Food for thought
As thousands of people eliminate whole food groups from their diet to tackle dairy or gluten intolerance, scientists are trying to better understand what’s going on in their gut.
As thousands of people eliminate whole food groups from their diet to tackle dairy or gluten intolerance, scientists are trying to better understand what’s going on in their gut.
Weeks after an Auckland clinical trial found nursing student Diane Novio was probably neither lactose nor dairy intolerant, she decided to go vegan. It’s not that she doesn’t believe the test results, but she knows her stomach feels better, lighter and less bloated if she doesn’t have dairy foods. She well remembers the way her guts gurgled after she ordered a coffee with soy milk and got cows’ milk instead, and how gassy she felt after a cheese-topped pizza.
The science might say Novio, 23, doesn’t need to go dairy-free, but like many others, she’s going with her gut rather than the graphs.
Liggins Institute professor David Cameron-Smith, principal investigator on this year’s milk-gut comfort trial in which Novio was one of 40 young female participants, hopes the study will enable researchers to better understand the symptoms that are driving some people away from dairy. “There’s fire behind the smoke. Perceptions are real, so we have to not dismiss people outright but to understand it.”
Cameron-Smith, a professor of nutrition at the University of Auckland, says people who think they’re intolerant to one or more foods are likely to head down “a pathway of restrictive eating” unless they’re committed to focusing on the nutritional value of what they’re eating.
PREPARING FOR TSUNAMI
With food allergies and intolerance inexplicably on the rise, doctors are preparing for a tsunami of adult patients as an increase in paediatric cases flows through to adulthood. Dietitians and other nutrition experts say they’re seeing clients who are following ever-more-restrictive dietary regimes – often on the recommendation of friends or “Dr Google” – and putting their health at risk.
“What’s available to you if you walk down the dairy-free aisle or the glutenfree aisle of the supermarket may not be up to scratch simply because it makes statements about what it excludes,” says Cameron-Smith. “That doesn’t mean it’s healthier or better for you, and when you start eating a more restrictive diet, your intake of things like calcium and iron, in particular, really suffers.”
The Liggins study found that half the people who report having dairy intolerance can actually digest lactose and therefore don’t need to eliminate dairy foods that are much lower in lactose, such as cheese and yogurt. Lactose intolerance is a genetic condition that causes a lack of the enzyme lactase to break down lactose, a sugar found in dairy products.
Cameron-Smith says the study is trying to define the less-well-understood dairy intolerance, for which there is no objective test. Participants were divided into three groups – lactose intolerant, lactose and dairy tolerant, and dairy intolerant – and were challenged with drinks of lactose, lactose-free milk, ordinary milk and a2 milk before having blood, urine and breath tests and MRI scans to measure their reactions. The a2 results are not yet in.
The research found that for up to two hours after taking the lactose-free or ordinary milk, the group who were dairy intolerant reported more abdominal rumbling and bloating than the dairy- tolerant women, but they then improved. For the lactose-intolerant women, the symptoms became progressively worse over the three hours they were monitored.
Intriguingly, waist measurements of the women varied enormously after they drank the same amount of milk – some ballooned by 4-10cm within 30 minutes – but the increase did not correlate to their symptoms of gut discomfort.
In another unexpected result, Novio and a number of the other women had late-onset symptoms after the lactose challenge. Novio says she felt sick and suffered diarrhoea and a rumbling stomach about six hours after drinking it, but she was already home, so the symptoms couldn’t be monitored.
Waist measurements of the women varied enormously after they drank the same amount of milk – some ballooned by 4-10cm.
MIND A POWERFUL INFLUENCE
Cameron-Smith and Novio acknowledge that the mind can be a powerful influence on the body’s symptoms. “Maybe I’m
subconsciously thinking it will make me feel sick,” Novio admits, although she’s adamant her symptoms were real.
They are, says Cameron-Smith. “What you report is what you perceive and what you have.”
The main allergen in milk is a protein known as beta-lactoglobulin, and it’s normally a reaction to this that causes milk intolerance in children, although they usually grow out of it as they age. CameronSmith says it’s not known whether some kind of low-grade immunological response might explain the gut symptoms of Novio and others.
“Immune cell release and localised histamine release can trigger a whole range of responses, but little is known of what occurs in the gut.”
Study leader Amber Milan, a nutritional scientist, says the dairy-intolerant women had slightly different symptoms to the lactose-intolerant group and they came on earlier. “They experienced quite severe symptoms 30-60 minutes after drinking milk, whereas in the lactose-intolerant group, the symptoms typically happened two to three hours later.”
This makes sense, says Milan, because lactose is normally digested in the small intestine by the enzyme lactase. If lactase is lacking, the lactose keeps going through the digestive system to the large bowel, where it’s processed by gut bacteria, producing gas and causing bloating, flatulence and possibly diarrhoea.
“SHOT IN THE DARK”
Milan says the scientists are still evaluating the blood tests to determine whether the dairy-intolerant women have a common biomarker, and they are looking for markers of inflammation. But the work is very experimental. “The problem with biomarkers is we don’t know what we are looking for; we don’t know which ones are relevant, so it’s a shot in the dark.”
Another aim of the study is to discover objective measures of discomfort. Some tests, such as for breath hydrogen and galactose (which literally means milk sugar) in urine, already exist to measure how much lactose isn’t absorbed. The scientists are looking for what they call “breath volatiles”, hoping they can detect a chemical that matches discomfort scores for dairy
“We see more of the worried well excluding whole food groups from their diet in Australia and New Zealand.”
intolerance the same way breath hydrogen matches lactose intolerance.
About two-thirds of people internationally are estimated to have some degree of lactose intolerance, with a higher prevalence in East Asia, so teasing out the differences between lactose and dairy intolerance has important ramifications for our dairy industry. The research is a collaboration between the University of Auckland and AgResearch, with funding from the High Value Nutrition National Science Challenge, The a2 Milk Company and the university.
Auckland dietitian and food allergy specialist Anna Richards says people who have an adverse reaction to milk “don’t really understand what the mechanism is”
and assume they can’t have any dairy at all because they feel unwell after drinking a milkshake.
“For most of us who feel better not drinking a milkshake, the answer is just reduce your lactose and you’re fine, but the next thing you know, they say they have a milk allergy and they’re reading the back of every packet of crackers and avoiding anything that says ‘may contain traces of milk’. People are making their lives more complicated than they need to be.”
NOT THE SAME THING
Allergies and intolerance tend to be lumped into the same basket, but they’re not the same thing, she says. “Allergies are driven by the immune system, but there’s a whole range of other reasons why you may have an adverse food reaction that has absolutely nothing to do with your immune system.”
Richards’ 28-year-old daughter was recently diagnosed with coeliac disease – an auto-immune disorder that causes bowel damage in reaction to dietary gluten. As with dairy intolerance, there is no objective test for intolerance to gluten, but Richards regularly sees patients who unnecessarily eliminate gluten from their diet when they aren’t coeliac.
“It’s a bit like the milk thing – using a cricket bat when a fly swat would do. We see more of the worried well excluding whole food groups from their diet in Australia and New Zealand.”
For food providers such as restaurants and bakeries, that causes a blurring of the distinction between those with coeliac disease, who will become ill with any gluten at all, and those who might feel better if they ate a little less.
“One of the biggest issues for my daughter when she eats out is she gets asked, ‘How coeliac are you?’ Well, coeliac disease is like pregnancy, you either are or you aren’t.”
When she travelled in Europe, however, her daughter had no such problems. “There, they don’t have lifestylers excluding gluten. When she went to eat out in Italy, they knew what coeliac disease was and they knew she needed complete exclusion of gluten.”
There, she says, breads are still made out of what we’d call ancient grains and are typically sourdough risen over four to 24 hours.
“They buy bread three times a day, but that doesn’t fit our lifestyle. We want to buy a squishy loaf that’s going to be fresh for a week.”
Here, gluten is added to bread to keep it soft and moist for longer, and yeast helps it rise faster but gives the wheat, which contains the gluten, less time to break down.
“A significant number of patients of mine who say they don’t feel great on bread here then travel to Europe and can eat all the breads on offer.”
Tokoroa-based chef Jimmy Boswell, a “chef ambassador” for Coeliac NZ who says he’s been medically diagnosed as “non-coeliac gluten intolerant”, says restaurants usually fall into one of three groups: those that go “hard out” offering mainly gluten-free fare, those that try but can have cross-contamination issues, and those that don’t make a special effort.
It’s common for coeliacs or