From: Doug Skrecky (oberon@vcn.bc.ca)
Date: Wed Nov 11 1998 - 21:15:24 MST
Cancer Research 52: 6583-6587 December 1,1992
"Potent Preventive Action of Alpha-Carotene Against Carcinogensis and
Promoting Stage of Lung and Skin Carcinogenesis in Mice Are Suppressed More
Effectively by Alpha-Carotene Than by Beta-carotene"
Abstract:
Although beta-carotene has been considered to be a key cancer preventive
agent in green and yellow vegetables, other types of carotenoids, such as
alpha-carotene, may also contribute to anticarcinogenic action, since these
carotenoids usually coexist with beta-carotene and are detectable in human
blood and tissues. In this study, we compared the inhibitory effect of
natural alpha-carotene, obtained from palm oil, with that of beta-carotene
on spontaneous liver carcinogensis in C3H/He male mice. The mean number of
hepatomas per mouse was significantly decreased by alpha-carotene
supplementation (per os administration in drinking water at a concentration
of 0.05%, ad libitum) as compared with that in the control group (P<0.001,
Student's t test). On the other hand, beta-carotene, at the same dose as
alpha-carotene, did not show any such significant difference from the
control group. Furthermore, we also compared the antitumor-promoting
activity of alpha-carotene with that of beta-carotene against two-stage
mouse lung carcinogenesis (initiator, 4-nitroquinoline l-oxide; promotor,
glycerol). Alpha-carotene, but not beta-carotene, reduced the number of
lung tumors per mouse to about 30% of that in the control group (P<0.001,
Student's t test). The higher potency of the anti-tumor-promoting action of
alpha-carotene compared to beta-carotene was confirmed in other
experimental system; e.g., alpha-carotene was also found to have a stronger
effect than beta-carotene in suppressing the promoting activity of
12-O-tetradecanoylphorbol-13-acetate on skin carcinogenesis in
7,12-dimethylbenz(a)anthracene-initiated mice.
These results suggest that not only beta-carotene, but also other types
of carotenoids, such as alpha-carotene, may play an important role in
cancer prevention.
Additional data from table 3:
Group Mean number of tumors/mouse
Control 6.31
0.005% alpha-carotene 5.07
0.05% alpha-carotene 3.00
0.005% beta-carotene 7.38
0.05% beta-carotene 4.71
0.005% palm-oil carotenes 3.60
0.05% palm-oil carotenes 2.06
Note: Palm-oil carotenes consist of 30% alpha-carotene, 60% beta-carotene
and 10% other (gamma-carotene, lycopene, etc). The best dietary sources
for alpha-carotene are (cooked) pumpkin, followed by carrots.
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