In a corner of Harpenden, a leafy commuter belt town a short train ride north of London, a storeroom houses the world’s longest-running agricultural experiment.
Here, kept in an eclectic collection of glass bottles, jam jars, and even biscuit tins, are thousands of dried wheat stalks, painstakingly collected and preserved annually for the past 183 years. The practice was instigated by a Victorian landowner, keen to monitor the effects of different fertilisers on his crops, and, nearly two centuries later, this remarkable archive has become a time capsule for scientists at Harpenden’s Rothamsted Research Institute. In particular, it’s helped shed new light on an alarming trend – the nutritional quality of many staple foods is on the decline.
I was visiting the institute while researching my new book, The Age Code, on the science linking what we eat to how well we age. It had been prompted by some rather startling findings showing that many of us are failing to get adequate amounts of numerous key micronutrients. These vitamins and minerals play an essential role in all kinds of bodily processes. Yet, the UK’s National Diet and Nutrition Survey – the primary data source on the nation’s dietary habits and nutritional status – shows the majority of us are getting insufficient amounts of the likes of vitamin A, iron, zinc, magnesium and more.
Why? One obvious explanation is simply that we’re eating less whole foods in favour of ultra-processed foods (UPFs), but that’s not the whole story.
Investigations around the world have revealed similar patterns: our produce is becoming less nutritious.
One major study of fruits and vegetables found that everything from protein to calcium, iron and vitamin C waned across many commonly consumed crops between the 1950s and the 1990s. In another study, Australian scientists found that the iron content of foods such as sweetcorn, cauliflower and green beans had declined by 30-50 per cent over an 80-year period.
One likely culprit is industrial fertilisers depleting minerals in the soil and modern farming practices, incentivised to prioritise yield and appearance above nutritional quality. But there’s another compelling, yet terrifying, explanation which is often ignored: climate change. Rising levels of atmospheric CO2 are causing micronutrients to disappear from our food.
This idea was first proposed back in 2002 by Irakli Loladze, now an associate professor at Bryan College of Health Sciences in Nebraska. Loladze noted that rising CO2 levels rev up plant photosynthesis. This makes fruits and vegetables grow faster, making farmers more productive – which seems like a good thing. The problem is that it also causes the production of more and more starch and when fruits and vegetables become starchier, they have less space for different micronutrients.
“I started to look at it more and more and I was horrified,” says Loladze. “I mapped out that as CO2 continues to rise, the entire balance of nutrients is going to shift. All these essential minerals important for health and ageing like magnesium and zinc, they will decrease.”
Loladze’s original predictions have since been replicated in experiments which took more than 130 different fruits and vegetables and grew them in conditions designed to artificially simulate the projected levels of atmospheric CO2 in 2050. The levels of micronutrients, ranging from B vitamins to minerals like calcium, potassium, iron, zinc and magnesium, all fell.
Dwindling micronutrient levels in our food could already be having a very real impact on our health. For example, according to analyses of data from the National Diet and Nutrition Survey, 90 per cent of adults are now failing to reach the recommended dietary allowance (RDA) for magnesium and over 80 per cent of adults do not meet the RDA for iron intake.
A similar proportion are not getting as much zinc and selenium as they need. According to Dr Lindsy Kass, nutrition and public health researcher at the University of Hertfordshire, it’s becoming more common for people to have so-called “subclinical deficiencies”, where a person is depleted in a particular micronutrient, but not quite to the extent where they are displaying overt clinical symptoms.
For many of us, this may be contributing in a more subtle way to many of the midlife ailments, which are often simply attributed to signs of ageing. Kass points out that insufficient amounts of iron, for example, can create an increased susceptibility to infections, while a lack of zinc can disrupt vital metabolic pathways and cause persistent fatigue.
“Magnesium is also involved in regulating sleep and the stress response, so a lack of it can disrupt sleep which can further contribute to fatigue,” says Kass.
Over time, getting insufficient amounts of vital micronutrients can also play a role in accelerating many aspects of ageing. According to Dr Avni Vyas, a senior lecturer in nutrition and dietetics at Manchester Metropolitan University, a lack of magnesium, calcium, vitamin D and phosphorus, for example, can drive the progression of the bone disease osteoporosis. “Any one of these deficiencies could be having a subclinical impact which may not become apparent until later life,” she says.
Various ideas are being explored for getting more micronutrients back into our food. Regenerative farming methods, which encourage less mechanical churning, fewer synthetic fertilisers, and greater use of practices like composting, have been shown to be effective ways of boosting the mineral content of the soil. Scientists are also researching how new technologies, such as gene editing, might be used to artificially boost certain micronutrients, such as vitamin D levels, in common foods like tomatoes and potatoes.
What can consumers do? While it may be tempting to stock up on supplements in the face of rising atmospheric CO2 levels, Kass says that such an approach should be taken with caution. “There can be a negative impact of people buying lots of singular vitamins and minerals without understanding the interaction that these micronutrients may have on each other,” she says. “For example, a high dose of iron may impact the absorption of calcium. I would always recommend taking a multivitamin and mineral supplement rather than single supplements.”
Experts feel that it’s best to focus on increasing the amounts of nutrient-dense whole foods you’re eating in your diet, particularly at the expense of ultra-processed foods (UPFs). So, rather than aiming for five a day, try and have seven or 10 a day, a target which can also be reached through adding things like beans, seeds or herbs to meals. Buying organic foods where possible is also a good option, as some studies have shown that, on average, organic fruits and vegetables contain significantly more vitamins and minerals because they haven’t been exposed to as many pesticides and potent synthetic fertilisers.
One problem with some UPFs is that, while they are often fortified with various micronutrients, different food processing steps – from heating to the addition of preservatives such as sulphites – can actively degrade certain vitamins. Instead of snacking on these foods, nuts, seeds and dried fruits are brimming with a whole array of micronutrients.
The people who are least affected by declining micronutrient levels in foods will be those who already consume a large variety of fruits and vegetables because they’re more likely to be accumulating all the vitamins and minerals they need from a variety of sources.
“We should encourage minimisation of processed foods, and encourage people to have a variety of foods, particularly fruits and vegetables,” says Vyas.
The Age Code: The New Science of Food and How It Can Save Us by David Cox is published by Fourth Estate