SARAH DI LORENZO: How to beat brain fog with better sleep, hydration and best foods for memory, focus

Brain fog is a very common complaint I hear in the clinic. Patients describe it as feeling mentally sluggish, forgetful, or like they’re operating through a haze, struggling to concentrate on a task that should be simple. Brain fog is not a formal medical diagnosis, it is a cluster of cognitive symptoms describing a general sense that your brain is not working the way it should.

Brain fog is not a single symptom. It is a collection of experiences that includes mental sluggishness, difficulty concentrating, poor short term memory, struggling to find words, losing words mid sentence, reduced mental clarity, slower processing speed, a sense of disconnection, reduced motivation and difficulty multi-tasking.

People just say to me “I am just not myself” and that intuition is usually right. Around 30 per cent of Australian adults report brain fog and particularly high in women aged 40 to 55.

The top drivers of brain fog include poor sleep being the single biggest cause and this by definition is less than seven hours, poor quality, or undiagnosed sleep apnoea. Blood sugar dysregulation such as spikes and crashes, insulin resistance, reactive hypoglycaemia. Nutrient deficiencies including B12, vitamin D, iron, omega-3s, magnesium, folate, iodine, zinc. Hormonal changes including perimenopause, menopause, thyroid dysfunction, cortisol imbalance.

Gut health issues such as dysbiosis, leaky gut, SIBO, food intolerances and low stomach acid can all contribute. Chronic inflammation and neuroinflammation from diet, stress, infections or autoimmune conditions are also common causes. Chronic stress and burnout, with elevated cortisol, shrink memory regions and impair focus. Dehydration, with even a 1–2 per cent fluid loss, measurably impairs cognition. Digital overload, including constant notifications, multitasking and excessive screen time, can also play a role.

Medications including antihistamines, sleep medications, statins, PPIs and some blood pressure drugs may contribute. Long COVID and post-viral syndromes are now among the largest new causes. Environmental toxins including mould, heavy metals, air pollution and endocrine disruptors can also be factors. Alcohol impairs cognition for days, depletes B vitamins and disrupts sleep.

Gut health issues such as dysbiosis, leaky gut, SIBO, food intolerances, low stomach acid. Chronic inflammation, neuroinflammation from diet, stress, infections, or autoimmune conditions. Chronic stress and burnout, elevated cortisol shrinks memory regions and impairs focus. Dehydration, even 1–2 per cent fluid loss measurably impairs cognition. Digital overload, constant notifications, multitasking, excessive screen time. Medications including antihistamines, sleep meds, statins, PPIs, some blood pressure drugs. Long COVID and post-viral syndromes is now one of the largest new causes. Environmental toxins including mould, heavy metals, air pollution, endocrine disruptors. Alcohol as it impairs cognition for days, depletes B vitamins and disrupts sleep.

Low iron is one of the most commonly missed causes of brain fog, particularly in women. Iron delivers oxygen to your brain, produces dopamine and serotonin, myelinates nerves so signals travel quickly, and powers your mitochondria.

When it drops, all of these suffer, showing up as fog, poor focus, slow processing, mental fatigue, and low motivation, often long before anaemia develops. Standard testing frequently misses it. Ferritin below 50 mcg/L can produce real cognitive symptoms.

The most impactful fixes include stabilising blood sugar, prioritising sleep, addressing nutrient deficiencies, supporting gut health, avoiding or reducing alcohol, exercising daily and being well hydrated.

The good news is that what you eat has a real, measurable impact on mental clarity. Your brain is an energy-hungry organ, using around 20 per cent of your daily calories, and it’s remarkably sensitive to what you feed it.

Here are some of the top foods to include in your diet.

Fatty fish

Salmon, sardines and mackerel are rich in omega-3 fatty acids, particularly DHA, which makes up a significant portion of your brain’s structural fat. Omega-3s support communication between brain cells and are linked to sharper memory and concentration. Aim for two to three serves a week.

Iron rich foods

The best iron sources are red meat, liver, oysters, sardines, and chicken thigh, these contain haem iron, which is absorbed 3–4 times better than plant iron. For plant sources, focus on lentils, chickpeas, tofu, pumpkin seeds, tahini, dark leafy greens, and quinoa and always pair them with vitamin C foods (capsicum, kiwi, citrus, tomato) to boost absorption. Avoid tea and coffee within an hour of iron-rich meals, as tannins block uptake.

Blueberries and Other Berries

Berries are packed with antioxidants called flavonoids, which help reduce oxidative stress and inflammation in the brain — both linked to cognitive decline and that foggy feeling. A daily handful is an easy habit that genuinely supports focus over time.

Eggs

Egg yolks are one of the best dietary sources of choline, a nutrient your body uses to make acetylcholine, a neurotransmitter essential for memory and concentration. Most of my clients aren’t getting nearly enough choline, and eggs are a simple, affordable fix.

Leafy Greens

Spinach, kale and silverbeet are rich in folate, vitamin K and antioxidants, all linked to slower cognitive decline and better mental clarity. Folate in particular plays a role in producing neurotransmitters that regulate mood and focus.

Nuts and Seeds

Walnuts, almonds and pumpkin seeds provide vitamin E, healthy fats, magnesium and zinc, all of which support brain function and protect against oxidative stress. A small daily handful is an easy way to build this into your routine.

Whole Grains

Your brain runs on glucose, and whole grains like oats, quinoa and brown rice provide a slow, steady release of energy rather than the sharp spike and crash you get from refined carbohydrates. This steadier fuel supply is key to sustained focus across the day, rather than the mid-afternoon fog so many people experience after a sugary lunch.

Water

This one isn’t food, but it deserves a mention because it’s the most common cause of brain fog I see. Even mild dehydration, as little as 1–2 per cent of body weight in fluid loss measurably impairs concentration and short-term memory. Before reaching for another coffee, check whether you’ve actually had enough water today.

What to avoid

Refined sugar and ultra-processed foods cause rapid blood sugar spikes followed by crashes, which is a direct driver of afternoon brain fog. Excess alcohol and poor sleep compound the problem further, no matter how well you’re eating.

Brain fog is rarely caused by one single thing, but diet and lifestyle changes are one of the most powerful and immediate levers you have. Stabilise your blood sugar with whole foods, stay hydrated, and prioritise the brain-specific nutrients above, and most people notice a genuine difference in mental clarity within a couple of weeks.