Tree Nuts/Tree Nuts and Pregnancy: Avoid or not???

Should a mother eat peanuts or tree nuts during pregnancy? Will the avoidance of these foods help decrease the occurrence of peanut sensitization and allergic disease in the child? These are questions that we have struggled with for ages.

This is an impossible question to answer definitively. How could you ever set-up an ‘experiment’ in which the only variable is the exposure to tree nuts and/or peanut. You could not use animal experiments and relate the results to the human experience. The only way we can begin to look at this is through the use of epidemiology, specifically the cohort study in which a large number of families and children are observed over a long period of time. The results of these observations provide an odds ratio for the occurrence of a difference. This would be the chances of something happening with the given behavior. It is not an absolute guarantee.

The pros/cons of peanuts and tree nuts (related to allergy to these foods);

                Cons

                                Life-long sensitivity

                                The risk of a life-threatening allergic reaction

                                Lack of established treatments other than avoidance

                                The need of specific avoidance behaviors

                Pros

                                For peanuts- cheap, accessible, tasty, source of nutrition

                                Nutritional benefits

                                                Rich in polyunsaturated fats

                                                Fiber

                                                Micronutrients

                                                Antioxidants

                                Preventing other allergic conditions (an interesting concept)?

That last entry was not an error- there is evidence that a mother who eats peanuts/tree nuts during pregnancy may decrease the risk of the child developing asthma and allergic rhinitis. The issue of maternal ingestion of peanuts/tree nuts and sensitization to these foods in the child does however remain ‘controversial’.  It leaves an interesting dilemma, eat to prevent allergic respiratory tract disease, but run the risk of reactivity to the food? A recent article on this topic caught my eye. I hoped it would have included something about sensitization in the children. The article was true to its purpose and that was to look at the risk of developing respiratory tract allergy. The title of the article was- Peanut and tree nut consumption during pregnancy and allergic disease in children—should mothers decrease their intake? Longitudinal evidence from the Danish National Birth Cohort.

Purpose– To look at maternal peanut/tree nut ingestion during pregnancy and the occurrence of allergic respiratory tract disease in children.

Methods– This was part of the Danish National Birth Cohort. Enrollment occurred between the years 1996 to 2002. About 60% of all Danish women who were eligible signed on. There were over 100,000 pregnancies.

                There were phone interviews and a Food Frequency Questionnaire that was administered at 25 weeks gestation. Questions about food were also asked at birth, 6 month, and 18 months. The last set of questions was asked when the child was 7 years old.

                After all the screens were performed, there were 45,010 participants eligible for the study.

Results

                Study Cohort

                                61% reported no peanut or tree nut ingestion during pregnancy

                                Consumption >1 time per week- Peanut 3%, Tree nuts 9%

                                Maternal asthma- 9%

                                Maternal allergy- 32%

                Odds ratio (OR) for childhood asthma at 18 months with >1 time/week peanut ingestion- 0.79

                OR for childhood asthma at 18 months of age with >1 time/week tree nut ingestion- 0.75

                OR  for asthma at age 7 with >1 time/week peanut ingestion – 0.66

                OR for asthma at age 7 with >1 time/week tree nut ingestion- 0.89

                No relationship with peanut ingestion and nasal allergy

                OR for allergic rhinitis with tree nut ingestion- 0.8

Conclusions

                The higher frequency of tree nuts and peanuts eaten during pregnancy was associated with a decreased chance that the child will have the diagnosis asthma at 18 months of age. 

                Trying to explain this observation

                                Tree nuts and peanuts are rich in nutrients such as; linolenic acid, linoleic acid, vitamin E, magnesium, selenium, zinc, folate, and other micronutrients. It is speculated that there may be an impact on the immune system with these nutrients.

                Study limitations- the observations were all self-report. There was no way to assess for processed nut products- the study could not look at peanut butter, peanut/tree nut residues in candy, desserts, and cereals.  There was no accounting for differences in the type of tree nut. There was not enough information on maternal ingestion of peanuts/tree nuts during lactation.

                The study did not find any suggestion that consuming tree nuts or peanuts during pregnancy increased the risk of asthma. In fact, increased consumption was associated with a lower risk of asthma.

Reviewers Comments

                I was surprised by the findings in this article. To understand what the odds ratios tell us it is important to note that the group that never ingested peanuts/tree nuts was assigned a value of 1.0. If the OR was higher than 1.0 it would indicate an increased risk. If the value is less than 1.0, it indicates less risk or a protective effect.

                The study was performed on a large number of children. So it does not suffer from being a small study. It was conducted in Denmark. One concern would be the homogeneity of the population. In the United States we are quick of mixture of nationalities. When a study is performed in a different population, the results may not always translate to what happens here. There may be other risk factors that couldbe unique to a country. One question would be what is the usual frequency of in the diet. How does it compare to what we eat in this country? Is high tree nut/tree nut consumption in Denmark similar to the eating habits of pregnant women here?

                I was also frustrated- I kept looking for the answer to the other question- how many of these children were sensitized to peanut/tree nuts?

                Of note are comments made in the discussion. ‘These results support the recent withdrawal of United Kingdom recommendations to avoid peanuts during pregnancy, as well as report from the American Academy of Pediatrics that did not find any benefit of maternal dietary restrictions during pregnancy.’ There are many changes happening regarding previous recommendations that have never proven to be true or have been associated with contrary expectation.

                Scientists are picking away at those behaviors and recommendations regarding food allergy. This question of avoidance during pregnancy is a common one. We do not know all the factors involved in the development and the prevention of allergy. It is important to note that this deals with the risk of developing a condition. Even when the risk is low, the condition may still occur. It a risk, not a guarantee.

FEL (10-10-12)

October 10, 2012 · fleickly · No Comments
Tags: , , , ,  · Posted in: Allergies, Allergy in Children, Developing Allergy, Food Allergies, Interesting articles, Peanut Allergy, Preventing Allergy