Low Fiber

Unrefined plant foods typically have an abundance of fiber. Dairy products, eggs, and meat all have this in common – they contain no fiber. Refined grain products also have most of the dietary fiber removed from them. So, a diet high in animal products and refined grains (a typical diet in the USA) is low in fiber. In prospective health studies low fiber was not found to be a risk for breast cancer [25]. It is possible that fiber measurements are just a surrogate measure for unrefined plant food intake. Slattery et al [40] found an inverse correlation between vegetable, fruit and whole grain intake plant food intake and rectal cancer, while refined grains were associated with increased risk of rectal cancer. A threshold of about 5 daily servings of vegetables was needed to reduce cancer risk and the effect was stronger among older subjects [40]. Many other nutrients are co-variants with fiber, including folic acid, which is covered in detail below.

Red Meat

Red meat has been implicated in colon and rectal cancer. A Medline search in February 2003 uncovered 26 reports of human studies investigating the link between diet and colon or colorectal cancer. Of the 26 reports, 21 of them reported a significant positive relationship between red meat and colon or colorectal cancer [17,41-64]. A recent meta-analysis also found red meat, and processed meat, to be significantly associated with colorectal cancer [65]. Meat, and the heterocyclic amines formed in cooking, have been correlated to breast cancer in a case-control study in Uruguay as well [66].

Omega 3:6 Ratio Imbalance

Omega 3 fats (alpha-linolenic acid, EPA, DHA) have been shown in animal studies to be protect from cancer, while omega 6 fats (linoleic acid, arachidonic acid) have been found to be cancer promoting fats. Now there have been several studies that have tested this hypothesis in relation to breast cancer, summarized in Table 1. Except for the study by London et al [67], all of these studies found an association between a higher ratio of N-3 to N-6 fats and reduced risk of breast cancer. Long chain N-3 and N-6 fats have a different effect on the breast tumor suppressor genes BRCA1 and BRCA2. Treatment of breast cell cultures with N-3 fats (EPA or DHA) results in increased expression of these genes while arachadonic acid had no effect [68]. Flax seed oil and DHA (from an algae source) both can be used to increase the intake of N-3 fat, with DHA being a more efficient, sure source.