Looking for a carbohydrate-rich pre-workout snack? But not so keen on all those products that are bursting with refined sugars? Researchers at Oklahoma State University say that prunes boost your IGF-1 level.
We've written before on the amazing effect of prunes, or dried plums, on IGF-1 levels. But those referred to animal studies. This time we're talking about a human study in which dried plums had the same effect on post-menopausal women with an average age of 55.
The researchers wanted to know whether dried plums can help prevent osteoporosis. Plums contain selenium and boron, trace elements that are needed for the synthesis of bone tissue. They also contain the phenols neochlorogenic acid [structural formula shown below left] and chlorogenic acid [structural formula below right].
Dried plums' components mean they also have a high oxygen radical absorbance capacity, which in turn means that people who eat dried plums have fewer free radicals in their blood. Free radicals boost bone decay.
In 1999 the researchers published an abstract about an animal study in which dried plums had increased the bone mass in rats. [J Bone Miner Res 1999; 14:S394.] The study was interesting, because the rats no longer produced estradiol. When the study started their bone mass had already started to decrease.
It's not difficult to boost bone mass in healthy, young lab animals, but it's almost impossible to do it in animals that no longer produce estradiol. Studies in which post-menopausal women do weight training have shown that bone decay can be stopped, but what has already been lost cannot be replaced.
The researchers wanted to know whether dried plums would help bone build-up to increase, so they got 20 women to eat 100g dried plums every day for three months. That's about 12 dried plums a day.
One hundred grams dried plums contain about 240 kcal, derived mainly from glucose and fructose, but also sorbitol, which is less easily digested. One hundred grams dried plums contain about 15 g sorbitol. If you are sensitive to sorbitol, this is a dose that can have a laxative effect. But for most people, sorbitol only starts to have a laxative effect with an intake of 22-30 g. The researchers only lost one subject because of this problem.
A control group ate dried apples.
In the experimental group the concentration of the enzyme bone-specific alkaline phosphatase [BSAP] rose by 5.8 percent. BSAP is a marker for bone build-up.
What's more, the IGF-1 concentration rose by 17 percent in the experimental group. IGF-1 has an anabolic effect in bone tissue, but also in muscle tissue.
"The increased rates of markers of bone formation by dried plums further support our animal findings that dried plum consumption may be beneficial in maintaining skeletal health in postmenopausal women", the researchers write. "Longer-term studies assessing BMD and bone mineral content are necessary to confirm the positive effects of dried plums on bone in postmenopausal women."
In the YouTube clip below you can see an interview with Bahram Arjmandi, the first author of this study.
Arjmandi's research was funded by the California Dried Plum Board.
J Womens Health Gend Based Med. 2002 Jan-Feb; 11(1): 61-8.