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Study into links between breast cancer and red meat
In conclusion, women generally consuming most total meat, red and processed meat were at the highest increased risk compared with non-meat consumers, though red and processed meat were only statistically significant postmenopausally. Effect sizes were smaller in non-processed meat and only statistically significant in premenopausal women. There were no statistically significant linear associations with consumption of poultry or offal in either pre- or postmenopausal women. This study indicates relationships with certain meats and breast cancer in both pre- and postmenopausal women and merits further investigation in a larger study.
Does Red Meat Cause Breast Cancer?
The latest study published in the British Journal of Cancer, is not the first study to try to find a link between meat consumption and breast cancer. The study mentions another study from North America which failed to find a correlation, and a Chinese study that did find a correlation with consumption of deep fried meat with breast cancer. In science, a hypothesis is accepted as correct or good if the results can be reproduced, so if this latest study is proof that red meat consumption causes breast cancer, then it implies that other studies were incorrect for some reason. This latest study claims to be far more authoritative on the matter, but does not go into details as to what was specifically wrong with previous studies.
These sort of studies that measure dietary components and tally occurrences of risk events always have problems with proof, as there are generally many lifestyle factors associated with any component of a persons diet. In this study, the researchers have gone to great length to cater for these factors, this includes vegetable and fruit consumption, smoking and some others which may have been important. However some confounding factors they failed to look at, which I suspect are important were, sugar/refined carbohydrate consumption and refined vegetable oils - especially hydrogenated oils. Also, researchers did not or were not able to separate the consumption of processed meat from un-processed meat. I could be wrong here, but the results for un-processed meat do not mention that they adjusted for processed meat.
If this is the case then consumption of nitrates and other preservatives are likely to be still affecting results for consumption of unprocessed meat, assuming that consumers who consume the most unprocessed meat are likely to be consuming more processed meat as well.
The results of the study seem to be overall good news for vegetarians, as they seem to show at least that the vegetarian lifestyle gives some protection against breast cancer, however on closer inspection of these results, it does not seem to be the absence of meat that is the important factor.
The researchers did well to separate post-menopausal breast cancer from pre-menopausal breast cancer as there were substantially different trends between the two groups.
When looking at the pre-menopausal group, the lowest incidence of breast cancer was found among those consuming low levels of meat (<50gm per day) including read meat, not among vegetarians as might be expected, however vegetarians did have lower incidence of breast cancer than those consuming high levels of meat (>103gms per day), and slightly lower rates of breast cancer than those consuming a moderate level of meat (62-103gms per day), however not statistically significant. This result suggests that pre-menopausal women do best by having a low intake of meat, but are not served well by being a vegetarian. The study suggested that there were other aspects of a vegetarian lifestyle that may be affecting results. So while this study managed to find a dose response between meat consumption and breast cancer in pre-menopausal women, zero meat consumption was not proven to be optimal at all! So if red meat does really cause breast cancer, then we would expect zero consumption to be related to lowest incidence of breast cancer, so we must either accept more confounding variables to explain the vegetarian anomaly, the possibility that low levels have the opposite effect, or the possibility that these results are a non-causal relationship.
The results for post-menopausal women were different again. In this group, it was obvious that vegetarians did best of all, with meat eaters having about 50% higher incidence of breast cancer. So maybe we could then make an argument here that meat causes breast cancer in post menopausal women, however the results actually have a surprise twist again. In this subgroup, the results show a surprising result that it if you eat meat, it really doesn't matter how much, as low meat consumption had no benefit over high meat consumption. It is quite surprising that the researchers did not pick up on that fact, as it is quite clear in most of the results. With red meat, the highest risk group was those who ate a moderate amount and those that ate high amounts had slightly lower risk than those who had a low consumption. So if we exclude the vegetarian group (as the researchers suggested for the pre-menopausal group) then there is absolutely no correlation between red-meat consumption and breast cancer, but an interesting result showing that vegetarians do suffer lower incidence of post-menopausal breast cancer. This again would suggest we should be looking elsewhere for the cause of breast-cancer, as we would expect that a dose response should occur if red meat did cause breast cancer. This result does not leave us omnivores off scot-free, as there is obviously something about the vegetarian lifestyle that is particularly protective against post-menopausal breast cancer.
Given these results, I would have concluded that red-meat, or meat consumption in general is not the contributor to breast cancer, however significant lifestyle or dietary factors associated with meat consumption are. I believe that the researchers would do well to examine these anomalies in the data, and look for other confounding variables, particularly those that might cause vegetarians to have lower rates of post-menopausal breast cancer and slightly higher rates of pre-menopausal breast cancer than omnivores with low meat consumption. |
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1 Comments
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Comment By: Susan Haldeman |
6:33PM 5/1/2008 |
| I think that study misses the other factors as Estrogen dominance,long use of estrogen as birth control and HRT, radiation which would show more than just dietary. |
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Current Poll Results
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The milk I consume most is: |
Naturalea 4% unhomogenised (
13 %)
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Farmhouse (4%) unhomogenised (
5 %)
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Standard (3.3%) homogenised (
8 %)
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Low Fat Milk Homogenised (
33 %)
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Real Farm Milk - non pasteurised (
41 %)
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