Sue's Blog

Dementia - propionate preservatives: French study confirms the link


In 1984, the FDA (US food regulator) considered propionates generally regarded as safe because they occur naturally in the human body, so they were approved for use as preservatives.

In 2002-2019, propionate preservatives were linked to ADHD and ASD type symptoms (1,2,3). 

In 2021, researchers from the Department of Neurosurgery and Brain Repair at the University of South Florida reviewed the medical literature and concluded that excess levels of propionates from the diet “appear to be problematic” (4):

  • "most persons are exposed to dietary sources of propionate every day"
  • "excess levels of propionate may play a role in Alzheimer’s disease (AD)"

In 2022, the Three-City prospective study in France (5) followed over 6,000 seniors for 12 years. Looking for metabolic risk factors for vascular dementia, they examined seven possibilities and found only one increased the chances of cognitive decline:

  • "higher serum levels of propionic acid … were associated with increased odds of cognitive decline"

Where did the propionic acid come from? The researchers suggested a possible link:

  • "processed foods, in which propionic acid is a common preservative"

Dementia and Alzheimer’s

  • are NOT a normal part of aging
  • affect over 55 million people worldwide, and rising
  • are the leading cause of death of women in both the UK and Australia
  • will soon be the leading cause of death of all Australians
  • are increasingly at younger ages … eg early-onset Alzheimers increased by 200% in Americans aged 30-64 between 2013 and 2017 (6)
  • in 2023, a 19-year-old in Beijing became the youngest ever to be diagnosed with probable Alzheimer’s (7).

Autism and Alzheimer’s

According to researcher Dr B.Blair Braden middle-aged adults with autism are 2.6 times more likely to be diagnosed with Alzheimer's and other dementias than those without ASD (8).

ADHD and Alzheimer’s

A recent Brazilian study of over 200 seniors found genetic risk for ADHD appears to increase the risk of Alzheimer’s (9).

How to reduce the risk of dementia

The WHO (10) recommend 12 interventions including to eat a balanced diet, like the Mediterranean diet.

But according to a recent study from the prestigious Rice University Baker institute in the US (11), "Good Food is vital for brain health So we must change the food industry." 

YES!  So why not ban propionate preservatives?

Or at the very least, stop food manufacturers hiding propionate preservatives in unregulated amounts so we can choose to avoid them?


In the meantime, if we want to avoid dementia, we will just have to avoid ALL ultra-processed foods especially bread. The new Alzheimers drugs are very expensive, don’t seem to work, and can have extremely nasty side-effects including death (12).

If you eat ultra-processed food, you can be getting 2-3 times more propionate each day through diet than is naturally produced in your body (13).
Look out for propionate preservatives in a widening range of foods (14):

Oil emulsions
Fruit and vegetable spreads including jams, chutneys and related products
Flour products (including noodles and pasta)
Breads and bakery products
Processed meat, poultry and game products in whole cuts or pieces
Processed comminuted meat, poultry and game products, other than sausage and sausage meat containing raw, unprocessed meat
Solid formulated supplementary sports foods
Fruit and vegetable juices and fruit and vegetable juice products
Formulated Beverages containing fruit or vegetable products
Sauces and toppings (including mayonnaises and salad dressings)

And beware that propionates are increasingly hidden as INGREDIENTS such as cultured dextrose, cultured wheat flour,  cultured or fermented ANYTHING, or even starter culture (that can be propionate-rich)   

See our shopping list


1. Dengate S, Ruben A. Controlled trial of cumulative behavioural effects of a common bread preservative. J Paediatr Child Health. 2002 Aug;38(4):373-6. doi: 10.1046/j.1440-1754.2002.00009.x. PMID: 12173999. QUOTE Irritability, restlessness, inattention and sleep disturbance in some children may be caused by a preservative in healthy foods consumed daily.

2. Macfabe D. Autism: metabolism, mitochondria, and the microbiome. Glob Adv Health Med. 2013 Nov;2(6):52-66. doi: 10.7453/gahmj.2013.089. PMID: 24416709; PMCID: PMC3865378. Propionic acid has bioactive effects on (1) neurotransmitter systems, (2) intracellular acidification and calcium release, (3) fatty acid metabolism, (4) gap junction gating, (5) immune function, and (6) alteration of gene expression that warrant further exploration…. Human populations that are partial metabolizers of propionic acid are more common than previously thought.

3. Abdelli LS, Samsam A, Naser SA. Propionic Acid Induces Gliosis and Neuro-inflammation through Modulation of PTEN/AKT Pathway in Autism Spectrum Disorder. Sci Rep. 2019 Jun 19;9(1):8824. doi: 10.1038/s41598-019-45348-z. PMID: 31217543; PMCID: PMC6584527. Clearly, the data supports a significant role for PPA (propionic acid)  …leading to gliosis, disturbed neuro-circuitry, and inflammatory response as seen in ASD. 

4. Killingsworth J, Sawmiller D, Shytle RD. Propionate and Alzheimer's Disease. Front Aging Neurosci. 2021 Jan 11;12:580001. doi: 10.3389/fnagi.2020.580001. PMID: 33505301; PMCID: PMC7831739.

5. Neuffer J, González-Domínguez R, Lefèvre-Arbogast S, Low DY, Driollet B, Helmer C, Du Preez A, de Lucia C, Ruigrok SR, Altendorfer B, Aigner L, Lucassen PJ, Korosi A, Thuret S, Manach C, Pallàs M, Urpi-Sardà M, Sánchez-Pla A, Andres-Lacueva C, Samieri C. Exploration of the Gut-Brain Axis through Metabolomics Identifies Serum Propionic Acid Associated with Higher Cognitive Decline in Older Persons. Nutrients. 2022 Nov 5;14(21):4688. doi: 10.3390/nu14214688. PMID: 36364950; PMCID: PMC9655149

6. Blue Cross Blue Shield, Early-Onset Dementia and Alzheimer's Rates Grow for Younger American Adults, Published February 27, 2020

7. Jia J, Zhang Y, Shi Y, Yin X, Wang S, Li Y, Zhao T, Liu W, Zhou A, Jia L. A 19-Year-Old Adolescent with Probable Alzheimer's Disease. J Alzheimers Dis. 2023;91(3):915-922. doi: 10.3233/JAD-221065. and A 19-Year-Old Is Youngest Ever to Be Diagnosed with Alzheimer's,, 14th February 2014,

8. Autism and dementia

Quote is from Dr B. Blair Braden, PhD, Associate Professor of Speech and Hearing Sciences, and the Autism and Brain Aging Laboratory Director at Arizona State University's College of Health Solutions.
Pagni BA, Walsh MJM, Ofori E, Chen K, Sullivan G, Alvar J, Monahan L, Guerithault N, Delaney S, Braden BB. Effects of age on the hippocampus and verbal memory in adults with autism spectrum disorder: Longitudinal versus cross-sectional findings. Autism Res. 2022 Oct;15(10):1810-1823. doi: 10.1002/aur.2797. Epub 2022 Aug 24. PMID: 36053945; PMCID: PMC9561078.

9. ADHD and dementia

Leffa DT, Ferrari-Souza JP, Bellaver B, Tissot C, Ferreira PCL, Brum WS, Caye A, Lord J, Proitsi P, Martins-Silva T, Tovo-Rodrigues L, Tudorascu DL, Villemagne VL, Cohen AD, Lopez OL, Klunk WE, Karikari TK, Rosa-Neto P, Zimmer ER, Molina BSG, Rohde LA, Pascoal TA; Alzheimer’s Disease Neuroimaging Initiative. Genetic risk for attention-deficit/hyperactivity disorder predicts cognitive decline and development of Alzheimer's disease pathophysiology in cognitively unimpaired older adults. Mol Psychiatry. 2023 Mar;28(3):1248-1255. doi: 10.1038/s41380-022-01867-2. Epub 2022 Dec 8. PMID: 36476732.

10. The World Health Organisation 12 recommendations for reducing risk for cognitive decline, as above,

11. Eyre, H. A., Berk, R. A., Dunlop, S., et al. (2023). Good Food is Vital for Brain Health So We Must Change the Food Industry. Baker Institute. doi:10.25613/1XYC-TM97.

12. “YIKES! FDA Approves Lecanemab Against Alzheimer’s . The FDA granted "TRADITIONAL" approval to lecanemab for Alzheimer's. What's the back story? Reports of brain shrinkage are worrisome to us.” By pharmacologist Joe Gradeon July 11, 2023.

13. Morrison D. J., Preston T. (2016). Formation of short chain fatty acids by the gut microbiota and their impact on human metabolism. Gut Microbes 7, 189–200. 10.1080/19490976.2015.1134082. It is estimated that in a human being who weighs 85 kg, the gut microbiota produce approximately 29.5 mg/kg of propionate each day via fermentation. Therefore about 2.5g are produced in a body of this size. Daily consumption references in this blog.

14. Where to find propionate preservatives: Australia New Zealand Food Standards Code – Schedule 15 – Substances that may be used as food additives, amendments up to June 2021

See more in our blog Harm from bread preservative confirmed

See also earlier factsheet Dementia and food additives – and other food intolerance symptoms in seniors