HOUSTON • Mother's milk is not just for babies any more. Global chemical giants DowDuPont and BASF are investing millions to ramp up production of an indigestible sugar found naturally in breast milk.

Infant formula-makers such as Nestle cannot get enough of the synthetic ingredient. Now the companies are eyeing a potentially bigger customer: adults. DuPont estimates that the annual market could reach US$1 billion (S$1.35 billion).

Human milk oligosaccharide (HMO) is the third most common solid in breast milk, after lactose and fat. HMO escapes digestion, allowing it to reach the colon, where it feeds beneficial bacteria.

HMOs may explain why breast-fed babies tend to fare better than formula-fed children, said Dr Rachael Buck, who leads HMO research at Similac formula-maker Abbott Laboratories.

According to early research, HMOs strengthen the developing immune system in babies, helping fight infection and inflammation while aiding brain development.

New studies show those benefits may extend to people of all ages, fitting neatly into consumers' growing fascination with probiotics - the "good" bacteria that can help keep a human body healthy.

Synthetic HMOs come from the formula industry's quest to manufacture a breast-milk substitute as close to the real thing as possible.

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HMOs could lead to treatments for adult ailments such as irritable bowel syndrome, allergies and even the ageing brain, said Dr Buck.

Commercial production is typically accomplished through a fermentation process using giant vats filled with microbes genetically engineered to produce specific HMO varieties, such as 2'FL.

DuPont plans to spend US$40 million building its HMO production capacity this year.

After two decades of research, Abbott was first to bring HMOs to the US baby nutrition market in 2016. It has now expanded to 15 countries.

Nestle last year rolled out HMO formula in Gerber and other brands across 40 countries. The health claims propelled about US$600 million in sales of HMO formula last year each for Abbott and Nestle.

DuPont and BASF are focusing on making the most common version of HMO which consists of the 2'FL sugar. BASF began scaling up production of 2'FL earlier this year.

Dr Stefan Ruedenauer, BASF director of human nutrition research and development, said: "Our aim is to expand on our scientific know-how on specific health functions of HMOs to adults as well."

DuPont is marketing its 2'FL HMO, branded as Care4U, to consumer manufacturers who can use it in adult supplements for digestive and immune health, said DuPont global research and development leader Ratna Mukherjea.

"This is just the beginning for HMO," she added.

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