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What It Is:
CLA (conjugated linoleic acid) is a polyunsaturated fatty acid found naturally in milk and meat and produced from safflower and sunflower oils. There are various forms or isomers of CLA that may perform different functions. The cis-9, trans-11 isomer (also written as c9, t11) is the predominant type found in milk and meats. Supplements are typically made from safflower or sunflower oil and have an equal mixture of cis-9, trans-11 isomer and the trans-10, cis-12 isomer (also known as t10, c12).
What It Does:
CLA has been shown to help with slimming by increasing the ratio of muscle to fat, that is, increasing lean body mass. It has not been shown, however, to reduce overall weight. The trans-10, cis-12 form appears to be the form most associated with changes in body composition, but may have potential side effects. In diabetics, there had been some evidence that it this form might improve insulin levels. However, further studies indicate that CLA does not appear to be a useful supplement for people with diabetes, and might, in fact, contribute to a pre-diabetic state in obese people.
In animal and test tube studies, CLA has shown some ability to inhibit cancer cells. High dietary intake of CLA from high-fat dairy foods has been associated with a reduction of colorectal cancer by up to 39% in women, but it is not known if taking CLA supplements has the same association Preliminary research has also shown higher intake of CLA from foods, particularly from cheese, to be associated with a lower risk of developing breast cancer in postmenopausal women.
CLA may lower cholesterol levels, although it also lowers HDL ("good") cholesterol.
Quality Concerns :
Neither the FDA nor any other federal or state agency routinely tests supplements for quality prior to sale. It is important to know that a product contains the ingredients that it claims. Too little and you may not get the expected effect and waste your money. Too much, and you may experience negative effects with certain ingredients. ConsumerLab.com tested each supplement for its amount of CLA. All products were also tested for potential contamination with lead, which can occur in supplements.
What to Consider When Buying:
CLA from Food:CLA is found naturally in milk fat (typically about 5 mg of CLA per gram of fat, but ranging from 2 to 18 mg of CLA per gram of fat) and meat fat (particularly lamb (6 mg/g), beef (4 mg/g), and veal (2 mg/g). Grass fed “free range” animals will have higher CLA content than hay/grain fed animals in both milk and meat. Non-fat and low-fat products will have little CLA. Other food sources of CLA include eggs and mushrooms.
The predominant form of CLA in milk and meats is the cis-9, trans-11 isomer with much smaller amounts of the trans-10, cis-12 isomer (the form associated with slimming). Increasing the consumption of fatty food sources to achieve high intake of CLA is obviously not recommended for slimming purposes as it adds calories and does not provide much of the trans-10, cis-12 isomer.
CLA From Supplements: CLA in supplements is typically made from safflower oil. Most supplements use oil that is about 80% CLA with the remainder consisting of other fatty acids (e.g., palmitic, oleic, stearic, and linoleic acids). Tonalin and Clarinol are two common, branded sources of CLA made from safflower oil and both are typically around 80% CLA (Clarinol also sells a 95% CLA material).
It is important that you focus on the "conjugated linoleic acid (CLA)" content in the Supplement Facts ingredient listings. A product will sometimes will list the total amount of oil or the amount of one of the branded sources of oil, of which a percentage is CLA.
The effectiveness of a CLA supplement may depend on the proportion and amounts of the forms present. However, at this time, most products do not specify the ratio CLA forms. In general, supplements with CLA from safflower oil provide an equal mixture of the trans-10, cis-12 and cis-9, trans-11 forms.
What to Consider When Using:
Recent studies suggesting improvement in lean body mass used 3 to 4 grams (3,000 to 4,000 milligrams) per day of CLA. Six grams per day was used to improve insulin levels.
Concerns and Cautions:
CLA (conjugated linoleic acid) is a polyunsaturated fatty acid found naturally in milk and meat and produced from safflower and sunflower oils. There are various forms or isomers of CLA that may perform different functions. The cis-9, trans-11 isomer (also written as c9, t11) is the predominant type found in milk and meats. Supplements are typically made from safflower or sunflower oil and have an equal mixture of cis-9, trans-11 isomer and the trans-10, cis-12 isomer (also known as t10, c12).
What It Does:
CLA has been shown to help with slimming by increasing the ratio of muscle to fat, that is, increasing lean body mass. It has not been shown, however, to reduce overall weight. The trans-10, cis-12 form appears to be the form most associated with changes in body composition, but may have potential side effects. In diabetics, there had been some evidence that it this form might improve insulin levels. However, further studies indicate that CLA does not appear to be a useful supplement for people with diabetes, and might, in fact, contribute to a pre-diabetic state in obese people.
In animal and test tube studies, CLA has shown some ability to inhibit cancer cells. High dietary intake of CLA from high-fat dairy foods has been associated with a reduction of colorectal cancer by up to 39% in women, but it is not known if taking CLA supplements has the same association Preliminary research has also shown higher intake of CLA from foods, particularly from cheese, to be associated with a lower risk of developing breast cancer in postmenopausal women.
CLA may lower cholesterol levels, although it also lowers HDL ("good") cholesterol.
Quality Concerns :
Neither the FDA nor any other federal or state agency routinely tests supplements for quality prior to sale. It is important to know that a product contains the ingredients that it claims. Too little and you may not get the expected effect and waste your money. Too much, and you may experience negative effects with certain ingredients. ConsumerLab.com tested each supplement for its amount of CLA. All products were also tested for potential contamination with lead, which can occur in supplements.
What to Consider When Buying:
CLA from Food:CLA is found naturally in milk fat (typically about 5 mg of CLA per gram of fat, but ranging from 2 to 18 mg of CLA per gram of fat) and meat fat (particularly lamb (6 mg/g), beef (4 mg/g), and veal (2 mg/g). Grass fed “free range” animals will have higher CLA content than hay/grain fed animals in both milk and meat. Non-fat and low-fat products will have little CLA. Other food sources of CLA include eggs and mushrooms.
The predominant form of CLA in milk and meats is the cis-9, trans-11 isomer with much smaller amounts of the trans-10, cis-12 isomer (the form associated with slimming). Increasing the consumption of fatty food sources to achieve high intake of CLA is obviously not recommended for slimming purposes as it adds calories and does not provide much of the trans-10, cis-12 isomer.
CLA From Supplements: CLA in supplements is typically made from safflower oil. Most supplements use oil that is about 80% CLA with the remainder consisting of other fatty acids (e.g., palmitic, oleic, stearic, and linoleic acids). Tonalin and Clarinol are two common, branded sources of CLA made from safflower oil and both are typically around 80% CLA (Clarinol also sells a 95% CLA material).
It is important that you focus on the "conjugated linoleic acid (CLA)" content in the Supplement Facts ingredient listings. A product will sometimes will list the total amount of oil or the amount of one of the branded sources of oil, of which a percentage is CLA.
The effectiveness of a CLA supplement may depend on the proportion and amounts of the forms present. However, at this time, most products do not specify the ratio CLA forms. In general, supplements with CLA from safflower oil provide an equal mixture of the trans-10, cis-12 and cis-9, trans-11 forms.
What to Consider When Using:
Recent studies suggesting improvement in lean body mass used 3 to 4 grams (3,000 to 4,000 milligrams) per day of CLA. Six grams per day was used to improve insulin levels.
Concerns and Cautions:
- CLA is generally safe in healthy individuals. However, some people report feeling slightly nauseous after taking CLA or have gastrointestinal upset or loose stools. These side effects typically are reduced if it is taken with protein (such as milk), and usually decrease after about 2 weeks of taking the supplement. Studies using the trans-10, cis-12 isomer of CLA (the form associated with slimming) have found that it may worsen blood sugar control in diabetics and in obese people without diabetes. CLA may decrease insulin sensitivity, creating a pre-diabetic state and lower HDL cholesterol ("good" cholesterol). However, because most commercial CLA products contain a mixture of CLA isomers, it is not known if these products carry this same risk. It may be prudent, for individuals with metabolic syndrome or diabetes (or at risk for diabetes) not use CLA except under physician supervision. CLA also appears to reduce the fat content of human breast milk. It is probably prudent for nursing mothers to avoid CLA supplements.
- Maximum safe dosages of CLA for young children, pregnant women, or those with severe liver or kidney disease have not been determined.