Guide

Heavy Metals in Greens Supplements: What the Testing Found

Disclosure: If you buy Grüns through my links, I may earn a commission at no extra cost to you.

Why does a greens product even need heavy metal testing?

Because plants pull whatever is in the soil up along with the nutrients you want.

Trace amounts of arsenic, cadmium, lead and mercury occur naturally in soil and water almost everywhere, and leafy greens, algae and root vegetables are especially good at absorbing them. This is not a defect in any one brand. It is agriculture. A single scoop or pack of a greens product concentrates a lot of plant material into a small serving, which means it can concentrate trace metals along with it.

That is exactly why testing matters more here than on, say, a bottle of synthetic vitamin C. The question worth asking is not "does this contain any trace metal," because at a sensitive enough measurement, most plant-based food does. The real question is whether the amount is meaningfully below the level anyone should worry about, and whether the brand can actually show you the number instead of just telling you not to worry.

What "third-party tested" actually promises, and what it does not

This phrase appears on nearly every supplement label in the category, and it covers three very different levels of rigor.

• Registered facility. Manufacturing happens at a site registered with a regulatory body. This says something about where a product is made, nothing about what is inside any specific batch.
• Certified product. An independent body certifies that a finished formula meets a defined standard, usually based on periodic sampling. Stronger, but it is a snapshot, not every batch.
• Published per-lot results. An outside lab tests an actual production run and the brand shows you the numbers. This is the only version of "third-party tested" you can independently check.

The problem is that plenty of supplement pages say "third-party tested" without showing you the actual numbers. The difference matters, because "tested" without a number attached is a claim, and a claim is not evidence.

How to actually read a heavy metal test result

Two things determine whether a report is worth anything: the method, and whether it shows a number or just a pass.

The gold-standard method for trace metals is ICP-MS, inductively coupled plasma mass spectrometry, which can detect elements down to parts per billion. If a report names this method, the lab was capable of finding metals at genuinely tiny concentrations, not just gross contamination.

Then look at how the result is reported. "Not detected" means the metal did not show up at all at the lab's detection limit. A specific number, like 0.166 micrograms, means it was found and precisely measured. Both are informative. What is not informative is a badge that just says "passed" with no figure behind it, because you have no way to tell whether that means "far below the limit" or "just under it."

Finally, check what the number is being compared against. A result is only meaningful next to a stated guideline for that serving size. A lab report worth trusting shows the reference level it tested against, not just a green checkmark.

What the testing found for Grüns

Independent ICP-MS screening of Grüns, run through Oasis in October 2025, tested a full 20 gram serving for the four metals that matter most in this category.

Three of the four metals were not detected at the lab's reporting limit, using a method sensitive enough to catch trace amounts down to parts per billion. The fourth, lead, came in at roughly sixty times below the guideline the lab tested against.

Grüns says every production lot undergoes safety and quality testing, including heavy-metal and microbial screening. The company also reports regular third-party laboratory testing and lists screening across 70 pesticides, 4 heavy metals, 16 other contaminants and 9 microbial contaminants, with manufacturing in NSF, GMP and FDA-registered facilities. Testing every batch is a materially higher bar than the one-time certificate a lot of the category relies on.

How does that compare to federal safety levels?

For context, the FDA's current Interim Reference Level for dietary lead is 8.8 micrograms per day for females of childbearing age. The agency builds a 10x safety factor into that benchmark. A serving of Grüns tested at 0.166 micrograms, less than 2% of that reference level.

That framing matters more than the raw number, because a trace amount in isolation is meaningless. What matters is the size of that trace amount relative to an established reference level.

What to look for before you buy any greens product

This is not a category where you should have to take a brand's word for it, and you should not have to take mine either. The report on Grüns is public. Read it, check the method, and compare the numbers to the guideline yourself before you decide anything.

A note on health claims. Grüns is a wellness supplement, not a medicine or a medical device. It does not treat, cure or prevent anything, and nothing here is medical advice. I am not a doctor, a toxicologist or a food scientist. Talk to a professional before starting any supplement, especially if you are pregnant, nursing, taking medication or managing a health condition.

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