Can Vitamin B12 Deficiency Cause High Cholesterol?

Vitamin B12 deficiency has been consistently linked to unfavorable cholesterol profiles in observational research, with multiple clinical studies finding that people with low B12 tend to have higher total cholesterol, higher LDL cholesterol, and lower HDL cholesterol. Whether the deficiency directly causes those lipid changes, though, is a more complicated question. Cell and animal research points to plausible biological mechanisms, but a key genetic study designed to test causation came up empty. The picture that emerges is genuinely mixed, and worth unpacking.

What the Clinical Data Actually Shows

Several independent clinical studies have measured both B12 status and cholesterol levels in the same patients, and the pattern is hard to ignore. Three separate studies of women at different life stages found that low B12 status was associated with higher total cholesterol, higher LDL cholesterol, and a worse cholesterol-to-HDL ratio.¹ A cross-sectional study of patients who had experienced ischemic stroke found the same trend: those with B12 levels below 300 pg/mL had significantly higher triglycerides, LDL cholesterol, and total cholesterol compared to those above that threshold.²

Research in people with type 2 diabetes tells a similar story. In a study of both European and Indian patients, B12 deficiency was independently associated with higher triglycerides after adjusting for confounders. Among the European patients, those who were B12-deficient also had significantly higher odds of coexisting coronary artery disease.³ And in a large prospective study examining B vitamins and metabolic syndrome, B12’s protective association appeared to work primarily through its effects on body fat, triglycerides, and HDL cholesterol.⁴

The consistency across different populations and conditions is striking. But all of these are observational findings, which means they can tell you that B12 deficiency and bad cholesterol numbers tend to travel together. They cannot tell you which one is causing the other, or whether something else is driving both.

How B12 Could Plausibly Shift Cholesterol

B12 is a key player in what biochemists call one-carbon metabolism, a network of chemical reactions that generates the methyl groups your cells need for everything from building DNA to regulating gene activity.⁵ When B12 is scarce, this network stalls. One consequence is that homocysteine, an amino acid your body normally recycles into methionine with B12’s help, starts accumulating.

Elevated homocysteine appears to disrupt fat processing inside cells. In the liver, accumulated homocysteine triggers stress in a cellular structure called the endoplasmic reticulum, and that stress disturbs the pathways that regulate cholesterol production. The result can be a cascade where the liver produces more cholesterol while clearing less of it from the blood.⁶

But homocysteine is only one piece of the puzzle. B12 also serves as a cofactor for an enzyme that breaks down certain fatty acids, cholesterol, and specific amino acids. When this enzyme is impaired, toxic byproducts like methylmalonic acid build up.⁷ Methylmalonic acid is itself a well-known marker of B12 deficiency, and research in animal models has shown that its plasma levels correlate with triglyceride and fatty acid concentrations.⁸ So B12 deficiency potentially disrupts lipid handling from multiple angles at once.

What Happens Inside Cells Starved of B12

Cell-culture experiments have given researchers a close-up view of what low B12 does to cholesterol-related gene activity. When human liver cells were grown in B12-deficient conditions, genes that drive cholesterol production ramped up. This included the gene for HMG-CoA reductase, the same enzyme that statin drugs are designed to block, as well as the gene for the LDL receptor, which acts as a master regulator of how much cholesterol the liver pulls in and produces. In short, B12-starved liver cells behaved as though they were on a mission to make and accumulate more cholesterol.⁹

Fat cells tell a similar story. When human adipocytes were exposed to low B12 or an imbalance between B12 and folate, cholesterol biosynthesis genes and the proteins that regulate them were turned up. Total cholesterol and homocysteine levels in these cells both climbed.¹⁰ The researchers also saw increased endoplasmic reticulum stress, the same pathway implicated in liver cells, suggesting this is not a liver-specific quirk but a broader cellular response to B12 scarcity.

The mechanism that ties these observations together involves methylation, the process of attaching small chemical tags to DNA to turn genes on or off. One clinical study showed that low B12 limited the availability of the methyl donor S-adenosylmethionine, which in turn changed the methylation patterns on genes that control cholesterol synthesis and LDL receptor activity.¹ In plain terms, B12 deficiency may reprogram your cells at the genetic control level to produce more cholesterol.

The Mendelian Randomization Problem

If low B12 really causes high cholesterol, you would expect people who are genetically predisposed to lower B12 levels to also show worse lipid profiles, on average. This logic underpins a study design called Mendelian randomization, which uses genetic variants as a natural experiment to test causation. A Danish study that combined data from three large population-based cohorts applied exactly this approach. The result was a clear negative: genetic variants associated with lower B12 levels showed no association with blood pressure or any lipid-related outcome.¹¹

This is a significant piece of evidence. It suggests that the associations seen in observational studies could be driven by shared confounders, things like diet quality, body weight, or chronic disease, rather than B12 directly causing lipid changes. It does not prove that B12 has zero effect on cholesterol. Mendelian randomization instruments can lack statistical power, and the genetic variants used might not capture the full range of B12 deficiency experienced in real life. But it does inject serious uncertainty into what otherwise looks like a neat causal story.

Adding to the complexity, a separate Mendelian randomization study found that genetically predicted higher B12 concentrations were associated with increased risk of non-alcoholic fatty liver disease, with combined odds about 30% higher per standard-deviation increase in B12.¹² That seems paradoxical if you believe B12 is purely protective for metabolic health. The relationship between B12 and fat metabolism is clearly more tangled than “more B12, less cholesterol.”

Does Supplementing B12 Improve Cholesterol?

If you are hoping that taking a B12 supplement will bring your cholesterol numbers down, the evidence is thin but not entirely discouraging. In a study of elderly subjects with B12 deficiency, oral supplementation with folic acid and B12 significantly improved total cholesterol, along with homocysteine and insulin resistance.¹³ That is encouraging, but it combined two vitamins, making it impossible to isolate B12’s contribution.

A randomized controlled trial of B12 supplementation in patients with non-alcoholic fatty liver disease found that B12 significantly lowered homocysteine compared to placebo over 12 weeks.¹⁴ Since homocysteine appears to be one of the key intermediaries linking B12 deficiency to cholesterol problems, reducing it is theoretically a step in the right direction. But this particular trial did not report dramatic improvements in cholesterol itself.

The honest reading of the supplementation literature is that correcting a B12 deficiency is unlikely to replace a statin or other lipid-lowering therapy. What it might do is remove one contributor to an unfavorable lipid profile, especially if homocysteine is elevated. If your cholesterol is high and you also happen to be B12-deficient, fixing the deficiency is sensible for many reasons, and modestly improved lipids could be one of them.

Who Faces the Double Risk

Certain groups are prone to both B12 deficiency and metabolic trouble, making this question especially practical for them.

People taking metformin for type 2 diabetes are a prime example. Metformin is well known to deplete B12 over time, and when combined with proton pump inhibitors, another common medication that impairs B12 absorption, the risk increases further.¹⁵ Given that people with type 2 diabetes already struggle with dyslipidemia, an unrecognized B12 deficiency layered on top could compound their lipid problems. The study of type 2 diabetes patients described earlier found that B12-deficient individuals had worse triglycerides and a higher likelihood of coronary artery disease even after controlling for other risk factors.³

Vegans and long-term vegetarians are another group worth attention. A study of non-smoking vegetarians in Hong Kong found that despite having better total and LDL cholesterol profiles than omnivores, the vegetarians had lower B12 levels, higher homocysteine, higher triglycerides, and worse markers of vascular health. Their carotid artery walls were thicker and their blood vessels dilated less effectively, both signs of early atherosclerosis.¹⁶ This is a case where looking at LDL alone would be misleading. The vascular damage appeared to track with B12 deficiency and elevated homocysteine rather than with cholesterol itself.

Older adults represent a third vulnerable group. Stomach acid production declines with age, reducing B12 absorption. Compounding matters, this population is more likely to take acid-suppressing medications. Since cardiovascular disease risk already rises with age, an overlooked B12 deficiency that subtly worsens lipid profiles or drives up homocysteine could be clinically meaningful even if each effect is individually modest.

Maternal B12 and the Cholesterol Profile of Offspring

Some of the most striking research on B12 and cholesterol looks not at the deficient person’s own blood work, but at their children’s. In a study of white Caucasian women in the UK, mothers with low B12 had babies whose cord blood showed significantly lower HDL cholesterol, higher triglycerides, and higher homocysteine. After adjusting for maternal age and body weight, the mother’s B12 status still independently predicted the baby’s HDL cholesterol and homocysteine levels.¹⁷

Further research on pregnant women with low B12 found that their fat tissue showed increased expression of genes involved in fat synthesis and triglyceride production, along with reduced fat-burning capacity. When the researchers replicated these conditions in lab-grown fat cells, triglyceride production went up and mitochondrial function suffered.¹⁸

Animal studies push this further into the future. Rat offspring born to mothers on B12-restricted diets had lower birth weight but gained excess weight after weaning, accumulated more visceral fat, and by 12 months showed clear dyslipidemia along with elevated inflammatory markers.¹⁹ Their livers were also cranking out more fatty acids. The implication is that a mother’s B12 deficiency does not just affect lipids in the short term but may program her offspring for metabolic trouble later in life.

The Role of Genetics Beyond B12 Itself

Your genes influence how efficiently you use B12 and folate, and those same genetic variations can independently affect your cholesterol. Variants in the MTHFR gene, which encodes an enzyme critical to folate metabolism and closely tied to B12 function, have been studied in the context of coronary artery disease. Another gene, PON1, which encodes an enzyme that protects LDL particles from oxidation, has variants significantly associated with triglycerides, total cholesterol, HDL, LDL, and homocysteine levels in patients with coronary artery disease.²⁰

What this means in practice is that two people with the same B12 level might experience very different effects on their cholesterol, depending on what version of these enzymes they carry. Someone with a less efficient MTHFR variant might be more vulnerable to the cholesterol-raising effects of borderline B12 deficiency, while someone with a more efficient version might tolerate the same B12 level without lipid consequences. This genetic variability helps explain why population-level studies sometimes disagree with each other and why the Mendelian randomization results can diverge from observational data.

When B12 Deficiency Might Be Your Overlooked Problem

If your cholesterol is elevated and you have risk factors for B12 deficiency, it is worth getting your levels checked. The scenarios where B12 deficiency is most likely to be contributing to a worsened lipid profile include eating a plant-based diet without reliable B12 sources, long-term use of metformin or acid-suppressing medications, a history of gastrointestinal surgery that affects the part of the gut where B12 is absorbed, and being over 60 with declining stomach acid. A serum B12 test is inexpensive, and if homocysteine and methylmalonic acid are also elevated, the case for functional B12 deficiency becomes stronger.

None of this means that B12 is the reason your cholesterol is high. For most people, the usual suspects, diet, exercise, body weight, genetics, and age, remain the primary drivers. But B12 deficiency sits in an unusual position among nutritional shortfalls: it has plausible mechanisms linking it to cholesterol production, a consistent observational footprint across diverse populations, and is easy and cheap to correct. Whether that correction will meaningfully move your lipid numbers remains genuinely uncertain, but correcting a deficiency carries other well-established benefits for your nervous system, energy levels, and red blood cell production. If there is an upside for cholesterol as well, it comes at no extra cost.