Dr Joanna McMillan

Dr Joanna McMillan Nutrition scientist, speaker, author, TV presenter & food futurist Nutrition Scientist, TV Host, Speaker, Author & Food Futurist

08/09/2026

If you’re thinking about maintaining muscle as you get older, don’t just think about how much protein you eat — think about leucine too.

Leucine is an essential amino acid that helps trigger muscle protein synthesis — essentially giving your muscles the signal to build and repair.

And that matters more from midlife onwards, because our muscles become less responsive to protein as we age.

A useful target at a meal is roughly 2–3g leucine alongside around 25–30g protein.

🥩 100g cooked beef, chicken or tuna: ~2–2.5g leucine
🥛 200–250g high-protein Greek yoghurt: ~2g
🥚 2 eggs: ~1g
🌱 150g firm tofu: ~1.5g
🫘 1 cup cooked beans: ~1g

That doesn’t mean animal protein is better and plants don’t count. Plant proteins absolutely contribute — but you will need a larger serve or a combination of foods to reach the same leucine level.

And ideally, we want both: plant foods for fibre and protective plant compounds, alongside high-quality protein foods that help us maintain muscle.

The takeaway? Protein quality counts and don’t save all your protein for dinner. Spread it across the day and think about the leucine content of your protein food choices.

02/09/2026

Healthy eating isn’t about choosing between animal and plant foods—it’s about bringing the best of both together.

At this MLA masterclass, I shared one of my favourite examples of a plant-rich omnivorous meal: a colourful beef stir-fry packed with leafy greens, capsicum and edamame, cooked in extra virgin olive oil and finished with sesame seeds, peanuts and fresh herbs.

The beef provides high-quality protein and a bunch of nutrients including iron, zinc and vitamin B12, while the variety of plant foods brings fibre, phytonutrients and plenty of flavour.

It’s nutrient-dense, balanced, affordable and quick to make. Meeting my goal of ‘balanced meals with no food waste’.

01/09/2026

☕ How many coffees can you safely drink?

For most healthy adults, the new heart-health advice says up to three to five small cups a day may be fine.

But your personal limit may partly be written in your genes.

CYP1A2 helps determine how quickly your liver clears caffeine. Some people are fast metabolisers; others clear it more slowly, so caffeine stays in their system for longer.

Then there’s ADORA2A, a gene that may influence how strongly your brain responds to caffeine—including anxiety, jitters and disrupted sleep.

That helps explain why one person can enjoy an afternoon coffee and sleep perfectly, while another is still staring at the ceiling at midnight.

It doesn’t mean everyone needs genetic testing—or that a single gene decides whether coffee is healthy for you. The research is complex, and your medications, smoking, hormones, blood pressure, sleep and usual caffeine intake all matter.

Population guidelines are reassuring, but your body gives you useful information too.

If coffee triggers palpitations, anxiety, reflux, raised blood pressure or poor sleep, your healthy limit may be much lower—even if you’re below the official recommendation.

With coffee, the right dose isn’t just about the number of cups. It’s also about the person drinking them.

How does coffee affect you: calm and focused—or wired and wide awake?

31/08/2026

☕ Coffee lovers, this is good news.

For most healthy adults, up to 400mg of caffeine a day—roughly three to five small cups of coffee—is generally considered safe.

Regular coffee drinking has also been associated with a lower risk of heart disease, heart failure, stroke and type 2 diabetes.

But there’s an important catch: cup size matters.

We’re talking about 240ml cups—not five enormous café coffees. And a coffee loaded with sugar, flavoured syrups and cream is a very different drink nutritionally.

Coffee isn’t the same as an energy drink either. Coffee contains polyphenols and other potentially beneficial plant compounds, while energy drinks can deliver large doses of caffeine very quickly—often with sugar and additional stimulants.

And caffeine tolerance is highly individual. If it disrupts your sleep, increases anxiety, causes palpitations or raises your blood pressure, your personal limit may be much lower.

You don’t need to start drinking coffee for your health. But if you already enjoy it and tolerate it well, you can savour your daily cuppa without the guilt.

How many coffees do you drink each day? ☕️

27/08/2026

Did meat build the human brain? It was certainly key for nutrients required by the brain —but it couldn’t have done it alone. The brain needed fuel, and a lot of it.

A new paper in Science, led by my former PhD supervisor Professor Jennie Brand-Miller, argues that carbohydrate was also crucial to human brain evolution.

Our brains have enormous glucose demands. Ripe fruit and honey—and later, cooked roots, tubers and grains—helped provide the fuel that protein alone couldn’t efficiently deliver.

But this is not an argument for soft drinks, lollies or refined starches.

Our ancestors’ carbohydrates came from whole foods, packaged with fibre, water, vitamins and phytonutrients—and were eaten alongside high levels of physical activity.

The lesson from four million years of evolution?

Don’t fear carbohydrate. Pay attention to where it comes from.

Eat the fruit. Eat the beans, wholegrains, roots and tubers. Move your body. And keep refined carbohydrates at the edges of your diet—not the centre.

Carbophobia isn’t evolutionary. It’s just fashionable.

Jennie Brand-Miller et al. ,A central role for dietary sugars in human evolution.Science393,574-581(2026).DOI:10.1126/science.aed8437

25/08/2026

Magnesium is having a moment — but not all magnesium supplements are the same, and more is definitely not better.

Before reaching for a supplement, start with food. Nuts, seeds, legumes, tofu, wholegrains, leafy greens and even dark chocolate can all contribute meaningful amounts of magnesium.

If you do decide to supplement, the form matters too.

👉 Magnesium citrate: well absorbed, but can loosen the bowels.
👉 Magnesium glycinate/bisglycinate: well absorbed and generally gentler on the gut, but don’t believe all the hype around sleep.
👉 Magnesium oxide: cheap and often high-dose on the label, but poorly absorbed and more likely to cause diarrhoea.
👉 Magnesium L-threonate: interesting for brain health, but expensive and the human evidence is still preliminary.

And one of the most important things to look for on the label? Elemental magnesium — that’s the amount of magnesium you’re actually getting.

For general supplementation, around 200–300mg of elemental magnesium a day is usually plenty. The upper limit from supplements and medications is 350mg/day for adults.

Food first. Supplement when there’s a reason. And don’t assume the fanciest — or biggest dose — is necessarily better.

14/08/2026

Weight-loss drugs can treat obesity. But they can’t fix what made us sick.

Let me be clear: these medications can be enormously valuable for people living with obesity, type 2 diabetes and metabolic disease.

People deserve access to effective treatment—without shame.

But medication doesn’t stop children being relentlessly marketed unhealthy food.

It doesn’t make nutritious food more affordable or accessible.

It doesn’t give exhausted families more time, cooking skills or support.

And it doesn’t redesign sedentary jobs, create safe places to walk, improve sleep or reduce chronic stress.

Obesity is not simply the result of individual choices. It is also shaped by our food systems, commercial pressures, built environments and wider social conditions.

That means treatment and prevention must happen together.

We should also be wary of powerful medical treatments shifting from people with a genuine clinical need to healthy-weight people pursuing an ever-thinner beauty ideal.

Because that isn’t treating metabolic disease.

It’s medicalising diet culture.

Medicines can help treat the consequences of an unhealthy system. But they must never let governments, the food industry—or the rest of us—off the hook for changing that system.

What do you think: are we investing enough in prevention alongside treatment?

12/08/2026

Are you using a continuous glucose monitor — or thinking about trying one?

CGMs can be incredibly useful, and genuinely game-changing for people living with diabetes. But I’m also seeing more people without diabetes using them — and sometimes interpreting perfectly normal glucose responses as something to “fix”.

Your glucose line is not supposed to be flat.

When you eat a meal containing carbohydrate, your blood glucose rises. Insulin then helps move that glucose into your cells, where it can be used for energy, and levels come back down again.

That rise and fall is normal physiology.

What we’re more interested in are unusually high or prolonged glucose excursions, or significant drops — particularly when they happen repeatedly.

But a gentle rise after a nutritious meal? That doesn’t mean the meal was “bad” or that you need to start eliminating perfectly healthy foods.

CGMs can give us fascinating information. The trick is knowing what the data actually means before changing your diet because of it.

11/08/2026

If you’ve ever had a colonoscopy, you know that the bowel prep is the hard part! It can be pretty hard to know exactly what to eat when there’s so many things you’re not allowed to. In particular, it means almost no fibre. So it’s the opposite of what I’m usually recommending!

But it’s just for three days, and the purpose is to try to clear out your colon so that the doctor is able to have a really good look at the lining of the entire length of your colon.

So here’s what I ate for, well really two and a half days as I had to fast from midday the day before the procedure. I did also have a few slices of cheese when I was hungry on top of this.

Boy was I glad to tuck back into my fibre filled meals when it was all done!

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