Kernel-in-chiefby Donna Fleming
Scientists are discovering more about the wonder that is the walnut.
When I was a child, the only time I ever ate walnuts was when I found one plonked in the middle of the chocolate icing on top of an afghan biscuit. And to be honest, half the time I threw it away, in case it had gone off.
Many people have a love-hate relationship with these nuts, and if you’ve ever accidentally chomped down on a rancid one, it can be enough to put you off forever. But unless you’re allergic to walnuts, it’s worth making the effort to include them in your diet. They have long been lauded for their health benefits, particularly when it comes to the heart, largely thanks being a rich source of omega-3 fatty acids. Memory, cognitive ability, fertility and weight control may also be improved by these nuts, and they’re also thought to lower blood cholesterol and reduce the risk of diabetes.
New research from Harvard Medical School, published in the Journal of Nutritional Biochemistry, backs up earlier theories that walnuts may be able to reduce the growth of colorectal cancer tumours and may even slow the spread of cancer cells. The study results come with the usual caveat – “further investigation is needed” – and the disclosure that the research was partly funded by the California Walnut Commission, but they have created a buzz in the medical world, especially as colorectal is the third most common type of cancer worldwide and second only to lung cancer as the leading cause of death in Western countries.
Because the research was carried out on mice, there are still questions as to how it relates to humans, but the scientists found that the tumours of animals fed the equivalent of 56g of walnuts a day had 10 times as much protective omega-3s as those kept on a normal diet. Those omega-3 fatty acids include alpha-linoleic acid (ALA), which is believed to help reduce inflammation in the body. They also found that the growth of tumours in the walnut-fed mice was significantly slower than in the non-walnut group.
The results showed there were significant changes to acids produced by the body that control how genes adapt to environmental factors. The researchers are hopeful that including walnuts in our diets might help protect against the growth and spread of tumours, possibly by triggering a process that cuts off or reduces blood supply to a growing tumour.
Meanwhile, scientists are investigating whether ALA alone has this protective effect or whether it could be due to the combination of fatty acids and other nutrients found in walnuts, such as vitamin E, copper, manganese, magnesium and antioxidants called flavonoids. We know that switching to a healthier diet can help prevent some cancers, and it’s estimated that 30-50% of colorectal cancer in men and 20% in women may be prevented by diet changes – such as eating more fibre – and lifestyle improvements such as exercising more.
If that’s not enough to make you ditch the afghan biscuit and just eat the walnut (plus a few more), other studies into walnuts have shown promising outcomes when it comes to other types of cancer, including prostate and breast.
Because of their high oil content, shelled walnuts can go rancid quickly and should be kept in an airtight container, or in the fridge or freezer. Depending on how well they’re stored, they can last from four weeks to six months in the pantry, six months to a year in the fridge and a year or two in a tightly sealed bag in the freezer.
The oil in walnuts also makes them high in calories, so don’t overdo it. Around 30g a day is recommended – that’s 12-14 walnut halves.
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