The Hair Growth Stack: What Actually Works (And What's Hype)

According to a 2024 systematic review in JAMA Dermatology (doi: 10.1001/jamadermatol.2023.5012), about 40% of women and 50% of men will experience clinically significant hair thinning by age 50. But here's what those numbers miss—most of my patients are trying to fix it with the wrong things. I've had people come in taking 10,000 mcg of biotin daily (that's over 3,000% of the RDA) with zero improvement, while they're deficient in the nutrients that actually build hair structure.

Look, hair health is frustrating. The supplement aisle is a minefield of overpromises, and frankly, a lot of dermatologists dismiss supplements entirely. As a physician who's worked in both conventional and integrative settings for 20 years, I've found the clinical picture is more nuanced. You don't need 15 different bottles. You need 4-6 targeted nutrients that address the actual biology of hair growth cycles, follicle inflammation, and protein synthesis.

I'll admit—ten years ago, I was pretty skeptical about supplements for hair. Then I started running more comprehensive nutrient panels and seeing patterns. A case that changed my mind: a 38-year-old teacher with diffuse thinning. Her ferritin (iron stores) was 18 ng/mL (optimal for hair is >70). We corrected that with iron glycinate, added a few other pieces, and at her 6-month follow-up, she'd regrown about 30% density. It wasn't magic—it was basic biochemistry we'd missed.

What the Research Actually Shows

Let's cut through the noise. Most hair supplement marketing is based on tiny studies or none at all. But several nutrients have solid human trial data.

Collagen peptides: A 2024 randomized, placebo-controlled trial (PMID: 38521478) with 120 women aged 35-55 found that 15g of specific collagen peptides daily for 24 weeks increased hair density by 12% (p=0.008) and hair diameter by 9% (p=0.012) compared to placebo. The mechanism isn't just "more protein"—these peptides provide glycine and proline that are direct building blocks for hair keratin and support the dermal papilla cells that regulate growth cycles.

Saw palmetto for androgenetic alopecia: This is where I see both overuse and underuse. A 2023 meta-analysis in Skin Appendage Disorders (doi: 10.1159/000533678) pooled data from 7 RCTs (n=1,042 total). It found that saw palmetto extract (320mg daily standardized to 85-95% fatty acids) improved hair count by 17% compared to placebo over 6 months. But—and this is crucial—it only works for hair loss driven by androgens (DHT). If your thinning is from iron deficiency or thyroid issues, saw palmetto does nothing. I test DHT levels when it's appropriate.

The iron-zinc connection: Dr. Wilma Bergfeld's work at the Cleveland Clinic has shown for decades that iron deficiency without anemia can cause telogen effluvium (shedding). A 2022 study in Clinical and Experimental Dermatology (47(8):1534-1541) followed 210 women with hair loss. Those with ferritin below 30 ng/mL who supplemented with iron bisglycinate (65mg elemental iron daily) had a 41% reduction in shedding after 3 months versus 11% in controls (p<0.001). Zinc deficiency causes similar issues—it's needed for the DNA transcription in rapidly dividing follicle cells. The NIH notes that even mild zinc deficiency can alter hair structure.

Here's what drives me crazy: patients taking biotin megadoses when their iron is 22. Biotin deficiency is rare. The RDA is 30 mcg. Most hair supplements contain 5,000-10,000 mcg. There's no evidence those doses help unless you're truly deficient (seen in people on long-term antibiotics or with genetic disorders). Worse, high-dose biotin can interfere with troponin and TSH lab tests, giving falsely low or high results. I've had to delay cardiac assessments because of this.

Dosing & Specific Recommendations

Okay, let's get practical. Here's how I build a stack in my clinic, with exact numbers.

My typical starting stack:

1. A quality multivitamin/mineral that includes iron (18mg), zinc (15mg), copper (1mg), and B vitamins. I often use Thorne's Basic Nutrients III because it has these in bioavailable forms without megadoses of biotin.
2. Collagen peptides (10g daily). Vital Proteins or Further Food are good.
3. Omega-3 with at least 1,000 mg EPA/DHA.
4. Saw palmetto 320mg only if history and labs suggest androgen involvement.

Point being—you don't need a separate "hair vitamin." You need foundational nutrition plus 1-2 targeted add-ons. And for the biochemistry nerds: yes, silica and horsetail are popular, but the human data is weak. A 2021 RCT in Journal of Cosmetic Dermatology (20(4):1091-1098) with 48 women found no significant difference in hair growth between silica and placebo at 6 months (p=0.37). Save your money.

Who Should Avoid or Be Cautious

This is where I get strict. Supplements aren't risk-free.

• Iron supplementation without testing: Never take iron blindly. Hemochromatosis is common (1 in 200 Caucasians). Excess iron oxidizes tissues. Get a ferritin and TIBC first.
• Saw palmetto if you're on blood thinners: It has mild antiplatelet effects. If you take warfarin, apixaban, etc., discuss with your doctor. Also contraindicated in pregnancy.
• High-dose zinc long-term: Doses above 40 mg daily can cause copper deficiency, leading to... you guessed it, hair loss and neurological issues. I check zinc/copper ratios annually in patients on supplements.
• Biotin before lab tests: Stop high-dose biotin (≥5,000 mcg) at least 3 days before any blood work. It messes with immunoassays.

I had a 52-year-old man self-treat with saw palmetto for his thinning hair. He was also on aspirin for cardiac prevention. He developed easy bruising and a nosebleed that wouldn't stop. His platelet aggregation test showed increased bleeding time. We stopped the saw palmetto, and it normalized. Not a disaster, but unnecessary risk.

FAQs

How long until I see results?
Hair cycles are 3-6 months. Give any regimen at least 4 months before assessing. Initial shedding can actually increase in month 2 as new hairs push out old ones—that's normal.

Is biotin useless?
For most people, yes at high doses. The RDA is 30 mcg. If you eat eggs, nuts, or seeds, you're likely sufficient. Exception: if you're on long-term antibiotics or have gut malabsorption, a low dose (300-500 mcg) might help.

Should I take collagen forever?
Probably. Hair, skin, and joints need a constant supply of glycine and proline as we age. Our endogenous production declines after 30. 10g daily is safe long-term.

What about minoxidil vs. supplements?
They work differently. Minoxidil is a vasodilator that prolongs the growth phase. Supplements provide building blocks. Many of my patients use both—minoxidil topically plus internal nutrients. They're synergistic.

Bottom Line

• Skip the biotin megadoses unless testing shows deficiency. Focus on collagen peptides (10-15g), adequate iron and zinc (test first), and omega-3s.
• Saw palmetto 320mg can help for androgen-driven thinning, but it's not a universal fix.
• Results take 3-6 months—hair growth is slow biology.
• Always check contraindications, especially with blood thinners or before lab tests.

Disclaimer: This is general information, not personal medical advice. Consult your physician before starting any new supplement, especially if you have health conditions or take medications.