Boron

What is boron and what does it do in the body?

Boron is a trace element found naturally in many foods and also sold as a supplement; in plants it is a structural component of the cell wall and is needed for plant growth, pollination, and seed formation. NIH ODS states that boron is not classified as an essential nutrient for humans because research has not yet identified a clear biological function. The same source adds that boron may have beneficial effects on reproduction and development, calcium metabolism, bone formation, brain function, insulin and energy metabolism, immunity, and the function of steroid hormones (including vitamin D and estrogen). ^[1]

In foods and beverages, boron is found as inorganic borates and sugar-borate esters (e.g., calcium fructoborate). Most ingested boron is converted to boric acid in the intestine, and the body absorbs about 85–90% of ingested boron. Boron does not accumulate in most tissues; it is found at higher levels in bone, nails, and hair than in other tissues and at low levels in fat. That blood boron level does not change markedly despite large increases in dietary intake suggests that the body maintains boron balance, most likely by increasing urinary excretion; the regulatory mechanism has not been described. Boron is excreted mainly in urine. ^[1]

Boron status is not routinely measured in clinical practice. Most studies report that urinary boron level is related to intake; in postmenopausal women, fasting plasma boron concentration was found to range from 34 to 95 ng/mL. ^[1]

Forrest Nielsen’s 2014 narrative review suggests that boron is a bioactive element that favorably affects bone growth and central nervous system function in in vitro, animal, and human experiments; it states that intake below 1.0 mg/day prevents the benefits of boron and that intake at this level is not uncommon. This is the opinion of the review’s author and is not an RDA proposal. ^[2] NIH ODS relays that the World Health Organization (1996) estimated the acceptable safe range of boron intake for adults as 1–13 mg/day. ^[1]

Which foods contain boron, and what is the daily intake?

According to NIH ODS, the foods with the highest boron content are plant sources; fruits, tubers, and legumes stand out. The foods contributing most to boron intake in the US are coffee, milk, apples, dried and cooked beans, and potatoes, because they are consumed in large amounts. Wine, cider, and beer also contain boron. The boron content of plants depends on the soil and water they grow in; ODS notes that boron concentration in soil is higher in arid regions, including some regions of Türkiye. ^[1]

The table below shows selected values from NIH ODS based on US servings (1 cup ≈240 mL). ODS also notes that USDA FoodData Central does not list the boron content of foods, so data on boron in foods are limited. ^[1]

According to NHANES III (1988–1994) and CSFII (1994–1996) data, median dietary boron intake ranges from 0.87 to 1.35 mg/day in adults, 1.05–1.08 mg/day in pregnant women, and 0.75–0.96 mg/day in school-age children. Considering foods and supplements together, median total intake in adults is about 1.0–1.5 mg/day. Because boron is abundant in plant foods, vegetarians tend to have higher intake than non-vegetarians. ^[1]

In what forms is boron found in supplements?

Boron is found in supplements containing only boron and in products sold together with a few other nutrients (mostly minerals). NIH ODS reports the common amount of elemental boron in supplements as 0.15–6 mg. The forms used include sodium borate, sodium tetraborate, boron amino acid chelate, boron ascorbate, aspartate, citrate, gluconate, glycinate, picolinate, and calcium fructoborate. The supplement label declares the amount of elemental boron, not the weight of the whole compound. In a small human study, boron taken as sodium tetraborate significantly raised plasma boron level within 4–6 hours; however, there are no data on the relative bioavailability of different boron forms. ^[1]

Does boron work for joint pain and osteoarthritis?

NIH ODS states that observational evidence and a few small human studies suggest boron may reduce osteoarthritis symptoms, but that this needs confirmation in more controlled studies. The studies ODS relays are: two eight-week studies of 20 participants each (one a placebo-controlled pilot, the other unblinded and without a placebo control), a two-week double-blind placebo-controlled inflammation marker trial in 60 participants with osteoarthritis, and a two-week double-blind placebo-controlled trial in 60 adults with self-reported knee discomfort. ^[1]

One of these trials is the 2014 study by Pietrzkowski and colleagues: 60 participants with self-reported knee discomfort received calcium fructoborate, a sugar-borate complex containing boron, or placebo. The McGill Pain Questionnaire (MPQ) difference was −5.8 on day 7 (P=0.0009) and −8.9 on day 14 (P < 0.0001); the WOMAC difference was −5.3 on day 7 (P=0.06) and −13.73 on day 14 (P < 0.0001). No change in scores was seen in the placebo group. ^[4] Some of the study’s authors work at the company that funded the study and supplied the boron compound; one author is the inventor on several patents related to this compound. The journal required that the study be registered retrospectively after publication. ^[5] The duration is two weeks, and participants were selected by a criterion of self-reported knee discomfort, not an osteoarthritis diagnosis. ^[4]

For this reason, the joint evidence for boron is rated at grade D: the studies are small, short-term, and partly manufacturer-linked; ODS states that additional controlled studies are needed.

Does boron support bone health?

NIH ODS relays that in animal studies, boron deficiency led to abnormal limb development, delayed growth plate maturation, and reduced bone strength, and boron supplementation improved some measures of bone strength in animals. In humans the picture is different: in 134 Korean women (mean age 41), a mean boron intake of 0.9 mg/day was not significantly associated with bone mineral density in the lumbar spine and femur regions. In a placebo-controlled study of 17 female athletes and 11 sedentary women, 3 mg/day of boron for 10 months significantly lowered serum phosphorus and raised serum magnesium in sedentary women; however, the supplement did not directly affect bone mineral density. ODS states that additional research is needed to determine whether boron affects bone health in humans. ^[1]

Does boron affect testosterone and hormones?

The testosterone claim rests on the 2011 study by Naghii and colleagues. Eight healthy men made three visits: placebo on the first day, a capsule containing 10 mg of boron the next day, then 10 mg of boron daily for one week. Within six hours, sex hormone-binding globulin (SHBG), high-sensitivity CRP, and TNF-α fell; at the end of one week, mean plasma free testosterone rose and estradiol fell. The authors describe this as the first human study to show a rise in free testosterone after boron consumption. ^[6] The study has 8 people; its abstract does not mention a separate control group or randomization, and the results were not tied to a clinical benefit (muscle, sexual function, fertility). ^[6] This row is rated D.

Does boron affect cancer risk?

NIH ODS relays that observational studies found an inverse association between boron intake and the risk of prostate cancer (in men), and lung and cervical cancer (in women). For example, in a case-control study comparing 763 women with lung cancer and 838 healthy women, the risk in those in the lowest quartile of boron intake (less than 0.78 mg/day) was about twice that of the highest quartile (more than 1.25 mg). There are no clinical studies examining boron for cancer prevention or treatment. ^[1]

A community-based study in Türkiye examined 456 men: 159 were from villages rich in boron with drinking water boron levels above 1 mg/L (the study group), 63 from villages rich in boron but with water boron levels below 1 mg/L, and 234 from villages without boron mines. Total PSA levels did not differ significantly between groups; the authors report that they found no statistically significant association between prostate cancer and boron exposure, while also stating that high boron exposure may play a role in prostate cellular processes. ^[7] NIH ODS summarizes the same study as finding that prostate volume was significantly smaller in men with an intake of about 6 mg/day of boron (compared with those with 0.64–0.88 mg/day), while PSA did not differ. ^[1]

Are boron supplements safe, and what is the upper limit?

The upper limit (UL) is a ceiling value for total usual daily intake; it is not a limit for a single serving. EFSA defines the UL as the highest level of chronic total daily intake from all sources at which no adverse health effect is expected in humans. ^[3] According to NIH ODS, the FNB based the boron UL values on levels associated with reproductive and developmental effects in animals; there are no data on side effects of high boron intake from food or water. ^[1] Because the two institutions’ age ranges differ, the values are given in separate tables.

In the NIH table, no upper limit has been set for 0–12 months; it is stated that the boron source for infants should be breast milk, formula, and food. ^[1]

The values in the EFSA table are taken from version 11 (August 2025) of EFSA’s “Overview on Tolerable Upper Intake Levels” document; EFSA refers to its own 2004 opinion for boron. ^[3]

Symptoms of ingesting high amounts of boron are mostly known from accidental ingestion of cleaning products and agricultural chemicals containing borax (sodium borate) or boric acid: nausea, gastrointestinal discomfort, vomiting, diarrhea, skin redness and rash, agitation, seizures, depression, and vascular collapse. In these cases the amount of boron ingested ranged from 18 to 9,713 mg and most were children younger than 6 years; in adults, 15,000–20,000 mg can lead to death. ^[1] In two poison control center series retrospectively examining 784 boric acid ingestions, 88.3% of cases were entirely asymptomatic and none developed serious toxicity; the most common symptoms were vomiting, abdominal pain, and diarrhea. ^[8] These data concern accidental ingestion and are not evidence of safety for amounts taken as a supplement.

NIH ODS states that there are no known clinically significant drug interactions with boron. ^[1]

How are boron supplements regulated in Türkiye?

In Türkiye, Ministry of Agriculture and Forestry approval is mandatory for every food supplement to be placed on the market; approval applications for imported products can be made only to the Istanbul and Ankara Provincial Directorates. ^[10]

In the latest update of the Ministry’s Restricted Substances List for food supplements (September 21, 2026), boron appears in the section titled “Sources of Vitamins and Minerals Used Before December 31, 2025,” in the row “Boron (mg)” among the minerals, and its source is written as “chemical synthesis”; there is no numerical upper limit in this row. ^[9] This information does not mean that a daily upper limit for boron has been set in Türkiye; it only shows that no figure appears in this row of the list.

Evidence table: claim, population, and limits

This guide does not recommend individual doses. In pregnancy, childhood, regular medication use, and chronic disease, the decision depends on individual assessment.