Common Restrictions
I have summarized the theories that commonly circulate on the internet.
In module #2 (Physiology Overview), we talked about food components. Each restriction is based on a food component. Some people are probably truly sensitive; however, the incidence is overblown. These food components are often labelled “bad,” and internet discussions create significant food fear. Here is a typical client conversation:
“I need a pasta topping. I can’t eat tomato sauce because tomatoes are high in histamine. Cream sauces are out because dairy damages the gut. I found a sauce based on spinach, but that’s high in oxalates.”
Pathology: The diamine oxidase (DAO) enzyme degrades dietary histamine in the small intestine. Reduced DAO activity may allow dietary histamine to be absorbed and increase blood histamine, potentially leading to various allergy-like symptoms.
Food-Symptom Interval: Clients report variable timing.
Diagnosis: Currently, no validated diagnostic laboratory tests are available in Canada or the US. The self-diagnosis is based on symptom improvement with restriction and the return of symptoms with reintroduction.
Treatment: A low histamine diet and/or diamine oxidase enzymes may reduce symptoms for some clients. However, several factors affect blood histamine levels, so diet changes rarely eliminate symptoms.
A few years ago, my focus shifted to helping clients rebuild food tolerance and expand their diet. Before that, I specialized in histamine intolerance and nutrition for mast cell disease.
Low salicylate diets have been recommended for hyperactivity, autism, hives, asthma, respiratory and digestive problems, etc.
What are salicylates?
Salicylate is a general term for several related compounds. The most well-known is acetylsalicylic acid (ASA) – the active ingredient in aspirin. ASA was initially isolated from willow bark. Food salicylates are mainly in the non-acetylated form, so they are a little different than ASA. They are considered nutraceuticals.
Can low-salicylate diets improve symptoms?
The concept of salicylate food sensitivity was popularized in the 1960s and 70s. The Feingold diet (reduced salicylates, food colours, certain additives, etc.) claimed to treat hyperactivity in children. In the 1980s, a research team at the Royal Prince Alfred Hospital (RPAH) in Australia studied a diet that eliminated the above compounds, plus amines and glutamate. The Feingold and RPAH diets still have followers but are not widely accepted in the medical community.
Research interest has shifted toward low salicylate diets for individuals sensitive to aspirin. A recent Canadian study demonstrated improved nasal symptoms in aspirin-exacerbated respiratory disease. The subjects followed a low salicylate diet compared with their usual diet for six weeks and then switched. A blinded physician evaluated their symptoms with objective measurements at the beginning of the study and the end of each diet. These results are exciting because it is the first scientific study evaluating a low salicylate diet. Some internet websites have used this study as proof that a low salicylate diet is effective, but it is essential to keep the following in mind:
Despite the drawbacks, these results are exciting and will hopefully encourage future research.
Salicylates in food
An exact list of high-salicylate foods is impossible due to the lack of research and tremendous variation. Many conflicting low-salicylate diet lists are available on the internet. It is impossible to say which one is “right.” The most recent information comes from the article: A systematic review of salicylates in foods: estimated daily intake of a Scottish population. There was only one sample for most foods. When more than one sample was analyzed, the results were variable. For example, five blueberry samples ranged from 0.33 – 27.80 mg/kg, and three chilli powder samples ranged from less than 0.2 – 1466 mg/kg. Salicylate content is affected by growing conditions (soil, temperature, etc.) and storage/processing. Therefore, salicylate food levels grown in one area, such as Australia (the location of most of the research), may differ from another.
Because of this variability, someone sensitive to salicylates will experience inconsistent food reactions.
There is moderate evidence that a low oxalate diet reduces the risk of calcium oxalate kidney stones, and this is a standard recommendation in conventional medicine.
An unvalidated theory that oxalate crystals deposit in tissues, causing various inflammatory conditions, has circulated on the internet for many years. Urogenital inflammation, particularly vulvodynia, has received the most attention. Other purported sequelae include fibromyalgia, rheumatoid arthritis, and various auto-immune diseases.
The book The Plant Paradox: The Hidden Dangers in “Healthy” Foods That Cause Disease and Weight Gain (2017) brought widespread attention to lectins.
Lectins are a group of proteins found primarily in plant foods, such as:
Some lectins, such as those in raw legumes, are toxic. However, boiling denatures the lectins, and we rarely eat raw legumes (note: sprouting does not destroy lectins, so raw, sprouted legumes may still be problematic).
When clients have asked about this theory, I have found it helpful to point out that vegetarian diets would be higher in lectins than the typical meat-based diet. If lectins were problematic, the rate of inflammatory conditions would increase after adopting a vegetarian diet. Since we have not seen this, it questions the lectin theory.
Once again, individual variation exists; some may be sensitive to lectins (or specific lectins). A few clients say they tolerate refined grains better than whole grains. One possibility is the lectin content in the germ.