Research suggests that this nutrient may be needed in the metabolism of calcium, magnesium, copper, phosphorus and Vitamin D. Bones contain the highest concentrations of boron. Vegetables are the best food source of boron, but levels vary based on the amount of boron in the soil. Boron can also be acquired through dairy products, fish and meat. Gluconic acid occurs naturally in fruit, honey, kombucha tea, and wine. As a food additive (E574), it is an acidity regulator. It is also used in cleaning products where it dissolves mineral deposits especially in alkaline solution. The gluconate anion chelates Ca2+, Fe2+, Al3+, and other heavy metals. Calcium gluconate, in the form of a gel, is used to treat burns from hydrofluoric acid.