Field Notes

Study: People ‘Right Size’ Portions of High-Calorie Foods

New research has revealed that humans moderate the size of energy-rich meals they eat, suggesting people are smarter eaters than previously thought.

The findings, led by the University of Bristol, revisit the long-held belief that humans are insensitive to the energy content of the foods they consume and are therefore prone to eating the same amount of food (in weight) regardless of whether it’s energy rich or energy poor.

The study, published recently in The American Journal of Clinical Nutrition, is especially significant as it challenges a common view among researchers that people are apt to overconsume high-energy foods.

This idea stems from previous studies that manipulated the energy content of foods or meals to create low- and high-energy versions. In those studies, people weren’t told whether they were eating a low- or a high-energy version, and findings showed they tended to eat meals of the same weight, resulting in greater calorie intake with the high-energy version.

“For years we’ve believed that humans mindlessly overeat energy-rich meals. Remarkably, this study indicates a degree of nutritional intelligence whereby humans manage to adjust the amount they consume of high-energy density options,” says lead author Annika Flynn, a doctoral researcher in nutrition and behavior at the University of Bristol.

Rather than artificially manipulating the calories in single foods, this study looked at data from a trial using normal, everyday meals with different energy densities, such as a chicken salad sandwich with biscuits or oatmeal with blueberries and almonds. The trial involved 20 healthy adults who temporarily lived in a hospital ward, where they were served a variety of meals for four weeks.

The team of international researchers, including leading experts in diet and metabolism from the National Institutes of Health in the United States, calculated the calories, grams, and energy density (calories per gram) for every meal each participant consumed. The results demonstrated that meal calorie intake increased with energy density in energy-poor meals as previous observations with artificially manipulated foods also found. However, surprisingly, with greater energy density a turning point was observed whereby people start to respond to increases in calories by reducing the size of the meals they consume. This suggests a previously unrecognized sensitivity to the energy content of the meals people were eating.

As this finding was based on data from a small, highly controlled trial, the researchers went on to see if this pattern remained when participants lived freely, choosing their own meals. Using data from the United Kingdom National Diet and Nutrition Survey, researchers again found meal calorie intake increased with energy density in meals that were energy poor and then decreased in energy-rich meals. Importantly, for this turning point pattern to occur, participants would have needed to consume smaller meals, by weight, of the more energy-rich meals.

“For instance,” Flynn says, “people ate smaller portions of a creamy cheese pasta dish, which is an energy-rich meal, than a salad with lots of different vegetables, which is relatively energy poor.”

This research sheds new light on human eating behavior, specifically an apparent subtle sensitivity to calories in energy-rich meals.

Coauthor Jeff Brunstrom, PhD, MSc, a professor of experimental psychology at the University of Bristol, says, “This research gives added weight to the idea humans aren’t passive overeaters after all, but show the discerning ability to moderate how much of an energy-rich meal they consume.

“This work is particularly exciting as it reveals a hidden complexity to how humans interact with modern energy-rich foods, something we’ve been referring to as ‘nutritional intelligence,’” he continues. “What this tells us is we don’t seem to passively overconsume these foods and so the reason why they’re associated with obesity is more nuanced than previously thought. For now, at least this offers a new perspective on a longstanding issue, and it opens the door to a range of important new questions and avenues for future research.”

— Source: University of Bristol


Study Suggests Neuroprotective Potential of Cranberries

Adding cranberries to your diet could help improve memory and brain function, and lower “bad” cholesterol, according to new research from the University of East Anglia in the United Kingdom.

A new study published recently highlights the neuroprotective potential of cranberries.

The research team studied the benefits of consuming the equivalent of 1 cup of cranberries per day among adults aged 50 to 80.

They hope their findings could have implications for the prevention of neurodegenerative diseases, such as dementia.

“Dementia is expected to affect around 152 million people by 2050. There’s no known cure, so it’s crucial that we seek modifiable lifestyle interventions, such as diet, that could help lessen disease risk and burden,” says lead researcher David Vauzour, PhD, of the University of East Anglia’s Norwich Medical School. “Past studies have shown that higher dietary flavonoid intake is associated with slower rates of cognitive decline and dementia. And foods rich in anthocyanins and proanthocyanidins, which give berries their red, blue, or purple color, have been found to improve cognition.

“Cranberries are rich in these micronutrients and have been recognized for their antioxidant and anti-inflammatory properties,” he continues. “We wanted to find out more about how cranberries could help reduce age-related neurodegeneration.”

The research team investigated the impact of eating cranberries for 12 weeks on brain function and cholesterol among 60 cognitively healthy participants.

One-half of the participants consumed freeze-dried cranberry powder, equivalent to 1 cup or 100 g of fresh cranberries, daily. The other half consumed a placebo.

The study is one of the first to examine cranberries and their long-term impact on cognition and brain health in humans.

The results showed that consuming cranberries significantly improved the participants’ memory of everyday events (visual episodic memory), neural functioning, and delivery of blood to the brain (brain perfusion).

“We found that the participants who consumed the cranberry powder showed significantly improved episodic memory performance in combination with improved circulation of essential nutrients, such as oxygen and glucose, to important parts of the brain that support cognition, specifically memory consolidation and retrieval,” Vazour says. “The cranberry group also exhibited a significant decrease in LDL or “bad” cholesterol levels, known to contribute to atherosclerosis, the thickening or hardening of the arteries caused by a build-up of plaque in the inner lining of an artery. This supports the idea that cranberries can improve vascular health and may, in part, contribute to the improvement in brain perfusion and cognition.

“Demonstrating in humans that cranberry supplementation can improve cognitive performance and identifying some of the mechanisms responsible is an important step for this research field,” he continues. “The findings of this study are very encouraging, especially considering that a relatively short 12-week cranberry intervention was able to produce significant improvements in memory and neural function,” he adds.

“This,” he concludes, “establishes an important foundation for future research in the area of cranberries and neurological health.”

— Source: University of East Anglia