Wheatgrass and barley grass

What it is

These are the young leaves of the wheat plant (Triticum aestivum) and barley plant (Hordeum vulgare), harvested before the grain forms and sold as juice, powders and tablets. Young barley powders contain minerals such as iron and manganese, and have also been found to carry heavy metals and pesticide residues.

What the research says

Very little human trial evidence exists. We found one small randomized placebo-controlled trial of wheatgrass juice (23 patients with ulcerative colitis, one month) and one non-randomized pilot study in women on chemotherapy; both reported benefits, both were tiny, and neither has been confirmed. We found no controlled human trial of barley grass powder on a health outcome. Memorial Sloan Kettering's herb database says the popular claims are not backed by scientific studies. Product tests of young barley supplements found mercury, arsenic risk and pesticide residues above limits in some samples.

Evidence grade: Not supported by the research.

What goes wrong

In the chemotherapy pilot study, wheatgrass juice made nausea worse in six patients, who stopped taking it. (Source 1)

• Cohort study, Very low certainty.
• Size: 60 patients.
• Who: Women on chemotherapy.
• How long: First three cycles.
• Result: Worsened nausea in 6 patients.
• Funding: not stated.

Side effects related to WGJ were minimal, including worsening of nausea in six patients, causing cessation of WGJ intake.

Memorial Sloan Kettering lists nausea and possible microbial contamination as adverse issues with wheatgrass because it is grown for 7 to 10 days before harvest. (Source 2)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: Not applicable.
• How long: Not applicable.
• Result: Not applicable.
• Funding: independent.

Because wheat grass is grown for a period of 7–10 days before harvesting leaves, microbial contamination is possible.

Testing of young green barley supplements found mercury, imidacloprid (a pesticide) and PAHs above EU limits in some samples, and estimated a significant health risk from arsenic with regular use. (Source 3)

• Survey study, Low certainty.
• Size: Tablets, powders and juices from the market (numbered samples)
• Who: Commercial young barley supplements.
• How long: Not applicable.
• Result: Mercury above limit in 2 powders and 3 tablets; imidacloprid above limit in 6 powders; PAH4 above limit in 1 powder.
• Funding: not stated.

Calculated risk assessment also indicated that regular consumption of these dietary supplements could pose a significant health risk in case of arsenic.

What the evidence supports

In a small randomized, double-blind trial, wheatgrass juice for one month reduced a disease activity index and rectal bleeding in active distal ulcerative colitis. (Source 4)

• Randomized trial, Very low certainty.
• Size: 23 randomized; 19 with full data.
• Who: Adults with active distal ulcerative colitis, Israel.
• How long: 1 month.
• Result: Disease activity index P = 0.031; rectal bleeding severity P = 0.025.
• Funding: not stated.

Treatment with wheat grass juice was associated with significant reductions in the overall disease activity index (P = 0.031) and in the severity of rectal bleeding (P = 0.025).

A non-randomized matched-control pilot study in 60 women with breast cancer suggested wheatgrass juice during chemotherapy was linked with fewer blood-toxicity-related treatment changes; the authors say it needs confirming. (Source 1)

• Cohort study, Very low certainty.
• Size: 60 patients.
• Who: Women with breast carcinoma on FAC chemotherapy.
• How long: First three chemotherapy cycles.
• Result: Censoring events 5 in wheatgrass arm vs 15 in control (P = 0.01)
• Funding: not stated.

Analysis of the results showed that five censoring events occurred in Arm A and 15 in Arm B (P = 0.01).

What the evidence does not support

Before that 2002 trial, wheatgrass juice had never been tested in a controlled clinical trial despite 30 years of claims. (Source 4)

• Randomized trial, Very low certainty.
• Size: Not applicable.
• Who: Not applicable.
• How long: Not applicable.
• Result: Not applicable.
• Funding: not stated.

but was never clinically assessed in a controlled trial

Memorial Sloan Kettering's herb database (updated 2023) states that the claims made for wheatgrass are not backed by studies and that it has not been shown to treat cancer or AIDS. (Source 2)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: Not applicable.
• How long: Not applicable.
• Result: Not applicable.
• Funding: independent.

Wheat grass juice has not been shown effective in treating cancer or AIDS.

Where the evidence is mixed

The only placebo-controlled trial of a greens blend we found (AG1, which contains grass ingredients among many others) was small, short and manufacturer-funded, and found no difference in digestive quality of life. (Source 5)

• Randomized trial, Low certainty.
• Size: 20 adults.
• Who: Healthy resistance-trained adults.
• How long: 14 days per arm.
• Result: Digestive quality of life p = 0.777.
• Funding: industry-funded (AG1)

This research was funded by AG1 (Carson City, NV, USA).

Where the research disagrees

Whether wheatgrass juice has shown any clinical benefit

• Ben-Arye et al. 2002 trial authors, RCT, 23 patients: Wheat grass juice appeared effective and safe as a single or adjuvant treatment of active distal UC. (Source 4)
• Memorial Sloan Kettering herb database (2023), expert summary: However, none of these claims is backed by scientific studies. (Source 2)

How much

• Reference intake: No recommended intake exists for wheatgrass or barley grass; neither is an essential nutrient. (Source 2)
• Upper limit: No upper limit has been set for cereal grass powders in the sources we read. (Source 2)
• Studied: The ulcerative colitis trial gave 100 cc of wheatgrass juice daily for one month. (Source 4)
• Studied: The chemotherapy pilot gave 60 cc of wheatgrass juice daily during the first three cycles. (Source 1)

A common belief, and what the research shows

The belief: Wheatgrass and barley grass are always safe on a gluten-free diet.

What the research shows: The grass leaves themselves are not the grain, but gluten can enter through cross contact with seeds, which is why US labelling depends on the final product testing under 20 ppm: "INCLUDING the presence of any gluten due to cross contact with gluten-containing grains."

Questions and answers

What is it?

Wheatgrass and barley grass are the young leaves of wheat and barley, harvested before the grain forms. They are dried into powders or juiced. (Source 6)

What does it do in the body?

Almost nothing is established. One small trial in ulcerative colitis and one small pilot study in chemotherapy reported benefits; neither has been repeated. (Source 1)

Is it good or bad for you?

The evidence does not show a clear benefit. Risks noted in the literature are nausea, microbial contamination, and heavy metals or pesticides in some commercial barley grass products. (Source 3)

How do you get more of it?

Only as juice or powder supplements, or in greens blends. Trials gave 60 to 100 cc of fresh juice daily. (Source 4)

If it is harmful, what reduces it?

Does not apply to the grass itself. The harms come from contaminants in some products, which a product analysis found above EU limits in some samples. (Source 3)

Why might someone be low in it or missing it?

Does not apply. Cereal grass is not an essential nutrient, so nobody is deficient in it. (Source 2)

Which whole foods contain it or feed it?

The grasses are themselves the whole food, usually eaten as juice or powder. Young barley powders supply minerals such as iron and manganese, which many ordinary foods also provide. (Source 3)

What happens if you do not have it?

Nothing is known to happen. No health outcome has been shown to depend on eating cereal grass. (Source 2)

How can you test for it?

No test measures wheatgrass or barley grass intake. For people with coeliac disease, US gluten-free labelling rests on testing the product, not the person. (Source 6)

We searched: Searched trials (Ben-Arye 2002, Bar-Sela 2007), MSKCC herb monograph and product-testing studies for any biomarker; none described.

References

1. Nutrition and Cancer. Wheat grass juice may improve hematological toxicity related to chemotherapy in breast cancer patients: A pilot study. 2007. PMID 17571966, DOI 10.1080/01635580701308083. Read the source
2. Memorial Sloan Kettering Cancer Center. Wheat Grass (About Herbs). 2023. Read the source
3. NFS Journal. Investigation on nutritional compounds and toxic elements in dietary supplements from young green barley (Hordeum vulgare L.). 2024. DOI 10.1016/j.nfs.2024.100201. Read the source
4. Scandinavian Journal of Gastroenterology. Wheat grass juice in the treatment of active distal ulcerative colitis: A randomized double-blind placebo-controlled trial. 2002. DOI 10.1080/003655202317316088. Read the source
5. Frontiers in Nutrition. Effect of AG1® supplementation on nutritional adequacy and gut microbial composition in trained adults. 2026. DOI 10.3389/fnut.2026.1783951. Read the source
6. National Celiac Association. Do wheat grass and barley grass contain gluten?. 2022. Read the source