Hyaluronan's crucial role in joint health is to absorb water so it can give your synovial fluid its naturally thick, lubricating, and jelly-like quality.

The synovial fluid sits inside the joint cavity where it hydrates, cushions and nourishes the cartilage tissue and helps to support a healthy inflammatory response, promoting optimum joint comfort and flexibility.

The problem for most of us is that our joints begin to lose hyaluronan at an accelerated pace once we pass 30 years of age.

The result is that our synovial fluid thins and dries out, the cartilage becomes exposed, and an unhealthy inflammatory response takes hold. At which point, typical age-related joint issues arise.

But thanks to the satsumaimo – and other hyaluronan-rich foods that make up much of their diet – those Japanese villagers are able to support healthy hyaluronan levels.

This means their synovial fluid remains thick and healthy.