White bread (made primarily from refined wheat flour) is a source of iron and B vitamins (thiamin, niacin, riboflavin and folic acid). It contains essentially no fiber. Whole grain bread is a good source of fiber, iron, vitamin E and B vitamins. Whole grain bread typically has a lower glycemic index than white bread.
High levels of bread and pasta consumption were found to be associated with higher risk of ovarian cancer among Italian women in one study. The B vitamins found in bread have been found to be protective against cervical cancer. However, note that any B vitamins in white bread are the result of enrichment — the naturally occurring vitamins in whole wheat are eliminated when white flour is manufactured. In fact, commercial white bread is a highly processed food. Note that separate webpages cover the effects of consuming wheat bran or rye on risk of breast cancer.

Breast cancer-related effects of eating bread

Generally speaking, white bread is associated with some risk for breast cancer patients and survivors, whereas whole grain bread has some beneficial properties (although not enough to make it a recommended food).

White bread is not recommended

The relatively high glycemic index of white bread might promote breast cancer growth and development if it is part of a high glycemic load diet. In addition, bread is a source of acrylamide, a suspected carcinogen.

Population studies link bread intake with cancer

One study of Italian women found an increased risk of breast cancer among those consuming high levels of bread and pasta. Another study reported that white bread consumption increased breast cancer risk slightly both before and after menopause for every additional two servings per week. Still another study found a link between increased starch intake after a diagnosis of early stage breast cancer and greater risk of recurrence. However, the link between bread intake in and of itself and breast cancer risk does not appear to be strong. The main problem with frequent white bread consumption appears to be that it may contribute significantly to glycemic load.

White bread has relatively high glycemic index

The glycemic index of a food is calculated based on the typical increase in blood sugar occurring after the food is eaten; glycemic load takes portion size and frequency into account as well. Glucose itself has a glycemic index of 100 and other foods are ranked in relation to it. White bread has a glycemic index of approximately 75, compared to 36 for an apple. Diets dominated by high glycemic index foods have a high glycemic load.
High glycemic load diets tend to eventually result in chronically elevated insulin levels, which are thought to increase breast cancer risk by stimulating insulin receptors or through insulin-like growth factor 1 (IGF-1)-mediated cell division. Insulin resistance increases the body's insulin response to carbohydrate consumption.
Based on the available evidence, diets with high glycemic load appear to increase the risk of breast cancer and its recurrence, even in women who are not overweight. For example, a 2021 French study with 81,526 participants reported that higher glycemic load diets were associated with increased postmenopausal breast cancer risk. In addition, relatively high percentages of carbohydrates from medium/high-glycemic index foods in the diets were associated with higher breast cancer risk in both premenopausal and postmenopausal women. In addition, a 2020 study reported that high glycemic load after diagnosis was associated with increased risk of breast cancer–specific mortality. The results held when adjusted for BMI (i.e., being overweight was not an explanation for the association).

Bread is a source of acrylamide

Both white and whole grain breads are sources of acrylamide, which is produced primarily in the crust when subjecting bread to high heat during baking. Toasting bread increases its acrylamide content significantly. The majority of the studies that have examined the association between acrylamide and breast cancer have reported negative or inconclusive results. However, a 2021 meta-analysis of data from 18 previous studies found that high acrylamide intake was associated with increased breast cancer risk among premenopausal (but not postmenopausal) women. In addition, a 2024 study reported that DNA damage caused by acrylamide exposure is exacerbated by obesity in a mouse model of breast cancer.

100% whole grain bread is a better choice

Few studies are available concerning 100% whole grain bread and breast cancer. One major study of Swedish women found an inverse association between consumption of high-fiber bread and breast cancer, especially ER+ breast cancer.
100% whole grain bread (wheat or rye) appears to be a better choice for breast cancer patients and survivors since it is a good source of chemopreventive dietary fiber, as well as compounds sucb as ferulic acid, niacin, selenium and vitamin B6. However, such bread often has a glycemic index that is almost as high as that of white bread since the grains are crushed. Naturally high fiber breads such as authentic pumpernickel bread (glycemic index of 40 to 50) or sprouted grain brain (glycemic index of 36 for Ezekiel 4:9 bread) are the best choice.

Sourdough bread falls in between

Sourdough bread is made using fermentation to make the bread rise. This process introduces potentially beneficial probiotics. It also reduces the phytic acid content of wheat bran. Phytic acid is an anti-nutrient which binds to and limits the bioavailability of minerals such as iron, zinc, copper and calcium. However, these minerals are not the most important micronutrients in wheat (in fact, iron and copper both can promote breast cancer in some circumstances).
The glycemic index of white sourdough bread has been determined to be approximately 53 to 65, considerably lower than that of conventional white bread (75). The reason for the lower glycemic index is that the bacteria used in sourdough produce organic acids that delay the absorption of starch in the bread, slowing the rate at which glucose is released into the bloodstream.
However, questions have been raised as to whether this holds for all people. One study reported that some participants experienced the same rise in their blood sugar whether they consumed white bread or sourdough bread (those who regularly test their own blood sugar can conduct their own experiments). Several studies have demonstrated that the glycemic index of a sourdough bread is influenced by the fermentation type and temperature used in preparation.

Additional comments

What is to be avoided is a diet that includes many types of white bread on a daily or regular basis, for example croissants, baguettes, toast, bagels, sandwiches, kaiser rolls, flatbread, focaccia, pita bread, crackers, dinner rolls, hamburger buns or pizza.

Sources of information provided in this webpage

The information above, which is updated continually as new research becomes available, has been developed based solely on the results of academic studies. Clicking on any of the underlined terms will take you to its tag or webpage, which contain more extensive information.
Below are links to 20 recent studies concerning this food and its components. For a more complete list of studies, please click on bread.