As Hong Kong’s summer temperatures continue to shatter records, reaching sweltering highs that leave residents drenched in sweat, many instinctively reach for an ice-cold soda or fruit juice to cool down. But according to Japanese medical experts, this seemingly refreshing habit could be doing more harm than good—dramatically increasing the risk of dehydration and heatstroke.
The Hidden Danger in Your Favourite Cool Drink
Japanese health programme “The Reason Lies in X” recently highlighted a startling truth: high-sugar beverages actually accelerate dehydration rather than quench thirst. When blood sugar levels spike after consuming sugary drinks, the body responds by drawing water from cells into the bloodstream to dilute the sugar concentration. This excess sugar is then flushed out through urine, taking precious fluids with it.
Dr. Shintaro Yagami, a diabetes specialist and director of Ginza Yagami Internal Medicine Clinic, explains that “high blood sugar” is an overlooked trigger for summer heatstroke. The numbers are alarming: a standard 500ml soda contains approximately 18 sugar cubes, while the same amount of sports drink packs around 8 sugar cubes.
“It’s a vicious cycle,” Dr. Yagami warns. “The more sugary drinks you consume, the more fluid your body loses, leaving you paradoxically more dehydrated and vulnerable to heatstroke.”
The Surprising Summer Saviour: Tomato Juice
In stark contrast to sugary beverages, Dr. Yasushi Yasue of Ginza Yasue Internal Medicine Clinic recommends a simple, accessible alternative: tomatoes or pure tomato juice. The key lies in lycopene, a powerful antioxidant found abundantly in tomatoes.
Lycopene stimulates insulin secretion, helping to stabilise blood sugar levels. When blood sugar remains steady, the body doesn’t need to divert cellular water to dilute the bloodstream, effectively preventing dehydration. Research supports this approach—a long-term study found that individuals who consumed tomato juice daily for one year showed significantly lower blood glucose levels compared to non-drinkers.
Three Cooling Drinks That Actually Work
For those seeking effective hydration, experts suggest these alternatives:
- Natural coconut water: Often called nature’s sports drink, it’s rich in potassium, sodium, and magnesium—electrolytes lost through sweat—with minimal calories
- Unsweetened or low-sugar lemon water: Packed with vitamin C and citric acid, it stimulates saliva production and aids digestion
- Plain water with a pinch of salt: Ideal for prolonged outdoor activity, helping maintain electrolyte balance
What About Tea? Choose Wisely
Office workers frequently turn to tea for relief, but caution is needed. Strong coffee and black tea contain caffeine, a diuretic that can worsen dehydration. Better options include:
- Barley tea (caffeine-free): Japan’s summer staple, promoting blood circulation and heat dissipation, safe for all ages
- Green tea or matcha: Rich in catechins and vitamin C, offering superior cooling effects, ideal for air-conditioned environments
- Chrysanthemum and mint tea: Mint’s menthol provides natural cooling, while chrysanthemum soothes eye strain and internal heat
What to Do When Heatstroke Strikes
If someone shows early signs of heatstroke—dizziness, flushed skin, heavy sweating, muscle cramps—immediate action is crucial. Move them to a shaded, cool area immediately. Avoid gulping ice water, which can trigger stomach cramps.
Instead, offer isotonic sports drinks diluted with equal parts warm water, sipped slowly in small amounts. For more severe cases, oral rehydration salts (ORS) from pharmacies are rapidly absorbed by the intestines. However, if the person experiences confusion or vomiting, do not administer anything by mouth—seek emergency medical care immediately.
Top 10 Heat-Busting Foods to Add to Your Diet
Beyond drinks, incorporating water-rich, electrolyte-packed foods into daily meals offers a foundational approach to beating the heat. Here is the countdown of the most effective cooling foods, according to nutrition experts:
10. Kiwi Fruit
Packed with potassium and vitamin C, kiwi replenishes electrolytes lost through sweat and combats fatigue. Its tangy flavour also stimulates appetite during oppressive heat.
9. Bean Sprouts
Whether mung or soybean sprouts, they are loaded with water and dietary fibre. Traditional Chinese medicine recognises them for clearing internal heat and dampness, promoting natural body cooling.
8. Lotus Root
Raw lotus root has cooling properties that clear heat and generate body fluids. A glass of fresh lotus root juice or a plate of chilled lotus root slices can effectively calm internal fire on restless summer days.
7. Tomatoes
Beyond their lycopene content for blood sugar stability, tomatoes also help build the skin’s natural sun protection barrier—a dual benefit for summer.
6. Mung Beans
Renowned for detoxifying and promoting urination, a bowl of chilled mung bean soup or mung bean barley dessert prevents heat-induced mouth ulcers and acne.
5. Loofah (Sponge Gourd)
With its naturally cooling properties and rich vitamin B and C content, loofah not only beats the heat but also nourishes the skin—perfect for summer soups.
4. Cucumber
At over 95% water content and nearly zero calories, cucumber contains tartronic acid, which inhibits carbohydrate-to-fat conversion. A spicy, sour cucumber salad is a summer classic.
3. Bitter Gourd
Rich in vitamin C and charantin, bitter gourd clears the mind, brightens the eyes, and stimulates saliva and gastric juice production—combating summer-induced loss of appetite.
2. Winter Melon
This powerhouse clears heat, detoxifies, and reduces water retention. For maximum effect, cook it with the skin and seeds intact. Winter melon soup with barley or duck meat is a traditional cooling remedy.
1. Watermelon
The undisputed king of summer fruits, watermelon boasts 92% water content. Rich in potassium and citrulline, it rapidly rehydrates while promoting urination to expel excess heat and waste.
A Note on Individual Differences
Health experts emphasise that individual constitutions vary. Those with specific medical conditions or dietary restrictions should consult a healthcare professional before making significant changes to their summer diet or hydration habits.
As Hong Kong’s heatwaves intensify, making informed choices about what we drink and eat could mean the difference between a refreshing summer day and a dangerous trip to the emergency room. Sometimes, the simplest solutions—a glass of tomato juice, a slice of watermelon, or a pinch of salt in water—are the most effective guardians against the heat.