Tim Spector on why detoxes are 'rubbish' and how better quality food will benefit your gut

He’s highly qualified to do so. Spector is a professor of genetic epidemiology at King’s College London and one of the top 100 most-cited scientists in the world. He also co-founded Zoe, a personalised nutrition app with more than 130,000 subscribers. Somehow, he also finds time to write best-selling books.

January is a time when many are feeling the ill effects of festive feasting. Would he advise undergoing a detox to boost your health and vitality?

“It’s rubbish,” he says flatly. “It gives the wrong idea about how our body works. It assumes that millions of years of evolution haven’t taught us how to deal with natural toxins. And that we need some artificial ways of helping ourselves. We have a liver and kidney, urine and faeces to get rid of the things we need to get rid of.”

His main bone of contention with the detox movement is that “none of it is backed up by science”.

He is keen to highlight the difference between detoxing and fasting: “Our body does not build up with malodorous toxins that would otherwise kill us. Our body and our intestines do need a rest. We weren’t designed in evolution to be eating as continuously as we are these days. And to eat artificial foods.”

He says there’s good evidence that “some forms of intermittent fasting”, particularly time-restricted eating, are beneficial.

‘Food-like substances’

Just like you need sleep at night, so does your gut. We should all be taking 12-hour eating breaks, he says. “It gives your gut time to recover and repair itself. Ideally, it’s a 14-hour break, but some people find that very difficult.”

He refers to a large-scale community study on intermittent fasting undertaken by Zoe. Participants were asked to adopt a 10-hour eating window and a 14-hour fast over three weeks. So, if they ate breakfast at 8am, their last meal of the day should be at 6pm. Those who completed the task said they felt they had higher energy levels. “They also had better mood. Interestingly, they had less hunger, not more.”

He is concerned about the quality of food in our supermarkets. “Around 60% of all the food we consume is ultra-processed, which is what I call ‘fake food’ or ‘edible food-like substances’,” he says.

“Virtually all food we eat is processed. Yoghurt is processed, for example. Ultra-processed foods include most biscuits, cakes, supermarket bread, and children’s yoghurts.”

Most children’s foods found in supermarkets are ultra-processed, he adds.

Breakfast cereals are on his ultra-processed hitlist too. But what about those healthy-looking boxes of granola with nuts, seeds, and dried fruit?

“I would say, ‘don’t go there’. Look at the ingredients list, but in general, they will have things you wouldn’t find at home in your kitchen... They will have fairly low levels of fibre and high levels of sugar, palm oils, gums, and emulsifiers. And the result is they make you overeat by 25%.”

We overeat because we’re not satiated?

“Yes,” he says. “You also eat much faster. And [these foods] don’t engage with your gut microbes to produce the right signals of fullness.”

If you feel you need to detox, he suggests looking at changing your diet instead. “Think about helping your gut microbes.”

More plants, more variety

We’re on the second floor of Soho Works 180 for the M&S Festival of Health. The place is fizzing with energy — there are flat-out exercise classes, an entertaining vegan food demonstration, nutritional advice and indepth expert panel discussions, one hosted by TV presenter Emma Willis.

The central focus is the launch of M&S Food X Zoe Gut Shot — a pocket-sized bottle packed with live cultures and friendly bacteria.

The accompanying information notes that the gut microbiome plays a vital role in our general health, including the immune system, metabolism and mood. A healthy, balanced diet which includes high-fibre whole foods has been proven to support gut health.

I sampled the kefir and berry drink earlier and found it tart and filling. My stomach, crotchety after weeks of festive feasting, cheered up immediately. It costs €3 per bottle, which seems a small price for a healthy gut microbiome. But a daily gut shot may be beyond the budget of people stretching to pay their monthly bills. So, what can they do to promote their gut health?

“There are several simple steps you can take,” says Spector. “One is to try and increase the number of different plants you eat every week. Aim for 30 — most people consume about seven.”

His interpretation of the word ‘plant’ is broad: “A fruit or vegetable, a nut, a seed, a herb, a spice — all of those are food for your gut microbes. That way, you get more interesting food, tastes, and texture, more variety.”

The mantra of getting your five-a-day is ‘old fashioned’, he says, dismissing an age-old public nutrition message.

“It doesn’t give your microbes the diversity they crave. The way to hack this is to get packets of mixed nuts, for example. Mixed seeds, and add them to your
yoghurt.”

The next step to improve your gut health is to eat the rainbow: “Different-coloured cabbage counts as a different plant. A green pepper is different from a red pepper. A purple carrot is different from an orange carrot.

“You got at least 10 different types of [tinned] beans. And all of them are really cheap.”

Spend money on food

Spector is also outspoken about the role of multivitamins, a multi-billion euro global industry.

“I’m against spending money on things that detract you from getting the vitamins from real food,” he says. “A lot of people can spend €10-20 a week on multivitamins. I’d rather they spend that on fruit, vegetables, nuts, and seeds, which have the real stuff in them. Especially when multivitamins have never been proven to be beneficial for health.”

But I’ve been taking vitamin B complex and vitamin D for years and can attest to the benefits.

“That’s mainly because you don’t have your full variety of plants,” he shoots back.

So, does he think there’s a placebo effect with multivitamins?

“Yes”, he replies.

I’m not entirely convinced. What about the research highlighting the health benefits of vitamin D supplementation?

“All the trials show that vitamin D has no effect on your bone health, no effect on your muscles,” he says emphatically. “It may help prevent things like multiple sclerosis, but it’s vastly exaggerated. People are much better off just going in the sun for 10 minutes. Or eating food which has vitamin D in it, like mushrooms and oily fish.

“I studied [vitamin D] for 30 years and gave it to my patients for 30 years. I was a rheumatologist ... but science says it doesn’t work.”

There’s no arguing against the central role of a balanced whole-food diet. But surely enjoying your food matters too.

“That’s why I’m adding more to your plate rather than less,” says Spector. “It is what we’re all about. My attitude is more flavours, more textures, more tastes. It’s getting out of the rut.”

That’s why he recommends consuming 30 plants weekly along with several fermented foods. “Apart from the gut shot, yoghurt is good — it’s got to be full-fat plain yoghurt. There’s also kombucha, sauerkraut, and kimchi — you can mix that with cream cheese. Good Irish artisanal cheese is fantastic, but not the highly processed ones that come in blocks and plastic bags.”

Our time is up, and Spector is still in professor mode — focused and serious. He gives me a gift of the paperback version of his book Food for Life: The New Science of Eating Well, and we head off in different directions.

I check my pockets and my phone is missing. Could the professor have accidentally picked it up? I catch up with him and there it is, hidden under another copy of his book.

He hands it over with a chuckle and broad smile, a flash of the man behind the serious academic.

• Food for Life: The New Science of Eating Well by Tim Spector, €16