Is there a correlation between eating suya – a kind of Nigerian kebab – and cancer? This was claimed by a Nigerian nutritionist, Professor Ignatius Onimawo.
“While there is a strong link between consumption of suya and increased risk of cancer, consumption of suya garnished with onions and other vegetables, has a strong cancer-lowering effect,” he reportedly said.
The professor added that “women who consume suya, are more prone to cancer (breast cancer) than men because they tend to consume just the suya and ignore the vegetables”. His advice was to always eat suya with “generous portions of… onions, cabbage, tomatoes”.
Is there a link between eating suya and cancer? And are women more at risk? And will adding vegetables help? Africa Check looked for evidence.
Well-done meat may increase risk of human cancers
A file picture of meat being flame-grilled. Photo: AFP/Ander Gillenea" />
Suya is grilled over an open flame. Cooking meat at high temperatures in this way has been shown to cause the formation of chemicals known as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs).
There is good evidence that exposure to high levels of these chemicals can cause cancer in animals. However, it is still unclear whether they can cause cancer in humans.
A 2009 paper found that “high intake of well-done meat and high exposure to meat carcinogens, particularly HCAs, may increase the risk of human cancer.”
Another paper published last year said: “A vast majority [of epidemiological reports] have shown that high intake of well-done meat prepared at high temperatures may increase the risk of human cancers”.
We found three papers (published earlier this year, in 2013, and in 2009) that examined the exposure of Nigerians to some of these chemicals. In all three, samples of suya tested positive for those potentially carcinogenic chemicals.
Therefore, people eating high quantities of suya may have an increased risk of cancer. But that does not mean that eating suya causes cancer, as there may be a number of possible explanations for the association found in epidemiological studies.
Lots of fruit, veg lowers risk
A file picture of suya sold at a presidential rally in Lagos in 2003. Photo: AFP/Pius Utomi Ekpei" />
We could find no evidence to support the professor’s suggestion that Nigerian women eat the meat, while men eat the vegetables too. Nor did we find a subsequent link to different patterns of cancer, including breast cancer.
Animal studies have shown that rodents fed a diet high in HCAs developed cancers of the breast, colon and liver, as well as the skin, lung, prostate, and other organs. Epidemiological studies in humans have also suggested an association between HCAs and a number of different kinds of cancer.
Does eating vegetables with suya reduce your risk of cancer? Evidence suggests that for most cancers, people who don’t eat a lot of fruit and vegetables have about twice the risk of cancer compared to people who do.
But that does not necessarily mean that helping yourself to veggies with suya would counter the effects of potential meat carcinogens.
Conclusion: No direct link established
Although there is evidence of an association between eating grilled meats like suya and certain kinds of cancer in humans, a direct causative effect has not been established. The professor was therefore right in suggesting that there was a strong link, but could have emphasised that the links found in studies were not evidence of causation, and may have several possible explanations
We could find no evidence to support his claims that women are more at risk because of differing eating patterns.
Eating lots of vegetables is linked to a reduced risk of cancer, and therefore a diet high in fruits and vegetables is encouraged but that does not necessarily mean someone eating vegetables with suya would be lowering their specific risk.
Dr Ike Anya is a Nigerian doctor, specialist in public health medicine, and co-editor of Nigeria Health Watch.
Edited by Eleanor Whitehead
Chemicals in meat cooked at high temperatures and cancer risk, by the US National Cancer Institute. (Basically “avoiding direct exposure of meat to an open flame or a hot metal surface, reducing the cooking time, and using a microwave oven to partially cook meat before exposing it to high temperatures.”)
A Backyard Chef's Guide to Healthier Grilling, by the American Cancer Society.