Navigating Nutrition in a Heatwave - How Hot Weather Disrupts Your Metabolism

Hydration: why it matters more than you think in summer

Even mild dehydration disrupts metabolism in ways that are easy to miss:

• Raises cortisol (stress hormone)

• Impairs glucose regulation

• Reduces cognitive function and mood — significant for anyone managing ADHD, fatigue, or treatment side effects

• Concentrates inflammatory markers in the blood

• Can trigger or worsen hot flushes and vasomotor symptoms in perimenopause and menopause

In summer heat, the baseline advice of 2 litres of water daily becomes a minimum, not a target.

Practical hydration strategies:

• Start with a large glass of water before any caffeine — caffeine is mildly diuretic and if it's the first thing in, you're already behind.

• Electrolytes matter in heat as you're losing sodium, potassium and magnesium through sweat, not just water. Plain water doesn't replace these. Add a pinch of good salt and a squeeze of lemon to water, eat potassium-rich foods (avocado, banana, sweet potato, leafy greens), and consider coconut water as a natural electrolyte source.

• Eat Hydrating foods such as cucumber, watermelon, celery, courgette, strawberries, lettuce, tomatoes. These Foods offer hydration through their cellular structure, making fluid intake something you can literally chew.

• Herbal teas (cooled) — hibiscus, peppermint, and rooibos are all anti-inflammatory and contribute to fluid intake. Hibiscus in particular has evidence for modest blood pressure reduction.

• Aim for pale straw-coloured urine. If your urine is dark yellow, you are already dehydrated.

• Cancer patients and those on treatment: some treatments (including bisphosphonates) require strong hydration — please follow your oncology team's specific guidance.

A note on alcohol in the heat: alcohol is dehydrating, inflammatory, and in the context of cancer and metabolic health, carries its own risks — including impairing bile flow, raising oestrogen levels, and adding inflammatory load. Summer is a natural moment to experiment with lower-alcohol or alcohol-free alternatives without social pressure feeling as acute.

Sun-Protective Eating: Feeding Your Skin From the Inside

Sunscreen is non-negotiable. This is not a replacement for sunscreen. However, the emerging field of nutritional photoprotection offers compelling connections to this newsletter’s core themes of metabolic and cancer biology.

Sun exposure generates free radicals in skin cells — oxidative stress that mitochondrial dysfunction makes worse and that a well-stocked antioxidant system normally keeps in check. For people whose antioxidant capacity is already reduced, whether through genetic variants (SOD2, GPX1, GSTM1) or simply a diet low in polyphenols, the same afternoon in the sun does more damage than it would otherwise. (Click here you would like to find out more about genomic testing and book a free 30 min discovery call with me)

Foods with meaningful evidence for photoprotection:

🍅 Tomatoes and lycopene are the most studied foods and nutrients in photoprotection. Cooked tomatoes (passata, sauce, roasted) deliver lycopene in a far more bioavailable form than raw. Regular intake is associated with reduced UV-induced skin damage. PMID: 16465309.

🍫 Dark chocolate (>85% cocoa) — flavanols improve skin density, hydration, and blood flow; one study found high-flavanol cocoa intake increased the UV dose needed to cause redness. PMID: 24970388 A genuine reason to eat good chocolate.

🍉 Watermelon provides both lycopene and hydration simultaneously. This is a seasonally perfect food.

🐟 Omega-3 (oily fish) — EPA (one of the constituents of omega 3) reduces UV-induced inflammation in skin cells and is associated with reduced risk of some skin cancers. PMID: 21569104.Another reason oily fish belongs on the summer menu.

🍵 Green tea / matcha — EGCG (epigallocatechin gallate) has direct photoprotective activity and reduces UV-induced oxidative damage. A cold matcha in July is functional, not just fashionable.

🥕 Carotenoids rich foods — beta-carotene, lutein, zeaxanthin from carrots, sweet potato, spinach, kale, peppers all deposit in skin tissue and provide meaningful antioxidant defence against UV.

🫐 Berries — anthocyanins from blueberries, blackberries, pomegranate reduce systemic oxidative stress and support skin repair mechanisms.

The practical summer plate looks like:Tomato-based sauces, oily fish, colourful roasted vegetables, berries, a square of dark chocolate, watermelon, a cold green tea. This is Mediterranean diet and lifestyle pattern.

For those on cancer therapy: some treatments increase photosensitivity significantly. If you're on exemestane, chemotherapy, or targeted therapies, discuss sun exposure specifically with your oncology team as food-based photoprotection is supportive but not sufficient protection in high-sensitivity contexts.