If you've compared ashwagandha supplements, you'll have seen "KSM-66" on the better ones — and "withanolides" in the small print. This guide explains what KSM-66 is, what withanolides are, and whether KSM-66 is better than plain ashwagandha — as composition facts.
For transparency: ashwagandha is a botanical with no authorised health claims in the UK. This is a composition and quality explainer — what these terms mean — not a claim that ashwagandha treats stress, anxiety, sleep or anything else. Where our formula can make claims, it's through the added vitamin B6, noted below.
What is ashwagandha?
Ashwagandha (Withania somnifera) is a plant used in traditional Ayurvedic practice for centuries, classed in that tradition as an "adaptogen". The root is the part most valued. Like all botanicals in the UK, it's described by its heritage and composition, not by health claims — so the meaningful questions for a buyer are about quality, which is where KSM-66 and withanolides come in.
What is KSM-66?
KSM-66 is a specific, branded ashwagandha extract — one of the most well-known and extensively produced on the market. It's a root-only extract made by a particular standardised process, and it's standardised to a high withanolide content. When a label says KSM-66, you're getting a defined, consistent, branded extract rather than generic ashwagandha powder of unknown strength. Our Ashwagandha uses KSM-66 for exactly that consistency.
What are withanolides?
Withanolides are the group of naturally occurring compounds in ashwagandha that extracts are standardised to. They're the marker used to express an extract's strength — so "standardised to 5% withanolides", for example, tells you the concentration of these characteristic compounds. A stated withanolide percentage is the single most useful quality signal on an ashwagandha label, much as silymarin is for milk thistle or curcuminoids for turmeric.
Is KSM-66 better than regular ashwagandha?
Honestly, "better" depends on what you mean — but there are real, factual reasons KSM-66 is regarded as premium: it's a root-only extract (some cheaper products use leaves or a root-and-leaf mix), it's standardised to a consistent withanolide content, and it's a defined branded extract rather than variable raw powder. So the case for it is consistency and quality of composition, not a health claim. That's the honest distinction.
Which ashwagandha is best?
- A standardised, branded extract like KSM-66 — defined and consistent.
- Root-only — the traditionally valued part.
- A stated withanolide percentage — your concentration signal.
- Quality — made in a GMP-certified facility, tested for purity.
The takeaway
KSM-66 is a specific, root-only, standardised branded ashwagandha extract; withanolides are the compounds its strength is measured by; and the case for KSM-66 is consistency and quality, not a health claim. Our Ashwagandha pairs KSM-66 with L-theanine and vitamin B6. For when and how to take it, see when to take ashwagandha.
Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you are pregnant, breastfeeding, taking medication or managing a medical condition, speak to your GP or pharmacist before starting a new supplement. Signed, Dr. Miron, Founder of Pure Vitamins UK.
