From the Winter 2004 issue of Allergy Today. For more articles like this, subscribe to Allergy Today, click here.

Naming the diet of a Hollywood star is pretty easy these days. Jennifer Aniston shed kilos while on the Zone diet. Gwyneth Paltrow attributed her svelte figure to the macrobiotic diet. And Madonna switched to a macrobiotic diet after giving birth to daughter Lourdes and achieved what is considered the fastest ever post-pregnancy weight loss. But who in Hollywood has raved about low-allergen diets? No one so far but as the rate of allergic disease climbs, it’s a diet more pregnant women are considering. Shelley Ashdown investigates whether it works.

Eating carefully for two

So the question for soon-to-be mums is this: do low-allergen diets reduce the risk of baby developing food allergies? “The results to date don’t show strong evidence of any benefit,” says Dr Jan Sinclair, a paediatric allergist and immunologist at Starship Hospital in Auckland.

As it stands, studies into whether low-allergen diets during pregnancy reduce the risk of baby developing allergic disease have mixed results. “It’s a controversial area and recommendations vary because they [studies] are not based on solid evidence,” says Dr Rohan Ameratunga, an allergist and immunologist in Auckland.

A case in point is a recent study that was presented at the American Academy of Allergy, Asthma and Immunology’s annual meeting in March, where researchers found a low-allergen diet during pregnancy and breastfeeding made no significant difference in warding off food allergy in children. But because the data set was relatively small, no firm conclusions could be drawn from the study, the researchers said.

Be cautious

And this, dietitians and allergists say, is a big reason for pregnant woman to be cautious. The evidence so far hailing low-allergen diets just doesn’t stack up. Cutting out major food groups is not worth the risk of achieving something that, quite frankly at this stage, has not been proven, says Dr Ameratunga.

This, of course, has not stopped and will not stop pregnant woman all over the world following low-allergen diets. But if a low-allergen diet is being considered, then it’s strongly advised to consult with a dietitian and an allergist to ensure the diet is balanced. This is because high-allergen foods fall into some of the vital food groups, says Dr Sinclair.

“The most common food allergens are milk, egg, peanut, wheat and soy, so if you cut all of those foods then you can end up with limited calories,” she says.

There is, however, one food experts say can be avoided while pregnant without jeopardising the diet — all types of nut and peanut. “Nuts are a high-allergen food and are easy to avoid. Nobody’s going to fall to pieces if they don’t have nuts,” says dietitian Anna Richards.

Dr Ameratunga also recommends avoiding fish and shellfish, but not to restrict dairy or eggs. For Dr Sinclair, who agrees with avoiding obvious peanut/nuts, her advice for pregnant women contemplating the more extreme low-allergen diets is clear: the beneficial effects of these diets are not strong.

Well-balanced diet a must

If there is one stage in a woman’s life where a balanced and nutritious diet is paramount, it is during pregnancy. In short, women need to eat well. Plenty of fresh fruit, vegetables, breads, cereals, meat, chicken and dairy should be on the menu. But when women start on extreme low-allergen diets without first seeking professional advice, the diet can become very restrictive.

This is the biggest worry for dietitians like Richards. “Some women cut out a vast number of foods in an effort to avoid the risk of food allergy, but instead end up with low-birth weight babies. And the problems associated with a low-birth weight baby outstrip any benefits of protection from allergy,” Richards says.

While pregnant with her second child, Sandra Sheard went on a low-allergen diet that, she freely admits, she did completely wrong.

“I didn’t consult a dietitian and all I ate while pregnant with Georgia and for the 14 months I breastfed her was meat, fruit and vegetables,” Sandra says.

Her oldest child, nine-year-old Alastair, is anaphylactic to peanut, egg, fish and dairy, and he also has asthma and eczema. Looking back, Sandra says she felt Alastair’s allergies might have stemmed from her eating a lot of dairy and peanut while she was pregnant with him. When she was breastfeeding Alastair, a Plunket nurse urged Sandra to keeping eating dairy and peanuts because, the nurse said, these foods were good for milk production.

Since being involved with Allergy New Zealand Sandra now knows her low-allergen diet was unbalanced, and she was recently diagnosed with the condition osteopenia, the stage before osteoporosis. “I’m not sure if it’s directly linked to the low-allergen diet because osteoporosis runs in my family,” she says.

Sandra now tells women who are considering a low-allergen diet to consult a dietitian and allergist beforehand.

If the first child has multiple allergies, then a low-allergen diet may be followed for the last four weeks of pregnancy and the first six months of breastfeeding, says Richards.

This is exactly what Kate Misa did after she fell pregnant with her second child. At eight weeks old, her first daughter three-year-old Estella started showing signs of eczema. Allergy tests revealed Estella was allergic to peanut, dairy, egg and soy. She has since grown out of her egg allergy and should grow out of her peanut allergy.

Wanting to avoid the same situation for her second child, Kate did a lot of reading and sought advice about low-allergen diets. She cut out peanut while pregnant and also avoided dairy, egg and fish while breastfeeding. At six months, her second daughter Sofia was tested for food allergies and showed only a slight reaction to wheat. Kate says she feels the low-allergen diet did make a difference and she would do it again.

Genetics more than diet

But genetics rather than low-allergen diets may have a stronger influence in determining allergic disease. If one parent has an allergy then there’s a 20-30 per cent chance the child will have an allergy. If both parents have allergies then this figure rises to 50-60 per cent. Add in an older sibling with allergies and this figure jumps to 80 per cent. But this doesn’t mean a child will inherit the same allergies as his or her parents. The complex mix of parents’ genes means a child will have a tendency or genetic predisposition to develop allergic disease.

“Say you have child who’s allergic to milk and peanut, so you cut them out of the diet. But the next baby may have a wheat allergy. Or the next child could be completely allergy free,” says Dr Sinclair.

For five-year-old Georgia, Sandra’s second child, this so far appears to be the case. “She may have never had allergies, anyway, and taken after my side where we have no family history of allergies,” says Sandra.

With New Zealand having one of the highest rates of allergic disease in the world, research into allergies is ongoing. One study looking at the effectiveness of “probiotics” was recently started by the medical schools in Auckland and Wellington.

Five hundred pregnant women are being recruited to feed a mix of special bacteria to their child everyday from the day they are born until they turn two. Probiotics are lactose-fermenting bacteria that occur naturally in the gastro-intestinal tract. Associate Professor Peter Black from the University of Auckland says modern diets and antibiotics have completely changed the mix of bacteria in the guts of people over the last 30-40 years. In essence, changes in the bowel flora in infancy may influence the development of allergic disease.

In the case of mothers who have allergies themselves, avoidance of anaphylaxis is critical. There is a significant risk to the baby if the mother suffers anaphylaxis while pregnant. There are case reports of severe foetal damage caused by anaphylaxis during pregnancy.

Breastfeeding and low allergen diets

“Breast is best” is one recommendation medical experts unequivocally agree on. In April, UNICEF and the World Health Organisation (WHO) launched a global campaign to encourage more mothers to breastfeed. According to their figures, 39 per cent of women breastfeed exclusively for the first six months, and it’s hoped the campaign will double this figure in 10 years.

Over the past two decades researchers have analysed the complex constitution of breast milk. And scientists say it is the perfect food for infants. Breast milk has water, protein, carbohydrates, fats, vitamins and minerals in just the right amounts for baby. It has been well documented that breast milk protects baby from infectious and chronic diseases and may provide some protection against allergies, asthma and eczema. So should a nursing mum follow a low-allergen diet?

Again, the lack of well-designed studies means experts disagree on whether low-allergen diets while breastfeeding make a difference in warding off allergic disease in children.

“The American Academy of Paediatrics has got a very strong position on the maternal avoidance of allergens during breastfeeding as a preventative measure, but it is not based on good studies,” says Dr Sinclair. Some studies have found the maternal avoidance of highly allergenic foods, such as milk, egg, peanut and fish, may have a small but beneficial effect on reducing food allergy and eczema in at-risk infants. But this may delay the onset of allergy rather than prevent it, and the effects on other allergic diseases later in life were not significant.

Richards says a low-allergen diet poses no real danger to baby because baby will get all the nourishment it needs from mum. Research has found even when a mother's own supply of nutrients and energy is limited, she will still produce breast milk of sufficient quantity and quality to support the growth and health of her infant.

Baby may be happy, but a low-allergen diet may not be providing mum with the nourishment she needs.

“If mum avoids vast food groups then you get a mum that’s poorly nourished, not gaining weight and lacking energy to breastfeed,” Richards says. Despite small amounts of food allergens passing into breast milk, medical experts say all babies should be breast fed for at least six months, even those at- risk of developing food allergy.

Starting baby on solids

It’s thought if an infant is exposed to allergens during a certain period they maybe more likely to develop allergic disease. And this is thought to be early on in life, which is why it’s suggested that solids aren’t introduced until baby is six months old. This is because of the anatomical structure of an infant’s gut.

A very young gut is very porous, says Dr Ameratunga, to allow mother’s antibodies and lymphocytes (immune cells) in breast milk to be easily absorbed. But it also means allergens can easily pass through the gut wall, which could lead to sensitisation in a baby at risk of developing an allergy. As baby gets older the gut becomes less porous and allergens are less likely to pass through the wall. When it’s time to start solids, it’s best to start with the least allergenic foods like baby rice, pureed pears and bananas and yellow vegetables.

Dr Sinclair says delaying the introduction of highly allergenic foods, such as milk until one year, egg until two years, peanut, tree nuts and fish until three years, may reduce the chance of allergy to these foods. If a child does have a definite diagnosis of a food allergy, then it’s vital to avoid the food allergen, says Dr Sinclair.

By giving a little bit of food in small amounts, hoping to build up tolerance, doesn’t work, she says. “If a person has a true food allergy, multiple exposures will not make their allergies go away. There’s also the risk of causing a significant allergic reaction.”
Avoiding aero-allergens during pregnancy

Something that’s difficult to avoid is aeroallergens, in particular ones that embed themselves in household objects like pillows, beds and carpets. Indoor aeroallergens such as house dust mites, pet dander and moulds have the notorious reputation of triggering asthma and hay fever. At the moment the best way to reduce the amount of these common indoor aeroallergens involves impervious covers and good old-fashioned cleaning.

The question of whether being exposed to aeroallergens while pregnant or breastfeeding has any affect on baby is still being debated in medical circles. Dr Ameratunga points out that studies into the effectiveness of dust mite covers have been mixed, but anecdotally people say they work.

A more pressing issue for pregnant women is asthma. According to the American Academy of Allergy, Asthma and Immunology, a severe asthma attack can threaten the growth and survival of an unborn baby. Because the foetus is dependant on its mother’s oxygen, decreased levels of oxygen in the mother’s blood, brought on by an asthma attack, can reduce the amount of oxygen getting to the foetus.

Pinpointing the exact causes behind the global surge in allergic disease and finding ways to prevent infants and children falling victim to this epidemic continues to challenge experts. “Genetics is the most powerful factor along with other things that I don’t think we completely understand,” concludes Dr Sinclair.

Medical reviewers: Dr Jan Sinclair and Dr Rohan Ameratunga