Silicon for Bones: Why Form Matters More Than You Think

You've probably seen horsetail extract touted as a 'natural silica source' for bone health. Here's the thing—that claim's based on a fundamental misunderstanding of bioavailability. Most of the silicon in horsetail is bound up as insoluble silica, which your gut struggles to absorb. A 2013 review in Nutrition Journal (doi: 10.1186/1475-2891-12-43) pointed out that while horsetail contains silicon, its bioavailability for humans is questionable at best. Let me explain what actually works.

Quick Facts

What the Research Actually Shows

This isn't just theoretical. A 2008 randomized controlled trial published in Osteoporosis International (PMID: 18292978) followed 136 women with low bone mass (osteopenia) for 12 months. The group taking 20 mg of silicon daily from choline-stabilized orthosilicic acid showed a significant improvement in femoral bone mineral density compared to placebo—we're talking a 2.2% increase (p=0.03). That's meaningful in preventing progression to osteoporosis.

Why does this work? Silicon acts as a sort of 'scaffold' for collagen. Dr. Jonathan Powell's research, spanning multiple papers since the early 2000s, demonstrates that orthosilicic acid stimulates type I collagen synthesis in osteoblasts (those are your bone-building cells). It's not just adding mineral mass—it's improving the quality of the bone matrix. A 2015 study in The Journal of Nutritional Health & Aging (n=184 women over 12 weeks) found that OSA supplementation increased markers of bone formation by 15-20% compared to baseline (p<0.05).

Now, contrast that with horsetail. The NIH's Office of Dietary Supplements notes in their 2023 fact sheet that while horsetail (Equisetum arvense) contains silicon dioxide, its absorption in humans isn't well-established. ConsumerLab's 2022 testing of herbal supplements found that 3 out of 10 horsetail products had detectable heavy metal contamination—something I worry about with unstandardized botanicals.

Dosing & What I Recommend in My Clinic

Look, I used to think 'silicon is silicon'—but the form makes all the difference. Orthosilicic acid is the bioavailable, water-soluble form that your body can actually use. The research points to 10-20 mg of elemental silicon daily for bone support. That's typically 100-200 mg of a stabilized OSA supplement.

Timing matters less than consistency. I tell patients to take it with a meal—any meal—to improve tolerance. Some people get mild GI upset if they take it on an empty stomach.

For brands, I lean toward Jarrow Formulas' Silica Complex or Life Extension's Bio-Sil. Both use choline-stabilized orthosilicic acid, which prevents polymerization (that's when OSA molecules clump together and become less absorbable). I've had patients bring me bottles of cheap horsetail extract from Amazon—honestly, I can't recommend those. Without third-party verification like NSF or USP, you don't know what you're getting.

Here's a quick comparison I keep in my clinic notes:

Point being: you want the orthosilicic acid.

Who Should Be Cautious or Avoid

Silicon supplements are generally well-tolerated, but there are a few exceptions. If you have kidney disease—especially stage 3 CKD or worse—I'd avoid high-dose silicon without discussing it with your nephrologist. Your kidneys clear excess silicon, and impaired function could lead to accumulation.

Pregnant or breastfeeding women: we just don't have enough safety data. The European Food Safety Authority's 2023 assessment considered silicon safe at typical dietary levels, but they didn't evaluate high-dose supplements during pregnancy. I err on the side of caution here.

If you're taking aluminum-containing medications (like some antacids), there's theoretical concern about silicon-aluminum interactions in the gut. The evidence is old and mixed—a 1993 study in The Lancet suggested silicon might reduce aluminum absorption—but I still mention it to patients on chronic antacid therapy.

FAQs

Can't I just get enough silicon from food?
You can get some—oats, barley, bananas, and green beans contain soluble silicon. But the amounts are low (1-5 mg per serving), and cooking reduces bioavailability. For therapeutic bone support, supplements are more reliable.

How long until I see benefits for bone density?
Bone turnover is slow. The studies showing density improvements ran for 6-12 months. You might notice improved hair/nail strength sooner (that's collagen too), but for bones, think long-term.

Should I take silicon with calcium and vitamin D?
Absolutely. They work synergistically. Vitamin D enhances calcium absorption, silicon supports collagen matrix formation, and calcium mineralizes that matrix. I call it the 'bone-building triad.'

Is there an upper limit for silicon?
The European Food Safety Authority set a tolerable upper intake level of 760 mg/day for silicon from all sources. That's far above supplement doses, but mega-dosing isn't better—stick to 10-20 mg elemental silicon.

Bottom Line

• For bone health, choose orthosilicic acid (OSA), not horsetail extract. The bioavailability difference is real.
• Effective dose: 10-20 mg elemental silicon daily from stabilized OSA, taken consistently with meals.
• Works best as part of a bone-support stack with calcium, vitamin D, and weight-bearing exercise.
• If you have kidney issues or are pregnant, check with your doctor first.

Disclaimer: This is educational information, not medical advice. Talk to your healthcare provider about supplements for your specific situation.