For the past 20 years, scientists have been devoting increasing attention to dietary fatty acids to determine their impact of health and disease. One, which has been receiving a great deal of attention is linoleic acid (also known as Omega 6) and conjugated linoleic acid (CLA).
Most people associate CLA with weight loss, but there is a growing body of research that seems to indicate that CLA has many more benefits. In fact, the first recorded claims about the health benefits of CLA was made nearly some 30 years ago when a study indicated that ground beef contained an anti-carcinogenic (anti-cancer) factor that consisted of CLAs.
Since then, there have been many different studies – usually animal as opposed to human studies – that indicate that CLA has anti-inflammatory, anti-carcinogenic, anti-diabetic, anti-hypertensive and anti-adipogenic (fat forming) functions. This has resulted in an intense interest to determine whether CLA could possibly represent a nutritional way to prevent lifestyle diseases such as some cancers, diabetes, high blood pressure, atherosclerosis and, of course, contributing factor to all of these – obesity.
However, while many studies indicate that CLA does indeed offer a pretty potent pathway to good (or improved) health, there are others that do not support these assertions.
In this article, we’ll take a closer look at CLA and try to determine just how beneficial this fatty acid is to your health and wellbeing.
What Is CLA?
Let’s start at the beginning and take a closer look at exactly what conjugated linoleic acid is.
CLA has many different names – Acide Linoléique Conjugué, Acide Linoléique Conjugué Cis-9,trans-11, Acide Linoléique Conjugué trans-10,cis-12, Acido Linoleico Conjugado, ALC, Cis-9,trans-11 Conjugated Linoleic Acid, Cis-Linoleic Acid, CLA, CLA-Free Fatty Acid, CLA-Triacylglycerol, LA, Linoleic Acid, Trans-10, and cis-12 Conjugated Linoleic Acid.
Whatever name is used, CLA is the term used for a group of chemicals found in linoleic acid, which is an essential fatty acid.
The term CLA denotes a group of isomers of linoleic acid (C18:2, n-6) with a conjugated double bond. That sounds complicated but basically, an isomer is the name given to compounds that have the same number of atoms, but with a different arrangement of the atoms in the molecule. As a result, they have different properties.
The main sources of dietary CLA are dairy products and meat derived from cattle although mutton may also be a rich source. Milk generally contains more CLA than beef, while the quantity and quality of CLA found in these products depends on the diet of the animals. Manipulation of the animal’s diet can result in up to an 8 to 10-fold increase in the concentration of CLA in milk. It has been found that feeding the animals crushed seeds that are high in fat such as soybean, cottonseed, sunflower, and flax (linseed) increases CLA in milk; and supplementing the feed with fish oil increases the CLA content further.
On the other hand, while grass fed beef tends to have a slightly higher CLA content compared to grain fed, it has been found that diet has an insignificant impact on the amount of CLA in beef.
Chicken eggs – particularly if the birds have been fed CLA – have also been found to be rich in CLA.
What About Plant Sources Of CLA?
Some mushrooms, such as white button mushrooms, have been found to contain CLA.
However, safflower oil is a far more recognized source of CLA. In fact, many people believe – incorrectly, it turns out – that safflower oil is a rich source of CLA. While safflower oil is a rich source of linoleic acid, it contains only very small amounts of CLA – about 0.7ml CLA per gram of fat while milk can contain between 3 ml and up to 22 ml of CLA per gram of milk fat, depending on what the cow was fed. It is, however, also worth bearing in mind that the lower the fat content of the milk, the lower the amount of CLA it will contain.
The CLA found in dairy and beef is not the same as that found in vegetable oils. In addition, commercially made CLA which is often found in supplements, is produced from the isomerization (the process by which one molecule is transformed into another molecule which has exactly the same atoms, but the atoms have a different arrangement) of linoleic acid-rich oils. As a result, plant-based CLA supplements tend to have a different fatty acid profile to their milk- and beef-based CLAs, and there are reports that they may contain higher trans-10 and cis-12 fatty acids.
It is the trans-10,cis-12 isomer that may be effective in reducing body fat. However, other isomers appear to have different capabilities. such as the cis-9,trans-11 isomer, which is believed to be responsible for the anticarcinogenic properties that CLA is said to have.
In other words, not all CLAs are the same and they do not all offer the same health benefits.
A study conducted in 2000 states that “while the average dietary intake of an adult, as well as the suggested requirement, is not well defined, it is estimated that the average North American’s intake of CLA is only approximately 25% of that required for a “healthy diet”.
What Are The Health Benefits Of CLA?
There is a long list of benefits associated with CLA. Among these are:
- Weight management. Obesity is one of the most common underlying causes of the many so-called lifestyle diseases from diabetes and insulin resistance, to heart disease and even infertility. There are literally dozens of studies that have looked at the effectiveness of CLA on weight loss within different populations groups, and the amount needed to deliver the best results. Some studies showed that CLA was effective in reducing body fat mass (BFM) significantly; others indicated that it was effective in reducing belly fat, but not body weight or BMI (body mass index); while yet others showed that it was indeed effective in reducing weight and BMI and/or increasing lean body mass. These results were attained using CLA of different isomers, and different doses. Some studies also help to reduce feelings of hunger. On the other hand, there have also been numerous studies that show that CLA has no effect on the various measures of obesity at all.
- Cardiovascular health. High cholesterol and hyper-triacylglycerolemia (abnormally high level of triacylglycerols in the bloodstream) contribute to hardening of the arteries or thickening of the artery walls (arteriosclerosis). This increases the risk of heart attack, stroke and heart disease. There are studies that suggest that some CLA isomers may help to reduce the risk of atherosclerosis by decreasing bad (LDL) cholesterol and blood lipid (fat) profile, although it also lowers good HDL cholesterol. As a result, CLA is not regarded as a standard treatment for dealing with high cholesterol and reducing the risk of developing arteriosclerosis.
- High blood pressure. There are indications that taking CLA in conjunction with some antihypertensive medication in people with uncontrolled high blood pressure may be more effective than taking the medication alone.
- Pancreatic health. Very high levels of triglycerides in the blood may cause acute inflammation of the pancreas (pancreatitis). Some studies indicate that CLA supplementation may help to reduce blood triglyceride levels.
- Diabetes. Diabetes, like obesity, is considered one of the major causes of morbidity and mortality all over the world; while obesity and weight gain are closely linked to the risk of developing diabetes. Insulin is a hormone that’s responsible for regulating the concentration of glucose (sugar) in the blood. When body cells do not respond properly to insulin, this is called insulin resistance. There are some animal studies that indicate that CLA supplementation may boost insulin sensitivity. However, there are very few studies that have focused on the anti-diabetic properties of CLA in humans, and those that have been undertaken have produced mixed results. Some even indicated that consumption of CLA might actually result in a reduction in insulin sensitivity.
- Cancer. The initial interest in the health benefits of CLA was based on the discovery of what appeared to be the anticancer property of CLAs. However, there are no clinical studies that have conclusively shown that CLA consumption reduces the incidence of cancer. However, some studies indicate that high consumption of CLA may reduce the risk of colorectal cancer and could play a role in preventing testicular cancer. Studies that attempted to prove a link between CLA and the development of breast cancer have also been inconclusive.
- Asthma. CLA is reported to modify the inflammatory responses associated with allergic airway disease, improve airway sensitivity and ability of people with asthma to exercise. However, most studies to investigate this have largely been inconclusive.
People also take CLA supplements for other reasons, ranging from dry skin and strength improvement, to reducing the symptoms of Rheumatoid arthritis and multiple sclerosis (MS). However, there is (as yet) no clinical evidence to support the consumption of CLA to treat these conditions.
What Are The Risks Associated With CLA?
CLA was categorized as “generally recognized as safe” In 2008 by the United States Food and Drug Administration.
While some of the studies involving CLA consumption in humans reported some adverse effects such as insulin resistance and how your body absorbs sugar, particularly in people with diabetes; or gastrointestinal irritation including diarrhea, nausea, bloating, indigestion and flatulence (gas), most side effects can be categorized as “mild to moderate”. Side effects such as headaches, backache and increased risk of bleeding (which means that it should not be consumed for at least two weeks before any scheduled surgery), have also been reported as has (in very rare cases) liver toxicity.
One little-reported side effect which one study into the effect of CLA on the reduction of body fat mass in overweight and obese humans that the authors of the study reported as “severe” was fatigue.
There have also been concerns about the effect of CLA consumption on the fat content of the milk produced by breast-feeding mothers, particularly if their babies are exclusively breastfed. This stems from studies that indicate that consumption of commercial CLA by cows reduced the fat content of their milk. However, a couple of short studies appeared to indicate that these fears were unfounded – but because of their duration, they may not be conclusive, and it’s recommended that mothers who are breastfeeding their babies avoid CLA supplementation for now.
What is also of concern is that some research shows that taking a particular form of CLA (the trans-10,cis-12 isomer) could possible increase risk factors for developing type 2 diabetes and heart disease, but it’s not certain whether supplements containing other forms of CLA have the same risk.
The jury about the benefits of CLA as a health supplement is still out. Animals studies into the effects of a CLA diet on various conditions have often been exceptionally promising, but there still appears to be insufficient evidence that these results can be extrapolated to humans. Many clinical trials that appear to support the claims of the positive effects of CLA are often countered by others that don’t – or that produce inconclusive results.
So, for example, In their book The Health Professional’s Guide to Dietary Supplements, Shawn M Talbot, PhD, Chief Scientific Officer, Supplement Watch of Utah, and Kerry Hughes, MSc, gave CLA five stars for fat loss in moderately overweight adults and one star for control of blood lipids.
What is clear is that one type of CLA supplement may be effective for certain conditions and not for others.
It is therefore recommended that before taking CLA supplementation, you discuss this with your doctor. You should also be aware of the potential complications and side effects, and – unless advised otherwise by your healthcare professional – cease taking it if you experience any of these. There is an abundance of CLA safflower oil reviews online which are very helpful when looking for a reputable manufacturer of these types of supplement.