Conjugated Linoleic Acid, commonly known as CLA, has become one of the most talked about fatty acids in recent years. As research continues to uncover its many health benefits, demand for CLA-rich foods has skyrocketed. But what exactly is CLA, and why does it matter so much? Keep reading to find out.
What is CLA?
CLA is a type of polyunsaturated fatty acid that occurs naturally in the meat and dairy products of ruminant animals like cows, sheep, and goats The name “conjugated linoleic acid” refers to its unique chemical structure – it contains two conjugated double bonds that give it special properties
Specifically, the most common and beneficial form of CLA contains what’s known as the cis-9, trans-11 isomer This means it has a cis double bond at carbon 9 and a trans double bond at carbon 11 The rumen (first stomach compartment) of ruminant animals contains specific bacteria that can convert linoleic acid from the animal’s diet into conjugated linoleic acid or CLA.
Where is CLA Found?
The top dietary sources of CLA include:
- Grass-fed beef and lamb
- Whole milk and cheeses from grass-fed cows
- Grass-fed butter
- Grass-fed yogurt
Meat and dairy from grass-fed ruminants contains significantly more CLA than products from conventionally-raised animals This is because fresh grasses are rich in linoleic acid, the precursor to CLA When ruminant animals eat linoleic acid from green grasses, their gut bacteria convert it into CLA.
On the other hand, grain-fed animals produce only minimal amounts of CLA. Replacing grass with grain in cattle diets nearly eliminates CLA production in the rumen.
For example, grass-fed beef contains 2-3 times more CLA than grain-fed beef. And grass-fed dairy products like whole milk can contain up to 5 times more CLA than conventional dairy.
Health Benefits of CLA
Extensive research over the past few decades points to some very impressive health benefits of consuming conjugated linoleic acid:
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Powerful antioxidant: CLA is a powerful antioxidant that can help reduce oxidative stress and cellular damage in the body. This helps protect against chronic disease and aging.
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Fights cancer: Studies show CLA may inhibit tumor growth and metastasis. Early research suggests it may be protective against breast, colon, prostate and skin cancers.
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Enhances fat loss: CLA can reduce body fat mass, increase lean muscle mass and boost metabolism. These effects are most notable in overweight individuals.
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Improves heart health: CLA has been shown to reduce atherosclerosis, lower blood pressure and improve cholesterol levels. This may lower heart disease risk.
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Boosts immunity: CLA enhances immune function and immune-related cell activity. This may help fight infections and prevent certain cancers.
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Manages diabetes: CLA has been shown to lower blood sugar, improve insulin sensitivity and positively affect diabetic biomarkers. This can help manage type 2 diabetes.
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Protects bone health: CLA promotes increased bone mineral density and calcium absorption. This can reduce bone loss and risk of osteoporosis.
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Reduces inflammation: The anti-inflammatory effects of CLA can help alleviate inflammatory conditions like asthma, arthritis, IBS and certain skin conditions.
With benefits ranging from enhanced weight loss to cancer prevention, it’s easy to see why CLA has generated so much buzz in the health and fitness communities. But it’s important to note that consuming CLA from natural food sources is far more beneficial than taking purified CLA supplements.
How Much CLA Do You Need?
Based on most research, health experts recommend consuming 3-5 grams of CLA per day to reap the key benefits. This equates to:
- 5-8 ounces of grass-fed beef
- 1-2 servings of whole grass-fed dairy
- 2-4 tablespoons of grass-fed butter
While individual needs vary, aiming for at least 3 grams of CLA from grass-fed animal foods is a simple way to maximize the health benefits. Those following plant-based diets can also consume small amounts of CLA from safflower oil and other plant sources.
The Bottom Line
Conjugated Linoleic Acid (CLA) is a beneficial fatty acid found primarily in grass-fed meats and dairy. Consuming 3-5 grams per day from food sources like grass-fed beef and butter can offer powerful antioxidant, anti-cancer, fat-burning and other health effects. Seeking out grass-fed animal products whenever possible is the best way to increase your CLA intake. Along with supplying more CLA, grass-fed meats and dairy also provide higher levels of other healthy fats like omega-3s. Overall, making the switch to grass-fed can go a long way in boosting your nutrition and overall health.
Dietary Sources of CLA for Humans
Dairy products are the major dietary source of CLA, but CLA is also found in the meat from ruminants. Of the many different isomers of CLA, 85 to 90% are the biologically active (cis 9, trans 11) anti-carcinogen form. Concentrations of CLA are generally expressed as milligrams (mg) of CLA per gram (g) of fat. Most dairy products contain about 3.5 to 6.0 mg/g fat, or 0.35 to 0.65% of the milk fat (Table 1).
Homogenized whole milk contains about 5 mg CLA/g of fat. The CLA concentration in milk is relatively stable over a range of processing, manufacturing, and storage conditions. Thus, the CLA levels found in dairy products are dependent on the CLA concentration in raw milk. The CLA concentrations in meat (beef and lamb) are clearly higher than the CLA in poultry and fish (Table 1).
| Food | Total CLA (mg/g fat)a |
|---|---|
| Dairy Products | |
| Homogenized milk | 4.5 |
| Butter | 6.0 |
| Sour cream | 4.6 |
| Plain yogurt | 4.8 |
| Ice cream | 3.6 |
| Cheddar cheese | 3.6 |
| Mozzarella cheese | 4.9 |
| Cottage cheese | 4.5 |
| Meat | |
| Fresh ground beef | 4.3 |
| Beef round | 2.9 |
| Veal | 2.7 |
| Lamb | 5.6 |
| Pork | 0.6 |
| Chicken | 0.9 |
| Fish | 0.3 |
| Fresh ground turkey | 2.5 |
| Seafood | |
| Salmon | 0.3 |
| Trout | 0.5 |
| Shrimp | 0.6 |
a80 to 90% of the CLA is the cis-9, trans-11 isomer.
Boosting Concentrations of CLA in Milk
Surveys have found an eight-to-ten fold variation in CLA concentrations in milk. This suggests that nutrition and herd management practices may create a rumen environment that alters biohydrogenation of fatty acids and, in turn, the CLA concentrations in milk. In Table 2 are listed the nutritional and ruminal factors that affect CLA concentration in milk fat.
| Forages | |
| Pasture versus TMR1 | Increased with consumption of pasture |
| Forage to concentrate ratio2 | Increased with high forage diet |
| Maturity of forage1 | Increased with less mature forage |
| Plant oils | |
| Unsaturated versus saturated3 | Increased with the addition of unsaturated oils |
| Amount of plant oils3 | Increased by feeding higher levels |
| Calcium salts of plant oils3 | Increased with increasing amounts |
| Plant seeds | |
| Raw seeds | No effect |
| Processed seeds3 | Increased over raw seeds |
| Other | |
| Plant oil versus animal fats3 | Increased with plant oils |
| Fish oil2 | Increased in relation to level fed in the diet |
1CLA increases may be due to both addition of lipid substrate and modified rumen environment. 2CLA increases may be due to a modified rumen environment. 3CLA increases may be due to addition of a lipid substrate.
Increases in CLA in milk were first noticed over 65 years ago when cows were turned onto spring pasture. The interest in CLA has renewed the interest in increasing the CLA content of milk. A study at Penn State reported a two-fold increase in CLA with pasture (5.4 to 10.9 mg/g of fat) (Table 3). Wisconsin research reported a four-fold increase (Table 3). This increase has been attributed to increased supply of fat substrate, and to potential changes in the rumen environment and synthesis in the mammary gland. Adding supplements to the ration of grazing cows may diminish this effect.
| Research Location | TMR mg CLA/g fat | Pasture mg CLA/g fat |
|---|---|---|
| Penn State | 5.4 | 10.9 |
| Wisconsin | 5.6 | 22.7 |
Replacing conserved forages with fresh pasture clearly increases CLA concentrations in milk. A study comparing confinement feeding of a TMR to pasture + TMR (pTMR) and pasture plus concentrate (PC) clearly shows that feeding pasture elevated the CLA in milk (Figure 3). CLA in the milk of cows fed a TMR was constant at 6 mg/g fat for the 18-week study. Cows fed pasture plus concentrate had elevated CLA in milk by week 4 and 6, and the concentration peaked at 18 mg/g fat at week 18. Cows fed pasture plus a TMR had CLA concentrations closer to that of cows fed TMR in confinement. Figure 3. The content of CLA (cis9, trans11) in milk of 45 dairy cows with three different feeding systems: pasture plus concentrate (PC), pasture plus total mixed ration (pTMR), or total mixed ration (TMR) in confinement.
Fat supplementation and feed sources richer in unsaturated fatty acids have been shown to increase CLA in milk. Unsaturated plant oils increase CLA more than feeding saturated animal fat sources. This is due to the lipid substrate available by the plant oils for biohydrogenation to CLA and CLA precursors in the rumen. It follows then that increasing levels of plant oil and feeding calcium salts of plant oils will increase levels of CLA in milk.
Feeding plant seeds high in fat such as soybean, cottonseed, sunflower, and flax (linseed) has also increases CLA in milk. However, if seeds are fed in a raw form, there is little change on CLA in milk (Table 2). The seed coat must be broken making the fat available to rumen biohydrogenation for CLA production. Supplementing with fish oil has been shown to increase CLA content of milk when dairy cows on pasture were fed high oil seeds, the CLA content of milk increased more than when feeding pasture alone.
If we think back to the biosynthesis of CLA (Figure 3) and the nutritional factors that increases CLA in milk, it is obvious there are many pathways and nutritional factors that can increase CLA content of milk. Employing these nutritional factors together may increase CLA content of milk beyond any one factor.
A study was conducted to increase the levels of CLA in milk by affecting rumen biohydrogenation and supplying lipid substrate. Cows were fed a TMR with the addition of corn oil, fish oil, or both. Including fish oil has been shown to inhibit biohydrogenation allowing more intermediate products of biohydrogenation, including CLA and CLA precursors, to escape the rumen and be incorporated into milk. Lipid substrates such as corn oil has shown to increase CLA content of milk by providing more unsaturated fatty acids for biohydrogenation. When cows were fed both corn oil and fish oil in combination, CLA content in milk increased ten-fold (Table 4).
| Factors | Effect on CLA concentration in milk fat |
|---|---|
| Pasture | |
| Pasture and oil seeds | Increased higher than feeding each individually |
| Pasture and calcium salts of plant oil | Increased higher than feeding each individually |
| Confinement | |
| Corn oil and fish oil | Increased higher than feeding each individually (ten-fold increases) |
The CLA content of meat from ruminant animals is generally less than the CLA in dairy products (Table 1). Grass fed beef tends to have small increases in CLA compared to grain fed. However, if grass fed beef are finished on higher grain diets prior to slaughter, the CLA content in meat decreases. In general, diet has a small effect on CLA in beef compared to the dietary influence on dairy products.
The potential benefit of CLA in human health is the major reason for the excitement and interest in CLA. The major interest surrounding CLA is the anti-carcinogenic or anti-cancer effects. The National Academy of Science publication entitled “Carcinogens and Anti-carcinogens in the Human Diet” stated that “conjugated linoleic acid is the only fatty acid shown unequivocally to inhibit carcinogenesis in experimental animals.” Much of the research to date has been with laboratory animal models. CLA can reduce new tumor growth and destroy existing tumor cells. CLA has killed existing cancer cells in colon, ovarian and prostate carcinoma, leukemia, melanoma, and breast tumors. CLA-enriched butter inhibited rat mammary tumor yield by 53%, clearly showing the cis-9, trans-11 isomer was anti-carcinogenic. In addition to the anti-carcinogenic properties, other positive health benefits demonstrated in animal models include:
- Reduced atherosclerosis
- Enhanced immune system
- Prevention and treatment of diabetes
- Weight reduction; reduced body fat and increased body protein
- Enhanced bone formation
Although much research has been conducted with laboratory animals, specific studies comparing risk of cancer and CLA consumption by humans have been limited to date. Caution is needed when applying these results to humans. However, an epidemiological study in Finland revealed that as women consumed more dairy products, the risk of breast cancer dropped. Researchers concluded there was a “protective effect” associated with milk. A study in France showed an inverse relationship between CLA concentrations in milk and the risk of severity of breast cancer. As research continues on many fronts, the specific physiological effects and the responses will be better defined.
What Is Conjugated Linoleic Acid? – Dr. Berg
FAQ
What does CLA do for my body?
CLA might help reduce body fat deposits and improve immune function. The average diet supplies 15-174 mg of CLA daily. People commonly take CLA by mouth for weight loss. It is also often used for bodybuilding and fitness, but there is limited scientific evidence to support these uses.
What is CLA in meat?
CLA is conjugated linoleic acid and it’s a bit of a magic ingredient as it’s one of the very few healthy trans fats. It’s got a range of health benefits and it’s easy to include in your diet, coming as it does from 100% grass fed beef and butter produced from cows raised exclusively on grass.
What does linoleic acid do to the body?
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Zero Acre Farmshttps://www.zeroacre.comWhat Is Linoleic Acid? Facts, Health Effects, and How to Avoid ItJul 8, 2022 — Is Linoleic Acid Good or Bad? Low amounts of 1-2% linoleic acid are necessary for survival, but research links higher intakes to health problems, inc…
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ScienceDirect.comhttps://www.sciencedirect.comLinoleic Acid – an overview | ScienceDirect TopicsLinoleic acid (LA), an essential fatty acid, is metabolized to gamma linolenic acid (GLA), which serves as an important constituent of neuronal membrane phospho…
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Curologyhttps://curology.comWhat is linoleic acid and how can it help your skin? – CurologyOct 2, 2023 — Yes. Linoleic acid is an essential fatty acid that is important for many functions in the body like serving as building blocks for important substanc…
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ScienceDirect.comhttps://www.sciencedirect.comLinoleic Acid – an overview | ScienceDirect TopicsLinoleic Acid and Other Omega-6 Fatty Acids Linoleic acid and the family of fatty acids derived from it are called the omega-6 fatty acids (Figure 9.96). This i…
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National Institutes of Health (NIH) (.gov)https://pmc.ncbi.nlm.nih.govThe Role of Linoleic Acid in Skin and Hair Health: A Review – PMCDec 30, 2024 — Incorporation of Linoleic Acid into Ceramides. In the skin, free LA is also used to synthesize other lipids, including ceramides (CERs), triglycerid…
What are the side effects of conjugated linoleic acid?
- nausea.
- stomachache.
- diarrhea.
- bloating.
- headaches.
- skin rashes.