The claimEvidence A · guideline-tier
Fish oil 1000 mg = 1 g EPA+DHA
The evidence
1000 mg is the total weight of the fish oil; the EPA and DHA in it are usually only 300-500 mg. Read the active content, not the headline number.
Why the claim spreads
Labels print the big '1000 mg fish oil' number, not the much smaller EPA+DHA actually inside — the headline number is what sells.
The mechanism, in brief
What actually does the work in fish oil is two long-chain omega-3s: EPA and DHA. Whether a bottle is worth buying and can be trusted comes down mainly to two things: which chemical form it is made in (which decides how much you absorb), and how fresh it is (with time it oxidizes and spoils).
Sources (2)
- National Institutes of Health, Office of Dietary Supplements. (2023). Omega-3 Fatty Acids — Fact Sheet for Health Professionals.
- Albert, B. B., Derraik, J. G., Cameron-Smith, D., Hofman, P. L., Tumanov, S., Villas-Boas, S. G., Garg, M. L., & Cutfield, W. S. (2015). Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA. Scientific Reports, 5, 7928.