Research published in 2002 revealed that selenium levels in British bread-making wheats are 10 to 50 times lower than in their American or Canadian counterparts, caused by bread-makers switching from Canadian to European wheat. Soil in Europe has lower levels of the mineral, influencing the amount absorbed by wheat.
Daily intake of the mineral is therefore often lower than the recommended amount in Britain. Yet research over recent years has shown a link between higher levels of selenium and reduced risk of a number of cancers, including breast, prostate and colon.
It is also thought to benefit the immune system and regulate blood pressure.
The new bread, introduced by Waitrose this month, is the result of an eight-year research project by the Cambridge company, Nutrilaw, which has been working with farmers to increase selenium in the soil.
Waitrose suggests that eating two to four slices of the bread per day would provide the recommended daily intake of the mineral. Two slices contain 40 micrograms of the mineral.