ALA in diet necessary for betacarotene protective effect against breast cancer

[Lani]

ABSTRACT: Dietary ?-carotene inhibits mammary carcinogenesis in rats depending on dietary ?-linolenic acid content [British Journal of Nutrition]
To investigate whether dietary ?-linolenic acid (ALA) content alters the effect of ?-carotene on mammary carcinogenesis, we conducted a chemically induced mammary tumorigenesis experiment in rats randomly assigned to four nutritional groups (15 rats per group) varying in ?-carotene supplementation and ALA content. Two oil formula-enriched diets (15 %) were used: one with 6 g ALA/kg diet in an essential fatty acids (EFA) ratio of linoleic acid:ALA of 5:1 w/w (EFA 5 diet), the other with 24 g ALA/kg diet in an EFA ratio of 1:1 w/w (EFA 1 diet), both designed with a similar linoleic acid content. -Carotene was either added (10 mg/kg diet per d) or not added to these diets. -Carotene supplementation led to decreased tumour incidence and tumour growth when added to the EFA 5 diet, whereas it had no effect when added to the EFA 1 diet. The decreased tumour growth did not result from an involvement of lipoperoxidation (tumour malondialdehyde content being similar between the groups) or from an inhibition of tumour cell proliferation (as there was an unchanged S phase fraction in the tumours). We concluded that an adequate content of ALA in the diet is required to allow a protective effect of ?-carotene in mammary carcinogenesis. Whether such an interaction between ALA and ?-carotene influences the risk of breast cancer in women needs to be investigated.

[R.B.]

I have seen some bits on beta carotene and fats but I did not take much notice as I am struggling with what I am looking at.

Here is another trial on a similar subject.

Would they have got a different result if they had used a different measure of oxidative stress re the mechanism?

Thanks for clearing up the question mark use. I had long wondered what they were doing in reports.

RB

http://www.ncbi.nlm.nih.gov/entrez/q..._uids=12947433

1: Eur J Clin Nutr. 2003 Sep;57(9):1135-40.Click here to read Links
Dietary supplementation with a natural carotenoid mixture decreases oxidative stress.

* Kiokias S,
* Gordon MH.

Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, The University of Reading, Whiteknights, Reading, UK.

OBJECTIVE: To determine whether dietary supplementation with a natural carotenoid mixture counteracts the enhancement of oxidative stress induced by consumption of fish oil. DESIGN: A randomised double-blind crossover dietary intervention. SETTING: Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, The University of Reading, Whiteknights PO Box 226, Reading RG6 6AP, UK. SUBJECTS AND INTERVENTION: A total of 32 free-living healthy nonsmoking volunteers were recruited by posters and e-mails in The University of Reading. One volunteer withdrew during the study. The volunteers consumed a daily supplement comprising capsules containing fish oil (4 x 1 g) or fish oil (4 x 1 g) containing a natural carotenoid mixture (4 x 7.6 mg) for 3 weeks in a randomised crossover design separated by a 12 week washout phase. The carotenoid mixture provided a daily intake of beta-carotene (6.0 mg), alpha-carotene (1.4 mg), lycopene (4.5 mg), bixin (11.7 mg), lutein (4.4 mg) and paprika carotenoids (2.2 mg). Blood and urine samples were collected on days 0 and 21 of each dietary period. RESULTS: The carotenoid mixture reduced the fall in ex vivo oxidative stability of low-density lipoprotein (LDL) induced by the fish oil (P=0.045) and it reduced the extent of DNA damage assessed by the concentration of 8-hydroxy-2'-deoxyguanosine in urine (P=0.005). There was no effect on the oxidative stability of plasma ex vivo assessed by the oxygen radical absorbance capacity test. beta-Carotene, alpha-carotene, lycopene and lutein were increased in the plasma of subjects consuming the carotenoid mixture. Plasma triglyceride levels were reduced significantly more than the reduction for the fish oil control (P=0.035), but total cholesterol, HDL and LDL levels were not significantly changed by the consumption of the carotenoid mixture. CONCLUSIONS: Consumption of the natural carotenoid mixture lowered the increase in oxidative stress induced by the fish oil as assessed by ex vivo oxidative stability of LDL and DNA degradation product in urine. The carotenoid mixture also enhanced the plasma triglyceride-lowering effect of the fish oil. SPONSORSHIP:: The study was supported by funding from the Greek Studentship Foundation and from Unilever Bestfoods plc. Carotenoids were contributed by Overseal Foods plc.

PMID: 12947433 [PubMed - indexed for MEDLINE]