Alpha-linolenic acid no impact on prostate cancer
Alpha-linolenic acid (ALA), the most common omega-3 fatty acid in the Western diet, has no impact on prostate cancer, according to a large dietary study slated to appear in the August issue of Cancer Causes Control.
This study evaluated total intake of ALA from animal, fish, and plant sources in 29,592 men age 55-74 years in the screening arm of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The men were followed for an average of 5.1 years.
During the study 1,898 men were found to have developed prostate cancer. Most of these men (1,631) were diagnosed with organ-confined disease, stage T1b to T3a and no nodal involvement. A small number, 285 , were diagnosed with advanced prostate cancer at a stage equal to or higher than T3b, with one or more nodes or one or more metastases.
The authors found “no association between total alpha-linolenic acid intake and overall risk of prostate cancer. “In addition, no relations were observed between ALA intake from any specific food source and the risks of total, organ-confined, or advanced grostate cancer.” ALA intake also bore no association with low grade tumors or high grade tumors.
They conclude: “In this prospective study of predominantly Caucasian men who were screened annually for newly incident prostate cancer, dietary intake of total ALA and ALA from specific food sources was not associated with risk of total prostate cancer or prostate tumors that were defined by stage and grade.”
Another study of diet questionaires filled in by men in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial announced that antioxidant supplements have weak, mixed results for prostate cancer.
But methods and results are not consistent. Another study, from Brigham and Women’s Hospital and Harvard Medical School. reported that antioxidant blood levels are “key” to a gene-associated prostate cancer risk.
Source: A Prospective Study of Dietary Alpha-linolenic Acid and the Risk of Prostate Cancer (United States). Koralek DO, et al. Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA.
Bad news for vegetarians.
While animal studies have found ALA to be protective, human studies have found that DHA & EPA are the only omega-3 fatty acids that seem to reduce PC risk. These fatty acids are not available in sufficient quantity in the diet, and must be obtained through fish oil supplementation. Very little ALA is converted to DHA/EPA in the body - a negligable amount if there is a vitamin B6 deficiency.
ALA supplementation from flax seed oil (which is subject to rapid oxidation) is associated with a poorer prognosis, so some have proposed chewing on flax seeds, or grinding the seeds immediately before eating them. (I doubt that there were many in the study who did that!) But overall, the study casts doubt on this strategy.
Vegetarians may nonetheless have dietary habits that moderate their risk, but flax seed consumption appears not to be one of them.
Comment by Patrick OShea — July 10, 2006 @ 5:51 pmA widely cited study at John Hopkins University of prostate cancer patients who were to undergo treatment, showed that their eating two tablespoons of ground flaxseed with cereal or juice 2x a day for about a month before their procedure reduced their prostate tumors compared to a control group.
I’ll have to look for a copy of the article but one could probably type flaxseed in search here and find it.
There are other articles posted on site now that show that soy genisten and sulfurophane from broccoli etc. also prevent prostate cancer.
Comment by Arthur — August 24, 2006 @ 4:18 amFound the article in PSA Rising search. It was Duke University. Flaxseed and Low Fat Diet slows growth of some Proatate Cancers, July, 2001.
25 patients who were scheduled to have prostate removal surgery.
Asked to use 3 rounded tablespoons of ground flaxseed once a day for 34 days.
This group showed lowered testosterone levels, early stage cancer patients showed a trend of reduced PSA levels and slightly reduced tumors
compared to a control group.
Personally, I grind up flaxseed and can store in my freezer for almost a month and use each day.
Comment by Arthur — August 24, 2006 @ 4:29 am