Deficiencies: In vitamin D deficient animals fed very low intakes of boron there were increases in total calcium loss, interference with the use of blood sugar (glucose), fat, and insulin, and dminished bone development. In humans, no deficiencies have been documented in free-living populations. However, careful study of volunteers in special living quarters shows that reducing the amount of dietary boron causes changes in blood glucose and fat similar to that seen in boron-deficient animals. For reasons not fully understood, boron supplementation increases the percent of calcium intake lost in the urine of both pre- and post-menopausal volunteers. Very low intakes of boron may aggravate the symptoms of arthritis.

Diet recommendations: The usual adult dietary boron intake in the US is about 1 mg/day. Use of boron supplements is not recommended because neither an Estimated Safe and Adequate Dietary Intake (ESADDI) or Recommended Daily Allowance (RDA) has been set for boron.

Food sources: The main sources of boron in the diet are drinking water (which varies considerably between geographical locations), milk and dairy products, and juices and beverages. On a wet weight basis, fruits, vegetables, legumes and nuts (dicotyledonous plants) contain much more boron than grains, breads, and cereals (monocotyledonous plants). Animal products (meats, poultry, fish, etc.) contain very little boron but milk and dairy products are major contributors to total boron intake because of the large quantities consumed.

Toxicity: Almost all the boron that enters the body from diet or absorption through damaged skin is promptly excreted in the urine. However, this control process can be overwhelmed by very high boron intakes that cause acute boron toxicity with nausea, vomiting, headache, diarrhea, hypothermia, restlessness, skin loss, kidney damage, and death from circulatory collapse and shock. The minimum lethal dose for humans is not known although single doses of 18 to 20 g in adults have been fatal. Chronic boron toxicity symptoms include poor appetite, nausea, weight loss, and decreased sexual activity, seminal volume, and sperm count. Death from boron poisoning is rare probably because of the emphasis placed on maintaining electrolytic balance and supporting kidney function during the worst part of the illness.

Recent research: In animal studies, boron improves the production of antibodies that help fight infection and markedly decreases peak secretion of insulin from the pancreas.