In 2025, a groundbreaking study conducted by American food scientists revealed that a healthy diet could inadvertently lead to jaw pain.
Researchers at the University of Missouri uncovered that kale, often dubbed the king of superfoods, doesn’t deliver the nutrient boost we expect when included in our meals.
While kale is packed with carotenoids, vitamins, and various beneficial compounds, our bodies struggle to absorb these vital micronutrients.
“Kale’s primary nutrients, especially carotenoids, are fat-soluble,” explains Professor Ruojie (Vanessa) Zhang, a lead researcher in the study. The findings reveal that when kale is consumed alone, it does not dissolve optimally in our digestive tract, significantly limiting nutrient absorption.
Fortunately, Zhang and her team demonstrated a simple, enjoyable solution through a laboratory model simulating human digestion.
By pairing kale with an oil-based dressing, they found that the absorption of fat-soluble nutrients from the leafy green was doubled.
“When these nutrients are combined with oil-based foods, such as dressings containing olive oil, the oil breaks down in the intestines, forming structures called ‘mixed micelles,'” explains Chan.
“These micelles facilitate the transport of carotenoids to the intestinal lining, significantly enhancing absorption.” This principle also applies to fat-soluble vitamins including A, D, E, and K.
This kale research exemplifies the concept of bioavailability, highlighting that while foods may be nutrient-rich, the actual rate of absorption is heavily influenced by how they are consumed.
Numerous examples exist illustrating how food combinations can amplify nutrient intake compared to consuming items in isolation.
For instance, adding olive oil or avocado to salads with tomatoes or carrots enhances the absorption of lycopene, a fat-soluble antioxidant, according to Zhang.
Incorporating black pepper and turmeric into your next curry can boost the absorption of curcumin, a nutrient linked to reduced dementia risk. This effect is due to a compound called piperine in black pepper, which slows curcumin metabolism, enhancing its bioavailability.
Take spinach as another example; while it seems rich in iron, its absorption is compromised when consumed alone due to antinutrients like oxalate that bind to minerals, diminishing their bioavailability,” explains Chan.
However, when paired with vitamin C-rich foods such as lemon juice, the absorption of iron from spinach significantly improves, as ascorbic acid neutralizes inhibitory compounds, promoting iron dissolution in the intestines.
Food preparation and cooking also play vital roles in nutrient availability. For instance, fermenting certain foods can enhance the bioavailability of minerals, while consuming some items raw may result in nutrient loss.
“Carrots are a great source of beta-carotene, a precursor to vitamin A essential for visual health,” note Chan.
“Nevertheless, when raw, less than 5 percent may be absorbed. However, intake can soar if carrots are consumed with dietary fats like meat, fish, butter, and olive oil—potentially increasing absorption up to six times!”
Cooking methods can either increase or decrease the bioavailability of nutrients based on the food type and preparation techniques.
“Heat treatment often disrupts plant cell structures, enhancing nutrient availability by releasing bound bioactive compounds,” Zhang explains.
Past studies conducted by her team showed that cooking carrots and tomatoes boosted the release and absorption of nutrients like beta-carotene and lycopene.
“Light steaming can improve nutrient availability while minimizing nutrient loss by softening plant cell walls,” she adds. However, be cautious of overcooking.
“Excessive heat can degrade heat-sensitive nutrients and lead to a loss of water-soluble vitamins such as vitamin C and B vitamins.”
Undoubtedly, navigating all these nuances is challenging when interpreting food labels. Complicating matters further are the variations in individual gut microbiomes.
Nonetheless, by keeping essential ingredients handy—like drizzling olive oil and lemon juice over vegetables and leafy greens—one can maintain a healthy diet.
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Source: www.sciencefocus.com
