With recent discussion of the use of Roundup on food crops and its links with cancer, and in the lead up to the Cancer Society's Daffodil Day, it's worth reflecting on what we know about cancer prevention.
It can be easy to think of things such as agricultural chemicals as the big baddies when it comes to cancer. Glyphosate, the chemical compound on which Roundup is based, is classified by the World Health Organization's (WHO) International Agency for Research on Cancer (IARC) as a Group 2A carcinogen; described as "probable carcinogens". There seems little doubt that repeated exposure to it is not the best idea. But these classifications don't tell the full story. It pays to look at the bigger picture.
For most of us, exposure to agricultural chemicals is not likely to be a major problem – or at least, if we're going to get cancer, it's probably not going to be from that.
It's worth keeping in mind the other things we do every day that are likely to have more of an impact.
The biggies are really smoking and alcohol. Both tobacco smoke and alcoholic beverages are classified by the IARC as Group 1A: that's "carcinogenic to humans". In other words, there's no doubt about it. Other things in this category include arsenic, asbestos and plutonium.
We have a big blind spot about alcohol; we know how bad it is for us, but we don't want to hear it or do anything about it. Nevertheless, alcohol is linked with at least seven cancers, and the level of drinking that increases our cancer risk is lower than we'd probably like to hear. The less we drink, really, the better. If we're choosing organic produce, or raw food, or vegan food in order to be healthier but still drinking regularly, it's likely to be a zero-sum game.
It may surprise you to know that processed meats are also in the WHO's 1A cancer category. That's things like bacon, ham and cured sausages. It's recommended that to reduce our cancer rink we eat "little, if any" processed meat, because of its links with colorectal cancer.
Red meat is in category 2A (the same as glyphosate), due to its association with several cancers. This doesn't mean, of course, that eating a steak poses the same cancer risk as inhaling glyphosate. They are not equally dangerous; the IARC classifications describe the strength of the scientific evidence for something being a cause of cancer, not the level of risk.
So what does this mean in context? Is everything fun off the menu?
Here's what the Cancer Society says: We can still have a healthy life that includes steak and wine, although we are wise to limit alcohol or cut it altogether for lowest risk. We can also lower our cancer risk by eating a diet high in fruit and vegetables and low in saturated fat and sugar; being a healthy weight; being regularly physically active and being sun smart. It's basic stuff, but all too easily forgotten.
• Niki Bezzant is editor-at-large for Healthy Food Guide www.healthyfood.co.nz