Can we make wheat healthier for people to eat?

Scientists have used crop genetics approaches to enhance resistant starch in staple food crops such as wheat.

Why is wheat one of our most important crops?

Wheat is one of the most widely grown agricultural crops due to the plant’s ability to adapt to many different growing regions and for making a wide range of food products like bread.

Bread is the world’s favourite staple food and an important energy source, providing nearly a fifth of the calories consumed globally, mainly in the form of carbohydrates.

In addition to carbohydrates, wheat also provides significant amounts of protein, dietary fibre and micronutrients.

What are the concerns about refined flour?

Although wheat is a valuable source of nutrition, there is growing concern about the effects of wheat foods on health, including the rising incidence of obesity and type 2 diabetes.

Most wheat food products are made from refined white flour and tend to be low in fibre compared to wholegrain products.

To make refined white flour, wheat grains are milled — a process in which the outer bran layers of the grain (which contain most of the fibre as well as other nutrients) are removed from the inner tissue, which is mostly starch.

Although starch is an important source of carbohydrate in our diet, much of the starch in refined food products like bread tends to be easily accessible and rapidly digested in our upper gut, which may not be ideal for sustaining energy over prolonged periods of time or for maintaining healthy blood sugar levels.

How can we improve the dietary fibre in wheat?

A small portion of the starch in wheat foods is resistant to digestion in the upper gut (resistant starch) and is an important component of dietary fibre. Thus, a focus of many wheat genetic improvement programmes is to increase the resistant starch in the grain.

The structure and composition of starch molecules can affect starch digestibility, so the main approach has been to harness our genetic knowledge of wheat and generate wheat plants with altered starch production genes using non-genetically modified (non-GM) approaches.

In this way, scientists have achieved over 10-fold increases of resistant starch in wheat flour, which is great news for our gut microbiota.

What are the problems with high resistant starch wheats?

It is important to remember that processing wheat flour into foods affects the digestibility of starch in the end product.

For example, the resistant starch levels measured in typical bread (~1-2%) tend to be higher than levels measured in flour (<0.5%). This is likely due to processes such as retrogradation.

Thus, future research needs to consider the levels of resistant starch that can be achieved in processed foods like bread to understand what could be delivered to the consumer.

Another significant challenge is that some of these high resistant starch wheat plants have reduced crop yield and changes to their end-product quality. These include changes to how the dough behaves, how much it rises, and how the final bread loaf looks.

This is an exciting area of research and is bringing together plant scientists, food scientists, nutritionists, and health professionals together to solve the issue.