Is glycine profitable to sell on Amazon United States?

The niche generates $6.2M/yr across 16 tracked products. 1 of 1 products launched in the last 360 days are still selling. 90-day search growth is -15.6%. Flapen's verdict: Worth a look (61/100).

How competitive is the glycine niche?

11 brands and 31 sellers compete. The top 5 products take 65% of clicks and top 5 brands hold 75% of demand.

What do buyers complain about in glycine?

Top complaints mined from reviews: Sleep Quality, Functionality-Overall, Dosage. The return rate is 0.0%.

When does demand for glycine peak?

Demand is steady year-round — the busiest month runs 2.1× the quietest.

What does it cost to enter the glycine niche?

Listings span $9.89–$33.29; the average listing price is $19.40 (sweet spot $15–$100). The average incumbent carries 1,701 reviews — the moat a new listing must climb.

glycine

Worth a look

Shows low returns (0.0%), but a failed launch gate (market size, growth, or returns) keeps it on the watch list.

Returns

Incredible0.0%

return rate — above 5% kills the launch gate

Market size

Incredible$6.2M

$6.2M/yr · 2.1M searches

Conversion

Incredible15.6%

search→purchase rate — share of searches ending in a sale

Avg price

Great$19.40

avg listing price — sweet spot $15–$100

Price range

Great$9.89–$33.29

cheapest to priciest tracked listing — scored on the share inside $15–$100

Brand share

Good75%

top-5 brand share — brands hold most of the demand

Review moat

Okay1,701.06

avg incumbent reviews — the moat a new listing must climb

Competition

Okay65%

top-5 click share — leaders hold, buyers still browse

Quality gap

Okay4.6★

avg incumbent rating — lower means beatable quality

Growth

Bad-15.6%

90-day search growth — must beat 0% to launch

According to Flapen's Amazon United States niche tracking, glycine is a $6.2M/yr Amazon United States market (2.1M searches/yr). The top 5 brands hold 75% of demand. Verdict: Worth a look — 61/100.

Data updated Jul 25, 2026 · scored weekly · How we score niches

glycine market data

Units sold / yr: 300K–400K; avg 15,000–20,000/product
Revenue / yr: $5.8M–$7.8M; units × avg price
Conversion rate: 15.6%
Avg BSR: #434
Page quality: 0%
Prime: 100%
Sponsored: 88%
Out of stock: 1.7%
Avg brand age: 56 months
Avg seller age: 152 days

Competition & brand share

The top 5 products take 65% of clicks — established leaders, but buyers still shop beyond them.

Brands

11 flat

Sellers

Top-5 brand share

75%

Top 20: 100%

Top-5 click share

65%

Top 20: 100%

Open market

14%

NOW Foods22%
Life Extension15%
THORNE14%
Pure Encapsulations13%
Nutricost12%
BulkSupplements11%
Open — no brand owns it (5 brands, 14%)

Demand & seasonality

Weekly Amazon search volume, last 99 weeks — -15.6% search growth over the last 90 days.

No pronounced peak months · busiest ÷ quietest = 2.1×

Open Trend

Top glycine search terms

glycine1.3M/yr -14.7%14.5% conv.
glycine supplements348K/yr -28.1%12.3% conv.
glicina74K/yr +55.7%3.5% conv.
glycine 3g77K/yr -32.9%10.8% conv.
glycine 3000mg34K/yr +2.8%10.8% conv.
thorne glycine27K/yr -8.9%23.6% conv.
glycine for sleep54K/yr -52.6%11.6% conv.
glycine capsules28K/yr -5.9%11.4% conv.
l glycine16K/yr +18.3%13.3% conv.
now glycine19K/yr -21.1%18.0% conv.

All search terms

Top glycine products on Amazon

Each bubble is one product — market share against review moat; bubble size tracks estimated sales, color grades how beatable the incumbent looks.

Beatable (≤4.3★) Contested Strong incumbent (>4.7★)

All 16 tracked products in this niche — three views at once, no toggling.

Top sellers

by 90-day click share

NOW Foods Supplements Glycine 1 000 mg Free-Form Neurotransmitter Support* 100 Veg Capsules

NOW Foods$10.774.6★6,256 rev

Life Extension Glycine 1000 mg Amino Acid that Promotes Healthy Sleep Gluten-Free Non-GMO Vegetarian 100 Capsules

Life Extension$11.594.6★3,365 rev

THORNE - Glycine - Supports Relaxation Stress Management Detoxification & Healthy Muscle Function* - Amino Acid Supplement - Third-Party Certified - Gluten Dairy & Soy-Free - 250 Capsules

THORNE$30.124.6★1,472 rev

Pure Encapsulations Glycine - Supports Restful Sleep & Liver Detox* - Liver Supplement - Vegan & Gluten-Free - 180 Capsules

Pure Encapsulations$33.294.6★921 rev

Nutricost Glycine Powder 1lb - Non-GMO Gluten Free

Nutricost$21.804.6★1,593 rev

Newest

by launch date

duwhot Glycine Gummies 3g(3000 mg) Glycine Supplements for Sleep Detox Relax Nerve Support Blueberry Flavor Sugar-Free Vegan Non-GMO Gluten-Free 60 Ct.

duwhot$20.72121 rev

8mo ago

Glycine 2 000mg Per Serving 240 Veggie Capsules | Free Form | Double Strength Amino Acids | Restful Sleep and Neurotransmitter Support Supplements | Non-GMO Gluten Free

Micro Ingredients$16.13254 rev

1y ago

Puregen Labs Glycine 1000mg [High Potency] 100 Vegetarian Capsules Promotes Healthy Rest | No Harmful Additives | Non-GMO NO Gluten and Dairy -100 Servings

P Puregen Labs$9.89563 rev

1y ago

Now Foods Glycine 1000mg Free-Form Pharmaceutical Grade Neurotransmitter Support* Promotes restful Sleep* Gluten Free Vegan Kosher 200 Vegetarian Capsules (Pack of 1)

NOW Foods$22.98898 rev

3y ago

BulkSupplements.com Glycine Capsules - Amino Acid Supplement 3000mg - Gluten Free 4 Capsules per Serving 360 Count (Pack of 1)

BulkSupplements$20.84758 rev

3y ago

What buyers say about glycine

What buyers praise and complain about, mined from review topics.

What buyers love

Sleep Quality32%

“Helps me sleep”

Quality-Overall13%

“quality seems consistent”

Value For Money5%

“Great value”

Taste-Overall5%

“no funky aftertaste”

Vitamin4%

“NOW Vitamins - Good Quality Brand”

Solubility3%

“It dissolves super easily”

Sweetness2%

“It has a pleasant slightly sweet taste”

Nutritional Content2%

“that it would be good for making protein ice cream”

Advertised Vs Actual Product2%

“As advertised”

Dosage2%

“Great 1000mg dosage”

What buyers complain about

Sleep Quality18%

“Not for sleep”

Functionality-Overall8%

“Didn't work for me”

Dosage6%

“Not even half that many servings at the advertised dosage”

Quality-Overall6%

“Poor Quality Control”

Taste-Overall5%

“Taste is horrible”

Solubility5%

“it did not dissolve”

Smell4%

“Chemical Smell”

Side Effects4%

“Now I have dizziness and vertigo”

Size-Overall2%

“The capsule is big”

Stress/Anxiety2%

“My next day was wrecked with exhaustion”

Top return reasons

Sleep Quality26%

Functionality-Overall21%

Dosage11%

Muscle Pain Relief5%

Advertised Vs Actual Product5%

Calcium5%

Acid Regulator/Stomach Ache Relief5%

Blood Sugar Level5%

Adhesion/Stickiness5%

Hard Feel5%

Common questions

Is glycine profitable to sell on Amazon United States?: The niche generates $6.2M/yr across 16 tracked products. 1 of 1 products launched in the last 360 days are still selling. 90-day search growth is -15.6%. Flapen's verdict: Worth a look (61/100).
How competitive is the glycine niche?: 11 brands and 31 sellers compete. The top 5 products take 65% of clicks and top 5 brands hold 75% of demand.
What do buyers complain about in glycine?: Top complaints mined from reviews: Sleep Quality, Functionality-Overall, Dosage. The return rate is 0.0%.
When does demand for glycine peak?: Demand is steady year-round — the busiest month runs 2.1× the quietest.
What does it cost to enter the glycine niche?: Listings span $9.89–$33.29; the average listing price is $19.40 (sweet spot $15–$100). The average incumbent carries 1,701 reviews — the moat a new listing must climb.