Conjugated linoleic acids (CLA) are antihypertensive and anti-obesity fatty acids found in meat and dairy products. Learn about their health benefits and potential risks here.
What is CLA?
Conjugated linoleic acids (CLA) are poly-unsaturated fatty acids containing both cis- and trans- bonds as well as double bonds.
These molecules are categorized into a family of 28 different types of linoleic acids. The fatty acids are found primarily in meat and dairy products but are also found in supplement form.
The CLA cis-9,trans-11 is mostly found in foods, whereas trans-10,cis-12 is found in supplements [1].
CLAs are often marketed and sold as dietary supplements because of their reputation for helping with weight loss [2].
Health Benefits of Conjugated Linoleic Acid
CLA supplements have not been approved by the FDA for medical use and generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
Possibly Effective For
1) Heart Health
Blood Pressure
In a study of 80 obese and hypertensive people, CLA combined with ramipril reduced blood pressure more than ramipril alone [3].
Cholesterol
A study found that high intakes of both cis-9,trans-11 and trans-10,cis-12 CLA raised the level of HDL cholesterol in healthy women.
HDL cholesterol promotes low cholesterol levels and healthy heart function [4].
Animal & Cell Studies
High levels of glucose result in major heart damage and heart disease. A study in rat cells found that cells pre-treated with CLA and then exposed to high glucose levels had reduced heart damage and a decreased risk of heart disease than cells not pre-treated in the same conditions [5].
In another study, mice with heart disease who were treated with a combination of nitrate and CLA prior to a heart attack had improved heart function post-heart attack [6].
Hardening of the arteries is a heart disease that is caused by the buildup of fat in arteries. This eventually leads to hypertension and strokes. In a cell study, cis-9,trans-11 conjugated linoleic acid prevented fat from building up in the arteries [7].
2) Obesity & Weight Management
A study done in overweight Chinese subjects found that CLA supplementation (twice daily dissolved in milk) helped with weight loss over a 12-week period [8].
The supplementation was found to reduce body weight, reduce BMI, reduce total fat mass, and reduce fat percentage [8].
The treatment also reduced waist to hip ratio and reduced subcutaneous fat mass [8].
Studies have shown that CLAs decrease lipid storage by increasing the rate of fat breakdown in fat tissue [9].
The fatty acids also increase fatty acid oxidation and reduce glucose uptake in cultured fat cells [9].
It should be noted, though, that in a similar study, CLA supplementation did not prevent weight or fat regain in obese peoples after initial weight loss [10, 11].
It should also be noted that some studies have found no association between CLA and weight loss [11, 12, 13].
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of CLA for any of the below-listed uses. Remember to speak with a doctor before taking CLA supplements, and never use them in place of something your doctor recommends or prescribes.
3) Fatty Liver Disease
Fatty liver disease is often an issue in overweight subjects. The disease causes high levels of oxidative stress in the liver, which eventually leads to liver failure. An eight-week study of 38 obese patients with fatty liver disease found that CLA supplementation helped reduce oxidative stress in the liver [14].
CLA also helped decrease cholesterol levels and improve the fats profile in the liver [14].
4) Type 2 Diabetes
A study done in 55 obese, postmenopausal women with type 2 diabetes found that CLA supplementation reduced BMI and improved diabetic symptoms in the subjects [15].
Decreased insulin sensitivity is a major symptom of type 2 diabetes. In mice, it was found that CLA supplementation led to a decreased fat gain. It was also found that while CLA supplementation decreased fat gain, the fatty acids also maintained fat tissue function and maintained insulin sensitivity [16].
CLA increased AMPK levels in mice [17].
Animal & Cell Research (Lacking Evidence)
No clinical evidence supports the use of CLA for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
5) Muscle Efficiency
A combination of CLA and omega-3 has been found to increase mitochondrial efficiency in muscle cells [18].
This causes an increased amount of energy production from glucose and fat in muscles [18].
6) Bone Mass
A study done in aged mice found that CLA and fish oil work to reduce fat deposits in the bone marrow and increase bone mass [19].
Cancer Research
Not enough evidence is available in humans to know if CLA is useful in any kind of cancer. However, there are some preliminary studies that warrant further investigation.
Breast Cancer
Breast cancer is a devastating disease that affects many lives. One of the reasons that breast cancer is so devastating is that it spreads to other parts of the body both easily and quickly.
One study performed in women with lipogenic phenotype breast cancer found that treatment with CLA over the course of 12 days reduced breast cancer tissue production [20].
Additionally, studies in rat breast cancer tumor cells have found that Gemcitabine (a drug designed to prevent the spreading of tumors) was more effective when used in combination with CLA [21].
Rectal Cancer
A study in patients with rectal cancer who were currently undergoing chemoradiotherapy was conducted. In the study, CLA supplementation was found to reduce tumor angiogenesis and decrease tumor resistance [22].
CLA was shown to improve the efficacy of chemoradiotherapy treatment [22].
In human colorectal cancer cells, CLA has been shown to promote growth arrest by inhibiting energy production in cancer cells [23].
Bladder Cancer
In human bladder cancer cells, Trans-10,cis-12 CLA has been shown to stop growth factor receptor transmission, decreasing rapid cell production and increased cell death [24].
Side Effects & Safety
In obese rats suffering from kidney disease, intake of CLA resulted in worsened kidney function and increased kidney damage due to kidney enlargement [25].
Large doses of supplemental CLC (high in trans-10,cis-12 CLC’s) in rats caused abnormal fat accumulation in the liver [26, 27].
This was also seen in hamsters, mice, and humans who took high doses of CLC. The fat accumulation led to fatty liver disease and decreased liver functionality [26, 27].
Men with metabolic syndrome taking Trans-10,cis-12 CLA had increased insulin resistance and oxidative stress.
These complications led to increased inflammation and diabetes [28].
Less serious side effects of CLA supplementation include excessive flatulence, bloating, nausea, and diarrhea.
Dosage
There is no safe and effective dose of CLA for any health purpose because no sufficiently powered study has been conducted to find one. The majority of the studies outlined in this post used around 5 grams of CLA daily for positive effects without harmful side effects.
Supplements sold in the store are low in grams per pill. This limits the chance that somebody could overdose on CLA.
Sources
Natural sources of CLA are dairy products and meat from animals. However, supplements sold in stores are derived from industrially hydrogenated vegetable products and other synthetic products [29].
CLA coming from animal products consist primarily of cis-9,trans-11 CLA whereas industrially hydrogenated vegetable supplements contain primarily trans-10,cis-12 CLA [30].
