Brain health and cognitive ageing: a doctor’s guide for adults 45+ in NZ

Somewhere in your fifties, you start to notice it. A name that won’t come. The reason you walked into the kitchen, gone. A sense that the mental sharpness you took for granted has softened at the edges. It’s unsettling — and the supplement industry knows it, which is why the “brain” aisle is full of expensive promises. This guide is the honest version.

I’m Dr Roderick Mulgan, an Auckland GP and the founder of Lifeguard Health. I’m going to tell you what genuinely protects an ageing brain, what the evidence says about the nutrients that matter, and where the heavily marketed “longevity” ingredients like NAD+ actually sit — because the gap between the marketing and the science here is wider than in almost any other category.

Normal ageing or something more?

The first thing worth saying, because it quietly worries a lot of people, is that some cognitive change with age is completely normal. From our forties on, the brain processes information a little more slowly, multitasking gets harder, and names and words take longer to surface. This is the cognitive equivalent of needing reading glasses — a change in performance, not a disease.

Normal ageing looks like occasionally forgetting an appointment and remembering it later, losing your keys but retracing your steps, or blanking on a word that comes to you an hour on. What’s not in the normal range is memory loss that disrupts daily life: getting lost in familiar places, struggling with steps you’ve done for years, repeating yourself in a single conversation, or changes in language and judgement that the people around you notice. That pattern deserves a GP visit — not because it’s necessarily dementia, but because several causes are treatable and worth finding.

What actually changes in the brain after 50

A few things shift together. Blood flow to the brain becomes a little less efficient, which is one reason heart health and brain health are so tightly linked. The connections between brain cells — the wiring that makes recall fast — aren’t maintained quite as briskly. And the brain becomes more sensitive to the things that were always bad for it: poor sleep, high blood pressure, high blood sugar, inactivity and isolation. The encouraging flip side is that most of those levers are things you can act on.

The foundations that protect an ageing brain

This is the part the supplement ads skip, because you can’t sell it in a bottle. But it’s where the real protection is, and as a GP I’d be doing you a disservice to lead with anything else. The evidence here is genuinely strong.

Move your body. Regular physical activity is the single best-evidenced thing you can do for a healthy brain as you age. Aerobic exercise supports the blood flow your brain depends on, and strength training protects the muscle and independence that keep you active. You don’t need to be an athlete — brisk walking most days counts.

Protect your sleep. Deep sleep is when the brain consolidates memory and clears metabolic waste. Chronically short or broken sleep is bad for thinking in the short term and for brain health over the long term. If menopause or a busy mind has wrecked your nights, that’s worth fixing — see our guide to sleep through menopause.

Mind your heart. What’s good for your heart is good for your brain. Keeping blood pressure, blood sugar and cholesterol in a healthy range — with your GP’s help — is one of the most powerful long-term protections there is. High blood pressure in midlife is a particularly important one to treat.

Stay socially and mentally engaged. Connection, conversation, learning and purpose all protect cognition. Loneliness and inactivity do the opposite. This isn’t soft advice — it’s one of the better-evidenced protections we have.

Look after your hearing. Untreated hearing loss is one of the most significant — and most overlooked — risk factors for cognitive decline in later life. If your hearing has dropped, getting it checked and addressed matters more than most supplements ever will.

Be sensible with alcohol, and don’t smoke. Both harm the brain’s blood supply over time. Cutting back on alcohol and stopping smoking pay dividends here as everywhere.

Eat for your blood vessels. A Mediterranean-style pattern — vegetables, legumes, nuts, olive oil, whole grains and oily fish — is the eating pattern most consistently associated with better brain ageing. There’s no single “brain food”; it’s the overall pattern that counts.

If you do all of that, you’ve done more for your brain than any supplement can. Nutrition sits on top of these foundations — it doesn’t replace them.

The nutrients that genuinely matter

With the foundations in place, a few nutrients have a real role — mostly by closing the gaps that quietly impair thinking, which is a different and more honest claim than “boosting” a healthy brain.

Vitamin B12. This is the big one. B12 is essential for normal nervous-system function, and a deficiency directly clouds memory and thinking. It’s also genuinely common after 50, because the body absorbs it less efficiently with age and certain common medicines (like metformin and long-term reflux tablets) reduce it further. A B12 deficiency is one of the treatable causes of fog and forgetfulness that I always want to rule out — more on this in our B12 after 50 guide.

Omega-3 (fish oil). The omega-3 fats EPA and DHA are building blocks of brain tissue and support both heart and brain health. Most New Zealanders don’t eat oily fish often enough to get a steady supply. The evidence that omega-3 prevents dementia is not settled, but as a foundation for brain and cardiovascular health from midlife on, it’s sensible — see our omega-3 for over-50s guide.

Vitamin D. Widely low in New Zealand over winter, vitamin D receptors are found throughout the brain, and very low levels are associated with poorer cognitive outcomes. Keeping your level topped up is worth doing for several reasons — our vitamin D guide covers how.

The B-group, including folate and B6. These work together in processes that matter for the nervous system and energy metabolism. They’re part of why a solid daily multivitamin foundation is a reasonable insurance policy as diets narrow with age.

Notice the through-line: these nutrients help most when you’re short of them. They’re a foundation and a gap-filler, not a performance drug. That’s the honest framing — and it’s deliberately different from the way this category is usually sold.

The NAD+ and NMN question — an honest answer

If you’ve been reading about brain and longevity supplements, you’ll have met NAD+, and its precursors NMN and NR. They’re marketed hard in New Zealand as anti-ageing, energy and brain products, often at premium prices. So let me give you the straight version, because someone should.

NAD+ is a real and important molecule — every cell uses it for energy metabolism, and levels do tend to fall with age. That much is genuine biology, and it’s why the idea is attractive. The early research, much of it in mice and in the laboratory, has been interesting enough to take seriously.

But here’s the part the marketing glides over: the human evidence is still early. Trials in people are mostly small and short, and while some show that supplements can raise NAD+ levels in the blood, that hasn’t reliably translated into the outcomes people actually care about — better memory, sharper thinking, a younger brain. Raising a marker is not the same as improving your life. As a doctor, I won’t tell you NAD+ is proven for brain health, because it isn’t — not yet. It may prove useful in time, and the science is worth watching. But paying a premium today for a promise the evidence doesn’t back is exactly the kind of thing I built Lifeguard to steer people away from.

If you want to spend money on your brain, spend it on a good pair of walking shoes, a hearing check and the foundations above first. They have the evidence NAD+ doesn’t.

The other “brain” supplements people ask about

A handful come up again and again. In brief, and honestly:

• Ginkgo biloba — long marketed for memory; the evidence in healthy adults is weak and inconsistent, and it can interact with blood thinners.
• Lion’s mane — popular and promising in early lab work, but the human evidence is thin. Interesting, not proven.
• Phosphatidylserine and resveratrol — some early signals, nothing settled. Not foundations.
• Curcumin (turmeric) — better evidence for joint comfort than for cognition, though its anti-inflammatory role is part of general healthy ageing.

None of these is a substitute for the foundations, and none has the weight of evidence behind it that sleep, exercise and treating blood pressure do. If you choose to try one, do it with eyes open and a word to your pharmacist about interactions.

What a supplement can and can’t claim

This matters, so I’ll be plain. A dietary supplement can support normal brain and nervous-system function by helping you get enough of the nutrients involved. It cannot prevent, treat or cure dementia or any other disease, and you should be wary of any product that implies it can. That’s not a legal footnote — it’s the honest boundary of what these products do, and any brand blurring it is one to distrust.

When to see your GP

Book a visit if memory or thinking problems are getting steadily worse, disrupting daily life or work, or being noticed by the people around you — or if changes come on suddenly. Several causes of cognitive symptoms are treatable: an under-active thyroid, low B12, depression, poor sleep, medication side effects, and others. Finding them is exactly what a GP review is for. Going early is sensible, not alarmist — it’s how the fixable things get fixed.

Where Lifeguard fits

Lifeguard doesn’t sell a “brain pill”, and you’ve probably gathered by now that I’d be sceptical of anyone who did. What we make is an honest daily foundation — Lifeguard Essentials brings together the B-group, B12 and vitamin D among the nutrients that support healthy ageing, doctor-formulated and NZ-made. It sits underneath good sleep, exercise and a brain-friendly diet, not in place of them.

That’s the difference worth knowing: Lifeguard is one doctor’s focused range, not a catalogue chasing every longevity trend. If you came here from menopause, our post on brain fog during menopause covers that specific overlap; for the wider picture, see our healthy ageing supplements guide.

A supplement supports good nutrition — it isn’t a substitute for medical care. If you’re worried about your memory or thinking, see your GP.

Frequently asked questions

What are the best brain health supplements for over 50s in NZ?

The nutrients with the best case are vitamin B12, omega-3, vitamin D and the B-group — mostly because being short of them harms thinking, and they’re common gaps after 50. A solid daily foundation like Lifeguard Essentials covers most of them. But supplements sit on top of the real protectors: sleep, exercise, blood pressure control, hearing and staying mentally and socially active.

Do NAD+ or NMN supplements improve brain health?

Not on the current evidence. NAD+ is a genuine and important molecule that declines with age, and early lab and animal research is interesting, but human trials are small and short, and raising NAD+ levels hasn’t reliably improved memory or thinking. It’s worth watching, not worth a premium today. The foundations have far stronger evidence.

Can supplements prevent dementia?

No. No supplement is proven to prevent or treat dementia, and you should be cautious of any product that implies it can. Supplements can support normal brain and nervous-system function by closing nutritional gaps. The best-evidenced ways to protect your brain are exercise, sleep, treating high blood pressure, addressing hearing loss, not smoking, and staying active and connected.

What vitamin deficiency causes memory problems and brain fog?

Vitamin B12 deficiency is the classic one — it directly affects the nervous system, becomes more common after 50, and is worsened by some common medicines. Low vitamin D and an under-active thyroid can also cloud thinking. These are treatable, which is why a blood test through your GP is worthwhile if fog is persistent.

Is some memory loss normal as you age?

Yes. Slower processing and taking longer to recall names or words is a normal part of ageing, like needing reading glasses. What’s not normal is memory loss that disrupts daily life — getting lost in familiar places, repeating yourself in one conversation, or changes others notice. That pattern warrants a GP review.

Written by Dr Roderick Mulgan, NZ GP and founder of Lifeguard Health. This article is general information, not medical advice. If you’re concerned about your memory or thinking, see your GP.