CLA (Conjugated Linoleic Acid) for Cholesterol Management

CLA (conjugated linoleic acid) is not a cholesterol treatment. The largest meta-analysis, of 56 randomised trials, found that CLA did not reliably change total cholesterol, LDL cholesterol, triglycerides or apolipoprotein B, while HDL cholesterol fell slightly [1]. A second review of 35 trials found total cholesterol fell by just 0.08 mmol/L (about 3 mg/dL) against placebo, while triglycerides rose slightly against olive oil [2], and a 2024 review of people at risk of heart disease found no effect on blood lipids at all [3].

An older 2015 meta-analysis of healthy adults did report a small fall in LDL [4], but the larger and later analyses don't confirm it. NIH's Office of Dietary Supplements sums up the evidence as inconsistent, noting that CLA "might adversely affect lipid profiles" because some isomers may lower HDL and raise lipoprotein(a) [5]. For cholesterol management, CLA is best left out.

CLA is a group of linoleic acid isomers found mainly in dairy products and beef; supplements mostly contain the cis-9,trans-11 and trans-10,cis-12 isomers [5]. It drew interest for cholesterol because animal studies reported antiatherogenic properties [6], and because it may change how the body handles fat: ODS describes proposed effects on fat breakdown, fat-burning in muscle, fat building and fat-cell death [5]. Those proposed effects concern body fat; none of them is a known way of lowering LDL cholesterol.

In a crossover trial in healthy men, the two main isomers had opposite effects. The trans-10,cis-12 isomer raised the LDL-to-HDL and total-to-HDL cholesterol ratios and triglycerides compared with the cis-9,trans-11 isomer, which lowered the ratios [6]. In abdominally obese men, purified trans-10,cis-12 CLA lowered HDL cholesterol by 4% against placebo, and the usual isomer mixture lowered it by 2% [7].

The cis-9,trans-11 isomer doesn't rescue the picture either: on its own, as capsules or in enriched milk, it did not improve blood lipids in people with borderline high cholesterol [8][9]. So neither isomer is a route to lower LDL, and animal results don't carry over to the softgels on a shop shelf.

There is no dose that lowers cholesterol, so this page doesn't recommend one. For context, lipid outcomes were measured at about 0.6-2.5 g a day of single isomers [6], 3-3.5 g a day of isomer mixtures [7][8], and up to 6.4 g a day [10]; CLA-enriched milk provided 1.3 g a day [9]. The higher 6.4 g dose lowered HDL cholesterol and raised C-reactive protein [10].

If you already take CLA for weight, know that its effect there is also small (see CLA for weight loss), and recheck your lipids rather than assuming it is helping your cholesterol.

The broadest review pooled 56 randomised trials (73 effect sizes). Its confidence intervals crossed zero for triglycerides, total cholesterol, LDL cholesterol and apolipoprotein B, meaning no reliable effect, while HDL changed by -0.40 (95% CI -0.72 to -0.07), a small fall [1]. (The paper's own summary misstates these results as rises and an HDL improvement; the confidence intervals are the reliable part.) A 2024 review of 35 trials found total cholesterol 0.08 mmol/L lower than placebo, with very high heterogeneity, and triglycerides 0.05 mmol/L higher than with olive oil [2].

In people at risk of cardiovascular disease, a GRADE-assessed review of 14 trials found "no effect on lipid profile and blood pressure" [3]. The only review to report an LDL fall, from 2015, found a small one in healthy adults [4], and a review of long-term use found that more than 24 weeks of CLA raised lipoprotein(a) and C-reactive protein [11].

The trials closest to this page's question are in people who already had raised lipids, and both were null. In 27 overweight men with borderline high LDL, 8 weeks of 3.5 g a day of a CLA mixture or the cis-9,trans-11 isomer did not change blood lipids compared with safflower oil [8]. In overweight adults with borderline high lipids, milk enriched with either natural or synthetic CLA failed to alter total, LDL or HDL cholesterol or triglycerides [9].

Other trials point the same way or worse. In healthy adults, 4.2 g a day for 12 weeks did not change serum lipoproteins [12], and in exercising adults, cholesterol fell in both the CLA and the sunflower-oil groups, so the trial gives no sign of a CLA-specific benefit [13]. A review of CLA added to exercise found no lipid improvement [14], and a year-long safety trial in obese adults found no adverse laboratory changes, lipids included [15].

Where CLA did move a lipid, it was often HDL, in the wrong direction. HDL fell by 2% with the usual mixture and by 4% with purified trans-10,cis-12 CLA in obese men [7], fell significantly at 6.4 g a day in obese adults [10], and fell by 5.1 mg/dL against 0.7 mg/dL with placebo in children [16].

The exception was 32 people with diet-controlled type 2 diabetes, whose HDL rose by 8% over 8 weeks; in the same trial fasting glucose rose by 6.3% and insulin sensitivity fell, and the authors concluded that a therapeutic nutrient should not carry those adverse effects [17]. See CLA and insulin sensitivity for more on the glucose findings.

CLA appears to be well tolerated; ODS lists mostly digestive complaints such as abdominal discomfort, constipation, diarrhoea, loose stools, nausea and indigestion [5]. For heart health, the concerns are metabolic: lower HDL in several trials [7][10][16], higher lipoprotein(a) and C-reactive protein with long-term use [11], and, with the trans-10,cis-12 isomer, more insulin resistance and higher glucose [5][7]. In people with type 2 diabetes, a 50:50 mixture raised fasting glucose by 6.3% [17].

ODS also notes that CLA might raise markers of oxidative stress and lower breast-milk fat, and that it has been linked to hepatitis in three case reports, although cause was not established because the products were not tested for contaminants [5]. CLA has not been tested in pregnancy for cholesterol, so it is best avoided while pregnant or breastfeeding.

No formal drug-interaction studies of CLA were found. The practical conflicts come from what trials measured: CLA can lower HDL cholesterol and raise glucose [7][17], and NHLBI notes that statins themselves can slightly raise the risk of diabetes in people already at high risk [18]. Adding CLA does nothing for LDL and could make your results harder to read.