What is boron

Boron is a naturally occurring element that occurs in nature that is often found combined with other substances to form compounds called borates in the oceans, sedimentary rocks, coal, shale, and some soils. Common borate compounds include boric acid, salts of borates, and boron oxide. Boron enters the environment mainly through the natural weathering of clay-rich sedimentary rocks, geothermal steam, boric acid volatilization from seawater, and volcanic activity. Boron is widely distributed in nature, with concentrations of about 10 mg/kg in the Earth’s crust (range: 5 mg/kg in basalts to 100 mg/kg in shales) and about 4.5 mg/liter in the ocean. Boron is also released from man made sources to a lesser extent. These sources include agricultural, refuse, and fuel wood burning, power generation using coal and oil, glass product manufacture, use of borates/perborates in the home and industry, borate mining/processing, leaching of treated wood/paper, and sewage/sludge disposal ¹⁾.

Boron accumulates in aquatic and terrestrial plants but does not magnify through the food-chain ²⁾. Concentrations of boron have been shown to range between 26 and 382 mg/kg in submerged aquatic freshwater plants, from 11.3 to 57 mg/kg in freshwater emergent vegetation, and from 2.3 to 94.7 mg/kg dry weight in terrestrial plants ³⁾. Based on wet weights, boron concentrations in marine invertebrates and fish are similar to the levels found in the exposure media, between 0.5 and 4 mg/kg. The ion concentration factor for two freshwater fish species was found to be 0.3. In humans and animals, boric acid and borate are absorbed from the gastrointestinal and respiratory tracts. More than 90% of administered doses of these compounds are absorbed, as evidenced by excretion in the urine, which is rapid, occurring over a few to several days. Animal experiments have shown that boron in the form of boric acid and borate demonstrates reproductive and developmental toxicity at levels that are approximately 100- to 1000-fold greater than normal exposure levels ⁴⁾. There is a lack of sufficient toxicity data on humans ⁵⁾.

Several companies in the United States produce most of the world’s borates by processing boron compounds. The most important commercial borate products and minerals are borax pentahydrate, borax, sodium perborate, boric acid, colemanite, and ulexite. Major end uses for borate include insulation- and textile-grade fiberglass,  glass production, laundry bleach (sodium perborate), borosilicate glass, fire retardants, agricultural fertilizers and herbicides (as a trace element), and enamels, frits, and ceramic glazes, as well as a myriad of miscellaneous applications. Borates are also used in leather tanning industries, cosmetics, photographic materials, soaps and cleaners, and for high-energy fuel. Some pesticides used for cockroach control and some wood preservatives also contain borates. Sodium perborate hydrolyses to give hydrogen peroxide plus metaborate; consequently, it may exhibit chemical and toxicological properties that are somewhat different from those of the other borates.

Human requirements for boron remain undefined and there is no Recommended Daily Allowance (RDA) for boron since an essential biological role for it has not been identified. For humans, boron exposure occurs primarily through the diet and drinking-water. The mean global boron concentration in drinking-water was considered to be between 0.1 and 0.3 mg boron/liter ⁶⁾. For the general population, the greatest boron exposure comes from the oral intake of food. The mean daily intake of boron in the diet is about 1.2 mg ⁷⁾. The tolerable intake of boron was set as 0.4 mg/kg body weight per day ⁸⁾. The allocation of the tolerable intake in various media should be based on the exposure data of individual countries ⁹⁾. The Tolerable Upper Intake Level (UL), the maximum dose at which no harmful effects would be expected, is 20 mg per day for adults and pregnant or breast-feeding women over 19 years of age ¹⁰⁾. For adolescents 14 to 18 years of age and pregnant or breast-feeding women 14 to 18 years of age, the Tolerable Upper Intake Level (UL) is 17 mg per day. For children 9 to 13 years old, the Tolerable Upper Intake Level (UL) is 11 mg per day; children 4 to 8 years old, 6 mg per day; and children 1 to 3 years old, 3 mg per day. A Tolerable Upper Intake Level (UL) has not been established for infants ¹¹⁾.

Only a few human studies have been conducted to assess health effects associated with exposure to boron compounds. The available data show that boron exposure is associated with short-term irritant effects on the upper respiratory tract, nasopharynx, and eye ¹²⁾. These effects, however, appear to be short-term and reversible ¹³⁾. The sole long-term (7-year) follow-up study failed to identify any long-term health effects, although a healthy worker effect cannot be entirely ruled out given the rate of attrition (47%). Two descriptive studies assessed fertility and secondary sex ratios in relation to exposure. Neither study reported a detrimental effect on demonstrated fertility for its select sample ¹⁴⁾. Although an excess percentage of female births has been suggested, the absence of statistical significance and attention to other co-variates known to affect sex ratios warrants careful interpretation of this finding ¹⁵⁾. No studies have been identified that
assess the spectrum of reproductive outcomes, such as time-to-pregnancy, conception delays, spontaneous abortions, and sperm analyses in males ¹⁶⁾. The role of other lifestyle or behavioral factors in relation to health and fertility requires further study to identify potentially sensitive populations and to evaluate reproductive effects more fully ¹⁷⁾. In another chronic poisoning with low levels of boron ingestion study, there may be little more than dry skin and mucous membranes, followed by appearance of a red tongue, patchy alopecia, cracked lips, conjunctivitis, and sometimes periorbital edema and irritability ¹⁸⁾. In people receiving doses of greater than or equal to 5 mg Boron/kg body weight per day, signs and symptoms most frequently seen were dermatitis, alopecia, anorexia, and indigestion ¹⁹⁾. Other more serious adverse effects from ingesting boron supplement/tablets are renal and hepatic toxicity, seizures, coma and death ²⁰⁾.

Based on the lack of human data and the limited animal data, boron is not classifiable as to its human carcinogenicity ²¹⁾. From animal studies data ²²⁾ regarding developmental and reproductive toxicity show that lower fetal body weight in rats is the critical effect of boron. As boron dose level increases, the effects seen include: further rib effects and testicular pathology in the rat, decreased fetal body weight and increased fetal cardiovascular malformations in the rabbit, and severe testicular pathology in the rat; testicular atrophy and sterility in the rat; reduced fetal body weight in the mouse ²³⁾. Animal studies on mice and rats showed no evidence of carcinogenicity of boric acid ²⁴⁾.

Boron supplement

People take boron supplements as medicine. Boron is used for boron deficiency, painful menstruation, building strong bones, treating osteoarthritis, as an aid for building muscles and increasing testosterone levels, and for improving thinking skills and muscle coordination.

Women sometimes use capsules containing boric acid, the most common form of boron, inside the vagina to treat yeast infections.

People also apply boric acid to the skin as an astringent or to prevent infection; or use it as an eye wash.

Boron was used as a food preservative between 1870 and 1920, and during World Wars I and II.

The following boron doses have been studied in scientific research:

Adults by mouth

• For painful periods: Boron 10 mg daily from two days before until three days after the start of menstrual flow.

There is no Recommended Daily Allowance (RDA) for boron since an essential biological role for it has not been identified. People consume varying amounts of boron depending on their diet. Diets considered to be high in boron provide approximately 3.25 mg of boron per 2000 kcal per day. Diets considered to be low in boron provide 0.25 mg of boron per 2000 kcal per day.

The Tolerable Upper Intake Level (UL), the maximum dose at which no harmful effects would be expected, is 20 mg per day for adults and pregnant or breast-feeding women over 19 years of age. For adolescents 14 to 18 years of age and pregnant or breast-feeding women 14 to 18 years of age, the UL is 17 mg per day. For children 9 to 13 years old, the UL is 11 mg per day; children 4 to 8 years old, 6 mg per day; and children 1 to 3 years old, 3 mg per day. A UL has not been established for infants.

Vaginally:

• For vaginal infections: 600 mg of boric acid powder once or twice a day.

Children by mouth

The Tolerable Upper Intake Level (UL), the maximum dose at which no harmful effects would be expected, is 17 mg per day for adolescents 14 to 18 years of age and pregnant or breast-feeding women 14 to 18 years of age. For children 9 to 13 years old, the UL is 11 mg per day; children 4 to 8 years old, 6 mg per day; and children 1 to 3 years old, 3 mg per day. A Tolerable Upper Intake Level (UL) has not been established for infants.

Are there safety concerns for boron supplement?

Boron is likely SAFE for adults and children when used in doses less than the Upper Tolerable Limit (UL) (see dosage section above). There is some concern that doses over 20 mg per day, the Tolerable Upper Intake Level (UL) for adults, might harm a man’s ability to father a child.

Boric acid, a common form of boron, is likely SAFE when used vaginally for up to six months. It can cause a sensation of vaginal burning.

Boron is POSSIBLY UNSAFE for adults and children when taken by mouth in high doses. Large quantities of boron can cause poisoning. Signs of poisoning include skin inflammation and peeling, irritability, tremors, convulsions, weakness, headaches, depression, diarrhea, vomiting, and other symptoms.

Also, boric acid powder, a common form of boron, is POSSIBLY UNSAFE when applied in large amounts to prevent diaper rash.

Special precautions and warnings

Pregnancy and breast-feeding: Boron is likely safe for pregnant and breast-feeding women age 19-50 when used in doses less that 20 mg per day. Pregnant and breast-feeding women age 14 to 18 should not take more than 17 mg per day. Taking boron by mouth in high doses is POSSIBLY UNSAFE while pregnant and breast feeding. Higher amounts may be harmful and should not be used by pregnant women because it has been linked to birth defects. Intravaginal boric acid has been associated with a 2.7-to 2.8-fold increased risk of birth defects when used during the first 4 months of pregnancy.

Hormone-sensitive condition such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Boron might act like estrogen. If you have any condition that might be made worse by exposure to estrogen, avoid supplemental boron or high amounts of boron from foods.

Kidney disease or problems with kidney function: Do NOT take boron supplements if you have kidney problems. The kidneys have to work hard to flush out boron.

Boron interactions with medications

Moderate – be cautious with this combination.

Estrogens

Boron might increase estrogen levels in the body. Taking boron along with estrogens might cause too much estrogen in the body.

Boron interactions with herbs and supplements

Magnesium

Boron supplements can lower the amount of magnesium that is flushed out in the urine. This can lead to blood levels of magnesium that are higher than usual. Among older women, this seems to happen more often in women who do not get much magnesium in their diet. Among younger women, the effect appears to be greater in women who exercise less. No one knows how important this finding is to health, or whether it happens in men.

Phosphorus

Supplemental boron might reduce blood phosphorus levels in some people.

Boron benefits

Boron seems to affect the way the body handles other minerals such as calcium, magnesium, and phosphorus. It also seems to increase estrogen levels in older (post-menopausal) women and healthy men. Estrogen is thought to be helpful in maintaining healthy bones and mental function. Boric acid, a common form of boron, can kill yeast that cause vaginal infections.

Boron likely effective for:

Boron deficiency. Taking boron by mouth prevents boron deficiency.

Boron possibly effective for:

• Painful periods. Some research shows that taking boron 10 mg by mouth daily around the time of menstrual bleeding reduces pain in young women with painful periods.
• Vaginal infections. Some research shows that boric acid, used inside the vagina, can successfully treat yeast infections (candidiasis), including infections that do not seem to get better with other treatments. However, the quality of this research is in question.

Boron possibly ineffective for:

Athletic performance. Taking boron by mouth does not seem to improve body mass, muscle mass, or testosterone levels in male bodybuilders.

Boron insufficient evidence to rate effectiveness for:

• Improving thinking and coordination in older people. There is some early evidence that taking boron by mouth might improve cognitive function and the ability to coordinate small muscle movements (fine motor skills) in older people.
• Osteoarthritis. Developing research suggests that boron might be useful for decreasing symptoms of osteoarthritis.
• Osteoporosis. Early research suggests that taking boron by mouth daily does not improve bone mass density in postmenopausal women.
• Increasing testosterone.
• Other conditions.

More evidence is needed to rate the effectiveness of boron for these uses.

What is boron used for?

The end uses of boron minerals and of borate products are diverse. Nearly all boron ore extracted from the earth is destined for refinement into boric acid and sodium tetraborate pentahydrate. In the United States, 70% of the boron is used for the production of glass and ceramics ²⁵⁾. The major global industrial-scale use of boron compounds (about 46% of end-use) is in production of glass fiber for boron-containing insulating and structural fiberglasses, especially in Asia. Boron is added to the glass as borax pentahydrate or boron oxide, to influence the strength or fluxing qualities of the glass fibers. Another 10% of global boron production is for borosilicate glass as used in high strength glassware. About 15% of global boron is used in boron ceramics, including super-hard materials discussed below. Agriculture consumes 11% of global boron production, and bleaches and detergents about 6%.

Boron compounds of commerce

• Borax pentahydrate (disodium tetraborate pentahydrate)
• Borax (disodium tetraborate decahydrate)
• Ulexite
• Colemanite
• Sodium perborate tetrahydrate
• Sodium perborate monohydrate
• Boric acid
• Anhydrous borax (disodium tetraborate)
• Boron oxide
• Boron

Boron uses

1. Insulation-grade fiberglass,
2. Textile-grade fiberglass,
3. Soaps and detergents,
4. Borosilicate glass,
5. Fire retardants,
6. Agriculture,
7. Enamels, frits, and ceramic glazes,
8. Metallurgy,
9. Nuclear applications.

Boron is an essential micronutrient for higher plants, required primarily for maintaining the integrity of cell walls, with interspecies differences in the levels required for optimum growth. The availability of boron in the soil is also influenced by pH. Maximum boron availability occurs between soil pH 5 and 7 ²⁶⁾. However, high soil concentrations of greater than 1.0 ppm lead to marginal and tip necrosis in leaves as well as poor overall growth performance. Levels as low as 0.8 ppm produce these same symptoms in plants that are particularly sensitive to boron in the soil. Nearly all plants, even those somewhat tolerant of soil boron, will show at least some symptoms of boron toxicity when soil boron content is greater than 1.8 ppm. When this content exceeds 2.0 ppm, few plants will perform well and some may not survive ²⁷⁾.

Boron foods

Table 1. Foods high in boron

Food	mg/100 g	mg in a Typical Serving
Avocado	2.06	2.06
Apricots (dried)	2.11	0.53
Currants	1.74	0.26
Grapes (red)	0.50	0.50
Peach	0.52	0.57
Prunes	1.88	0.94
Raisins	4.51	0.67
Red kidney beans	1.4	1.82
Lentils	0.74	0.96
Almonds	2.82	0.42
Brazil nutsa	1.72	0.34
Cashew nuts	1.15	0.17
Hazelnuts	2.77	0.68
Peanut butter	1.92	0.38
Pistachio nuts	1.20	0.18
Walnuts (California)	1.63	0.24
Wine (Shiraz Cabernet)	0.86	0.86

Footnotes: Food processor overestimated boron content of richest food sources. Unfortunately, the numbers are thought to be inaccurate, with an estimation of their being up to 3 to 4 times higher than the values found using chemical analysis ²⁸⁾.

[Source ²⁹⁾]

Table 2. Chemical Analysis of Boron Content (mg/100 g) in the Top 10 Foods

Food	mg/100 g
Avocado	1.43
Peanut butter	0.59
Peanuts, dry	0.58
Prune juice	0.56
Chocolate powder	0.43
Red wine	0.36
Granola-raisin cereal	0.36
Grape juice	0.34
Pecans	0.26
Raisin bran	0.26

[Source ³⁰⁾]