In the news: Kiwis Help Relieve Constipation; Restrict Calories to Live Longer?

Kiwi Improves GI Function & Comfort

Eating two green kiwifruits a day leads to easier bowel movements and greater abdominal comfort.

The findings, from an international multicenter controlled trial(1), could be good news for those who suffer from constipation due to irritable bowel syndrome (IBS) or functional constipation (difficult bowel movements often with no known cause). Both types of constipation are grouped under the term functional GI disorders, and are considered common and troublesome.

While several previous studies have found that regularly eating kiwifruit (Actinidia chinensis, variety deliciosa “Hayward”) may be beneficial, the studies have been small and measured different outcomes.

The current study provides convincing evidence since it is larger, includes a variety of people from New Zealand, Italy and Japan, and uses standardized tests.

Participants included healthy controls, patients with functional constipation, and patients with constipation – predominantly irritable bowel syndrome (about 60 people per group).

The patients were randomly assigned to consume 2 green kiwifruits or psyllium (7.5 g) per day for 4 weeks. That was followed by a 4-week washout (no treatment), and then the other treatment for 4 weeks. Both the kiwis and the psyllium provided close to the same amount of dietary fiber, about 6 grams daily.

Constipated participants eating kiwis experienced more easy bowel movements (called complete spontaneous bowel movements), as well as significantly improved measures of GI comfort.

Participants appeared to fare better when eating the kiwis compared to taking psyllium. Looking at the IBS and functional constipation groups combined, the effect of 2 green kiwifruits per day was significantly greater than the effect of psyllium, which is considered a first-line treatment for both types of constipation.

Can Calorie Restriction Slow Our Aging?

We’ve known for decades that restricting calories in short-lived species including worms, flies and mice can extend their lifespan. But the effects of calorie restriction in longer-living species (e.g. monkeys and humans, is more controversial).

Now, in the first-of-its-kind controlled trial(2) funded by the US National Institute of Aging, researchers from Columbia University Mailman School of Public Health report that cutting calories can slow the rate of biological aging in healthy, non-obese humans.

The trial randomized 220 healthy men and women at three research locations to a 25% calorie restriction or normal diet for two years.

Because humans live for a long time, it’s not possible to conduct a trial that could see differences in survival. So, the investigators used biomarkers to measure the pace and progress of aging over the study. The markers were developed over a 20-year period and are based on a DNA methylation blood test. Methylation marks are chemical tags on DNA that regulate genes and that change with age.

The calorie restriction slowed the pace of aging by 2-3%. While that doesn’t seem like a very big payoff for eating 25% fewer calories, other studies suggest that may translate to a 10-15% reduction in mortality risk.

A follow-up trial is now ongoing to determine if the restriction had long-term effects on healthy aging such as risk factors for chronic diseases. In the meantime, lots of questions remain. Many experts, for example, are skeptical about whether people can stick to a lower calorie diet long enough to make a meaningful difference in longevity. It’s also not yet clear whether intermittent fasting or time-restricted eating might offer similar benefits.

References

1. Gearry R, et al. Consumption of 2 green kiwifruits daily improves constipation and abdominal comfort—eesults of an international multicenter randomized controlled trial. Am J Gastroenterol. Epub Jan 9, 2023.
2. Waziry, R, et al. Effect of long-term caloric restriction on DNA methylation measures of biological aging in healthy adults from the CALERIE trial. Nat Aging. Feb 9, 2023.