone.

ZOE takes a personalized approach to nutrition with a diet plan based on the unique blood sugar, ... [+]

ZOE

“A lot has changed in habits in the last year and a half,” says Tim Spector, epidemiologist at King’s College London and author of The Diet Myth: The Science Behind What We Eat. The co-founder of personalized nutrition company ZOE is referring to our habits when it comes to food—all the time at home has put the spotlight on what and how we eat, creating what Spector describes as “fertile ground” for rethinking our relationship to food.

Young Woman Checking Food Delivery on Smartphone in kitchen.

With the pandemic increasing time spent in the kitchen, people are paying more attention to what and ... [+]

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With two thirds of ZOE users reporting their bodies changed during the pandemic—either having gained or lost weight—how we eat is certainly top of mind. But finding the right diet isn’t so easy when medical professionals are often poorly trained in nutrition and diet companies sell quick fixes that rarely last. “People are realizing the old mantras of ‘reduce your calories and exercise more’ simply aren’t working,” says Spector. “Billions of dollars are being spent on diet plans that may work for five to six weeks but then fail.”

Co-founder of ZOE Tim Spector.

Epidemiologist and author of The Diet Myth, Tim Spector, co-founded ZOE with Jonathan Wolf and ... [+]

ZOE

While frustration towards the medical system and diet industry is not new, what has changed is self-monitoring technology, and a growing interest in personalization—for the first time, people are taking health into their own hands. From glucose monitors to gut microbiome tests—it’s never been easier for people to become their own doctor and nutritionist at home. “The quality of the genetic sequencing on your microbiome just wasn’t good enough, even three years ago, at an affordable price,” Spector tells Forbes. The breakthrough in artificial intelligence and machine learning has enabled personalized nutrition to take off.

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“People want to know, ‘am I someone who can have a high-fat diet, high-carb diet, what’s the best way of eating for me?’” says Spector. Rather than a one-size-fits-all approach, ZOE offers personalized recommendations on what and when to eat based on how each person’s blood fat, blood sugar and gut microbiome responds to different foods. “Everyone following the same advice about eating identical foods and 2000 calories a day is non-sense,” says Spector. “A calorie is not a calorie when it has a different effect on different people.”

ZOE has done the research to prove it. The inspiration for the company’s personalized approach came 25 years ago, when Spector discovered that identical twins eating the same foods produced an eight- to ten-fold difference in blood glucose, insulin and fat and inflammation responses. The study of 13,000 twins proved to Spector the only “right” diet is one tailored to each unique body.

The ZOE at-home testing kit on a kitchen counter with muffins.

ZOE was inspired by the finding that the same blueberry muffin had an eight- to ten-fold difference ... [+]

ZOE

“I thought I was an expert on what to eat, but even I’ve changed my diet a lot based on my Zoe results,” the scientist says, describing how he’s replaced his morning porridge, orange juice and milky tea to black coffee and high fat yogurt with nuts and berries. “Doing that has made a big difference, I feel so much better,” says Spector, “but because my scores told me to do it, not because I read it in my book.”

It’s this openness to having his beliefs uprooted that enabled Spector to discover the importance of the gut microbiome in determining the body’s response to various foods. Having trained in genetics and studied twins for 27 years, the professor says he was “desperate to show that genes were important for nutrition.” But in an early PREDICT study, one of a series representing the world’s largest nutrition experiment, Spector found that identical twins with the same genes were affected differently by the same food. “What we saw was that your response to foods is hardly genetic at all, a little bit for sugar and insulin, but not at all for how you process fats,” the scientist tells Forbes.

The ZOE app on an iPhone.

The ZOE app provides personalized recommendations on what to eat based on how each individual's gut ... [+]

ZOE

Instead, Spector found that the microbes in the gut have a greater influence on metabolic health, a discovery that the researcher says is much more empowering than the “depressing” genetic angle. Instead of having your optimal food choices limited by the genes you’ve inherited, tailoring the diet to the gut allows room for flexibility.

“The great thing is that most gut microbes are modifiable by diet, so you can change your response to food over time if you feed them right,” says Spector. The ZOE co-founder also says a diet focused on the gut microbiome allows for the “occasional binge or odd takeaway, if you’ve got a healthy gut microbiome, it can cope with it.”

But what does eating for the gut microbiome look like? “It’s about getting a diversity of plants,” says Spector, citing studies that find eating thirty different plants a week provides the optimum diversity of gut microbes.

“There’s lots on Instagram about twenty different ways to have a kale smoothie every day and the latest trendy seed from Peru,” the co-founder says. “It’s not about that, the Zoe plan is geared towards diversity, pushing people to try new things.” Rather than encourage restriction or tell people “you must lose x pounds this week,” Spector says ZOE promotes adding in and introducing new foods.

Hands reaching over a dinner table filled with fruits and vegetables.

Rather than encourage restriction or weight loss, ZOE promotes a diverse diet, based on findings ... [+]

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The results? “Nearly everyone has lost weight but what they’re excited about is energy levels and not feeling hungry all the time,” Spector tells Forbes. “We’re trying to do something that’s more sustainable long-term, because every short-term diet fails. This is educating people on how to eat better for decades, not just a few weeks.”

The motivation behind adopting a diet centered on the gut microbiome stretches beyond weight and appearance, as research increasingly shows it’s one of the most important organs in the body. The microbes in the gut not only “influence how we metabolize foods, our sugar spikes, how we break down fats,” according to Spector, they produce thousands of vitamins and brain chemicals that affect our mood.

Citing the growing field of nutritional psychiatry—the use of nutrition to treat mental health conditions—the scientist says, “studies have shown switching to a gut-friendly diet has the same or better effects than anti-depressant medication in mild to moderate depression,” illuminating the incentive for psychiatrists to consider the a nutritional approach to treatment too.

Doctor nutritionist during consultation shows patient walnut kernels.

ZOE co-founder Tim Spector says the gut microbiome plays a vital role in determining how the body ... [+]

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But above all else, Spector says the gut is “absolutely key” to our immune system. “Virtually every Western disease is linked to having a poor quality gut microbiome,” the professor says. As the pandemic increases interest in preventative strategies for maintaining immune health, ZOE is leading the way in studying the link between nutrition and COVID-19. Their most recent research project monitored the food choices and COVID-19 symptoms of nearly 600,000 people, making it the largest study of its kind to date. People with the highest quality diet were found to be 10 percent less likely to develop COVID-19 and 40 percent less likely to have severe symptoms, compared to those with the lowest quality diet.

A woman choosing vegetables in a grocery store.

Landmark findings from ZOE's most recent study establish the link between nutrition and COVID-19, ... [+]

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The landmark findings are just the beginning for ZOE, a company that has made nutrition research its priority since the start. “We have the world’s biggest microbiome diet data set,” says Spector. “It’s basically one big ongoing study.” Unlike a traditional research program, users of ZOE see their results and are given the tools to act on them. While the focus on education separates the platform from feeling like a traditional diet company too. “It’s fairly novel because people are getting personal advice but they also know they’re contributing to science,” says Spector.

A woman uses the ZOE platform on her computer while eating a muffin.

With education at the core of the program, ZOE feels less like a traditional diet company—users ... [+]

ZOE

Should you skip your breakfast? Does intermittent fasting work for everyone? These are the types of questions Spector says ZOE hopes to answer within the next couple of years. With upcoming studies on sleep and timing of meals, the company is shifting its focus from what to eat, to how to eat for optimal health—all under the “general principle that we’re all unique,” says Spector.

Woman using calorie counter application on her smartphone.

Co-founder Tim Spector anticipates nutrition will only become more personalized as self-monitoring ... [+]

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From home blood test kits to tele-health appointments—as the technology continues to advance, Spector anticipates personalized health will become the new normal. “We’ve seen the glucose monitor, but fat monitors are going to happen in the future too,” Spector tells Forbes. “The Japanese are already inventing smart toilets so people can get a chemical read-out of your poop in near-real time.” Hospital visits will be replaced by at-home solutions, Spector says, “this is going to be very empowering for people to take back control over their health and their choices.”

Accessibility remains the greatest obstacle preventing the widespread adoption of a personalized nutrition plan like ZOE. But Spector anticipates the price will come down with scale. “At this moment, if you went to your physician to get your microbiome sequence, glucose monitored and lipids tested, it would cost you tens of thousands of dollars,” says Spector. But currently costing less than a cup of coffee a day, a ZOE membership continues to come down in price.

A woman opens a ZOE at-home testing kit.

Believing that everyone has the right to understand their body, ZOE continues to bring down the cost ... [+]

ZOE

“That’s the ultimate goal, to make this accessible to everybody,” Spector says. The co-founder dreams of the day when everyone uses the ZOE app for their diet, in the same way people use the Uber app to make their transport choices. At the rate with which ZOE is innovating, that future doesn’t seem so distant. Spector excitedly tells Forbes, “This is just the tip of the iceberg with what we can come up with, we’re just getting started.”

Some quotes have been edited for length and clarity.