Fae had turned blue, her lips had blistered, her face was horribly swollen and she had stopped breathing. Her mother was screaming. And this was all happening at 30,000 feet up in the air. Fae was a happy four-year-old from Essex, who five minutes before had been playing with her sister. The family were returning to the UK on board a Ryanair flight from a sunny holiday in Tenerife. The little girl had a severe allergy problem, and the crew had reminded the passengers three times not to open any bags of nuts. One man, sitting four rows behind Fae and her family, took no notice of the warnings because he thought, like many of the others, that they were exaggerating the danger. Despite his neighbour trying to stop him, his apparently desperate need to tuck into his bag of mixed nuts to help him cope with the three-hour flight got the better of him.
A few minutes later, because of the powerful air-conditioning system that circulates food and dust particles in aeroplanes, some nut dust must have got into the air. Fae started scratching her cheeks, became red, then lost consciousness. Her mother rushed her to the front of the plane, away from the source of the nuts, but the damage was done. Fae’s Dad found the adrenalin pen they always carried, but in his stressed state and with his hands shaking he couldn’t get it to work. Their daughter was dying in front of them.
The cabin crew hadn’t been well-trained either, and were helpless until one of the passengers, an ambulance worker, dashed forward and gave the injection. Fae slowly came back to life, to the relief of the entire plane including the nut-loving man, who felt very guilty and was nearly beaten up by his fellow passengers. He was subsequently banned from flying with Ryanair for two years.1
Nuts were part of the diet of many of our ancestors, are a common ingredient in many contemporary cuisines and a key part of the healthy Mediterranean diet we discussed earlier. There are many types of edible nuts, which contain a mixture of mainly unsaturated fats, some protein and polyphenols. For the average European and American they provide about a fifth of the total antioxidant polyphenol content of the diet. Walnuts contain the most, with over 20 polyphenol chemicals.2 One 30 gram serving of walnuts is equivalent to the average amounts of polyphenols from the same amount of fruit and vegetables combined. For peanut-butter-loving Americans, peanuts supply two-thirds of their antioxidant intake, making up for the sugar and calories that usually go with it. Generally, when you roast nuts you get 15 per cent more antioxidant polyphenols, but this varies widely between different nuts. There is a current vogue for soaking your nuts (not that kind) before eating, so as to release nutrients and eliminate toxins. This is not harmful – it makes sense with some beans – but by now you should be wary of anyone telling you to eliminate imaginary toxins in real food. Your gut microbes are responsible for making the nutrients available even from the toughest nuts.
In the 1980s, because of their high cholesterol and fat content nuts were especially targeted as bad for us, and I too used to think they weren’t healthy. But increasingly, studies show that if not over-salted they can suppress appetite, and they’ve been shown in prospective studies to help reduce weight and improve blood lipid levels.3 An extra 30 grams of mixed nuts, eaten raw (and unsoaked) in the famous PREDIMED randomised diet study, produced significant advantages over the low-fat heart-disease diet and was nearly as good as the extra olive oil group.4
There are many other chemicals in nuts we know little about, such as cachexins which may help with losing weight. If you don’t cover these complex bundles of food in sugar or salt, nuts overall are good for us. So when did they become associated with DANGER, as blazoned on food labels and in restaurant menus, and become deadly weapons on aeroplanes? Have nuts changed, or have we?
Food allergies – a modern phenomenon?
The first ever medical mention of a food allergy (eggs and cow’s milk) occurred the same year that the Titanic sank, 1912.5 Your chances of getting an allergy were, however, much less than hitting an iceberg. A hundred years ago, if a patient presented to a physician with a food allergy his eyes would light up. He could write up the patient’s story in articles and regale his colleagues with its exotic rarity, write a popular book and become a travelling celebrity. By contrast, the first food allergy case to appear in a modern medical journal happened the same year that man landed on the moon, in 1969.6
Stories of children like Fae collapsing dramatically in mid-air are becoming increasingly common, as are the numbers of people who are severely allergic with potentially fatal anaphylactic reactions. Nut-free schools now exist in California where worried parents can send their children. If the trends were to continue, a bag of peanuts could be seen as a weapon of mass destruction, and special flights would be needed to transport allergic kids on holiday as it would be impossible to totally protect them against some tiny allergen in the air, or minute particles of food on seats or clothes. But is this yet another urban myth?
I asked several leading allergy consultants in top London hospitals about this amazing Ryanair case, which had been a major topic of conversation and prompted calls for the banning of in-flight peanuts. The results were unexpected. All said they would have happily eaten a bag of peanuts next to the young allergic girl. According to them a piece of nut would have to have flicked directly into her mouth for any reaction to occur. Most allergenic foods don’t transmit in the air or in dust, and this includes the main peanut allergen protein ARAh2. The only explanation the allergy specialists have is that Fae’s problems were set off by some other unrelated triggering allergen that found its way directly to her mouth.
These doctors, who perform hundreds of allergy tests monthly on high-risk kids, say this kind of severe reaction is very rare and never occurs with peanuts transmitted by air. One exception to this is fish allergy because it’s the fish odour that contains the allergenic protein. This illustrates the power of rare-disease pressure groups and of the media in transmitting myths that can be long-lasting and have important sociological effects. The next time on a plane you get asked not to eat nuts because of some child with an allergy and understandably anxious parents, how will you react?
Notwithstanding the considerable hype and scaremongering, food allergy is definitely on the increase. Food intolerance is also increasing, but this is very different and much harder to define. Allergy is an obvious and immediate reaction to food, producing swelling, redness, numbness and often loss of breathing or consciousness. You can’t have a slight allergy any more than you can have a slight case of cancer or death. Intolerance, however, is usually described as involving bloating, nausea, gut pain, diarrhoea or constipation after eating. We don’t know whether all these have really increased recently, or if it’s that they existed before but people didn’t previously report them as an illness. Many of my patients with rheumatoid arthritis believed that different foods had caused their disease or worsened their symptoms. I always told them that rather than spend their money on pseudo-scientific allergy tests on their hair samples and bio-rhythms, they should try an exclusion diet of mineral water and vegetables for two weeks to see if they improved. No one did. The real rate of food allergies being related to diseases like this is less than 1 per cent.
But allergies are a real enough modern disease and the list of possible triggers is endless. These can range from one of the commonest, allergy to nickel – which in our set of middle-aged female twins affects one in five – to rarer ones like allergy to shrimps (one in fifty), bananas or tomatoes, and to even rarer ones as when people are allergic to the coating of pills or to sunlight (one in a thousand). Rarer still are people allergic to water (the condition has a name, ‘aquagenic urticaria’); these individuals can be allergic to their own tears or their husbands’ kisses. It’s a very distressing condition, but a good way to get out of doing the dishes. Some strange combination allergies are also appearing nowadays: one girl has an allergic shock only if she eats apples that are contaminated with birch pollen.
Protecting your baby
Australia has one of the most allergic populations in the world, for reasons we don’t understand, but it’s unlikely to be due to pollution. One in fifty children there now suffers from peanut allergy (compared with one in eighty in the UK), and rates double every twenty years. The increase is most rapid in those under the age of five. The first five generations of Australians, who mostly came from Ireland and the British Isles, encountered many strange allergens when they arrived; but, seemingly, most had few problems until the last thirty years. Since my mother was raised there – and my brother and I went to school there for a few years in the 1960s – Australian life has changed dramatically.
This original Aussie outdoor, sporty, BBQ lifestyle, with its picnics, snakes, spiders, dirty feet and outside toilets (the ‘dunny’), is no more. Children now rarely play outdoors, most stay inside with PlayStations and computers in clean, air-conditioned, vacuumed homes and eat clean and increasingly processed foods. Australia also has one of the highest child obesity rates in the world and, contrary to its image, few kids play sports. Drinking beer and watching sports have, however, survived pretty well.
When do kids become allergic? The latest research shows that babies are sensitised to the specific proteins in food (allergens) not only when they encounter the food as an infant but really early in life – in the womb.7 The traditional medical advice for worried mothers was to avoid certain foods such as French cheese or salamis, and there is a current tendency to progressively restrict what pregnant mothers eat because of risks of rare infections or allergies. Often the advice given is defensive and not evidence-based – and just at the time when the mother needs a healthy and diverse diet and when her body usually tells her what it needs, anyway. Specifically, women are told to avoid eating peanuts in pregnancy and hope for the best. Recent studies have shown, however, that the opposite is true: that women snacking on peanuts during pregnancy are actually much less likely to give birth to nut-allergic kids than those who abstain.8
Having a diverse microbiome when you are a newborn infant appears to be essential in reducing the future risk of allergies.9 The source of this diversity comes from breast milk assisted by a healthy maternal diet, late weaning or a bit less household cleanliness. By contrast, it’s a microbiome reduced in richness and diversity that is usually associated with allergies.10 Allergies are more common in bottle-fed babies with weakened immune systems; the current theory, as already mentioned, is that a healthy and diverse microbiome keeps the gut immune system stimulated and in a constant state of readiness so that there will be no overreaction to strange proteins.11
Hygeine hysteria
The babies of mothers who run ultra-clean homes and have super-clean babies are most at risk of allergies. A study recently found that babies who had their rubber dummies sucked clean by a parent then popped back into their mouths had considerably fewer allergies than those with parents dutifully replacing hygienic sterile dummies.12 The old-fashioned practice of mothers pre-chewing their baby’s food, which is rare in the West nowadays, served both to break down tough starchy foods and meats and to transmit a wide range of helpful microbes via saliva. Licking babies is common in most mammals and in some human cultures, and of course kissing is pretty universal.
The Hygiene Hypothesis is an idea you may have heard of. It was developed by a colleague I trained with in epidemiology, David Strachan, whose interest was sparked when he was looking at the national data of children followed up from birth for asthma and eczema. He found a correlation between damp housing conditions and allergy in the UK.13 But the link was not what we might intuitively have expected: the damp, poor conditions and overcrowded families were actually protective, even after adjusting for other possible sources of bias. The results were backed up and replicated in many other populations. Thus was the hypothesis that excess hygiene could lead to modern allergic diseases born.
People brought up in less sanitary conditions and regularly exposed to animals and worm infestations never seemed to develop asthma or food allergies. This was believed at first to be purely to do with the immune system, which needed to be stimulated by infections early in life to fine-tune its defences. This was how we had evolved over millions of years. Suddenly, from the 1960s onwards children were being brought up in increasingly hygienic environments without exposure to worms and dirt and a variety of mild diseases that in earlier times had served to educate the immune system. Thus the richer a country became and the more they protected themselves against the natural world, the more allergies would ensue.
We have probably seen the worst of the asthma epidemic, which was at its height in the 1980s and 1990s, but as these levels are falling we are encountering a massive increase in severe food and skin allergies. Unlike asthma, they don’t seem to disappear in adulthood. One in twenty children is allergic to peanuts, milk and other foods; the rate has increased by around 3 per cent annually over the last twenty years. Gluten allergy, too, is seen more often than before. Skin-prick and patch testing offer one way of quantifying how common allergies really are, without depending on unreliable questions. In recent US surveys 54 per cent of children show evidence of a mild allergy to something. We tested our older UK adult twins from both rural and urban areas, and one in three had a positive skin-patch test suggesting a potential allergy.
However, some groups in the US are relatively well protected from the allergy epidemic. Researchers from Indiana who studied the local Amish found only 7 per cent of Amish children had positive results from skin-prick tests, which is six times fewer than genetically similar Swiss children.14 The Amish way of living hasn’t changed much since they left Berne in Switzerland in the seventeenth century. All kids are raised communally and taught to walk and milk cows in dusty barns full of hay, straw, animal hair and manure. The workers that do most of the farming possess the most diverse sets of gut microbes, with large amounts of some species like Prevotella which, as we have seen, are rare in the rest of America but common in Africa.15
The Hygiene Hypothesis has stood the test of time so far, but now has to be adapted to our new knowledge of the importance of microbes. We need to remember that our gut microbes play a key role in training our immune systems. They do this via communication with the Treg cells in the gut walls, which are the main communicators and thermostats between what we eat and how our immune systems react.16 High Treg levels are generally healthy as they suppress the immune system. It is no surprise, therefore, that kids born to mothers with food allergy already have low levels of Treg cells at birth, because of a combination of their parents’ genes and their restrictive diets.17
One reason the Amish have such low rates of allergy is that they drink plenty of raw unpasteurised microbial milk. Similar studies have been carried out on European families. If we could design an Amish-style diet or probiotics specifically for mothers and their babies that would maximise the Tregs’ chemical signals, we could start to reverse the food allergy epidemic.18 19 Most of us were brought up with the idea that hygiene is top priority for healthy babies. But should we still be trying to keep our babies clean? The protection the Amish get from their natural but dirty environment comes not just from the dust and hair from all the animals around them, but from the trillions of microbes that live off them. European kids brought up near farms have less asthma and fewer allergies.
Not all farms nowadays are the same. In the US, living near giant CAFO feeding stations can reduce food allergies but also increase asthma.20 One study that allowed babies to play outside and roll about in the mud and dirt for most of the day showed fewer allergies and immune problems in their subjects, and their guts contained more friendly lactobacilli than babies regularly washed and kept inside. I’m talking about baby piglets here, by the way. But in terms of microbes, genes and our health we are very close to pigs.21
Many anxious mothers of children with allergies are racked with guilt, trying to protect them from attacks from deadly allergens in dust and animal hair. They try very hard to keep their houses in a state more appropriate to a sterile laboratory. Others are so worried about tiny particles of nuts, gluten, wheat or eggs getting into their food that eating becomes as relaxing as taking part in a feast at the Borgias’. These fears are understandable, given that nut allergies can cause death. But studies show that keeping your house more like a farm and having pets and even pigs in the house can reduce, not increase, allergy rates. Some of the health advantages of keeping pets in terms of human longevity, allergy and even avoiding depression come from not only sharing their hairs and dirt, but more intimately from their diverse range of gut microbes.22 Embracing dirt and diversity as our friends, and abandoning the notion that our food intolerances are in fact major medical problems, is a tall order, but could be crucial for the next generation.