MOTHER’S milk possesses specific nutritional and immunological advantages for infants. Proteins, carbohydrates, lipids, and other bioactive factors play a crucial role in growth of infants, immune protection and general health. Recent scientific research has revealed that apart from feeding advantages, molecular factors have been identified that help newborns and can even be taken to medical practice and the treatment of diseases.

MOLECULAR COMPLEXITY

Over the evolutionary period of mammals, mother's milk has attained the complex array of molecules now discovered in human breast milk.  Among the features to note are the human milk oligosaccharides (HMOs), essentially a short chain of sugar molecules. HMOs uniquely play their role in immune defence as they prevent babies from becoming victims of infections and inflammation. Beyond the HMOs, there are proteins, vitamins, hormones, and live cells in breast milk, all much needed for the development of infants. The molecules identified as of 2009 were more than 250 proteins and by about 2015 around 300 microRNAs (miRNAs), short chains of ribonucleic acids (RNA), implicated in the regulation of gene expression. The various classes of miRNAs play important roles in cellular growth, function of the immune system, and metabolism. These miRNAs in breast milk, for instance miR-148a-3p and miR-125b-5p have been associated with the regulation of infant development and modulating processes such as the regulation of gastrointestinal system development, epigenetic changes that control DNA function (epigenetic refers to changes in hereditary patterns, for example due to environmental factors, that do not change DNA sequence) and also regulation of immune responses.

Recently, it has been seen that there are cells – even stem cells – in breast milk, thousands to millions of maternal cells per millilitre. Technology breakthroughs have shown cells in the mother's milk to be multi-lineage and thus able to differentiate from all other types of cell. Here lies the benefit from the stem cells that nursed babies and mothers alike acquire, while the benefits for regenerative medicine are enormous. The self-renewing, differentiating stem cells in mother's milk is a landmark in the study of its biological functions.

UNLOCKING MEDICINAL POTENTIAL

Recent studies have identified approximately 50,000 small molecules present in breast milk. Many of these have not yet been explored. Very recently, thanks to the use of artificial intelligence, researchers began to discover associations between these molecules and health outcomes in both infants and adults. Another very promising area of research is on the anti-inflammatory properties of HMOs and how these might be adapted into therapies for chronic conditions, such as heart disease or arthritis. For instance, work by Lars Bode at the University of California showed that HMOs could prevent blockage in the arteries, a major cause of heart attack.

Discovery of human breast milk stem cells (hBSCs) holding multi-lineage potency creates a new door for regenerative medicine. Their characteristics would most probably resemble those of human embryonic stem cells since they differentiate from all types of cells derived from the three germ layers or species of tissue, such as neural, mesodermal, and endodermal (mid- and inner layers of the embryo respectively) cells.

Their multi-lineage potential makes them good candidates for therapies against neurodegenerative diseases such as Parkinson's or Alzheimer's. The non-tumorigenic property of hBSCs adds safety to the use of stem cell therapies, particularly important in the context of commonly used induced Pluripotent Stem Cells (iPSCs), in which the possibility of tumorigenesis (leading to tumors) always exists.

Researchers at Lund University, Sweden, discovered that a molecular complex formed by alpha-lactalbumin and oleic acid, two components of breast milk, was a potent cytotoxin against lung carcinoma cancer cells. The molecule was christened HAMLET. It has proved to be clinically effective where results of complete shrinkage of the tumor were observed in 88 per cent of patients suffering from carcinoma of the bladder. This proved very encouraging and opened further avenues for research into cancer therapy using breast milk. In addition, many miRNAs from breast milk, like miR-375-3p, have been proved to show anti-cancerous properties mostly in the carcinoma of the breast. The microRNA plays a role in controlling apoptosis in tumor cells or cell death, presenting yet another route toward being examined for cancer therapy within the constituents in breast milk.

Prolacta Bioscience is researching how constituents of human breast milk aid in the recovery of adults who receive bone marrow transplants to treat blood cancer. Early pilot studies report that infection was reduced in children who have similar treatments.

Breast milk is very important to the infant gut microbiome because the bacterium Bifidobacterium which is present in it is a specific group that feeds on HMO. This interaction, therefore, creates an ideal gut microbiome for infants to live healthy. Now, since it has already proven to cure some cases of irritable bowel syndrome, scientists are researching its effectiveness or benefits to adults.

There is great interest in the neuro-protective properties of breast milk especially for premature infants. Experiments conducted at the Children's Hospital in Cologne proved that the nasal administration of breast milk into pre-term babies with brain injuries minimizes brain damage and need for surgical interventions. Another study by researchers of the Hospital for Sick Children in Toronto proved intra-nasal breast milk to be effective in preventing haemorrhages in the brains of preterm infants, especially on motor and cognitive outcomes. Researchers believe that stem cells present in breast milk have a neuro-protective effect.

Furthermore, neurotrophic factors in breast milk, such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) are concerned with the development of the enteric nervous system and survival of neurons. They seem of prime importance in health in infants, and quite conceivably in adults, though undoubtedly much less obviously, they play some role in managing neurodegenerative diseases.

CHALLENGES AND FUTURE

While the industry is constantly trying to implicate some of the benefits found in breast milk into its infant formula, it remains impossible to make an exact replica. More advances in technology have kept companies abreast with putting together HMOs and other bioactive components in the formulas which later translate to better gut health for infants fed on the formulas. Two start ups, Helaina and Biomilq, are also doing their best to develop a bioengineered version of breast milk proteins and fats, but these remain in nascent stages. In fact, other molecules like breast milk-derived miRNAs, which are basically absent in most formulas and play a pivotal role in the immune system and developmental programming, are still far from matching the complexity of human milk's biological functions. Continuing research into breast milk reveals potential in an increasing number of contexts. It is increasingly seen as a promising tool in the fight against major health challenges, such as cancer, heart disease, and neurodegenerative disorders. The challenge now is to harness its benefits ethically and equitably, so that the benefits of breast milk science continue to benefit society at large without compromising the natural integrity of human lactation. There is rather significant potential in breast milk molecules that will change the nursing of infants and transform adult medicine. Scientific knowledge today is still increasing, and soon, breast milk might become an excellent resource for modern medicine. Commercialising breast milk raises ethical questions,  mainly about equal access and sourcing. Harvesting and selling a breast milk component for money demand strict regulating principles to ensure ethical requirements. Scientists, policymakers, and the private companies themselves must work together to set clear ethical guidelines for the development and application of therapies made from breast milk. The context has to be the health and well-being of the public and not the profits that will benefit big pharma and businesses.