There are six names used for sulfites: sulfur dioxide, sodium sulfite, sodium bisulfite, potassium bisulfite, sodium metabisulfite, and potassium metabisulfite.
Stewart's mother thought Stewart had grown out of his childhood asthma, so she was unhappy when he developed 'exercise asthma' while playing soccer. She didn't know that asthma can be associated with sulphur dioxide and other sulphite preservatives (220-228) used in a wide range of common foods, including dried fruit. The soccer coach had advised his team to eat lots of muesli bars, and Stewart thought that was a great idea so his mother was buying two dozen at a time. When she realized that muesli bars are full of dried fruit including sulphur dioxide, she decided to make her own home-baked Anzac cookies instead - without the dried coconut, that is. Desiccated coconut contains sulphur dioxide too.
According to most asthma experts, food additives rarely trigger of asthma. In the course of their treatment, asthmatics may be asked if they have noticed any foods which affect their asthma. If so, they may be invited to undergo food additive challenge testing. Otherwise, it is assumed that their asthma is not related to foods.
However, when families try the failsafe diet for their child's behavior problems, I have noticed that any asthmatics in the family are likely to improve. This is despite comments from the parent such as 'his asthma isn't related to foods. He only gets it after he has a cold'.
Why don't asthmatics notice the connection between their asthma and foods?
When hundreds of asthmatics were tested for the effects of food chemicals at Duke University Medical Centre, researchers found that the majority had not seen a connection. 'Exposure to [food additives] is sufficiently frequent to mask any relationship between ingestion and symptoms in susceptible people,' the researchers concluded.
Sulphites (preservatives 220-228) are widely acknowledged as the food additives most likely to affect asthmatics. The Duke University researchers identified two groups of sulphite-sensitive asthmatics:
- A small group of very sulphite-sensitive asthmatics. These people see a connection between foods and their asthma because they react quickly, often within 15 minutes of ingesting sulphites. This group will choose to avoid sulphite-containing foods, drinks and medications.
- The second - and much larger - group of asthmatics are less sensitive to sulphites. They will not have an obvious reaction to a single exposure. In this group, repeated exposure to sulphites may cause subclinical inflammation of the lungs. This group may develop chronically inflamed lungs over the long term and could be at greater risk of lung function impairment because they are unaware of the effects of sulphites and therefore do not choose to avoid them.
When asthmatics with inflamed lungs are exposed to an environmental trigger such as a virus or exercise, the result may be asthma for which the trigger will be blamed. However, if these patients avoid sulphite preservatives, they can avoid lung inflammation. Exposure to their former triggers will not result in asthma.
How many asthmatics are affected by sulphites?
The US Food and Drug Administration estimates that about 5 per cent of asthmatics are sensitive to sulphites. These figures probably represent the group of very sulphite sensitive asthmatics identified in the Duke University research, above.
Standard challenge testing is likely to miss the much larger second group of sulphite responders, as demonstrated in a sophisticated study at Sydney's Royal Prince Alfred Hospital. The study compared standard challenge testing with testing using a comprehensive elimination diet. Using the standard method (no elimination diet), only 20 per cent of asthmatic patients were identified as sulphite-sensitive, but using the elimination diet, over 70 per cent of the same patients were found to react to the sulphite challenge.
More recently, researchers have realized that children are not 'little adults' but are more vulnerable than adults to chemicals and food additives because they eat, drink and breathe more - two to seven times as much as adults - as a result of their faster metabolism. In 1999, the Joint FAO/WHO Expert Committee on Food Additives revised their estimate of how many asthmatic children may be sulphite sensitive from 5% to 20-30%, but even this estimate is probably too low. A study published in Pediatrics in 1984 used a comprehensive elimination diet with children who were selected for the severity of their asthma. More than 65 per cent of the children were found to react to sulphites.
Should asthmatics avoid sulphites?
Avoiding all sulphites in foods and medications is not easy. For young children, cordial, sausages, instant mashed potato and dried fruit including fruit bars and muesli bars are common - but not the only - sources of sulphites. Although the use of sulphites in minced meat is illegal in Australia, a small Food Intolerance Network survey of butchers in the Northern Territory found three butchers out of four admitted to using preservatives in their mince. Duke University researchers complained about the abundance of small amounts of unlabelled sulphites in US foods. The situation is similar in Australia.
Takeaway foods do not have to be labeled. Small amounts of sulphites do not have to be labeled. Corn flour labeled '100% pure' may contain enough unlabeled sulphite residues from processing to affect sensitive asthmatics. It is possible to avoid all sulphites, but you really have to know what you are doing. Several groups of experts have recommended that sulphite preservatives in foods and drugs should be banned.
Asthmatics may be affected by other food chemicals. Avoiding sulphites will be useless if another frequently consumed food additive is causing the problem. A case history reported in a French medical journal describes a child diagnosed with asthma around her first birthday and treated with continuous medication for almost six years. At that time her condition worsened, requiring hospitalization about once a month. Challenges showed that the girl was sensitive to benzoate preservatives (211) in her asthma medication. After 12 months of avoiding benzoates in foods, drinks and medications, she remained asthma free.
Other food chemicals
As well as sulphites and benzoates, food additives which have been associated with asthma include artificial colors, nitrates (249-252), antioxidants BHA (320) and BHT (321), and MSG (621). For some asthmatics, naturally occurring salicylates in some fruits and vegetables, and salicylates in medications such as aspirin, can also be a problem.
Some asthmatics only need to make minor modifications to their diet. Stewart, above, just needed to cut down on the dried fruit. For some adults, switching from sweet white wine which is high in sulphites to red wine which is lower in sulphites can make a difference. One woman noticed that her diagnosis of adult-onset asthma coincided with a switch to diet cola.
After three months, she needed daily asthma preventers and relievers. The diet cola was preserved with benzoates, the regular cola was not. When she reverted to regular cola, her asthma disappeared. But for many asthmatics it will be more complicated than that.
Most asthmatics will react to only one or two food chemicals, but which ones?
If cutting down on sulphites isn't enough, the best way to find out exactly which food chemicals are associated with your asthma is to do a trial of the Royal Prince Alfred Hospital elimination (failsafe) diet with challenges, supervised by an experienced dietitian. Asthmatics should consult their doctor about any reduction in the use of their asthma medication, and also about the suitability of carrying out food challenges at home.
For motivated adults, the elimination diet is considered easy. It is also an excellent way to learn about which additives are in our foods. For difficult children, the elimination diet requires more effort. Parents report that they need support, recipes and access to safe foods. The Food Intolerance Network provides a support website, email support groups and local support groups who can advise on suitable foods such as preservative-free low salicylate sausages.
"Fed Up with Asthma" by Sue Dengate, published by Random House, 2003.
Asthma NT, phone 08 8922 8817 or your local asthma foundation.
Sulphites (aka sulfites)
· Drinks like wine, especially sweet white wine, champagne, alcoholic cider, beer
· Fruit-flavoured products like cordials, toppings, essences, soft drinks and fruit juice
· Dried fruits e.g. apples, apricots, pears, peaches, mixed dried fruit except sultanas and prunes, desiccated coconut
· Muesli and fruit bars with dried fruit, dried fruit leather
· Fresh salads and fruit salad
· Vegetables, pickles, pickled onions, dried vegetables e.g. peas, mashed potatoes, pre-cut potatoes, potato chips, crisps
· Meat/fish, sausages and sausage mince, Frankfurters, luncheon meat (Devon, chicken loaf)
· Prawns, fish (illegal but it happens), mince (ditto)
· Some breads and flour products (e.g. pastry) use 223 (sodium metabisulphite) as flour treatment agents
· Gelatin, glucose syrup, vinegar
· Drugs, eg Phenergan contains 220 and 223
Kay's Note: There are no sulfites in The SCD foods.