This is  with Clare Wilson, a subscriber-only newsletter from The i Paper. If you’d like to get this direct to your inbox every week, you can sign up here.

Hello, and welcome back to .

If you’ve been in a pharmacy lately, you may have noticed more and more shelf space taken up with a smorgasbord of health supplements, claimed to improve our well-being in various ways.

If you’ve read some of my previous articles, you might have already guessed that I am inherently sceptical about the evidence supporting any and all of them.

As a middle-aged woman, the ads I get sent most often are for collagen, a protein found widely in the body that is claimed to improve your skin, hair and nails as well as keeping your joints strong and supple.

So, I was fascinated to read a debunking of collagen supplements – and the wellness industry in general, in a new book by doctor and broadcaster, Xand van Tulleken, called Make Me Well: A Quest to Understand the Confusing World of Wellness.

A £2bn industry

Collagen is one of the most popular supplements worldwide, with people said to spend about £2bn a year globally on it. I can believe it, having taken a quick peek at the price of some of the high-end collagen products, which can cost £60 a month or more.

When I spoke to van Tulleken this week, he said it’s understandable why so many people believe consuming collagen will do them some good.

It is the most abundant protein in the human body, giving strength and elasticity to skin, cartilage, joints and ligaments. This is the basis for claims that collagen supplements will revitalise your skin, joints and so on.

People are very familiar with the idea that you can use supplements to boost your body’s levels of important substances like vitamins and minerals.

But there’s a difference between taking a daily vitamin tablet and one containing collagen. Unlike vitamins or minerals – which are small molecules – most proteins are large, complex molecules made of long chains of building blocks called amino acids.

Proteins are too big to be absorbed in the gut. Instead, digestive juices break them down into their amino acids, which can pass from the gut into the blood. Then, cells within bodily tissues build the amino acids back up into whatever proteins are most needed.

Because it is so difficult to orally absorb large protein molecules, drugs that take the form of proteins have to be injected – like insulin for diabetics or Wegovy for weight loss. The manufacturer has managed to create a pill form of Wegovy through some cunning chemistry, but this hasn’t been done for collagen.

In other words, the entire basis of the claim that you can improve the amount of collagen in your skin or joints by consuming more of it is biologically implausible. “It’s like saying that eating brains makes you more intelligent,” van Tulleken said in his book.

This is also why skin creams containing collagen also won’t build any collagen into your skin. The cream just gets into the outermost layer of mostly dead skin cells, and the collagen molecules are too large to get into deeper layers where collagen provides the structural support. That collagen has to be synthesised by special cells within lower layers, and they make it from its amino acid building blocks, delivered from the blood.

On oral supplements: some manufacturers claim that, rather than being completely broken down into individual amino acids in the gut, some of the collagen remains as tiny chains of two or three amino acids, with a few a little bit longer.

The claim is that these send messages to tissues such as the skin or joints to build the chains of amino acids back up into the full collagen molecules. This is why some supplements are described as hydrolysed collagen or collagen peptides, which means it is already in these short chains, rather than being the complete collagen molecules.

But there is no good evidence that the short amino acid chains act as a signalling mechanism for collagen synthesis.

‘Such clear evidence of industry manipulation’

The real test of whether any supplement or medicine works is a placebo-controlled, blinded randomised trial, ideally done in large numbers of people, using objective measures of whether their skin or joints have improved.

Here’s where it gets interesting. There have been several such trials carried out, and some showed a positive effect.

But last year, some independent researchers took a close look at all the randomised trials that had been done to investigate the effects of collagen supplements on the skin.

Taken together, the trials found that collagen reduced wrinkles and improved skin elasticity. But then, the researchers classified the trials by how rigorous they were, according to prespecified criteria (such as size and objectivity) and whether they were done by a manufacturer or independent researchers.

While the industry-run trials found positive effects, the independent ones found no benefit. Similarly, while the low-quality trials found positive effects, the high-quality ones did not. “It’s unusual to see such clear evidence of industry manipulation,” van Tulleken told me.

When it comes to benefits of collagen on the joints, a similar examination has not been done – so those wanting to protect their joints are left not knowing where the truth lies.

As for skin and hair, they are not even made of collagen – their main protein is one called keratin. The main claims for skin and hair seem to be that extra collagen in the skin surrounding hair follicles or nail beds would generally support their health – but again, there is little good supporting evidence here.

It is worth noting that not everyone agrees that the analysis from last year means all industry-funded trials can’t be trusted.

“Industry-funded trials still go through registration, ethics review and peer review like any other trial,” said Professor Lee Smith, a public health specialist at Anglia Ruskin Universty.

“If we threw out every industry-funded [trial] across medicine, we’d lose a huge share of the drug and device evidence base that underpins mainstream clinical practice.”

Nevertheless, the stark difference in results between the industry-run and independent research has made me more sceptical than ever of the collagen industry.

What to eat instead

If supplements don’t work, is there anything we can do to optimise our body’s collagen functioning? It is worth making sure that you are getting enough protein in your diet generally – as our tissues cannot synthesise any protein out of its constituent amino acids without them being present in our diet.

While it is often claimed that people on a typical Western diet get more than enough protein, there are concerns from several health bodies that the current UK recommendations for daily protein requirements have been set too low.

Nutritionists often find that older people in particular have higher protein requirements and are failing to eat enough. People who are vegetarian, vegan or who eat little meat may not be getting enough of “complete proteins”, which have all the essential amino acids.

Complete proteins are found in meat, dairy products, and good plant-based sources like soya beans, tofu, soy milk and quinoa. Ironically, collagen itself is not a complete protein, as it mainly consists of only three of the 20 amino acids found in the human body and completely lacks one of the essential amino acids.

After his in-depth investigation into the collagen industry, which included a trip to one of the biggest manufacturers, in China, van Tulleken ended up a complete sceptic.

He thinks the international market for collagen has been whipped up by the meat and fish-processing industries, which want a profitable use for their byproducts of cattle hides, bones and fish skins – which is what most collagen supplements are made from. When you think about how they are made, those high-end collagen powders, potions and pills seem a lot less appetising.

A study has found that drinking your tea and coffee too hot could cause cancer of the oesophagus, the tube that goes from the throat to the stomach. But how hot is too hot?

Hoorah for the arrival of the second season of , the BBC series about a professional puzzle-setter-turned-detective, masterfully played by David Mitchell. Mitchell seems born for this role of highly intelligent yet socially awkward sleuth, which is unsurprising considering the series was written especially for him.

In this second season, Mitchell is no longer impersonating his police detective twin, and has been given an official consultant role with the local police force for his unrivalled sleuthing skills. But Mitchell’s co-star, the excellent Anna Maxwell Martin, is now – equally improbably – impersonating a local journalist. What new type of logic puzzle will the next murder mystery replicate? The story is a little silly, but good fun.