The post was written by one of our contributors; registered nutritionist; Ghazal Abrishamchi.
As a nutritionist, I am often asked “Is wholemeal bread really better than white bread?”
And in short, I reply…
Yes, wholemeal bread may be more nutritious, but white bread can also be part of a healthy diet .
Consumption of bread in the average British diet has more than halved over the last few decades. While sales of white bread has reduced dramatically, sales of brown and wholemeal bread has increased. Nevertheless, white bread is still the most popular bread (1).
The most commonly consumed bread in the UK is wheat-based bread. Wheat grain is made up of:
- the endosperm which is rich in starch and gluten protein,
- the bran (i.e. the outer layers and the germ) where the dietary fibre, B vitamins, iron, zinc, and magnesium, as well as other bioactives are concentrated (2).
All these anatomical components are present in wholemeal flour which is used to make wholemeal bread (In the UK the word wholemeal bread and wholegrain bread basically mean the same thing, and are used interchangeably). To make white flour, however, the bran is entirely removed during the milling process, leaving only the starchy endosperm (3).
So, does this mean that white bread is devoid of vitamins and minerals?
Not quite…The Bread and Flour Regulation 1998, requires that all wheat flour, except for wholemeal flour, to be fortified with calcium. Also, addition of iron, niacin (B3) and thiamin (B1) to white flour, to replace what is lost in the process of milling, is a legal requirement (4). While white flour is not yet being fortified with folic acid in the UK (and therefore white bread is a poor source of folate (29 ug/100g)), wholemeal bread is considered a source of folate (40ug/100g). Wholemeal bread also contains more niacin, potassium, magnesium, phosphorous, iron, copper, zinc and manganese than white bread. But calcium content of white bread is higher than that of wholemeal bread (3).
Contribution of iron in bread to iron status
Bread contributes to 15-17% of intakes of iron in the UK diet. But, whether the consumed iron is absorbed by our body is unclear. Absorption of iron in wholemeal bread is limited by two factors; firstly, iron (and zinc) in wholemeal bread is bound to phytate which is a major inhibitor of iron absorption; secondly, iron is trapped within cell walls in the bran layer that are not easily digestible.
What about absorption of iron from white bread? White flour lacks endogenous iron, and the most common form of iron used to fortify white flour (elemental iron) is not well-absorbed (2).
What about dietary fibre?
A major difference between wholemeal bread and white bread is their fibre content; while wholemeal bread contains around 7 g of fibre per 100g, white bread provides only 2.9 g of fibre per 100g (3) .
Bread and blood sugar levels
The extent by which a slice of bread raises blood sugar levels seems to depend on the following factors (3):
- Characteristics of the bread; this includes its fibre type and content, how the flour is milled and baked. Generally, a slice of wholemeal bread, that is higher in fibre and has coarser grains, raises blood sugar levels to a lesser extent than a white slice of bread.
- The food/ingredients consumed with the bread; when bread is consumed in isolation, it raises blood sugar level to a greater extent than when it is consumed with fats and protein.
- Characteristics of the individuals; this includes how much salivary enzyme (the enzyme that breaks down carbohydrates in the mouth) one produces, and how well the bread is chewed. Interestingly, evidence from a small study suggests that our gut microbiota composition may be a major determinant of the extent by which a slice of bread (white or wholemeal) raises our blood sugar levels (5).
How to tell if your bread is actually wholemeal?
- Look at the ingredient list – most wholemeal breads have whole-wheat flour listed as their first ingredient
- Do a bit of math – registered dietitians Rosie Saunt & Helen West in their book, is Butter a Carb, suggest that we first multiply the fibre content found on the food label (per 100 grams or per portion) by 10. If the number that we get is larger than the carbohydrate content, then we can be pretty sure that we’ve found ourselves a wholemeal bread!
Overall, wholemeal bread provides higher amounts of most micronutrients, as well as fibre compared to white bread. We know that higher wholegrain consumption, is associated with a range of health benefits including reduced risk of type 2 diabetes, colorectal cancer, heart disease, as well as contributing to maintenance of a healthy weight (6). The Eat Well Guide also encourages the consumption of “wholegrain or higher fibre versions of starchy foods”. Therefore, we recommend that you opt for wholemeal bread most of the time. Having said that, there is no need to remove white bread from your diet as white bread is more than just carbs, and provides a number of important nutrients (thanks to the fortification strategies). Also, as Dr Hazel Wallace put it “not every piece of food that passes your lips needs to be the most nutritionally sound option, food is also for enjoyment.”
1. Family Food 2017/18 – GOV.UK [Internet]. [cited 2020 Jun 6]. Available from: https://www.gov.uk/government/publications/family-food-201718/family-food-201718#trends-in-spending-in-real-terms
2. Aslam MF, Ellis PR, Berry SE, Latunde-Dada GO, Sharp PA. Enhancing mineral bioavailability from cereals: Current strategies and future perspectives. Nutr Bull. 2018;43(2):184–8.
3. Lockyer S, Spiro A. The role of bread in the UK diet: An update. Nutr Bull [Internet]. 2020 Jun 2 [cited 2020 Jun 6];45(2):133–64. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1111/nbu.12435
4. The Bread and Flour Regulations 1998- a [Internet]. [cited 2020 Jun 7]. Available from: http://www.legislation.gov.uk/uksi/1998/141/contents/made
5. Korem T, Zeevi D, Zmora N, Weissbrod O, Bar N, Lotan-Pompan M, et al. Bread Affects Clinical Parameters and Induces Gut Microbiome-Associated Personal Glycemic Responses. Cell Metab [Internet]. 2017;25(6):1243-1253.e5. Available from: http://dx.doi.org/10.1016/j.cmet.2017.05.002
6. Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet [Internet]. 2019;393(10170):434–45. Available from: http://dx.doi.org/10.1016/S0140-6736(18)31809-9