Delicious Science with Dr Joanna McMillan

With Dr Joanna McMillan

Get straight-talking tips, science-backed insights, and everything you need to fuel your health, feed your gut, and power your brain—without the fluff. drjoannamcmillan.substack.com

  1. 3d ago

    Gaming the Stars: Health Stars, Ultra-Processed Foods and What Neither System Sees

    Let’s play a game. Food one is a raspberry cheesecake protein bar. Its ingredients include protein isolates, white chocolate sweetened with maltitol, polydextrose, glycerol, sorbitol, flavours, colour and emulsifiers, and there are more than twenty of them. Food two is a packet of shredded cheddar: milk, salt, culture, rennet and a little cellulose to stop the shreds sticking together. Which gets more Health Stars? Neither. They get four and a half stars each. And under the ultra-processed food classification, both count as ultra-processed. The cheese gets there because of that one anti-caking agent. These examples come from a peer-reviewed analysis of the Australian food supply. In this episode of Delicious Science, I use them to bring together two conversations that are now colliding in Australian food policy. FSANZ is working through a proposal to make the Health Star Rating mandatory. At the same time, ultra-processed foods have become one of the biggest topics in nutrition, and the NHMRC is reviewing the evidence on them as it updates our Dietary Guidelines. The problem is that the two ways of judging food often disagree, sometimes wildly. Delicious Science with Dr Joanna McMillan is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber. The star algorithm can be gamed Health Stars work on a balancing act. A product gets risk points for energy, saturated fat, sugars and sodium, and then has points taken off for protein, fibre and fruit, vegetable, nut and legume content. That means a manufacturer can raise the rating by adding protein isolates, inulin or fruit powders, or by swapping sugar for a sweetener, without changing what the food really is. Research from Deakin University found that in the first five years of the system, 73% of ultra-processed foods carrying the label scored two and a half stars or more. So did more than half of discretionary foods, the biscuits, confectionery and snack bars our dietary guidelines say we only need sometimes. “Ultra-processed” isn’t the whole answer either NOVA, the ultra-processed classification, judges how a food is made, and it misses the nutrients. It flags a perfectly good fava bean snack because of a little maltodextrin in the seasoning. Meanwhile it waves through salty beef jerky and a sugary kombucha because they’re made with “kitchen” ingredients. I also want to push back on the idea that every additive is something to fear. Preservatives, nitrites and antioxidants such as vitamin C are often there for food safety. Fortifying bread with folic acid and iodine has been a genuine public health win. There are emerging questions about some emulsifiers and the gut microbiome, and I take them seriously. But my concern is less about any single additive and more about what the overall product is, and what it’s pushing off your plate. In this episode · How the Health Star algorithm works, and the four moves manufacturers use to win more stars · The voluntary loophole, and why we mostly see the good scores · What the latest trials tell us about ultra-processed diets, including the UK UPDATE trial · A round of “guess the stars” with real Australian products · A new Australian model that starts with processing and then checks sugar and salt · Chile’s warning labels, and the first evidence that they’ve affected children’s weight · Six practical tips for your next supermarket trip My bottom line The Health Star Rating counts nutrients and NOVA judges processing. Both matter, and neither is enough on its own. If Australia is going to make front-of-pack labelling mandatory, and I think it should, so nobody can hide their low scores, let’s make sure we mandate a system that starts with the food and then checks the nutrients. In the meantime, you don’t need a perfect label to eat well. Eat mostly whole and minimally processed foods with lots of plants, use the processed foods that make life easier, and enjoy the occasional treat you really love. 🎧 Listen to the full episode above. Your turn: have you spotted a product with surprising stars? Tell me in the comments. I’d love to do a listener round of “guess the stars”. Studies and references Australian research (Dickie et al., Deakin University) · Dickie S, Woods JL, Baker P, Elizabeth L, Lawrence MA. How does the Australian Health Star Rating system perform after five years? Nutrients, 2020; 12: 1463. · Dickie S, Woods J, Machado P, Lawrence M. Nutrition classification schemes for informing nutrition policy in Australia. Current Developments in Nutrition, 2022; 6: nzac112. · Dickie S, Woods J, Machado P, Lawrence M. A novel food processing-based nutrition classification scheme applied to the Australian food supply. Frontiers in Nutrition, 2023; 10: 1071356. Front-of-pack labelling · Global Food Research Program, University of North Carolina. Front-of-Package Labeling Fact Sheet, January 2025. · Paraje G et al. The impact of Chile’s food labelling and advertising law on early childhood excess weight. The Lancet, 2026; 407: 2630–40. · Food Standards Australia New Zealand. Proposal P1067: Health Star Rating System. Ultra-processed food trials · Hall KD et al. Ultra-processed diets cause excess calorie intake and weight gain. Cell Metabolism, 2019. · Dicken SJ et al. Ultraprocessed or minimally processed diets following healthy dietary guidelines (UPDATE trial). Nature Medicine, 2025. · Monteiro CA et al. Ultra-processed foods and human health. The Lancet series, November 2025. Additives and the gut · Chassaing B et al. Randomized controlled-feeding study of dietary emulsifier carboxymethylcellulose. Gastroenterology, 2022. · Sellem L et al. Food additive emulsifiers and risk of cardiovascular disease in the NutriNet-Santé cohort. BMJ, 2023. · Food additive emulsifiers and the risk of type 2 diabetes (NutriNet-Santé cohort). The Lancet Diabetes & Endocrinology, 2024. Disclosure: I’m a non-executive director of Cobram Estate Olives, an Australian extra virgin olive oil company, and I’ve been involved in advocacy on how the Health Star Rating treats cooking oils. Delicious Science with Dr Joanna McMillan is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber. Get full access to Delicious Science with Dr Joanna McMillan at drjoannamcmillan.substack.com/subscribe

    Gaming the Stars: Health Stars, Ultra-Processed Foods and What Neither System Sees
  2. Sep 28

    HOLY SH!T: The Case for Fibre

    “Fibre isn’t sexy. But the science of fibre truly is.” Fibre has an image problem. Say the word out loud and most people think poo, farts, bloating — maybe your grandmother’s cereal box. Hardly the stuff of food joy. Delicious Science with Dr Joanna McMillan is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber. But fibre isn’t just about your bowels. It’s touching your gut microbiome, your heart, chronic inflammation, your weight, your blood sugar, your brain and your body’s own detox systems — often all at once, from the same humble, chewy part of real food that’s quietly disappeared from most of our plates. In this special episode, I take you inside my book, The Fibre Factor (Penguin, out now), chapter by chapter — the science, the surprises, and a taste of what’s waiting for you in each one. In This Episode · Why fibre vanished from our plates over the last century — and just how big the global “fibre famine” really is · Why “fibre” isn’t one thing: meeting the very different characters in the fibre line-up, from psyllium to resistant starch to beta-glucan · MACs and short-chain fatty acids: how your gut microbes turn fibre into butyrate, propionate and acetate — and why that matters for nearly every system in your body · What actually happens when fibre doesn’t agree with you, and how to work with your gut instead of against it · The real mechanism behind fibre and cholesterol — and how much you actually need · The gut–inflammation connection, and why it underpins so many chronic diseases · How fibre triggers your own GLP-1 and PYY release · What a genuinely normal blood sugar curve looks like — and where continuous glucose monitors can mislead healthy people · The gut–brain axis, the vagus nerve, and the 2025 Nurses’ Health Study finding on healthy ageing · Why “detox” doesn’t need a juice cleanse — and what fibre’s real job is in your body’s clean-up crew · How to actually get there: 30 grams of fibre a day, 30-plus plant foods a week, no gram-counting required About the Book The Fibre Factor by Dr Joanna McMillan Penguin | Trade paperback, ebook & audiobook | RRP $36.99 | Out now Also in Spanish - La Clave Esta En La Fibra Chapters: 1. The Fibre Fallout — how fibre fell off the plate, and why we need to bring it back 2. Fibre 101 — meet fibre in all its forms, from gritty to gummy, simple to sophisticated 3. The Prebiotic Powerhouses — microbiome fuel 101: MAC attack 4. Fibre and Your Gut — from first chew to final flush 5. Fibre and Your Heart — cholesterol, blood pressure and cardiovascular health 6. Fibre and Inflammation — why fibre helps calm the fire 7. Fibre and Your Waistline — satiety, GLP-1, and metabolism 8. Fibre and Blood Sugar — flatten the curve 9. Fibre and Your Brain — the gut–brain highway 10. Fibre and Detox Done Right — your microbiome’s own detox toolkit 11. Your Fibre Dream Team — meet the Grain Gang, Pod Squad, Veggie League, Fruit Force, Lovable Nutbags and Seedy Characters 12. Fibre in Play — your fibre-fuelled kitchen, where the science hits your plate Available now wherever you get your books. Related Episode GLP-1 Drugs: The Skinny on Weight Loss, Nutrition, and Health For the full mechanism behind the natural GLP-1 story referenced in this episode — plus nutritional risks to watch for on GLP-1 medications and how to support your own appetite hormones through diet — go back to this earlier episode. Connect with Jo · Website: drjoanna.com · Instagram / TikTok / Facebook / Threads / LinkedIn: @drjoannamcmillan · YouTube: @drjomcmillan · Substack: Delicious Science with Dr Joanna McMillan Enjoyed This Episode? If this gave you a taste for the full story, share it with someone whose gut could use the good news. Subscribe, leave a review, and grab a copy of The Fibre Factor — it genuinely helps others find both the show and the book. Dr Joanna McMillan is a PhD-qualified nutrition scientist and Accredited Practising Dietitian. This podcast is for educational purposes and does not constitute personal medical or dietary advice. If you have a diagnosed gut condition such as IBS or IBD, speak with your dietitian or GP before making significant changes to your fibre intake. Delicious Science with Dr Joanna McMillan is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber. Get full access to Delicious Science with Dr Joanna McMillan at drjoannamcmillan.substack.com/subscribe

  3. Season 2, Episode 4 Trailer

    Animals vs. Plants

    In this episode of Delicious Science, I’m diving into one of nutrition’s most heated debates: plants versus animals. Should we all be eating more plants? Are animal foods unfairly maligned? And can a diet include meat, fish, eggs and dairy while still supporting health and sustainability? My answer is a resounding yes — but with nuance. I explore why humans evolved as omnivores, why whole plant foods are essential for fibre, phytonutrients, gut health and long-term disease prevention, and why animal foods bring important nutrients that are harder to replace, including high-quality protein, haem iron, vitamin B12, zinc, iodine, omega-3s and lesser-known “zoonutrients” such as creatine, choline, taurine and carnosine. We also tackle sustainability, where the story is far more complex than “plants good, animals bad”. How food is produced, how much we waste, and how much ultra-processed food we eat all matter enormously. This episode introduces my Plant-Rich Omnivore approach — or PRO diet — a way of eating built on diversity, balance and joy: plenty of vegetables, legumes, whole grains, nuts, seeds, herbs, spices and olive oil, with quality animal foods included thoughtfully. Because nutrition should not make us more anxious. It should help us eat better, feel better, and enjoy food more. Listen in if you’re tired of the diet wars and ready for a more delicious, science-backed middle ground. Delicious Science with Dr Joanna McMillan is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber. Get full access to Delicious Science with Dr Joanna McMillan at drjoannamcmillan.substack.com/subscribe

    Animals vs. Plants
  4. Feb 6

    Iron Deficiency in Women

    Delicious Science with Dr Joanna McMillan is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber. Many women are walking around with low iron stores, feeling exhausted, brain foggy, and unaware their symptoms stem from something as fixable as micronutrient deficiency. Yet blood tests often miss the first signs—because iron deficiency symptoms happen long before anaemia. In this eye-opening episode, I talk about how small fluctuations in iron levels can quietly sabotage your energy, mood, and recovery long before your blood work shows any concerns. You’ll discover why women, especially those with heavy periods, pregnancy, or restrictive diets, are naturally more vulnerable to iron deficiency. I break down how iron fuels more than just oxygen transport—you’ll learn its vital roles in brain health, immune function, and overall energy. I introduce the concept of the “iron gatekeeper,” hepcidin, a hormone that regulates iron absorption and explains why your body might block iron even when you’re supplementing heavily or eating iron-rich foods. This episode provides practical strategies for boosting iron absorption naturally. From pairing plant-based iron sources with vitamin C-rich foods to timing your tea and coffee consumption away from meals, you’ll get clear guidance on how to optimise your diet. I give you insights tailored for women at every life stage, from teens to postmenopause. The stakes are high: untreated iron deficiency can diminish your physical performance, slow recovery, and impair cognitive function—yet it’s often overlooked until more severe anaemia develops. Learning to interpret your ferritin levels, understanding the influence of inflammation and chronic stress on iron regulation, and knowing when to seek medical guidance can empower you to take control of your health. If you’re tired, foggy, or just wanting to feel sharper and more energised—especially if symptoms don’t improve with sleep or stress management—this episode is essential listening. It’s your straightforward guide to understanding, diagnosing, and fixing iron deficiencies before they take a bigger toll. Don’t wait until fatigue becomes a crisis—arm yourself with science-backed strategies today. Get full access to Delicious Science with Dr Joanna McMillan at drjoannamcmillan.substack.com/subscribe

    Iron Deficiency in Women

Trailer

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Get straight-talking tips, science-backed insights, and everything you need to fuel your health, feed your gut, and power your brain—without the fluff. drjoannamcmillan.substack.com

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