Cancer alert over salad rocket: Trendy leaves exceed safe levels of nitrates in one-in-ten samples

Trendy rocket leaves, which have seen a huge boom in sales as a healthy salad option, are at the centre of cancer concerns.

Around one in ten British-grown samples were over the maximum permitted limit for nitrates, the Food Standards Agency said.

Watchdogs in the UK and EU have limits for nitrate residues on leafy vegetables because research has identified a link with cancer.

Rocket is seen as healthy as it has high levels of vitamins C, K and A. Its distinctive peppery taste means the leaf is very popular when included in bags of mixed salad – and sales are soaring.

But FSA investigations have established that while most types of leafy greens have seen falls in nitrate levels, the figures for rocket are higher and the trend is upwards.

Raised nitrate levels are associated with the use of artificial fertilisers, particularly for crops grown under glass or in polytunnels over the winter months.

The evidence around the effects of consuming nitrates suggests they are beneficial at low levels by, for example, helping reduce blood pressure, but harmful at intakes above World Health Organisation limits.

Watchdogs in the UK and EU have limits for nitrate residues on leafy vegetables because research has identified a link with cancer. Rocket is seen as healthy as it has high levels of vitamins C, K and A [File photo]

The FSA said: ‘Nitrates are chemicals that exist in plants, soils and water. The concentration of nitrate in plant tissues is variable but green leafy vegetables, when consumed raw, can contain relatively high amounts.

‘Concentration above a threshold value can pose a health risk and high nitrate levels have been associated with types of cancer.’

Research suggests rocket is a ‘hyper-accumulator’ of nitrates from soil, while these chemicals are reported to have a particular link to gastro-intestinal cancer.

The FSA research collected more than 1,000 samples of leafy greens and lettuce and found 4.76 per cent of imported rocket samples would have exceeded the permitted limit, compared with 9.21 per cent of domestic rocket.

It found that 11.4 per cent of imported spinach samples and 3.7 per cent of British samples would have exceeded the permitted limit.

Only a handful of lettuce samples were above the limit.

The FSA has acted on the findings, saying: ‘Where maximum limits were exceeded, they (growers) were required to review aspects of their agricultural practices that could have contributed to the exceedance.’ 

The watchdog plans to test other produce such as kale and baby leaf.

The FSA added: ‘It is generally known that rocket has higher levels of nitrate when compared to other varieties. It should also be noted that the number of samples tested can vary year to year and the number of samples of rocket are relatively small and therefore care should be taken in analysing trends.’

The British Leafy Salads Association, which speaks for growers, said it was unable to comment.

Research suggests rocket is a ‘hyper-accumulator’ of nitrates from soil, while these chemicals are reported to have a particular link to gastro-intestinal cancer [File photo]