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Why should you avoid cheap supermarket bread

Why should you avoid cheap supermarket bread and switch to sourdough — or even better, make your own using organic flour? 

Here are five good reasons:


1. Questionable preservatives Commercial breads often include preservatives such as propionates (280–283; labelled propionic acid, propionate, or cultured/fermented anything). These are used to prevent mould in warm bread kept in plastic. A clinical trial found that children challenged with calcium propionate (282) showed behavioural changes (Dengate 2002). Other research links chronic propionate exposure to neurological and depressive symptoms in animal models and humans (Dengate 2021).


2. Pesticide and herbicide residues

Wheat grown in Australia and New Zealand are usually sprayed post-harvest with insecticides (or pre-harvest) with herbicides such as glyphosate to aid harvest and pest control. Other countries may use cold storage of grain and avoid the heavy residues we have here. Bread and wheat items always feature in NZ's dirty dozen.


Residues of glyphosate and its metabolites show up in wheat-based foods here and around the world (Nomoreglyphosate 2025) (Soares 2021). Glyphosate has been classified by the International Agency for Research on Cancer as "probably carcinogenic" and other reviews express concerns about endocrine disruption and gut-microbiome effects (Myers 2016).


3. Limited microbial diversity in standard bread

Traditional sourdough fermentation uses a richer range of beneficial microorganisms (lactic-acid bacteria + wild yeasts) rather than a single commercial yeast strain. This microbial diversity can contribute to improved flavour, texture and potentially nutritional outcomes (for example through longer fermentation and acidification).


4. Lower fibre and fewer nutrients in many supermarket breads

Supermarket bread — especially white and even some "wholemeal" types — is typically made from refined flour that has had the wheatgerm and much of the bran removed. (Flour containing wheatgerm has a short shelf life.) This process strips away valuable fibre, minerals (like zinc, magnesium and iron) and B-vitamins naturally present in the grain.


Whole-grain and stoneground flours, by contrast, retain all parts of the grain and therefore offer more nutrients and dietary fibre. This extra fibre not only supports gut health but also helps regulate blood sugar and cholesterol levels, and keeps you feeling full for longer. In fact, one slice of genuine wholemeal bread can satisfy you as much as two or three slices of white bread.


Over time, diets low in fibre — common in populations relying heavily on refined carbohydrates — have been linked to higher rates of constipation, bowel disease and heart disease (Harvard 2023) 


5. Shorter fermentation time reduces nutrient availability Many commercial breads are produced with short fermentation times and high-speed processes, which limit the breakdown of antinutrient compounds such as phytic acid in whole-grain flours. Longer, slower fermentation (as in sourdough) greatly reduces phytic acid and thereby increases mineral solubility and bioavailability (for example magnesium, phosphorus) (Brouns 2021).  In other words: by fermenting longer, you get more out of the grain.



How much bread is good for you, then?

Bread made from wholegrain, organic, and freshly milled flour — especially sourdough — is far better for your health. For centuries, bread has been a staple food, but only in relatively recent times has it become highly refined and often made from grain sprayed with chemicals.

Today, more people are choosing gluten-free options to avoid some of these problems, or they’re simply cutting back on carbohydrates and eating more vegetables and protein instead. What’s right for you depends on your culture, upbringing and stage of life. Most importantly, notice how you feel after a meal — with or without bread. Do you feel hungry again in half an hour? Sluggish? Or comfortably satisfied for two or three hours?

In the end, eating a variety of foods and grains — such as buckwheat, corn, rice, soy, quinoa, and chickpeas — is likely to be healthier than relying on wheat several times a day, especially when it’s refined.

Alison White October 2025



References

Brouns 2021: Brouns F. (2021). Phytic Acid and Whole Grains for Health Controversy. Nutrients, 14(1), 25.https://pmc.ncbi.nlm.nih.gov/articles/PMC8746346/ 

Dengate 2002: Dengate, S., & Ruben, A. (2002). Controlled trial of cumulative behavioural effects of a common bread preservative. Journal of paediatrics and child health, 38(4), 373–376. https://pubmed.ncbi.nlm.nih.gov/12173999/ 

Several references given

Harvard 2023: Department of Nutrition, Harvard T.H. Chan School of Public Health Nutrition Source.https://nutritionsource.hsph.harvard.edu/what-should-you-eat/whole-grains/ 

Myers 2016: Myers, J.P., Antoniou, M.N., Blumberg, B. et al. (2016) Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement. Environ Health 15, 19 https://ehjournal.biomedcentral.com/articles/10.1186/s12940-016-0117-0 

Ribet 2022: Ribet, L., Dessalles, R., Lesens, C., Brusselaers, N., & Durand-Dubief, M. (2023). Nutritional benefits of sourdoughs: A systematic review. Advances in nutrition (Bethesda, Md.), 14(1), 22–29. https://pmc.ncbi.nlm.nih.gov/articles/PMC10103004 

Soares 2021: Soares, D., Silva, L., Duarte, S., Pena, A., & Pereira, A. (2021). Glyphosate Use, Toxicity and Occurrence in Food. Foods (Basel, Switzerland), 10(11), 2785. https://pmc.ncbi.nlm.nih.gov/articles/PMC8622992/ 


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