Consumption of the red grapefruit pulp led to a slow down in bone resorption, and an increase in bone mineral build-up and calcium absorption, according to researchers from Texas A&M University.
If the results can be repeated in humans, grapefruit pulp may offer a new ingredient to the growing bone health market dominated by calcium and vitamin D.
The study’s findings are published online ahead of print in the journal Nutrition.
Farzad Deyhim and co-workers castrated 42 male rats (orchidectomy) in order to cause oxidative stress and increases the development of osteoporosis. A control, non-castrated group containing 14 animals was used for comparison.
The orchidectomised animals were then divided into three groups: one fed a normal diet, one fed the diet plus five per cent grapefruit pulp, and one fed the diet plus 10 per cent grapefruit pulp, for 60 days.
At the end of the study, the researchers report that, as expected, orchidectomy caused a decrease in antioxidant status, bone mineral content and bone quality. It was also associated with increased calcium excretion, and higher levels of deoxypyridinoline in the urine. Urinary deoxypyridinoline is marker of bone resorption (weakening).
On the other hand, the orchidectomised rats supplemented with the grapefruit pulp maintained their antioxidant status, while urinary deoxypyridinoline were lower than their orchidectomised counterparts.
The protective effects of the grapefruit pulp were found to be dose-dependent with regards to bone turnover, and increased calcium and magnesium contents of the bones.
“In the present study, it was demonstrated that the lumbar in orchidectomy group was more sensitive to mineral loss than the femoral bone as seen from a 16 per cent decrease in lumbar calcium and a 24 per cent decrease in magnesium content compared with an average 10 per cent decrease in lumbar calcium content and a 16 per cent decrease in lumbar magnesium concentration in grapefruit-fed groups,” wrote the researchers.
“Furthermore, there was a seven per cent decrease in femoral calcium and magnesium contents in the orchidectomy group as opposed to a one per cent decrease in femoral calcium and a three per cent decrease in femoral magnesium content in the grapefruit-fed groups, when the mean average for the calcium and magnesium concentrations in the grapefruit-fed groups were compared with those of the sham-control group,” they added.
“Thus, the potential benefits of eating grapefruit on bone quality appears to be dose dependent as demonstrated from the bone calcium and magnesium concentrations.”
It is too early to count grapefruit pulp as a potential osteoporosis preventive, but the promising results from this study merit additional research in further animal, and then human studies.
The research may have important implications for osteoporosis, characterized by low bone mass, which leads to an increase risk of fractures, especially the hips, spine and wrists. An estimated 75 million people suffer from osteoporosis in Europe, the USA and Japan.
Women are four times more likely to develop osteoporosis than men.
Potential reduction of osteoporosis has traditionally been a two-pronged approach by either attempting to boost bone density in high-risk post-menopausal women by improved diet or supplements, or by maximising the build up of bone during the highly important pubescent years.
About 35 per cent of a mature adult's peak bone mass is built-up during puberty.
Source: Nutrition (Elsevier)Published online ahead of print, doi: 10.1016/j.nut.2008.05.005“Grapefruit pulp increases antioxidant status and improves bone quality in orchidectomized rats”Authors: F. Deyhim, K. Mandadi, B.S. Patil, B. Faraji