Effect of timing and duration of dietary conjugated linoleic acid on mammary cancer prevention

Abstract

Conjugated linoleic acid (CLA) is a minor fatty acid found predominantly in the form of triglycerides in beef and dairy products. Previous work by Ip and co-workers showed that free fatty acid-CLA at < or = 1% in the diet is protective against mammary carcinogenesis in rats. The present study verified that the anticancer activities of free fatty acid-CLA and triglyceride-CLA are essentially identical. This is an important finding, because it rules out a nonspecific free fatty acid effect. In terms of practical implication, we can continue the in vivo research with the less-expensive free fatty acid-CLA without compromising the physiological relevance of the data. A primary objective of this report was to investigate how the timing and duration of CLA feeding might affect the development of mammary carcinogenesis in the methylnitrosourea (MNU) model. We found that exposure to 1% CLA during the early postweaning and pubertal period only (from 21 to 42 days of age) was sufficient to reduce subsequent tumorigenesis induced by a single dose of MNU given at 56 days of age. This period incidentally corresponds to a time of active morphological development of the mammary gland to the mature state. In contrast to the above observation, a continuous intake of CLA was required for maximal inhibition of tumorigenesis when CLA feeding was started after MNU administration, suggesting that some active metabolite(s) of CLA might be involved in suppressing the process of neoplastic promotion/progression.

Effects of cis-9, trans-11 and trans-10, cis-12 conjugated linoleic acid (CLA) isomers on immune function in healthy men

“…Both preparations increased the incorporation of total CLA in PBMC by $ 35%. Moreover, the two studies that directly compared effects of CLA given as fatty acids and as glycerides found essentially identical effects on mammary cancer prevention (Ip et al, 1995) and body composition (Rahman et al, 2001). Recently, we also obtained identical effects on body composition when feeding mice CLA 50:50 either as free fatty acid or as glycerides (unpublished data).…”

The Change in Conjugated Linoleic Acid Concentration in Blood of Japanese Fed a Conjugated Linoleic Acid Diet

“…Twenty-four healthy subjects (12 men and 12 women) aged 22.3 Ϯ 0.3 y old with a mean body mass index of 20.2 Ϯ 0.4 kg/m 2 were randomly assigned to a CLA-treated group (6 men and 6 women) or a control group (6 men and 6 women). All subjects were generally healthy, as demonstrated by their medical history and a physical examination.…”

Genetic Factors that Determine the Meat Fatty Acids Composition

“…Some of these fats, such as CLA (conjugated linoleic acid), could be beneicial to human health. CLA is important in the prevention of speciic cancers and in the treatment of obesity, immune functions, and potential beneicial efects on coronary heart disease [8].…”

“…CLA has favorable efects on human health, increasing immunostimulatory, antimutagenic, and antioxidant activity [8]. In addition, polyunsaturated faty acids (PUFAs) present in bovine fat such as linoleic (C18: 2n−6) and linolenic (C18: 3n−3) and monounsaturated faty acids (AGMI), such as oleic acid (C18: 1, n−9), which ofer protection to the cardiovascular system, since balanced consumption of these drugs is associated with a reduction in serum cholesterol levels and an increase in high-density lipoprotein (HDL) [9].…”