Even just one serving a week reduced the risk of renal cell carcinoma (RCC) by 44 per cent compared with those who never or rarely ate fatty fish. Lean fish didn’t have the same protective qualities.

The association has already been noted in Sweden where consumption of salmon, the main fatty fish, has doubled since the late 1980s, while canned herring and other fatty fish has increased by around 50 per cent. Over the same period cases of RCC have gone down dramatically.

Fatty fish are rich in omega-3 fatty acids and vitamin D3. RCC patients had lower levels of the vitamin in their serum than among the general, healthy population, and those whose tumours were growing rapidly had dramatically lower levels of D3.

(Source: Journal of the American Medical Association, 2006; 296: 1371-6).