Highly Processed Foods Increase Dehydration Risk
Diets high in ultra-processed foods — aka junk food — make it harder to stay hydrated during hot summer days.
This article is part of a Wise & Well Special Report: Extreme Heat and Human Health.
I spent countless hours outside as a child in the humid Deep South, occasionally remembering to grab a sip of water or Sunny D before my next adventure. My parents never sent me on my way with a water bottle in tow, as I now do when my own children head off to summer camp. But my parents kept me well hydrated by stocking the kitchen with water-rich foods.
The typical Western-style diet leads us to consume less fluid overall at a time when adequate hydration is key to surviving the heat waves striking multiple countries. Sweltering temperatures have led to much more focus on staying hydrated with liquids, but disappointingly few headlines focus on the role diets play in hydration. Highly processed foods with a low water content are rapidly replacing more traditional, water-rich foods.
Bottled water purchases have increased by 40% over the past decade as more people focus on drinking enough fluids, but at least 20% of total daily water intake typically comes from water-rich foods like fruits and vegetables.
That 20% can be vitally important to prevent dehydration when temperatures soar. However, over half of daily calories consumed in Western-style diets now come from a type of highly processed food classified as “ultra-processed” that has most of the water removed during processing to extend shelf life at the store.
Eat more, hydrate less
A food is said to be ultra-processed if it has gone through several extra processing steps adding more fats, sugar, salt, and preservatives that change the final form of the food. This includes foods like breakfast cereals, potato chips, fast food burgers and chicken nuggets, and many frozen meals.
This junk food often masquerades as healthy with labels like “gluten free” or “sugar free,” but if you look at the nutrition label, most of these foods contain a lot more sodium, fat, and simple sugars than you need in a healthy diet. They also have a lot less water compared to the original food.
Not all processed foods are categorized as ultra-processed, so it helps to understand the spectrum of processing.
One-ingredient foods — the least processed — are ideal. For example, a strawberry can be eaten in its natural form. That strawberry can also be blended into a smoothie or mixed into plain yogurt — processed but still water-rich and healthy.
Further down the processing pipeline, that strawberry can have some of the water removed and be served as dried fruit. But it can also be ultra-processed, meaning it is blended, dried, and added to other food products and preservatives to make strawberry granola bars, flavored energy drinks, or candy that contain much less water than fresh strawberries.
This high level of processing, which removes much of the water and dietary fiber from foods, also means we take longer to become full when we consume them. Kevin Hall, PhD, a scientist with the National Institutes of Health, found that the same people consumed an extra 500 calories per day of food when eating a high ultra-processed food diet then compared to when they ate a diet low in ultra-processed foods.
Ultra-processed foods are challenging to limit for many people in today’s world, in which quick-service foods are so common and convenient. I even include some ultra-processed foods in my own family’s diet. And yet when compared to a person who eats few ultra-processed foods, someone with a high ultra-processed food diet will, on average, have a total daily fluid intake that is up to 24 ounces (3 cups) lower. When outdoor temperatures are high, reducing your total daily fluid intake by 3 cups can absolutely increase dehydration risk.
Foods that can turn down your internal thermostat
To stay properly hydrated, start with diet. Even foods not commonly thought of as water-rich, such as cooked fresh meats and breads, provide some water when eaten. Some of most common foods with a high-water content — some as much as 90% water — also happen to have a high nutrient content, including:
- Cucumbers
- Tomatoes
- Spinach
- Mushrooms
- Melons
- Cruciferous vegetables (broccoli, cauliflower, brussels sprouts, cabbage, collard greens)
- Citrus fruits (oranges, kiwis, lemons, limes)
- Apples
- Berries (blueberries, strawberries, raspberries)
- Avocadoes
- Yogurt
To reduce ultra-processed food consumption, look for areas where less processed versions of the same food can be eaten. Replace breakfast cereals with oatmeal a few days each week (or always if you really want a healthier diet). Switch out store-bought granola bars with fresh fruit and nuts.
If you must eat ultra-processed foods, combine them with less processed ingredients. For example, if you use jarred spaghetti sauce, select one with less sugar and combine it with frozen or fresh vegetables.
Quickly gulping down cups of water between meals causes the water to pass through the digestive tract much faster than when you take smaller, more frequent sips, leading to less water absorption. To maximize absorption when you do drink plain water, try to sip water slowly instead of quickly drinking all the beverage. This ensures that you absorb more of the water you do need.
Hot summers require more planning when it comes to food and beverage intake. This planning will become increasingly important with longer hot-weather seasons and stronger heat waves. Eating fewer ultra-processed foods, consuming more water-rich foods, and drinking more fluids with meals instead of alone can help effectively manage hydration and ward off heat exhaustion.
