No abstract

To make a broad survey of the effect of components of the human diet on bone resorption, a few items from the following categories were added to rat diets: vegetables, fruits, beans, nuts and seeds, mushrooms, carbohydrate sources and beverages. The effect on bone resorption was measured by the urinary excretion of tritium released from bones of 9-wk-old rats prelabeled with tritiated tetracycline from weeks 1 to 6. The number of rats per experiment was 26--6, 5, 5, 5 and 5 in the untreated control group fed the plain semipurified diet, the positive control group fed onions and three groups fed one of the newly investigated items, respectively. New experiments were added until 10 rats were fed each item in each of two separate experiments. The results for each item were compared to those for the untreated control group (n = 12) investigated simultaneously. We found that feeding rats 1 g/d of dry fennel, celeriac, oranges, prunes, French beans and farmed and wild mushrooms (Agaricus hortensis and Boletus edulis) as well as the freeze-dried residue from red wine significantly (P < 0.05 or lower) inhibited bone resorption. Eighteen items had no significant effect. To date we have found 25/53 items that exhibit inhibitory activity. Activity appears to be restricted to the following categories: vegetables, salads, herbs, mushrooms, fruits and red wine residue (25/36 items effective). Furthermore, as assessed in a similar experimental design with various doses of a mixture of active items, we determined the minimum effective dose of the dry items to be 170 mg/d. These results open the possibility for targeted interventions in humans.

Prevention of low bone mass is important to reduce the incidence of osteoporotic fractures. In man, the consumption of fruits and vegetables is associated with greater bone mineral density (BMD), an effect that is claimed to be caused by their base excess buffering metabolic acid, thought to dissolve bone. We showed previously that in the rat the consumption of several vegetables, salads, and herbs inhibits bone resorption and that onion increases bone mass. In this study we show that, although the intake of onion is associated with a decrease in urinary noncarbonic acid excretion and a concomitant inhibition of bone resorption of similar magnitude, the two findings are not causally related. Onion retains its bone resorption inhibitory activity in the rat even when added to a vegetarian diet with typical base excess. Onion and a mixture of vegetables, salads, and herbs retain their inhibitory activity even when metabolic acid is buffered with potassium citrate.