Are nitrates in your diet the key to a healthy heart, or a cancer risk? A team of Aussie scientists set out to answer that question.
Human understanding of diet and nutrition has come along in leaps and bounds in recent decades, but the role nitrates play in our health is still misunderstood.
Nitrates are chemical compounds made from nitrogen and oxygen atoms found naturally in certain vegetables, such as spinach, lettuce and beetroot, as well as in some fruits. It can also be found in certain processed meats and even in your drinking water.
It is a type of inorganic nitrate, which is converted into bioactive nitric oxide (NO) through a series of chemical reactions in the body.
Nitric oxide is a signalling molecule that plays various roles in the human body. It helps to regulate blood flow, supports cardiovascular health, and contributes to the function of the nervous system.
Nitric oxide also has vasodilatory effects, meaning it can widen and relax blood vessels, which can improve circulation.
Depending on which study you look at, nitrates can either provide a boost to your heart health and protect against cardiovascular disease or they can cause carcinogenic compounds to form and increase your risk of cancer.
As a result of these seemingly opposing viewpoints, current guidelines sit somewhere in the middle, advising the close monitoring of dietary nitrate intake.
So, how can one dietary compound have such contrasting potential risks and benefits? Researchers from Western Australia’s Edith Cowan University (ECU) set out to answer that question in a comprehensive review of existing nitrate research.
Dr Catherine Bondonno, lead author of the study, says whether or not a dietary nitrate will be beneficial or harmful may come down to where it originates.
“Nitrates’ reputation as a health threat stems from 1970, when two studies showed it can form N-nitrosamines, which are highly carcinogenic [compounds] in laboratory animals,” she says.
“However, no human studies have confirmed its potential dangers, and our clinical and observational studies support nitrate preventing cardiovascular disease, if it’s sourced from vegetables.
“So the review looked to unpack all of that, identify new ways forward and ways that we can solve this puzzle, because it’s really time to address it: it’s been 50 years.”
Dr Bondonno and her team found that the original 1970s studies that painted nitrates as carcinogenic didn’t differentiate between nitrate derived from vegetables, meat or in drinking water.
If they had, she said, they would have found evidence that it’s not fair that all nitrates are “tarred with the same brush”.
“For instance, unlike meat and water-derived nitrate, nitrate-rich vegetables contain high levels of vitamin C and/or polyphenols that may inhibit formation of those harmful N-nitrosamines associated with cancer,” Dr Bondonno says.
Somewhat frustratingly, the study concludes that while looking at all nitrates as bad for you is not correct, there is still some evidence for their harmful qualities, and that further study is needed before health guidelines can be changed.
“The public are unlikely to listen to messages to increase intake of nitrate-rich vegetables, if they are concerned about a link between nitrate intake and cancer,” Dr Bondonno says.
“It just further emphasises the need to investigate dietary nitrate to clarify the message for people.”
Do you eat a lot of fresh fruit and vegetables? How does your diet affect your health? Let us know what you think in the comments section below.
Also read: What different coloured vegetables do in your body
