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We all love the convenience of eating bought bread, it’s especially handy for busy parents if it lasts in the bread bin for a few extra days before it starts to go stale and mouldy. However, one of the preservatives used in many mainstream supermarket bread brands is inflammatory, and is now thought to be affecting some babies’ brains during pregnancy, which may play a role in the development of autism and other neurodevelopmental presentations. This is a preservative called Calcium Propionate (E282).

What is the background? Emerging clinical studies suggest that out-of-sync gut bacteria known as gut dysbiosis may be one of the key factors that is driving the increased onset of neurodevelopmental differences including higher numbers of people with autism. It is now well established that there is a noticeable shift in the bacterial balance in the gut microbiome in autistic people compared with that of their neurotypical peers.

These include elevated levels of pro-inflammatory and neurotoxic bacteria such as Clostridia, Klebsiella, Citrobacter, Bacteriodetes, and Desulfovibrio found in abundance in the guts of those people with autism. It seems that the higher the levels of these lipopolysaccharide (LPS) bacteria, the higher the severity of the autism traits. These pro-inflammatory bacteria can also generate high levels of toxic metabolites in the brain via gut permeability, which can contribute to the development of neurological abnormalities.

Research on Clostridia

Most research in this area has been on the overgrowth of clostridia species in the gut which has been associated with common autistic traits such as:

  • Spinning
  • Repetitive behaviours
  • Hyperactivity
  • Pushing away

There are many reasons why an overabundance of these unwanted bacteria can affect a child’s development and can become dominant in the gut. It has been postulated that clostridia may become a leading gut bacterium for reasons which include:

  • Low levels of bifidobacterium strains in the gut (which should be the most dominant friendly gut bacteria from birth)
  • Long-term use of proton pump inhibitors such as omeprazole for excess stomach acid or reflux
  • Multiple courses of antibiotics which reduce friendly microbes, allowing inflammatory microbes to proliferate
  • Excess exposure to glyphosate pesticides on grain crops (clostridia and salmonella are resistant to glyphosate)
  • An excess of propionic short chain fatty acid in the gut due to dietary propionic acid

More on Propionic Acid

Gut bacteria are known to be active fermenters of dietary carbohydrates and fibres leading to production of energy metabolism by-products such as acetate, propionate, and butyrate short-chain fatty acids (SCFA’s). These SCFA’s are all important and essential to a healthy gut and brain however, getting the balance right between the SCFAs is essential for optimal neurodevelopment.

Butyrate SCFA’s should be in abundance in the gut; they are anti-inflammatory and build a healthy immune response to infection. Butyrate produced by bacteria in our guts and from our diet enters our bloodstream and crosses the blood-brain barrier, where it facilitates the production of Brain-Derived Neurotrophic Factor (BDNF). BDNF supports our ability to learn, remember and form a good short-term memory. It helps to feed the brain cells and it enhances our brain neuroplasticity. Loss of neuroplasticity can lead to mental decline as well as brain fog and general inflexibility of the mind. Dietary butyrate is found in grass-fed butter and ghee (clarified butter), in the zest of citrus fruits and fibrous grains and fruits, as well as alliums (onions, leeks and garlic).

Propionic acid, on the other hand, when it is found in excess, can negatively alter metabolic and immune pathways, gene expression, and synaptic plasticity (the ability of the brain to change and adapt to new information) consistent in autistic and other neurodevelopmental behaviours. It can also alter systemic mitochondrial function which is critical for cell health and function as well as energy production. This is known as propionic acidaemia, and excess propionate levels have been linked to:

  • developmental delay
  • motor and cognitive delays
  • poor social and communications skills
  • speech and language delay
  • brain fog
  • epileptic seizures

Propionate is the SCFA that is most abundantly produced by the gut micro-organisms such as clostridia which are often more prevalent in the bellies of people with autism. It has also found its way into the food chain and is used as an ingredient in some ultra-processed convenience foods. Calcium propionate (E282) is very popular with food manufacturers, and it is used in most branded sliced bread as a preservative due to its anti-fungal characteristics. It keeps the bread fresher for longer and increases shelf life.

A 2019 study found that excess propionic acid in the gut during pregnancy damages developing brain cells and may cause inflammation, which they said is associated with the development of autism. There are two main ways that propionic acid gets there; the mother may produce some of it naturally anyway during pregancy, and ultra-processed food is another significant source.

We don’t know yet if consuming foods containing propionic acid during childhood can affect the neurons of babies and children as directly as it can in the womb. However knowing that we need to keep the balance of propionic acid in the gut low overall, it may be prudent for you to avoid bread and other bakery products that contain added calcium propionate. This is especially so, if you are pregnant or have concerns about your child’s neurological development.

Calcium propionate may also appear on the food label as propionic acid, cultured wheat starch, cultured whey and E282 and these are clearly marked so you cannot miss them. Organic bread brands and most sourdough bread that I have seen do not contain calcium propionate.

You may also want to consider taking additional steps to reduce your own gut clostridia if pregnant, or your child’s levels via probiotic supplements as well as working on bolstering butyrate levels.

If you are curious to know whether high levels of propionate or clostridia are affecting you or your child, then markers in both urine and stool testing can check to see if this is likely. Excess propionic acid can be tested in the urine (marked as high Dihydroxyphenylpropionic Acid or DHPPA) via an organic acid test. Excess clostridia bacteria and/or high levels of propionate compared with butyrate in a SCFA found in a comprehensive stool analysis may also be indicators that this is an issue. Both organic acid and stool testing can be organised by a naturopath or nutritional therapist who understands the dynamics of the potential effects of excess propionate.

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