Cancer prevention with milk consumption: Conjugated Linoleic Acid

Diets as a means of controlling and reducing incidence of cancer have received considerable attention. Interest in natural nutrients and non- nutrients present in food that may have health benefits in humans such as conjugated linoleic acid (CLA) is growing.

Biological synthesis of CLA occurs through the microbial isomerization of dietary linoleic acid in the digestive tracts of ruminant animals. Therefore, ruminant species and their products are rich dietary sources of CLA.

CLA occurs naturally in many foods, however, the principle dietary sources are dairy products and other food derived from ruminant animal (such as cow). The CLA content of common foods in given in table 1.


Table 1 .The CLA content of common foods (mg/g of fat)

Potential Health Benefits of CLA

Growing evidence suggests that CLA has numerous potential health benefits. Milk and meat from ruminants is interest natural dietary sources of CLA, which has been shown to have anticancer properties. Conjugated linoleic acid reduced plasma lipoproteins and early aortic atherosclerosis in laboratory animals.

CLA has also been shown to have positive effects on immune function and body composition. CLA was able to normalize impaired glucose tolerance in the diabetic rats. Feeding CLA – enriched butter fat to rat inhibited mammary tumor growth by 53% compared with rats fed butter fat with normal levels of CLA.

Other research has been shown CLA – enriched butter fat (naturally) accumulated more total CLA in mammary gland and other tissues compared with those consuming synthetic at same dietary level of intake. This study suggests that naturally occurring CLA may be metabolized and utilized differently than synthetic CLA. A study shown patient consumed milk with higher level of CLA in adipose tissues had less tumor growth.

CLA in unusual among anticancer compounds because it reduces the incidences of cancer and also suppresses the growth of existing cancers.

Mechanism by which CLA influences carcinogenesis are not well understood .Some researchers have suggested that CLA may act by antioxidant mechanisms, pro-oxidant cytotoxicity and reduction in cell proliferation activity.

CLA has role in decreasing body fat and increasing lean body mass. CLA is an acronym of series of conjugated dienoic isomers of linoleic acids. The cis9, Trans 11 isomer of CLA accounts for > 90 % of total CLA in milk fat. Total CLA in human mother's ranged from 3.7 to 7.5 with a mean value of 5.4 mg/g of fat. The cis 9, trans11 isomer accounted for majority of CLA found in human milk, averaging 71 % of total CLA.

Therefore milk fat is the richest natural dietary source of CLA .Presently whole milk contains an average 4.5 mg CLA/g fat. In human one serving of whole milk and one serving of cheese (30 g) daily can provide 81 mg of CLA.

Using 600 gram as a value for the daily food intake by an adult, the 81 mg of CLA represents a daily intake of 0.014 % CLA. Unfortunately this figure is only 25% of the lowest effective dose for reducing incidences of cancer. Increasing the CLA concentration in milk and meat has the potential of increasing the nutritive and therapeutic value of their products. The intake of CLA can be increased either by increasing the consumption of foods of ruminant origin or by increasing the CLA content of milk and meat.

The latter approach is more practical. Studies suggests that diets fed to ruminants have a major influence on CLA content of milk.

Cows grazing natural permanent pasture had 500 % higher CLA content in milk compared commercial condition. Therefore CLA content of milk will vary with diets consumed by the cows. Consequently daily intake of CLA by human from dairy products will vary with source of milk. Additionally consuming dairy products low in fat will proportionally reduce the consumption of CLA.

However long-term studies with humans are needed to demonstrate health benefits. The animal industry has a unique opportunity to enhance the image of dairy and meat with consumers by demonstrating the health benefits of CLA in humans.



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