The Reason Your Brain Feels Foggy (Despite Your Healthy Lifestyle)

You eat your greens, stay active, and usually reach your protein targets. But you're still left wondering, "why does my brain still feel foggy?"

Do you lose your train of thought mid-sentence? Do tasks take longer than they should because you're so distracted? Do you find yourself in a room knowing you went to do something but can't remember what?

What is happening? Is it normal to feel this way even when you're living a healthy lifestyle? Let's take a look at some of the most common (and often overlooked) reasons behind brain fog in active,

health-aware people like you.

Does Your Diet Affect Your Brain Health?

In short… yes, and much more than most people realise.

Your brain is small (no offence intended), but very greedy! Although it makes up only 2% of your body weight, it uses approximately 20% of your daily energy intake. It relies on a steady supply of specific vitamins, fats, and phytonutrients to function well day to day, and to stay sharp as you age.

Without the right nutrients, your brain cells can quite literally run low on energy and lack the tools to function properly. This is especially problematic if they're struggling to use glucose efficiently, which may happen with age, chronic stress, or insulin resistance. That's when you might start experiencing cognitive symptoms like brain fog, forgetfulness, and sugar cravings.

Here are some of the nutrients that play a major role in supporting brain health:

Omega-3s (especially DHA): DHA is a key constituent of healthy brain structure and often in short supply in a modern diet. Without these essential fats, your neurons will struggle to communicate efficiently. Oily fish is the richest source - aim to regularly include salmon, mackerel, anchovies, sardines, herring (S.M.A.S.H). Algae is a rich plant source.

Phospholipids: Making up over half of the brain cell membrane, phospholipids are the structural foundation of healthy brain cells. Dietary sources include egg yolks, organ meat, herring and soybeans.

B Vitamins (especially B6, B12, folate): B vitamins are needed for energy production and neurotransmitter synthesis. They are also essential for creating the chemical messengers your brain uses for function and mood regulation. B vitamins are found in leafy greens, while B12 tends to come from animal sources like meat, seafood, eggs, and dairy.

Interesting note: Research shows that B vitamins and omega-3s work even better together. By helping to reduce oxidative stress in your brain cells and support mitochondrial energy production, cognitive function was better supported.

Polyphenols: Found in colourful plant foods, antioxidant phytonutrients such as anthocyanins can reduce inflammation and protect your brain from damage. The more variety in colour, the more you’ll naturally support your brain’s defences.

Magnesium: Magnesium supports nerve function, reduces inflammation and protects the brain, which supports memory, learning, and nervous system regulation. Include plenty of leafy greens, whole grains, nuts and seeds to increase your magnesium intake.

Choline: Needed to produce acetylcholine, a neurotransmitter vital for memory and attention. Egg yolks are a fantastic source, but you can also get choline from organ meat, poultry, fish and some legumes.

Even with a "healthy" diet, it's easy to fall short on one or more of these nutrients, especially if you're eating the same meals on rotation, avoiding key food groups, or simply not eating enough to meet your needs.

Are You Eating Enough to Prevent Your Brain Feeling Foggy?

This is particularly relevant if you train regularly, lead an active lifestyle or are restricting calories to reduce body fat. Low energy availability (LEA) can become an issue when your food intake doesn't match the energy your body needs, not just for training, but for all the other functions taking place behind the scenes, including cognitive function.

You may be eating a diet that looks very healthy, but if it's not enough to cover both exercise and daily function, cognitive symptoms become likely. This can look like:

• Impaired concentration and memory

• Poor decision-making and slower reaction time

• Reduced ability to handle training stress

• Increased risk of low mood or less motivation

Symptoms of LEA are not confined to brain health. Ongoing LEA can disrupt hormonal balance, impact bone density, suppress immune function and affect gut health.

To prevent this, focus on adding more nutrient dense carbohydrates such as root vegetables and whole grains. Women especially should focus on eating carbohydrates earlier in the day and before training to signal to your brain that energy is present.

The Gut-Brain Connection

There's growing evidence that your gut and brain are closely connected, a relationship known as the gut-brain axis.

Certain foods, especially alcohol, sugar, and ultra-processed products, can disrupt the balance of bacteria in your gut. This includes many "health" or "sports" foods that contain additives known to affect the microbiome.

When the gut becomes inflamed, the gut wall can also become more permeable, sometimes referred to as "leaky gut." This allows undigested food particles and toxins to enter the bloodstream, triggering immune responses and contributing to the development of food intolerances, which can further exacerbate cognitive symptoms.

The result? Even if your diet may appear healthy, food intolerances and ongoing gut inflammation can manifest as brain fog, forgetfulness, low mood, or poor focus, all signs that the brain isn't functioning at its best.

What Should I Eat to Improve My Brain Function?

If you're looking for better focus, sharper memory, and fewer flat, foggy days, these five simple dietary changes are a practical and effective place to start.

1. Eat oily fish three times a week

Many diets fall short of the omega-3 fats that are essential for brain structure and mood regulation.

Try this: Add some anchovies in olive oil to sauce based meals (like pasta sauce) for a salty umami taste. If you are vegan, look for algae-based DHA supplements.

2. Prioritise leafy greens and colourful plants

These are packed with B vitamins, magnesium and polyphenols, nutrients that reduce inflammation and support energy production in the brain.

Try this: Aim for one full portion of leafy greens and at least 5 different plant colours each day.

3. Don't under-fuel, especially around training

Low energy availability can impair memory, focus and recovery. Your brain needs fuel just as much as your muscles do.

Try this: Add a portion of fruit (a banana is ideal) to a pre-workout smoothie so you are properly fuelled for the activity.

4. Focus on real food over processed options

Even "healthy" sports foods can contain additives that affect gut health, and through the gut-brain axis, your mental clarity too.

Try this: Go for whole food snacks like boiled eggs, apple with nut butter, or Greek yoghurt with berries, instead of bars or powders. If you do use protein powders, always check the ingredients and avoid anything with additives.

5. Don't skip the yolks

Eggs, especially the yolks, are rich in choline and phospholipids, both of which are essential for memory, focus, and maintaining healthy brain cell structure.

Try this: If porridge is your breakfast preference, mix in an egg as it cooks for the extra nutrients (and a protein boost). No it doesn’t scramble, in fact you won’t know it’s in there at all!

Brain fog is surprisingly common, even in active, health-focused people. But the good news is, a few simple dietary shifts can make a real difference, helping your brain get the fuel and nutrients it needs to think clearly, focus better, and feel more like you.

You don't need expensive supplements or complicated protocols to start seeing improvements. Often, it's about addressing the gaps in an otherwise healthy diet, eating enough to support both your training and cognitive function, and being mindful of how your gut health affects your brain.

Start with one change from the list above. Give it a couple of weeks. See how you feel.

Frequently Asked Questions

Q: How long before I notice improvements in brain fog? A: Some people notice changes within a few days (especially with better fuelling), while others need a few weeks. The key is consistency rather than perfection.

Q: Do I need to take supplements for brain health? A: Not necessarily. Food first is always my approach, however I commonly recommend omega-3s. Targeted supplements are something I discuss with clients depending on their needs.

Q: Could my brain fog be caused by something medical? A: Absolutely. If these dietary changes don't help after 4-6 weeks, it's worth discussing with your GP. Thyroid issues, hormonal changes, and other conditions can all cause cognitive symptoms and should be thoroughly explored.

Q: Is it normal to have brain fog during perimenopause? A: Very normal, unfortunately. Hormonal changes can significantly impact cognitive function. The dietary strategies above can help, but you might also benefit from speaking to a healthcare provider about hormone support.

Q: What if I'm already doing all these things? A: Then it might be time to look deeper and explore food intolerances, chronic stress, sleep quality, or underlying health issues. Consider working with a qualified nutritional therapist who can help identify what's specifically affecting you and refer you to a healthcare provider if appropriate.

If your current approach isn’t delivering the clarity and focus you’d expect, it may be time to take a closer look. You can book a Cognitive Nutrition Audit or arrange a call to explore what could be affecting your brain function.

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