Tim Spector OBE is a leading nutrition scientist, medical doctor and founder of the Zoe health study and app.

What do we really know about food?

From fasting and calorie counting to supplements and how much fruit and veg to eat – nutrition scientist Tim Spector debunks myths on food and what it does for us.

Wicked Leeks (WL): Why is fasting good for you?

Tim Spector (TS): Fasting in simple terms means giving your body a break from digesting food and absorbing nutrients overnight, which is known as Time Restricted Eating (TRE). It allows our body and our gut microbes to rest and repair, which is beneficial for good health. It’s important to eat when we’re feeling hungry though so remember to listen to your body.

WL: Is following five-a-day on fruit and veg actually a good rule to follow?

TS: We now know five-a-day doesn’t cover the diversity of plants that our body needs to thrive. Aiming for 30 different plants every week is more beneficial. Eating only a combination of the same lettuce, apple, cucumber, tomato and carrot is simply not enough for us to be in great health; we need to change it up and start using more spices, herbs and seasonal plants grown locally.

WL: Do extreme diets like Keto and 5:2 actually help you lose weight? What is a better measurement of overall health and nutrition?

TS: Any extreme diet will help you lose weight initially. Drastically reducing energy and nutrients from food, which is what most of these diets do, will cause initial weight loss. We also know that these diets are not sustainable in the long-term and the initial weight loss associated with them almost never lasts more than two years. Our health is so much more than our weight; good gut microbiome health and a diet that makes you feel good are often measures that better reflect a person’s energy levels, mood, positive relationship with food and better immune function.

WL: Can you get all your nutritional needs from plants, without supplements?

TS: Being a well-nourished vegan is hard work. Of course, it is possible to get all we need from plants alone, but it requires careful planning and knowledge. I believe eating small occasional amounts of high-quality animal products is a better balance for most of us, though I appreciate that everyone has their own ethical and dietary preferences.

WL: What are the lesser-known immune boosting fruit and vegetables?

TS: I would beware of calling any food ‘immune boosting’. We need to maintain good immune function, not ‘boost’ it. We know that plants containing prebiotic fibres like onions, legumes, garlic, leeks and artichokes help our gut microbiome function at its best and that is a key part of our immune health – with 80 per cent of our immune system based in our gut. Polyphenols are bioactive compounds found in the colour of fruit and vegetables that also have a prebiotic-like effect on our gut microbiome. So the best thing to do is enjoy plenty of colourful, fibre-rich foods every day, including beans and pulses, nuts and seeds as well as berries and seasonal fruits.

WL: Is red meat bad for your health?

TS: It depends. For some of us having too much red meat may increase inflammation in the gut due to specific gut microbes that produce inflammatory postbiotics when we eat red meat. For others this isn’t so much of an issue. What is clear is that eating a lot of processed red meat is associated with increased risks of poor health. For me, a little red meat on rare occasions seems to be a good balance.

WL: Is breakfast really the most important meal of the day?

TS: No, it isn’t. Every meal is important for our health regardless of the timing, and it’s best to make sure we have a good fast overnight until we feel hungry the next day instead of eating breakfast as soon as we wake up because a cereal company has convinced us it’s a good idea to do so.

WL: What is the link between organic food and human health, and is there any evidence to support that?

TS: There is some moderate evidence to support that organic foods can have a small increase in nutrients versus conventional farmed foods. Association does not mean causation, however it seems there are benefits to reducing our consumption of environmental contaminants like herbicides, which may disrupt our internal microbes. However, the key is to get enough plants in your diet full stop.

WL: How do you know what vitamins you may be deficient in?

TS: Nowadays it’s rarely about individual vitamins (such as vitamin C deficiency and scurvy) and more often about a diet that lacks overall nutrition quality. Unless you have a restricted diet like being vegan, a lack of overall nutritious food will result in a suboptimal level of nutrients. If you don’t feel like yourself, are constantly battling with exhaustion or other ailments and physical signs such as hair loss, we shouldn’t live with it. Always ask for help from a registered dietitian or talk to your GP before the issues become more serious.

Exclusive reader giveaway

The first five people to share this article and tag @wickedleeksmag on social media, will win a copy of Tim Spector’s new book, Food for Life: The New Science of Eating Well.

A diverse diet is most likely to be nutritionally sufficient.

Food for Life

By Tim Spector

Some of us want to know about food to keep our weight under control, but we have been brainwashed into thinking that counting calories is the best way to do this.

Even if calorie counts were accurate (which they rarely are), this would mean that eating equal calories of bread or yogurt, ultra-processed foods or whole foods would have precisely the same effect on metabolism and appetite, or that eating the same meal at breakfast or lunch would have an identical effect.

Unfortunately for the food industry, calorie-control diet companies, and the hundreds of millions of followers of traditional diet plans, none of these statements is true. Calorie counting has been the main obsession in nutrition for decades. Much like counting the macros of fat, protein and carbohydrates, keeping count completely ignores the complexity of our metabolism and the individual and variable response we each have at every meal.

Yet food and ingredient labels continue to rely on outdated notions about the importance of calories, and are made purposefully more complicated than necessary.

Take this one: Aqua, vegetable oils, fructose, sucrose, dextrose, starch, carotene, E306, E101, nicotinamide, pantothenic acid, biotin, ascorbic acid (E300), palmitic acid, stearic acid, (E570), oleic acid, linoleic acid, malic acid (E296), oxalic acid, salicylic acid, soluble fibre, purines, sodium, potassium, manganese, iron, copper, zinc, phosphorus, chloride, pigments, chlorogenic acid, procyanidins, flavanones, dihydrochalcones, prussic acid, 50 k calories per 100 grams.

You might assume it is a margarine spread, instant noodles, ketchup, or perhaps salad cream. You probably wouldn’t guess that it is in fact an ordinary apple.

An apple might seem like a simple food: best known for giving us plenty of vitamins, fibre, making a good pie, and keeping the doctor away. But a food label only tells us so much, and in practice, it tells us very little that is useful. No two apples are the same in their nutritional properties, and no two human beings will respond to eating an apple in exactly the same way. And what about what happens when you cook the apple, or combine it with fat, or ship it around the world in cold storage? As we’ll see, there are many different questions we should ask about our foods, rather than obsessing about calorie counts.

Our theoretical apple food label, which you won’t find in your local supermarket, also reminds us just how astonishingly complex even the most familiar ingredients can be – and this is just a list of the chemical components we know about. We experience food in colour, with its associated memories, emotions and flavours, but have tended to view food science and nutrition in monochrome.

We often associate foods with a single chemical; oranges for vitamin C; bananas for potassium, coffee for caffeine; sardines for omega- 3. In fact, most foods contain hundreds of chemicals we still know very little about.

The true complexity of food has only recently been revealed with technology called high-resolution mass spectrophotometry, which clearly identifies at least 26,000 different chemicals in the foods we eat; yet modern nutritional databases focus on a mere 150 nutrients – individual chemicals identified in foods that have clinically identified functions in the body – we actually know something about.

In the past when we talked about garlic, we would be focusing on the one chemical, allicin, that gives it its pungent flavours, but we would be ignoring the other 4,249 chemicals that we can now identify. As we will see, this new holistic big-data approach to nutrition is in its infancy but will soon reveal the complexity of our foods with even greater precision.

Our concern with individual nutrients, chemicals and minerals has its origins in the aftermath of World War Two, a time of mass starvation, nutritional deficiencies and food rationing. We no longer see scurvy, nutritional blindness and protein efficiencies in most countries, yet this mentality lives on. There are countless articles, interviews, books and products to help us reach the perfect levels of vitamin D, chlorella or magnesium, when most of us aren’t deficient in these components at all.

This nutrient and vitamin obsession in the last two decades has fuelled a $30 billion industry. The irony is that healthy people who know how to eat well shouldn’t need them, even if there was proof that they work.

Many of our problems around the science of food come down to over-simplifying the properties of foods and our responses to them.

I want to restore the complexity and the wonder to our food. I want to show you what we now do know about food, but also what we don’t yet know.

Food for Life: The New Science of Eating Well by Tim Spector (£17.99, Vintage) is out now.

Exclusive reader giveaway

The first five people to share this article and tag @wickedleeksmag on social media, will win a copy of Tim Spector’s new book, Food for Life: The New Science of Eating Well.


Leave a Reply

  1. Why do we often get told ‘a nutritious, plant based way of eating is hard work’. I wonder if the elk or the hippo tucks into a ‘healthy’ steak to make sure he/she is well nourished? Are people scared to upset the animal agriculture industry?

    1. On the other hand, I doubt a lion, tiger or cheetah would be terribly happy with a bowl of fruit. We should eat what we’ve evolved to eat, as Prof Spector says, “a little red meat on rare occasions seems to be a good balance”. It’s variety in our diets that’s vital for good health. I commend Prof Spector books to you, they’re very informative and also quite entertaining.


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