This study is a great follow-up to the story I posted last year questioning whether or not you really needed calcium to build strong bones. In childhood, building strong bones reflects the genetic and environmental influences on calcium and bone metabolism. The amount of calcium excreted in the urine is one factor of calcium balance that provides insights into the effects of dietary intake on calcium and bone metabolism. Over 90 percent of the calcium excreted in urine reflects bone turnover rather than calcium that is consumed in the diet. This study showed that girls who consumed fruit and vegetables three times or more a day had, when compared with similar girls who reported consuming fruit and vegetables less than three times a day:
- Lower levels of calcium
- Lower parathyroid hormone concentrations, which improves bone density
- Larger bone size as indicated by bone area of the whole body and of the nondominant wrist after control for age, BMI and physical activity
Additionally, the girls with high fruit and vegetable intakes, relative to those who consumed lower amounts, reported higher concentrations of:
- Potassium
- Magnesium
- Vitamin A
- Vitamin C
Diets in Westernized countries are characterized as rich in meat products and lower in fruit and vegetables than is recommended for optimal health. The net metabolic acid load of these diets is considered to produce larger quantities of acid, as indicated by the bicarbonate and pH of the blood. In humans with normal kidney function, the acid-base balance is dependent on the ability of the kidney to excrete excess acid and the availability of a base for buffering. Fruit and vegetables provide a natural source of base to buffer the acid produced by other dietary components.
In the early phase, potassium and sodium contained in the bone-fluid barrier are the first line of defense for buffering metabolic acidosis, and thus they spare the bone tissue. In a long-term state of metabolic acidosis, bone crystals are dissolved to provide calcium, carbonate and citrate for buffering.
American Journal of Clinical Nutrition February 2004;79(2) 311-317