Fancy a roach-milk shake?

Think milk, and you could soon be thinking of a brand-new ‘superfood’ — cockroach milk.

What, exactly, is cockroach milk? It is a highly nutritious protein with non-lactose sugars and fats as its other components.

This protein serves as complete food for little cockroach embryos growing inside their mother. A key feature of this milk protein is its ability to crystallize inside the embryos.

Ninety per cent of proteins in an organism exist in liquid state, which helps in cell activity. Crystallization of proteins inside any organism is usually associated with disease conditions — evolution exerts negative natural selection pressure on proteins for crystallization.

A small group of proteins like the cockroach milk protein are, however, favoured by evolution for crystallizing inside an organism. This occurs since the proteins carry out biological functions in an organism only in their crystalline form.

This cockroach protein could well be the stuff of nutritional revolution. Making it widely available could strengthen the fight against nutritional deficiencies and disorders. In additional to its high calorific value, roach milk’s property to crystallize on its own gives it a longer shelf life. Athletes, for instance, will be able to derive more energy over a longer period of time due to the crystalline nature of these proteins.

The protein can have equally useful benefits as part of a fortified food or even as food for astronauts.

The evolution of nutrition

Cockroaches have survived — and evolved — for the past 320 million years, making them one of the most successful stories in evolution.

They present a very strong example of the inter-relationship of evolution, adaptive survival strategies and successful continuity of the species.

One of the methods by which cockroaches achieve this is by adopting different reproductive strategies. Some cockroach species lay eggs while pregnant females in other species carry the eggs for physical support until they hatch. In both cases, the egg yolk is the sole form of nourishment for the embryos.

In a third type, the eggs are deposited in birth sacs of pregnant females, similar to the uterus in humans. In this species, the cockroach mother provides both physical support and nourishment to embryos. Also known as viviparity, this is a highly-evolved condition in cockroaches. And only  one species of cockroach — the Pacific beetle cockroach — is known to reproduce through viviparity, a feature that increases the chances of survival of the offspring due to increased availability of nutrition and reduced chances of predation.

The Pacific beetle cockroach is found in Fiji and Hawaii. Pregnant mothers provide nutrition to their babies by feeding them with milk proteins. This milk serves as their complete food.

After fertilisation, embryos depend on the egg yolk for their initial nutrition. This enables them to form muscles around their mouth, and allows them to swallow food. The embryos then use these muscles to drink the milk secreted by pregnant females into the birth sac.

This process starts during pregnancy and goes on until the birth of the young ones. As the amount of milk increases inside the gut — or the gastrointestinal tract — of the embryos, the excess amount starts crystallizing naturally for storage as protein. As the milk is used up, the protein crystals slowly dissolve to be available as liquid for nutrition.

Superfood of the future?

Researchers have isolated naturally occurring milk protein crystals from the gut of the developing cockroach embryos and analysed them.

These microscopic crystals are studied by mass spectrometry and X-ray crystallography.

The unique physiological property of the milk proteins is their high calorific value. For instance, a single milk protein crystal has an energy value of 3.7 x 105 Joules, which is three to four times that of cow, buffalo or goat milk. Due to this high-energy food provided by the mother, the babies take about one-third of the time that other cockroach species take to reach sexual maturity.

Further, secretion of the milk protein during pregnancy results in about nine times greater protein content in the viviparous species compared with the other species. These results indicate that the quality and quantity of food greatly affect the viability of the embryos, and the subsequent birth of the baby cockroaches.

If cockroach milk can actually be made into a next-generation food, the future could easily see two-minute noodles being replaced by two-minute energy-packed superfoods. Think roachshakes!

The writer is post-doctoral researcher with interest in protein crystallography.