Phenol Sensitivity


Phenols are chemicals found in basically all foods. The "phenol" category contains quite a few subgroups, both food and non-food. For example, salicylate is a subgroup of phenol. There are other chemicals found in foods that can cause similar symptoms as phenols, including amines, even though they are not technically "phenol".


Potentially over 80% of autistic children have a deficiency in a key detoxification pathway. The pathway involves using sulphur in the form of sulphate (known as sulphation). The enzyme involved is phenol sulphur-transferase (PST).


Phenol Sulphur-transferase Sulphate transport protein (Nas1)

Sulphur Sulphate Liver Detoxification (Sulphation)

This detoxification pathway processes other phenolic compounds including salicylates (salicylates are a subset of phenols), artificial food colourings, artificial flavourings, and some preservatives. Besides requiring PST, research has found the salicylates further suppress the activity of any PST enzyme present, making matters worse. Food dyes also have been shown to inhibit the PST enzyme.


Feeding large amounts of sulphur and phenolic-based foods to PST deficient children will cause a build up of phenols, amines, salicylates, and other toxic substances normally cleared by PST.


Symptoms Of Phenol Sulphur-Transferase Defect

If the sulphation pathway is not functioning well, a person may not be able to process out the phenolic compounds as fast as they consume them. There is a cumulative effect. When the phenols start backing up in the system, it can cause a myriad of negative reactions.


Symptoms of phenol intolerance include (not all of these need be present):

       night waking for several hours, night sweats, difficulty sleeping

       dark circles under eyes,

       irritability, hyperactivity, aggression

       red cheeks/face/ears,


       self-injurious behaviour, head banging

       inappropriate laughter


       eczema, and other skin conditions.


Not all foods with a high phenol level are also high in salicylates as not all phenols are salicylates.


It appears that this sub optimality of sulphur transferase activity is a function of low plasma sulphate levels rather than of deficits in the actual enzyme. Thus, any foodstuff that requires or uses up sulphate ions during its metabolism will make the situation worse. These foodstuffs include apple juice, citrus fruit juices, chocolate, and paracetamol (Tylenol).


This detoxification pathway processes other phenolic compounds including salicylates (salicylates are a subset of phenols), artificial food colourings, artificial flavourings, and some preservatives. Many colouring materials, whether of natural or synthetic origin, possess phenolic groupings.

This detoxification pathway also processes acetaminophen (paracetamol - Panadol, Tylenol).


Testing: A subjective test for PST efficiency is to observe a reaction to Tylenol or paracetamol either hyperactivity or lethargy. Therefore Panadol should be avoided for kids with a PST problem.


PST/sulphate deficiency also impairs the metabolism of classical neurotransmitters such as serotonin and dopamine; impaired breakdown and metabolism of the bile pigments bilirubin and biliverdin; and decreased secretion of pancreatic enzymes and of bile from the gall bladder and biliary tract into the intestines. This would result in low uptake of certain vitamins and other nutrients from the intestines; reduced activity of gastrin (and subsequent reduced secretion of stomach acid, mucus, and pepsin in the stomach), and, probably, reduced production of secretin further downstream.


Excess boron interferes with the metabolism (breakdown and excretion) of phenols. Ritalin, used in the treatment of ADHD, inhibits the metabolism of coumarins (phenols). Boron is found in apples, pears, grapes, nuts, leafy green vegetables, and legumes. Supplying these substances, especially apples, pears, and grapes, or their juices in large amounts to PST deficient children, will cause a build up of phenols, amines, salicylates, and other toxic substances normally cleared by PST.


The `bottleneck' can be cleared in one of two ways. One is reducing the amount of phenols and toxins entering the body. This is the basis of the Failsafe diet and the Feingold diet. These diets remove the hard-to-process artificial colourings, flavourings and preservatives.


The second method of enhancing the detoxification process is to supply more sulphate. This increases the amount of toxins processed out. Sulphate ions may not be absorbed well from the gut, so simply giving more sulphur directly by swallowing supplements may not produce satisfactory results. Therefore a way to get sulphate into the body is Epsom salt baths.

Many parents report that giving Epsom salt baths is beneficial to help their childs body process the phenols. Sulphate is thought to circulate in the body up to about nine hours.


Some parents have found supplementing with molybdenum has helped with phenols.

Generally more sulphur, magnesium, and molybdenum are helpful in processing phenols.


Vitamin B6 and/or P-5-P can aggravate the PST problem of some children, by making it difficult for the child to process phenols. B6 in the form of P5P (pyridoxal-5-phosphate) inhibits PST (phenol sulphur-transferase) activity. This could be why some children show adverse effects when supplements high in P5P are started. However the same study showed that increasing magnesium supplementation reverses this inhibition. ARI got Dr Rosemary Waring to do the research that showed that B6 can inhibit human sulfotransferases, but they are activated by magnesium so that if you have at least a 1:1 mix of B6:Mg there is no problem.  This is why, if you have a problem with B6, try to see if taking magnesium will help.


The main source of free sulphate in the body is the amino acid cysteine, which is obtained from the breakdown of protein. One of the sulphur containing amino-acids used for this purpose is taurine, which is reported to have an anti-opioid effect.


For limited periods, use of herbs that enhance liver enzyme action would seem beneficial to those with the PST/sulphoxidation problem.


Supplementation with digestive enzymes (pancreatic enzymes) seems particularly beneficial for those suffering the PST/sulphate problem.


Cranberry juice has been anecdotally reported to reduce or even eliminate these effects. Whether this due to the sulphur content of the juice or some other mechanism including placebo remains to be determined.