small boron pool that blood represents as well as efficient absorption and excretion. The excretory form of boron has not been studied. As a neutral molecule, blood borate should have high fractional renal clearance and easily enter the glomerular filtrate.

There is evidence supporting a biological role of boron in some microroganisms. In higher animals, boron has been shown to have a role in reproduction and development. The collective body of evidence, however, has yet to establish a clear biological function for boron in humans. Therefore, neither an Estimated Average Requirement, Recommended Dietary Allowance, nor Adequate Intake was established for boron.

Hunt and coworkers (1991) reported that the highest concentrations of boron were found in fruit-based beverages and products, tubers, and legumes. Depending on the geographic location, water could contribute a major portion of the dietary boron. Negligible or minimal amounts (less than 0.100 μg/g) were found in animal products, certain grain products, condiments, and confections. Similar findings were reported by Anderson and coworkers (1994). Meacham and Hunt (1998) reported that the ten foods with the highest concentration of boron were avocado, peanut butter, peanuts, prune and grape juice, chocolate powder, wine, pecans, and granola raisin and raisin bran cereals. Rainey and coworkers (1999), however, examined both the content and total food consumption (amount and frequency), reporting that the five major contributors of boron were coffee, milk, apples, dried beans, and potatoes, which collectively accounted for 27 percent of the dietary boron consumption. Although coffee and milk are low in boron, they were the top contributors due to the volumes consumed.

U.S. boron consumption was assessed by use of the Boron Nutrient Data Base linked to 2-day food records from respondents to the Third National Health and Nutrition Examination Survey (NHANES III) (Appendix Table C-12) and the Continuing Survey