No. Homocysteine is an amino acid your body makes while it processes protein, and high levels are linked to heart disease and stroke. B vitamins lower it, but in 12 trials with 46,699 people that did not prevent heart attacks. Its pull on CRP and IL-6, the usual inflammation markers, is small or unclear.
This article is part of our series on [how to test for inflammation](/articles/how-to-test-for-inflammation).
The claim
The claim usually shows up in two parts. Part one: homocysteine is an inflammation marker, like CRP. Part two: if yours is high, B vitamins will bring it down and protect your heart.
Both parts sound tidy. Only one of them was ever tested in people at scale, and that test did not go the way the theory said it would.
Where it comes from
Start with the chemistry. Homocysteine is an amino acid with a job in methionine metabolism, the way your body handles one of the building blocks of protein. Folate (vitamin B9), B6 and B12 help clear it, which is why B vitamins lower it.
B vitamins lowered homocysteine. Heart attacks did not drop.From a 2017 meta-analysis in Cochrane Database Syst Rev
Then add the heart. A high blood level has long been proposed as a risk factor for heart disease and stroke. A 2023 review of 35 studies called it a marker tied to hardened arteries, through harm to the cells that line blood vessels. Higher levels went along with thicker artery walls in most of those studies.
So where does inflammation come in? Partly by association. High homocysteine has been seen in autoimmune conditions such as rheumatoid arthritis. And when researchers gave folic acid, they often measured CRP (C-reactive protein, a protein your liver makes when inflammation is up) in the same trials. Put those side by side and it is easy to file homocysteine under "inflammation."
What does high homocysteine mean?
It means something in your metabolism is worth a closer look. The 2023 review found high levels went along with low B12 and folate, smoking, certain genes, some hormone and kidney problems, and some medicines.
Kidneys stand out. A 2025 meta-analysis, which pools the results of many studies, defined high homocysteine as more than 15 µmol/L. In people with chronic kidney disease, a high level was tied to weaker kidney filtering.
What a high level does not tell you is how inflamed you are. For that, doctors use CRP.
What the evidence shows
The best test of a risk factor is to lower it and see what happens. That is exactly what B-vitamin trials did.
A 2017 Cochrane review pooled 15 randomized trials with 71,422 people, followed for 1 to 7.3 years. In 12 of those trials (46,699 people), heart attacks happened in 7.1% of those taking B vitamins and 6.0% of those on placebo, a gap the review found was no real difference. Deaths from any cause did not differ either. The authors rated both results high-quality evidence.
Strokes were another story, though a small one. They happened in 4.3% of the vitamin groups and 5.1% of the placebo groups, across 10 trials. Run the numbers: that is 0.8 percentage points, or about 8 fewer strokes for every 1,000 people treated over several years.
A bigger 2024 meta-analysis of 21 trials and 115,559 people found folic acid lowered stroke risk by 10%. The benefit showed up in places without folic acid added to grain, where risk fell 17%. In countries that fortify grain, the result was close to no effect. A 2019 umbrella review rated the folic acid stroke link low certainty, and found vitamin B6 on its own had no significant effect on heart disease or death.
Genetics points the same way. People born with genes that raise homocysteine had 11% higher odds of stroke for each step up in level, in a 2021 study. A 2019 genetic study tied homocysteine to one stroke type, small vessel stroke, and not to others. Neither found a clear link to heart attacks.
Does lowering homocysteine help with inflammation?
Only a little, and not on every marker. Across 12 randomized trials, folic acid lowered CRP by 0.59 mg/L but did not change IL-6 or TNF-alpha, two other inflammation signals. An earlier review of 10 trials found a CRP drop too, but the trials disagreed with each other a great deal.
The diabetes trials show the gap most clearly. In 9 trials with 426 people, folic acid had a large effect on homocysteine. The CRP effect was borderline. IL-6 did not move at all, and the authors called the effect on inflammation inconclusive. If homocysteine were an inflammation marker, you would expect the two to fall together. They did not.
Our verdict
| Version of the claim | Best evidence | What it found | Our grade |
|---|---|---|---|
| Homocysteine is an inflammation marker | Reviews of what homocysteine is | An amino acid from protein metabolism, proposed as a heart risk factor | Not supported |
| High homocysteine is linked to heart and artery disease | Review of 35 studies; genetic studies | Linked to hardened arteries; genes tie it to stroke more than heart attack | Emerging |
| Lowering it with B vitamins prevents heart attacks | 12 randomized trials, 46,699 people | Heart attacks 7.1% vs 6.0%, no real difference | Not supported |
| Lowering it with B vitamins prevents stroke | 21 randomized trials, 115,559 people | 10% lower risk overall, mostly where grain is not fortified | Moderate |
| Folic acid lowers inflammation markers | 12 randomized trials | CRP down 0.59 mg/L; IL-6 and TNF-alpha unchanged | Early |
The headline claim, that lowering homocysteine protects your heart, is the one we grade. Large trials tested it, and heart attacks did not fall.
What to do with this
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you have kidney disease, you are pregnant or planning to be, you have had a stroke or heart attack, or you take medicines that affect folate or B12. Keep taking any medicine as prescribed and ask before adding high-dose vitamins.
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How this article was made
Researched and written from 10 peer-reviewed papers. Our automated check matched every claim against the exact words of its source, confirmed every paper exists in PubMed, and found none retracted. Checked November 6, 2026. Not individually reviewed by a doctor. Photos are illustrative; the people in them are not patients or readers.
Grades run Strong, Moderate, Emerging, Early and Not supported, and the grade decides the words we may use. How we grade evidence · Medical disclaimer
Sources
- Meta-analysisHomocysteine-lowering interventions for preventing cardiovascular events.Martí-Carvajal AJ, Solà I, Lathyris D et al. Cochrane Database Syst Rev, 2017.PubMedFull paper
- Meta-analysisHomocysteine as a predictor and prognostic marker of atherosclerotic cardiovascular disease: a systematic review and meta-analysis.Habib SS, Al-Khlaiwi T, Almushawah A et al. Eur Rev Med Pharmacol Sci, 2023.PubMedFull paper
- StudyHomocysteine, B vitamins, and cardiovascular disease: a Mendelian randomization study.Yuan S, Mason AM, Carter P et al. BMC Med, 2021.PubMedFull paper
- StudyHomocysteine and small vessel stroke: A mendelian randomization analysis.Larsson SC, Traylor M, Markus HS Ann Neurol, 2019.PubMedFull paper
- Meta-analysisFolic acid supplementation for stroke prevention: A systematic review and meta-analysis of 21 randomized clinical trials worldwide.Zhang N, Zhou Z, Chi X et al. Clin Nutr, 2024.PubMedFull paper
- Umbrella reviewEffects of Nutritional Supplements and Dietary Interventions on Cardiovascular Outcomes: An Umbrella Review and Evidence Map.Khan SU, Khan MU, Riaz H et al. Ann Intern Med, 2019.PubMedFull paper
- Meta-analysisEffects of folic acid supplementation on C-reactive protein: A systematic review and meta-analysis of randomized controlled trials.Fatahi S, Pezeshki M, Mousavi SM et al. Nutr Metab Cardiovasc Dis, 2019.PubMedFull paper
- Meta-analysisEffects of Folic Acid Supplementation on Inflammatory Markers: A Grade-Assessed Systematic Review and Dose-Response Meta-Analysis of Randomized Controlled Trials.Asbaghi O, Ashtary-Larky D, Bagheri R et al. Nutrients, 2021.PubMedFull paper
- Meta-analysisFolic acid supplementation on inflammation and homocysteine in type 2 diabetes mellitus: systematic review and meta-analysis of randomized controlled trials.Mokgalaboni K, Mashaba GR, Phoswa WN et al. Nutr Diabetes, 2024.PubMedFull paper
- Meta-analysisHyperhomocysteinemia and its association with decreased glomerular filtration rate in patients with chronic kidney disease: a comprehensive meta-analysis.Chen W, Liang X, Liang G et al. PeerJ, 2025.PubMedFull paper
