Saturday, January 26, 2008

Breast cancer and starch

Validated food frequency questionnaires strike me as a particularly blunt instrument for assessing nutrient intakes. Generating "dietary patterns" to slot people in to appears to allow the most appalling biases of the investigators to be embedded in to the study design. Couple that with the observational nature and you can see that this recent study by Edefonti does not have a great deal going for it in terms of usefulness, but it does have one plus factor. The research group appear to be able to countenance the possibility that factors other than fat intake may influence disease. This has not always been the case.

To requote Merchant's press release describing the intrinsic biases of "usual" dietary research:

"Previous research has identified ethnic differences in cholesterol and other blood fat levels that couldn't be explained by genes, obesity, lifestyle factors or diet, Merchant and his team note, but these analyses usually looked at dietary fat, not carbohydrate consumption"

When Edefonti did actually look at starch based diets and cancer he observed this sort of thing:

"In conclusion, the starch-rich pattern is potentially an unfavorable indicator of risk for both breast and ovarian cancers, while the animal products and the vitamins and fiber patterns may be associated with a reduced risk of breast and ovarian cancers, respectively"

Mind you, the same group has been saying the same thing since 1996!

Now, from where do low fat diets derive their calories?



Stan Bleszynski said...

Hi Peter,

Interesting studies, here are some more on this subject from my vault:

Isabelle Romieu, Eduardo Lazcano-Ponce, Luisa Maria Sanchez-Zamorano, Walter Willett,
and Mauricio Hernandez-Avila,

"Carbohydrates and the Risk of Breast Cancer among Mexican Women", Cancer Epidemiol Biomarkers Prev 2004 13: 1283-1289.

Comment: for every additional 1% of carbohydrate calories consumed above 52%, the relative risk of breast cancer was incrementally increasing by about 10%!

The following paper demonstrated that a low fat high vegetable diet was useless for fighting cancer!

John P. Pierce, PhD; Loki Natarajan, PhD; Bette J. Caan, et al.

"Influence of a Diet Very High in Vegetables, Fruit, and Fiber and Low in Fat on Prognosis Following Treatment for Breast Cancer."

The Women's Healthy Eating and Living (WHEL) Randomized Trial. JAMA. 2007;298:289-298.



Among survivors of early stage breast cancer, adoption of a diet that was very high in vegetables, fruit, and fiber and low in fat did not reduce additional breast cancer events or mortality during a 7.3-year follow-up period.

See also more comments on:

Stan (Heretic)

Peter said...

Hi Stan,

I found this one too, flipside this time.

These people are more typical researchers, notice they only included studies looking at fat intake in their meta-analysis.

Unfortunately they're using this flawed information to try and save people's lives, and failing.



Puddleg said...

I notice they say in 1996 that PUFA was protective; not what I'd expect.
Some theories; the PUFA was associated with Oleic, therefore came from olive oil; ergo a protective effect of squalene and/or olive "polyphenols" may be involved (some polyphenols, e.g. sesame lignans, tend to divert omega 6 conversion at the GLA stage; thus sesame though high in lineolic acid can be antiinflammatory). Alternatively the beneficial PUFA came from fish.
There is a similar Italian study of fibrosis and response to antivirals in Hep C patients by diet (I can't always find this online, but when it comes up again I'll link it). This indicates a protective effect of oleic, a neutral effect of SFAs, and a harmful effect of PUFA in this context. Again, this could be indicating some special property of olive oil, esp vs. other oils.