Your sweat holds a lot of information about the state of your health
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Wow, you’re quite salty,” says Stefan van der Fluit, looking over my numbers. I could have told him that. I have just done a sweaty, 45-minute workout on an exercise bike and the salt is already starting to crystallise on my T-shirt. But van der Fluit knows exactly how salty. I have just sweated out 347 milligrams of sodium in 370 millilitres of water. That’s on the high side, sodium-wise, and I need to replenish.
Van der Fluit is the co-founder of a company called Flowbio, based in London, which specialises in sweat analysis for athletes. During my workout, I was wearing a sensor called the S1 on my upper arm, which collects sweat in a tiny channel, automatically measures its volume and sodium concentration, and transmits the data to a smartphone app. Using that data, the app calculates my total losses.
If I were an endurance athlete, that data would be extremely valuable, perhaps the difference between winning and losing. I’m not, but van der Fluit is. As a competitive cyclist, he has had long-standing problems with dehydration. But since he started using the sweat sensor, they have gone away, and his performance has improved.
Flowbio’s S1 is one of a handful of wearable sweat sensors that have come onto the market in the past few years. They are mainly aimed at people who sweat a lot in the course of their jobs – athletes and manual workers – but they are also available to…
Produce has been the source of many foodborne illness outbreaks in the US this year
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Apple sauce containing lead. Onions carrying E. coli. Deli meat spreading listeria. The past year has seen alert after alert from US public health officials warning of contamination in the food supply, both in packaged and prepared foods. Going to the grocery store – or even out to eat – has seemingly become a real gamble.
But lately, much of the public worry over food safety has been hijacked by Robert…
Candy-floss effect: a childhood diet rich in sugar has been linked to higher risk of high-blood pressure and other conditions in adulthood.Credit: Getty
It’s tough news to hear on Halloween: a sugary diet in the first two years of life is linked to a higher risk of diabetes and high blood pressure decades later, according to an analysis of UK sugar rationing in the 1950s.
The amount of sugar a child consumed after turning six months old seemed to have the biggest effect on the risk of developing a chronic disease later in life. But people exposed to more sugar in the womb also had a higher risk of diabetes and high blood pressure compared to those who were conceived when access to sugar was limited.
Economist Tadeja Gračner was pregnant with her first child and on doctor-ordered bed rest when she and her colleagues first arrived at these conclusions, which are published in Science on 31 October1. “I was like, ‘No, no, no. This is the last thing I need.’,” she says. “I was probably eating a chocolate at the time.”
The results do not mean that pregnant people and parents of young children need to eliminate added sugars from their own diet or their child’s, says Gračner, who works at the University of Southern California in Los Angeles. But there could be room for cutting back: in the United States, pregnant and lactating people typically eat more than three times the recommended amount of added sugar. “It’s all about moderation,” she says.
Childhood diet’s long shadow
The UK study is not the first to link early-life nutrition to disease risk later in life. Previous work has shown that experiencing famine while in the womb can double the risk of diabetes later in life.
But data from tragedies such as famines and war can be difficult to interpret, says Valentina Duque, an economist at American University in Washington DC. “Often, these big, historical shocks affect so many things,” she says. “You don’t know what’s because of nutrition, or stress, or changes in income or household dynamics.”
‘Smart’ insulin prevents diabetic highs — and deadly lows
Sugar rationing in the United Kingdom offered an opportunity to take a more detailed look at the impact of nutrition on later life. Economic hardship during the Second World War forced the government to institute food rations, and limits on sugar were not lifted until 1953, years after the war ended. By then, most other aspects of nutrition had normalized to meet standard daily recommendations.
Gračner first had the idea for the project years ago when she stumbled across an article about the lifting of the UK sugar rations and saw pictures of children flooding into bakeries when the restrictions ended.
By the time Gračner started her own research group and began piecing together a proposal with her colleagues to study the event, another tool had become available: the UK Biobank, a repository of genetic and medical data from half a million participants. After confirming that sugar intake had risen dramatically after the rations lifted, the team mined the biobank for people who had been conceived between October 1951 and June 1954, when the rations were in effect. They then compared the health of these people with the health of people who were conceived between July 1954 and March 1956, after the rations were removed.
Undeniable effect
The researchers found that the people conceived during the sugar limitations had a 35% lower risk of diabetes and a 20% lower risk of high blood pressure than people conceived after the rationing.
The magnitude of the effect is surprisingly large, says Duque. “It’s undeniable,” she says. “The big change here has to do with sugar.” Duque says that the results should add fuel to efforts to educate pregnant people about the importance of good nutrition.
Gračner agrees that education is crucial but doesn’t want anxious parents to overreact to her findings. “Pregnant people already have so much to worry about,” she says. “If it’s just a little sugar here and there, everybody’s going to be fine.”
Each of us has a different metabolic response to eating the same bread
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Consider two slices of bread, one from an artisanal sourdough boule, the other from a cheap, mass-produced white loaf. Which do you think is healthier?
The correct answer is that you don’t know until you try. Some people will have an unhealthy reaction to the cheap stuff, with surging blood sugar levels. But others won’t, and instead have a sharp rise in blood sugar after the sourdough. Some will surge on both, others barely at all.
This article is part of a series on nutrition that delves into some of the hottest trends of the moment. Read more here.
The same is true for other foods and other nutrients, especially fats, which can also surge dangerously in the bloodstream after eating. How our metabolisms respond to food is highly idiosyncratic, a shock discovery that is upending decades of nutritional orthodoxy and promising to finally answer that surprisingly knotty question: what should we eat to stay healthy?
Increases in blood glucose and lipids are quite normal after eating, but if they go too high too quickly – called spiking – they can cause trouble. Frequent spikes in glucose and a type of fat called triglyceride are associated with the risk of developing diabetes, obesity and heart disease. For decades, nutrition researchers assumed that all humans responded to a given food in roughly the same way, with uniform increases in blood sugar and fats.
Glycaemic index
Under that assumption, dietary advice was simple and one-size-fits-all. Reduce consumption of the foods that cause spikes. Unsurprisingly, those were mostly…
Loading up your plate has never seemed more complicated. Alongside appeals to avoid ultra-processed foods and “bad” fats, we are being bombarded by a growing array of sometimes conflicting dietary advice. Not only is it confusing, but it is hard to tell what difference these choices will really make in the long term.
Social media is filled with people talking about the health benefits of what they eat, with diets that promise a better hormonal balance going viral, for example. While it should go without saying that any nutritional advice delivered on TikTok should be taken with a pinch of salt, it is easy to get swept up in the excitement and start to believe that there must be a dollop of truth to such claims.
Then there are fermented foods, which are often sold as a dietary panacea. Do we really need to load up on kimchi and kombucha to be truly healthy?
Even nutrition science can add to the confusion. The more we hear about the latest discoveries, the more it seems we can tweak our diet to focus on specific outcomes, whether that is lowering chronic inflammation, improving our health and weight by eating at specific times or choosing what to eat based on our personal response to foods.
Not only is it confusing, it is hard to tell what difference these choices really make
To help navigate this minefield, we have put together a delectable special issue of New Scientist on how to eat better, focusing on seven of the hottest nutritional trends of the moment.
This has revealed a few surprises. Recent research, for instance, shows that snacking – long demonised as generally a bad thing – can actually be positive for our health and waistlines.
Then there is the surprisingly wide-reaching health effects of something that we already knew was good for our gut: dietary fibre. Unlike many ingredients touted as superfoods, this one does really live up to its promise, yet most of us aren’t getting enough of it.
So turn to our special feature for our evidence-based guide to what should really be on your plate to boost your chances of a longer and healthier life.
New studies are showing ever more reasons to eat up your greens
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When it comes to our diet, there is an ever-changing list of things touted as the key to better health: cutting out carbs, eating like a caveman or dosing up on supposed superfoods such as turmeric. Most fail to live up to the hype – but there is one supernutrient that bucks this trend.
It is common knowledge that dietary fibre is good for you, but few of us appreciate just how far-reaching its health benefits go. Being in the know is worth your while, though, especially given that the diets common in high-income nations mean it is all too easy to miss out.
This article is part of a series on nutrition that delves into some of the hottest trends of the moment. Read more here.
Many of us will have experienced first hand the effects of dietary fibre on our body. Sometimes dubbed “nature’s laxative”, a lack of it can cause constipation. But there is much more to fibre than bowel movements. Diets high in this constituent are associated with reduced risks of many health conditions, including cancers and heart disease. This is because fibre isn’t just cardboardy filler, it is also food for the microorganisms in our gut. That means its effects can be felt throughout your body, as this microbiome influences the health of our immune system, brain and more, via the chemicals it produces.
“Fibre is the part of our diet that we cannot digest. Most comes from plant cell walls,” says Petra Louis at the University of Aberdeen…
Humans have been fermenting food and drink for at least 13,000 years – and touting the health benefits for nearly as long. But despite our long history with them, we are only beginning to determine whether these foods are actually beneficial for our health.
Unlike our ancestors, however, we now know how fermentation works: microbes such as certain yeasts and bacteria break down sugars in grains, fruit, vegetables and dairy products in a way that prevents them from spoiling and produces unique flavours. But what does this mean for our health?
This article is part of a series on nutrition that delves into some of the hottest trends of the moment. Read more here.
Numerous studies have linked fermented foods – particularly dairy versions – to a reduced risk of heart disease, type 2 diabetes and obesity. For instance, a 2023 study involving more than 46,000 adults living in the US found that eating fermented foods was associated with lower blood pressure, body mass index and waist circumference.
But much of the research lumps all kinds of fermented foods together, and given the health halo around these products, we know that people who consume them probably tend to look after their health in other ways too. Both of these factors make it difficult to determine what is actually providing any observed benefits.
Benefits of yoghurt
That said, the case is strongest for yogurt. Many large studies have linked its consumption to improvements in immunity, bone density and longevity and to a reduced risk of cardiovascular disease and high blood pressure. Yet determining cause and effect from these observational…
Spend more than 5 minutes on Instagram or TikTok – especially as a woman of a certain age – and you are likely to meet a fit, attractive person showing you what they ate today. It is usually a bowl of oats, flaxseeds and berries, or a plate of leafy greens with lean meats or other “quality proteins”, or a salad of raw carrots and little else, all enviably presented and accompanied by the claim that these foods balance excess oestrogen, lower the stress hormone cortisol, support adrenal function or even help you get rid of that “hormonal belly”.
So-called hormone-balancing diets aren’t exactly new: self-help books positing hormonal balance as the way to wellness began appearing in the early 2000s, marrying scientific-sounding claims with weight-loss plans. But what does “hormone imbalance” really mean?
This article is part of a series on nutrition that delves into some of the hottest trends of the moment. Read more here.
Not a lot, as it turns out. Hormones are the chemical messengers produced by endocrine glands located throughout the body, such as the thyroid, pituitary gland, ovaries and testes, that orchestrate many essential functions. “Hormones basically run the show, so to speak, in our bodies,” says Amelia Sherry, a registered dietician in New York. “Different hormones regulate everything, including sleep, hunger and fullness, growth, sexual development and desire, pregnancy, energy metabolism, blood sugar and more.”
So the concept of “balance” makes little sense in the perpetually changing endocrine system. ” ‘Hormonal imbalance’ is not a term endocrinologists… readily use because it suggests that something is wrong if hormones, when measured, are not always in the ‘normal range’,” says …
We are often told not to eat between meals, and there is a general perception that snacking is unhealthy. But, as usual when it comes to food, temptation prevails.
Snacking is very common, and increasingly so. In the early 1970s, for example, US adults consumed about 18 per cent of their total calories in snack form. By 2010, that had risen to 23 per cent. Similar numbers have been recorded in the UK, Brazil and Norway.
This article is part of a series on nutrition that delves into some of the hottest trends of the moment. Read more here.
Given how common snacking is, it would be nice to know whether the received wisdom is true. But research on the health effects of snacking has produced a dog’s dinner of results. Some studies have found that, as expected, snacking has negative health consequences. But others have found the opposite.
To get a clearer picture, earlier this year, Sarah Berry at King’s College London, who is also chief scientist at the Zoe nutrition app, and her colleagues, re-analysed data they had gathered as part of an experiment carried out in 2018 and 2019, in which around 850 participants recorded everything they ate and when they ate it across two to four days. They were also tested on a range of measures of cardiovascular health, such as levels of blood fats and glucose.
It is one of the scourges of life in the modern world: chronic inflammation. This unhelpful response by the body’s immune system is linked to accelerated ageing and conditions such as stroke and heart disease.
What if we could dampen it down by consuming certain foods, such as spinach, walnuts and salmon? That is the promise of anti-inflammatory diets, often advocated in vague terms by the media and nutrition industry. That might prompt eye-rolling from the scientifically minded. But recent research reveals that this approach isn’t as faddish as it sounds and paints a nuanced picture of the links between food, inflammation and our long-term health.
This article is part of a series on nutrition that delves into some of the hottest trends of the moment. Read more here.
Inflammation is a crucial part of our response to injury and disease. But when the body continues to deploy it even when there is no trauma, this results in chronic inflammation. Exactly why this occurs is unclear, but genetics, environment and lifestyle play roles. It can be detected by measuring certain chemical markers in the blood, and has been increasingly linked with poor health.
“Chronic inflammation is a driver of many common diseases, including cardiovascular disease, cancer, arthritis and dementia,” says John Mathers at Newcastle University in the UK. It has also been implicated in some mental health conditions.
