Verified
“Calcium-ascorbate buffering is gentler on the stomach than plain ascorbic acid.”
Partial mineral buffering raises the pH of the dose and is widely reported to improve GI comfort versus unbuffered ascorbic acid.
Reviewed
Verified by SAC team
+20
XP on completion
Best Buffered All-Rounder
NOW Foods
NOW Supplements Vitamin C-1000 Complex with Bioflavonoids, Buffered, 180 Tablets Review
This is the bottle for the person whose stomach doesn't love plain vitamin C but who doesn't want to pay boutique prices to fix that. Partial calcium-ascorbate buffering softens the acidity, the price stays low, and NOW actually passes independent GMP audits. Just don't buy it for the 250 mg of bioflavonoids — treat those as a bonus, not a benefit.
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Read the complete Vitamin C guide →How we built the SAC Product Score™ — 7/10
Form & Bioavailability30%6.8/10
Partial buffering (calcium ascorbate + ascorbic acid) with 250 mg bioflavonoids. Buffering improves comfort, not uptake — bioavailability tracks any ascorbic acid — but the blend is a sensible middle ground.
Third-Party Testing & QA25%7.8/10
NPA-GMP certification is a genuine independent facility audit, brand-wide. It's a real check, though not a per-product USP/NSF potency seal like Nature Made carries.
Dose Strategy vs. Clinical Range15%5.2/10
A 1,000 mg single tablet overshoots the ~200 mg saturation ceiling and isn't easy to split. Standard for the category, but not optimized.
GI Tolerance & Suitability15%7/10
The calcium-ascorbate buffering gives a gentler pH than plain ascorbic acid, a real comfort upgrade for people who react to acidic C — though not as fully buffered as the mineral-ascorbate picks.
Value per Serving15%7.8/10
Around $0.09 per tablet with the highest bioflavonoid content in the set — strong value for a buffered, GMP-certified product.
The product at a glance
- Form
- Buffered (calcium ascorbate + ascorbic acid)
- Dose
- 1,000 mg C + 250 mg bioflavonoids
- Count
- 180 tablets / 180 servings
- Testing
- NPA-GMP certified brand-wide
- Cofactor
- 250 mg citrus bioflavonoids (highest here)
- Price
- ~$17
- Cost per serving
- ~$0.09 / tablet
Marketing claims vs. reality
False
“Buffering increases how much vitamin C you absorb.”
Buffered and plain ascorbic acid show equivalent bioavailability; buffering changes tolerance, not uptake. The saturable kinetics in Levine 1996 apply to both.
Not verified
“The 250 mg bioflavonoids boost vitamin C absorption.”
Human data supporting a bioflavonoid absorption boost at these doses are weak and inconsistent; treat the cofactor as a bonus, not a mechanism.
Verified
“NPA-GMP certified brand-wide.”
NOW holds Natural Products Association GMP certification, a real third-party audit of manufacturing practices across its facility.
What our test actually found
01Buffering buys comfort, not absorption
The calcium ascorbate raises the dose's pH so it's gentler going down — a genuine benefit if plain C bothers you. But it doesn't change how much vitamin C reaches your blood; that's still governed by the saturable absorption ceiling.
02The best value in the buffered tier
Fully mineral-buffered picks like Pure Encapsulations cost roughly four times as much per serving. NOW gets you most of the comfort for ~$0.09 a tablet, which is why it's our all-rounder.
03Ignore the bioflavonoid headline
250 mg is the highest cofactor dose here, but the human evidence that bioflavonoids meaningfully raise vitamin C uptake is thin. Nice to have, not a reason to choose it.
04Real GMP audit behind it
NPA-GMP certification is an independent check of NOW's manufacturing — more than a self-declared claim. It's not the per-product USP seal Nature Made carries, but it's a legitimate QA signal.
Pros & cons, no sugar-coating
Pros
- Partial calcium-ascorbate buffering gives a gentler pH than plain ascorbic acid
- NPA-GMP certification is a real independent audit, not just a brand claim
- Low cost per serving with the highest bioflavonoid dose in the set
- Tablet blends calcium ascorbate and ascorbic acid — a sensible middle ground between comfort and cost
Cons
- Buffering improves comfort but does not increase how much vitamin C you absorb
- The bioflavonoid 'absorption-boost' claim has weak human evidence
- Still a 1,000 mg single-tablet bolus that overshoots the saturation ceiling
The smart default for sensitive stomachs on a budget
The best everyday all-rounder — gentler than plain C, cheaper than the boutique buffered options, from a brand that actually passes independent GMP audits. Just don't buy it for the 250 mg bioflavonoids; treat those as a bonus, not a reason. A smart default if unbuffered C upsets your stomach but you don't want to pay a premium.
Check NOW Foods on AmazonIf this doesn’t fit — try these
Pure Encapsulations Buffered Ascorbic Acid
6.6/10Fully mineral-buffered and hypoallergenic if you need maximum gentleness.
See it on the list →Nature Made Extra Strength 1,000 mg
7.1/10USP Verified and cheaper still if your stomach tolerates plain ascorbic acid.
See it on the list →American Health Ester-C 1,000 mg
6.4/10Another gentle branded form if you specifically trust the Ester-C name.
See it on the list →Sources & further reading
- Levine M, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci USA. 1996;93(8):3704-3709.Levine M, Conry-Cantilena C, Wang Y, et al. · 1996 · Proceedings of the National Academy of Sciences USA · PMID 8623000
Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance
Buffered and unbuffered ascorbic acid share the same saturable absorption kinetics; buffering does not raise plasma vitamin C.
- Padayatty SJ, et al. Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med. 2004;140(7):533-537.Padayatty SJ, Sun H, Wang Y, et al. · 2004 · Annals of Internal Medicine · PMID 15068981
Vitamin C pharmacokinetics: implications for oral and intravenous use
Oral vitamin C plasma levels are tightly controlled, so a 1,000 mg tablet overshoots what the body will retain.