Dr Cameron Schauer
New Zealand has among the highest rates of obesity and bowel cancer globally, and worryingly, both are increasingly being diagnosed at younger ages. I am often asked as a gastroenterologist about the cause of this.
More evidence has now come to light about ultra-processed foods. These are foods made from refined ingredients, additives, and very little whole, or real food. This is something our ancestors were never exposed to and that the human gut has not evolved to handle. This includes emulsifiers, artificial sweeteners, flavour enhancers, and stabilisers. These are additions designed to improve taste, texture, and shelf life rather than nutrition.
Your gut is home to trillions of bacteria, called the microbiome, that play a crucial role in digestion, immunity, weight, and even mood. Diet is the strongest influencer of this. Diets high in ultra-processed foods are low in fibre and high in additives which then cause significant disruption in this ecosystem, leading to chronic inflammation. This can manifest in things like bloating, discomfort, fatigue, variable bowels and even polyps and cancer.
A large long term study recently published followed up nearly 30,000 nurses for 25 years (mean age 45), tracking their diet and results of colonoscopies. Ultra-processed foods made up 35% of total dietary intake. Those with the highest ultra-processed food consumption had 45% more precancerous polyps than those that had the least! This overwhelming finding was surprising, even to me, and really reinforces the link between diet and health outcomes.
It's not about perfection and eliminating all processed foods. The key is to prioritise whole or minimally processed foods: fruits, vegetables, legumes, whole grains, nuts, and lean meats. These foods are also more likely to fill you up. Ultra-processed foods are made to be delicious and less filling but also convenient and affordable. This can often cause overeating which drives calorie intake and weight gain.
A simple rule of thumb: if a product has a long ingredient list with unfamiliar names, it’s likely ultra-processed. If a food can be out of the fridge for days and still look good, it’s probably ultra-processed. Real, minimally processed foods—like fruits and vegetables or cooked leftovers tend to spoil, dry out, or grow mould because they don’t contain preservatives. Foods that never seem to go off are often the ones your gut sees as the most unnatural. Cooking more meals at home, even simple ones, can significantly improve your gut health over time.
Start being aware of what you are putting into your body, and then start making a change. Your gut thrives on real food.