It's found in drops, in powder form, and especially in shilajit, this high-altitude resin of which it is one of the main components. Fulvic acid has its advocates, who attribute many virtues to it, and its skeptics, who worry about heavy metals. What do studies actually measure, and what should you know before taking it?
This guide clarifies what fulvic acid is, its connection to shilajit, the benefits measured in humans and the strength of each finding, documented risks, side effects and precautions, then the criteria for choosing well and the doses used in trials.
What it is : fulvic acid is the fraction of humic substances, derived from the decomposition of organic matter, that remains soluble in water at all pH levels. It is found in soils, peat, lignite and shilajit, of which it is a major component alongside dibenzo-alpha-pyrones and minerals. Human trials are almost all conducted on purified and standardized shilajit: their results cannot be attributed to fulvic acid alone.
What studies show : increased testosterone in men ages 45 to 55 after 90 days, better-preserved strength after exhausting effort in the strongest individuals, slowed bone loss in postmenopausal women, improved sperm parameters in one study without a control group. The main risk lies in quality: unpurified shilajit can contain heavy metals and mycotoxins. Hence three criteria: a purified product, a declared content, an analysis certificate from an independent laboratory.
- Fulvic acid: what is it?
- Fulvic acid and shilajit: what's the connection?
- Benefits measured in humans: overview
- Testosterone and male fertility
- Strength, recovery and muscles
- Bones, brain, skin and microbiota
- Documented risks
- Side effects, interactions and contraindications
- How to choose and dose
- Frequently asked questions
Fulvic acid: what is it?
When organic matter decomposes, in soils, peatlands or certain rocks, it leaves behind humic substances. Chemists distinguish them according to their solubility:fulvic acid is the fraction that remains soluble in water at all pH levels,humic acid is the fraction that dissolves only in alkaline environments. Fulvic acid molecules are also smaller, around 2 kilodaltons, compared to 5 to 10 kilodaltons for humic acid.
Fulvic acid is therefore not a single molecule, but a mixture whose composition depends on its origin—soil, water, peat, lignite or shilajit—and on the extraction method. A 2018 review identified this as one of the reasons for divergent research results: depending on the source studied, fulvic acid proved anti-inflammatory in some studies and pro-inflammatory in others.
| Criterion | Fulvic acid | Humic acid |
|---|---|---|
| Solubility | Soluble at all pH levels | Soluble only in alkaline environments |
| Molecule size | Approximately 2 kilodaltons | 5 to 10 kilodaltons |
| Sources | Soils, waters, peat, lignite, shilajit | The same sources |
| In shilajit | One of the main components | Present also, in variable proportion |
Two families of products have been studied in humans. On one hand, a fulvic acid known as "carbohydrate-derived," obtained from sugars and not extracted from a natural deposit, tested on skin and orally. On the other, shilajit, the traditional source, used for a long time in Ayurvedic medicine, which accounts for the bulk of clinical trials.
<<<38>>> Humic substances substances humiques designate the whole, including humic acid and fulvic acid. shilajit is a natural resin that contains these substances, along with minerals and other active compounds. A supplement presented as "fulvic acid" can therefore be either an isolated extract or shilajit: the composition declared on the label and on the analysis certificate makes the difference.
Fulvic acid and shilajit: what's the connection?
Shilajit is a mineral and organic resin that seeps from rocks in high mountains, particularly in the Himalayas. A 2012 review estimates that humic substances, fulvic acid foremost, represent 60 to 80% of its composition. A 2014 review identifies fulvic acid and dibenzo-alpha-pyrones as its main active compounds, to which numerous minerals are added.
The authors describe shilajit as a phytocomplex in which humic substances, including fulvic acid, make up 60 to 80%. In vitro, fulvic acid blocks the aggregation of tau protein, which is involved in Alzheimer's disease. They also warn that unpurified shilajit may contain mycotoxins, heavy metals, polymeric quinones, and free radicals: only a purified, ready-to-use preparation should be used.
Carrasco-Gallardo C, Guzmán L, Maccioni RB. Int J Alzheimers Dis 2012;2012:674142. DOI: 10.1155/2012/674142
However, figures vary from one source to another. A 2018 review places shilajit's fulvic acid content at around 15 to 20%, while the purified extract used in several clinical trials contains at least 50%, with 10% dibenzo-alpha-pyrones. The difference stems from the origin of the resin, its purification, and the analysis method used. This is why a product's content is read on the analysis certificate of its batch.
Practical consequence: the effects observed with shilajit cannot be attributed to fulvic acid alone, since the resin also provides dibenzo-alpha-pyrones and minerals. Conversely, isolated fulvic acid has not been tested in the areas where shilajit has been, testosterone, muscle strength, or bone density. Our guide to shilajit benefits details all the studied uses.
Benefits measured in humans: overview
A 2014 review summed it up this way: shilajit safety is well documented in both animals and humans, but well-controlled trials remain relatively limited, and research needs standardized products. Since then, several randomized placebo-controlled trials have been published. Here's what they measure, and what makes each result solid.
| Area | Result | Study | Strength |
|---|---|---|---|
| Testosterone | Total and free testosterone, DHEAS increased; LH and FSH stable | Randomized placebo-controlled trial, men aged 45 to 55, 90 days | One trial; "possibly effective" according to a 2024 systematic review |
| Male fertility | Sperm count +61%, motility +12 to 17% | Before-after study, 28 oligospermic men, 90 days | Without control group |
| Strength and fatigue | Less strength lost after exhausting effort at 500 mg per day | Randomized placebo-controlled trial, 63 active men, 8 weeks | Difference from placebo in the stronger half of the group |
| Bone density | Bone loss slowed according to dose, at the spine and femoral neck | Randomized placebo-controlled trial, 60 postmenopausal women, 48 weeks | One trial, to be confirmed |
| Muscle | Genes of muscle support tissue activated | Study without placebo, overweight adults, 12 weeks | Biological measure, without performance testing |
| Cognition | Reduced apathy with shilajit combined with B vitamins | Randomized placebo-controlled trial, 82 patients with Alzheimer's disease | Combined product, effect not attributable to shilajit alone |
| Eczema, allergy | Better overall response in eczema, reduced allergic skin reaction | Small trials of a fulvic acid derived from carbohydrates | Fulvic acid alone, small sample sizes |
These trials need to be reproduced by other teams, and their results apply to purified and standardized extracts of known composition, not to raw resin. The following sections detail each of them.
Testosterone and male fertility
Healthy men aged 45 to 55 took 250 mg of purified shilajit or placebo twice daily for 90 days. Shilajit significantly increased total testosterone, free testosterone, and DHEA compared to placebo, while hormone levels that stimulate the testes, LH and FSH, remained stable.
Pandit S, Biswas S, Jana U, et al. Andrologia 2016;48(5):570-575. DOI: 10.1111/and.12482
A trial published in 2019 quantified these increases at approximately 20% for total testosterone, 19% for free testosterone, and 31% for DHEA. The stability of LH and FSH indicates that the effect does not occur through forced stimulation of the pituitary gland.
A 2024 systematic review devoted to "testosterone boosters" sold over-the-counter screened 52 studies covering 27 ingredients. The vast majority failed to demonstrate an increase in testosterone; purified shilajit is considered possibly effective in men with late-onset hypogonadism, the age-related decline in testosterone. It is one of the few ingredients to receive this rating.
For fertility, the data are more preliminary. In a 2010 study, 35 men with low sperm count took 100 mg of processed shilajit twice daily for 90 days. Among the 28 who completed the study, total sperm count increased by 61.4%, sperm motility increased from 12.4 to 17.4%, and testosterone increased by 23.5%, with liver and kidney function unchanged. The study had no control group and did not measure pregnancy rates: its results warrant a controlled trial.
These results concern men aged 45 to 55 for testosterone, and men with abnormal sperm analysis for fertility. Low testosterone is confirmed by blood testing and should be discussed with a physician: our guide low testosterone explains when to consult. For a conception plan, see our guide to male fertility.
Strength, recovery and muscles
Sixty-three active men averaging 21 years of age took 250 mg or 500 mg daily of purified shilajit, containing at least 50% fulvic acid, or placebo for 8 weeks. After two sets of 50 leg extensions at full power, the stronger half of the group lost only 8.9% of their strength at 500 mg, compared to 17.0% at 250 mg and 16.0% on placebo. Hydroxyproline, a marker of collagen breakdown, was also lower at 500 mg. No adverse effects were reported.
Keller JL, Housh TJ, Hill EC, et al. J Int Soc Sports Nutr 2019;16(1):3. DOI: 10.1186/s12970-019-0270-2
Across all participants, strength loss was 9.1% at 500 mg versus 15.7% at 250 mg, with no significant difference reported compared to placebo: the difference from placebo only appears in the analysis of the stronger half of the group. Dose matters: 250 mg daily performed no better than placebo. The effect focuses on maintaining strength during exertion and on connective tissue, not on maximum strength itself.
Another study, without placebo, followed overweight adults taking 250 mg twice daily for 8 weeks, then 4 weeks while adding exercise. Muscle biopsies showed activation of 17 genetic markers of the matrix surrounding fibers, collagen, elastin, decorin, with no changes in blood glucose, blood lipids, or muscle enzymes. This is a biological signal consistent with the previous trial, not yet a demonstrated performance gain.
For the athlete, the most solid lead remains therefore recovery between intense efforts, at 500 mg daily for at least 8 weeks. Our guide shilajit and sport details these uses.
Bones, brain, skin and microbiota
Sixty postmenopausal women aged 45 to 65 with osteopenia received a placebo, 250 mg or 500 mg daily of a standardized shilajit extract for 48 weeks. Under placebo, the bone mineral density of the lumbar spine and femoral neck continued to decline; with shilajit, this loss was slowed in a dose-dependent manner, with a significant difference at 24 and 48 weeks. Markers of bone remodeling, oxidative stress, and inflammation improved in both supplemented groups.
Pingali U, Nutalapati C. Phytomedicine 2022;105:154334. DOI: 10.1016/j.phymed.2022.154334
A promising result that remains to be confirmed by other research teams, and which is of particular interest to postmenopausal women. Our guide shilajit and women's health covers this topic.
On the brain side, fulvic acid prevents in vitro aggregation of tau protein, one of the markers of Alzheimer's disease. In humans, a randomized trial tested, in 82 patients with mild to moderate disease, a supplement combining Andean shilajit and B vitamins: apathy, the primary endpoint, decreased, homocysteine levels dropped, with no adverse effects related to the product. However, the combination with B vitamins makes it impossible to attribute the effect to shilajit alone.
Fulvic acid alone was tested in its carbohydrate-derived form. Applied topically at 3.5%, twice daily for 4 weeks, it showed a better overall response than a control cream in 36 patients with eczema. Taken orally in men with allergies, it reduced skin reaction to an allergen in 81% of participants, compared to 62% under placebo. In a pilot trial, fulvic acid derived from coal, applied at 4.5% topically, reduced an allergic reaction approximately as much as a 1% hydrocortisone cream.
Regarding the microbiota, finally, the data remain animal and in vitro: modified microbiota in fish, increased microbial diversity in guinea pigs, stimulated lactobacilli in culture. The only human trial cited, which combined probiotics and fulvic acid in patients with digestive disorders, did not improve digestive scores, but was well tolerated for 12 weeks. As for blood glucose, a 2018 review notes the absence of direct evidence for fulvic acid alone in type 2 diabetes. Our guide to intestinal microbiota covers the studied mechanisms.
Documented risks
The question "Is fulvic acid dangerous?" requires a two-part answer. The best-documented risk is not related to fulvic acid itself, but to product purity. Other signals come from animal studies, often at high doses or via routes that are not those of a supplement.
Researchers purchased 193 Ayurvedic products manufactured in the United States or India online and analyzed them. 20.7% contained detectable amounts of lead, mercury, or arsenic. Three-quarters of contaminated products nonetheless displayed good manufacturing practices, a designation that was not associated with lower contamination; the authors recommend testing by an independent laboratory.
Saper RB, Phillips RS, Sehgal A, et al. JAMA 2008;300(8):915-923. DOI: 10.1001/jama.300.8.915
Shilajit is directly affected: a 2024 review identifies approximately 65 metals reported in published analyses, including lead, arsenic, cadmium, and mercury. In most studies, levels remained below the limits set for herbal products, but not in all, and the authors conclude that consuming it without knowing its metal content is not safe. Unpurified shilajit may also contain mycotoxins.
| Risk | Data | Concerns |
|---|---|---|
| Heavy metals | Approximately 65 metals reported in shilajit, most often below limits, sometimes above | Unpurified or uncontrolled products |
| Mycotoxins | Possible in unpurified shilajit | Raw resins |
| Kashin-Beck disease | Hypothesis linking fulvic acid from well water and selenium deficiency, derived from cell and rat studies | Drinking water in certain regions of China, not supplements |
| Thyroid | TSH increase with dose in rats, mild hypothyroid effect | High dietary doses in animals |
| Immune stimulation | Antibody production increased more than fourfold in rats | Caution in case of autoimmune disease |
The Kashin-Beck disease, a condition affecting cartilage and joints observed in certain regions of China, is often cited. A 1999 study showed that fulvic acid isolated from water in these regions increased lipid peroxidation in cartilage cells, an effect mitigated by selenium, as well as in rats receiving injections, or water enriched with a diet low in selenium. A fulvic acid derived from peat did not have this effect. The hypothesis concerns prolonged environmental exposure, combined with selenium deficiency, not supplements.
In rats, diets containing 0.1 to 0.8% humic or fulvic acids over 26 days raised TSH and lowered thyroid hormones in a dose-dependent manner, a slight hypothyroid effect, while increasing antibody production more than fourfold at 0.4% fulvic acid. These doses, very high, do not correspond to a supplement, and no human data shows this effect; nevertheless, they warrant caution in cases of thyroid disease or autoimmune conditions.
A product without declared fulvic acid content, without mention of purification, or without a heavy metals analysis certificate from an independent laboratory. A mention of good manufacturing practices is not sufficient: in the JAMA study, it did not distinguish contaminated products. Our guide to choosing high-quality shilajit details the points to verify.
Side effects, interactions and contraindications
At trial doses, tolerance is good. No adverse effects were reported with 250 to 500 mg per day of purified shilajit for 8 weeks, and liver and kidney function tests remained normal at 200 mg per day for 90 days. Reported side effects mainly concern fulvic acid derived from carbohydrates, a highly acidic solution: diarrhea, headaches and sore throat, especially at the highest dose, and a brief burning sensation when applied to the skin.
Thirty men with allergies took a carbohydrate-derived fulvic acid at increasing doses up to 40 mL twice daily, then placebo, or vice versa, for 7 days each time. Blood tests and electrocardiograms remained stable. Adverse effects, diarrhea, headaches, sore throat, appeared mainly at the highest dose, which the authors link to the acidity of the solution; 15 mL per day, diluted, were considered safe.
Gandy JJ, Meeding JP, Snyman JR, van Rensburg CE. Clin Pharmacol 2012;4:7-11. DOI: 10.2147/CPAA.S25784
No human study has evaluated interactions with medications. However, a signal exists: in a rat intestinal model, fulvic acid increased the absorption of carbamazepine, an antiepileptic drug. And because shilajit raises testosterone and DHEA-S, medical advice is necessary in case of hormone treatment or pathology sensitive to hormones.
| Situation | Why | Recommendation |
|---|---|---|
| Pregnancy, breastfeeding | No data, situations excluded from trials | Avoid |
| Children | No oral studies | Avoid |
| Liver or kidney disease | Patients excluded from trials | Medical advice before |
| Thyroid disease | Hypothyroid effect at high dose in rats | Medical advice before |
| Autoimmune disease | Immune stimulation in rats, patients excluded from a trial | Medical advice before |
| Hormone-sensitive pathology | Increase in testosterone and DHEA-S | Medical advice before |
| Long-term treatment | Increased absorption of a medication in an animal model | Medical advice before |
Our article shilajit: dangers and contraindications completes this point, situation by situation.
Choosing and dosing correctly
The reviews all conclude in the same direction: promising results, and the need for standardized and controlled products. The selection criteria follow directly from this.
| Criterion | Why | What to verify |
|---|---|---|
| Purification | Raw shilajit may contain heavy metals, mycotoxins and other impurities | Mention of a purified resin, and the process used |
| Declared content | The proportion of fulvic acid ranges from 15 to over 50% depending on the origin and process | The percentage of fulvic acids, batch by batch |
| Independent analysis | A mention of good practices does not guarantee the absence of contamination | A certificate of analysis for heavy metals, with the laboratory and report number |
Trial doses range from 200 to 500 mg per day of purified extract: 250 mg twice daily for 90 days for testosterone, 500 mg daily for 8 weeks for strength, 250 to 500 mg daily for 48 weeks for bone density, 100 mg twice daily for fertility. A 30 g jar of resin used over 2 to 3 months corresponds to approximately 330 to 500 mg per day, within the studied range, even though no trial specifically tested a particular resin.
Hand-harvested beyond 5,100 meters in the Himalayas, purified by 40 successive filtrations and sun-dried for 45 to 60 days, our resin concentrates up to 70% fulvic acids. Each batch is analyzed by Eurofins, an independent laboratory, and its certificate of analysis for heavy metals, with report number, is accessible. A 30 g jar covers 2 to 3 months, or approximately 330 to 500 mg per day, within the trial range.
View the ShilajitOur guide When and how much shilajit to take Details the instructions for use.
Frequently Asked Questions
Fulvic acid, what is it?
It is the fraction of humic substances, derived from the decomposition of organic matter, that remains soluble in water at all pH levels. Its molecules are small, around 2 kilodaltons. It is found in soils, water, peat, lignite, and shilajit, of which it is one of the main components. Its composition varies depending on the origin and extraction method.
What is the difference between humic acid and fulvic acid?
Humic acid dissolves only in alkaline conditions and its molecules are larger, 5 to 10 kilodaltons; fulvic acid is soluble at all pH levels and its molecules weigh approximately 2 kilodaltons. Shilajit contains both, in proportions that vary depending on the origin of the resin and the analysis method.
What is the link between fulvic acid and shilajit?
Shilajit is a mineral and organic resin that seeps from high mountain rocks. Humic substances, fulvic acid foremost, make up 60 to 80% of it, alongside dibenzo-alpha-pyrones and numerous minerals. The extract used in several trials contained at least 50% fulvic acid: its effects cannot therefore be attributed to fulvic acid alone.
What benefits of fulvic acid are proven in humans?
The trials involved purified and standardized shilajit: increased testosterone in men aged 45 to 55, better-preserved strength after exhausting effort in the strongest, slowed bone loss in menopausal women, improved sperm parameters in a study without a control group. For fulvic acid alone, data is limited to small trials on eczema and cutaneous allergic reaction.
Does fulvic acid increase testosterone?
A placebo-controlled trial measured an increase in total and free testosterone and DHEAS with 250 mg of purified shilajit twice daily for 90 days in men aged 45 to 55, with LH and FSH hormones remaining stable. A 2024 systematic review considers it possibly effective for late-onset hypogonadism. This data concerns shilajit, not isolated fulvic acid.
Is fulvic acid good for the microbiota?
The data are animal and in vitro: modified microbiota in fish, increased microbial diversity in guinea pigs, lactobacilli stimulated in culture. The only human trial cited, combining probiotics and fulvic acid, did not improve digestive scores, while being well tolerated for 12 weeks.
Is fulvic acid dangerous?
The main risk lies in quality: unpurified shilajit can contain heavy metals and mycotoxins, and 20.7% of Ayurvedic products purchased online contained lead, mercury, or arsenic. Cell and rat studies also suggest a role for fulvic acid from well water in Kashin-Beck disease, in case of selenium deficiency, and a slight hypothyroid effect at high dietary doses.
What are the side effects of fulvic acid?
No adverse effects were reported with 250 to 500 mg per day of purified shilajit for 8 weeks, and liver and kidney function tests remained normal at 200 mg per day for 90 days. A carbohydrate-derived fulvic acid, highly acidic, caused diarrhea, headaches, and sore throat, especially at high doses. Pregnancy, breastfeeding, and childhood remain without data.
What dose of fulvic acid or shilajit to take?
The trials used 200 to 500 mg per day of purified shilajit, for 8 to 48 weeks depending on the objective: 250 mg twice daily for testosterone, 500 mg per day for strength. A 30 g jar of resin used over 2 to 3 months corresponds to approximately 330 to 500 mg per day. In case of treatment or chronic disease, the dose should be discussed with a doctor.
Fulvic acid review: how to choose well?
Reviews judge the results promising and demand standardized products. Three criteria follow from this: a purified product, a stated fulvic acid content, and a certificate of analysis for heavy metals from an independent laboratory, with its report number. A simple mention of good manufacturing practices is not sufficient.
Sources
The studies cited below were identified via PubMed.
- Winkler J, Ghosh S. Therapeutic potential of fulvic acid in chronic inflammatory diseases and diabetes. Journal of Diabetes Research, 2018;2018:5391014. DOI
- Carrasco-Gallardo C, Guzmán L, Maccioni RB. Shilajit, a natural phytocomplex with procognitive potential. International Journal of Alzheimer's Disease, 2012;2012:674142. DOI
- Stohs SJ. Safety and efficacy of shilajit (mumie, moomiyo). Phytotherapy Research, 2014;28(4):475-479. DOI
- Hussain A, Saeed A. Dangerous or beneficial: the role of heavy metals and humic substances in shilajit, and their toxicity. Biological Trace Element Research, 2024;202(12):5794-5814. DOI
- Pandit S, Biswas S, Jana U, et al. Clinical evaluation of purified shilajit on testosterone in healthy volunteers. Andrologia, 2016;48(5):570-575. DOI
- Biswas TK, Pandit S, Mondal S, et al. Clinical evaluation of the spermatogenic activity of treated shilajit in oligospermia. Andrologia, 2010;42(1):48-56. DOI
- Keller JL, Housh TJ, Hill EC, et al. Effects of shilajit supplementation on fatigue-induced loss of muscle strength and serum hydroxyproline. Journal of the International Society of Sports Nutrition, 2019;16(1):3. DOI
- Das A, Datta S, Rhea B, et al. The human skeletal muscle transcriptome in response to oral shilajit supplementation. Journal of Medicinal Food, 2016;19(7):701-709. DOI
- Pingali U, Nutalapati C. A shilajit extract reduces oxidative stress, inflammation, and bone loss in postmenopausal women with osteopenia: a randomized, double-blind, placebo-controlled trial. Phytomedicine, 2022;105:154334. DOI
- Guzman-Martinez L, Farías GA, Tapia JP, et al. Clinical effects and safety of the BrainUp-10 supplement in patients with Alzheimer's disease: a multicenter, randomized, double-blind, placebo-controlled trial. Journal of Alzheimer's Disease, 2021;81(3):1231-1241. DOI
- Morgado A, Tsampoukas G, Sokolakis I, et al. Do "testosterone boosters" really increase total testosterone? A systematic review. International Journal of Impotence Research, 2024;36(4):348-364. DOI
- Gandy JJ, Snyman JR, van Rensburg CE. Randomized double-blind trial of a carbohydrate-derived fulvic acid applied topically in eczema. Clinical, Cosmetic and Investigational Dermatology, 2011;4:145-148. DOI
- Gandy JJ, Meeding JP, Snyman JR, van Rensburg CE. Phase 1 clinical study of the acute and subacute safety of a carbohydrate-derived fulvic acid, and first evidence of efficacy. Clinical Pharmacology: Advances and Applications, 2012;4:7-11. DOI
- Szwed-Georgiou A, Płociński P, Włodarczyk M, et al. Safety and microbiome effects of fulvic acid formulations, in vitro and in vivo. Scientific Reports, 2026;16(1):6166. DOI
- Peng A, Wang WH, Wang CX, et al. The role of humic substances in drinking water in Kashin-Beck disease in China. Environmental Health Perspectives, 1999;107(4):293-296. DOI
- Vucskits AV, Hullár I, Bersényi A, et al. Effects of fulvic and humic acids on growth, immune response and thyroid function in rats. Journal of Animal Physiology and Animal Nutrition, 2010;94(6):721-728. DOI
- Saper RB, Phillips RS, Sehgal A, et al. Lead, mercury and arsenic in Ayurvedic medicines manufactured in the United States and India and sold online. JAMA, 2008;300(8):915-923. DOI
