Flaxseed oil increases the plasma concentrations of cardioprotective (n-3) fatty acids in humans

• Harper CR,
• Edwards MJ,
• DeFilipis AP,
• Jacobson TA.

Department of Medicine, Office of Health Promotion and Disease Prevention, Emory University, Atlanta, GA, USA. charper@emory.edu

Alpha-linolenic acid (ALA) is a major dietary (n-3) fatty acid. ALA is converted to longer-chain (n-3) PUFA, such as eicosapentaenoic acid (EPA) and possibly docosahexaenoic acid (DHA). EPA and DHA are fish-based (n-3) fatty acids that have proven cardioprotective properties. We studied the effect of daily supplementation with 3 g of ALA on the plasma concentration of long-chain (n-3) fatty acids in a predominantly African-American population with chronic illness. In a randomized, double-blind trial, 56 participants were given 3 g ALA/d from flaxseed oil capsules (n = 31) or olive oil placebo capsules (n = 25). Plasma EPA levels at 12 wk in the flaxseed oil group increased by 60%, from 24.09 +/- 16.71 to 38.56 +/- 28.92 micromol/L (P = 0.004), whereas no change occurred in the olive oil group. Plasma docosapentaenoic acid (DPA) levels in the flaxseed oil group increased by 25% from 19.94 +/- 9.22 to 27.03 +/- 17.17 micromol/L (P = 0.03) with no change in the olive oil group. Plasma DHA levels did not change in either group. This study demonstrates the efficacy of the conversion of ALA to EPA and DPA in a minority population with chronic disease. ALA may be an alternative to fish oil; however, additional clinical trials with ALA are warranted.

PMID: 16365063 [PubMed — indexed for MEDLINE]

Sowing the seed of cancer reduction

Colorectal cancer is the third most common cancer worldwide, after lung and breast cancers, and is one of the major causes of mortality in Western societies. Lifestyle factors that increase risk for the disease include diet, overweight, low physical activity nd smoking. The adenomatous polyposis coli (APC) gene is mutated in the majority of sporadic colon cancers and in patients with familial adenomatous polyposis.
Dysfunction of the APC protein causes chromosomal instability and improper regulation of cellular β-catenin pools. In addition to the APC-β-catenin pathway, there are also other factors involved in colon tumorigenesis, including cyclo-oxygenase expression and prostaglandin biosynthesis. Protein kinase C (PKC) isoenzymes are involved in different biological processes including cellular proliferation, differentiation and apoptosis as well as malignant transformation. The multiple intestinal neoplasia (Min) mouse carries one wild-type and one mutated APC allele in all somatic and germline cells and has multiple adenomas in the small intestine and colon. It is therefore widely used in studies on diet and colorectal cancer.

Flax seed is a dietary source of lignans and α-linolenic acid, which are thought to have a protective effect against cancer. It also contains a high amount of secoisolariciresinol diglucoside, which is metabolized into mammalian lignans by the gut microflora. Both plant and mammalian lignans may protect against cancer by modulating hormone metabolism, acting as antioxidants or inhibiting angiogenesis. However, previous studies have given conflicting results about the possible chemoproventive effects of flax seed in animal models.

A study by Oikarinen et al.1, investigated the effects of a commercial flax seed mixture on adenoma formation in Min mice. The mixture contained higher levels of defatted flax seed (2.7%) than in previous studies, wheat fibre, flax seed and rapeseed oils. The role of the oil component in adenoma formation was also evaluated with a lignan-free diet. Both diets changed the proportion of n-3 and n-6 fatty acids in the colonic mucosa, with reduced membrane β-catenin and PKC-ξ levels. There was an inverse association between the membrane PKC-ξ in the mucosa and the adenoma number. The findings suggest that the preventive effect of flax seed on colon carcinogenesis may be due to the oil component and the loss of β-catenin and PKC-ξ from the membranes of the mucosal tissue.

1 Oikarinen, SI; Pajari, A-M; Salminen, I; Heinonen, S-M; Adlercreutz, H; Mutanen, M (2005). Effects of a flaxseed mixture and plant oils rich in α-linolenic acid on the adenoma formation in multiple intestinal neoplasia (Min) mice. British Journal of Nutrition 94 (4) 510–518.a

Eating flaxseed may halt prostate cancer growth

4/2007 — Daily consumption of flaxseed may stop the growth of prostate cancer tumours, according to research presented this weekend.

Flaxseed, which is rich in omega 3-fatty acids and fibre-related compounds known as lignans, may interrupt the chain of events that cause cells to divide irregularly and become cancerous, suggest researchers from the Duke University Medical Center in the United States.

"Our previous studies in animals and humans had shown a correlation between flaxseed supplementation and slowed tumour growth, but the participants in those studies had taken flaxseed in conjunction with a low-fat diet," said Wendy Demark-Wahnefried, a researcher in Duke's School of Nursing and lead investigator on the study.

"For this study, we demonstrated that it is flaxseed that primarily offers the protective benefit," she confirmed.

The study involved men scheduled to undergo surgery for the treatment of prostate cancer. The researchers gave them 30 grams of flaxseed every day for an average of 30 days.

When the men's tumours were removed, the researchers were able to determine how quickly the cancer cells had multiplied.

The men taking flaxseed, either alone or in conjunction with a low-fat diet, were compared to men following just a low-fat diet, and men in a control group, who did not alter or supplement their daily diet. Each group was made up of about 40 participants.

Men in both of the flaxseed groups had the slowest rate of tumour growth, according to the researchers.

The study was presented at the annual meeting of the American Society of Clinical Oncology in Chicago on Saturday. NutraIngredients.com has not seen the full results, and publication status is unknown.

"The results showed that the men who took just flaxseed as well as those who took flaxseed combined with a low-fat diet did the best, indicating that it is the flaxseed which is making the difference," Demark-Wahnefried said.

She suggested that as a source of omega-3 fatty acids, flaxseed may alter how cancer cells lump together or cling to other body cells. It could therefore help halt the cellular activity that leads to cancer growth.

Moreover, lignans may have antiangiogenic properties, meaning they are able to choke off a tumour's blood supply and stop it spreading, added the researchers.

Participants took the flaxseed in a ground form to make it more digestible and mixed it in drinks or sprinkled it on food such as yogurt.

The researchers now hope to test the effectiveness of flaxseed supplementation in patients with recurrent prostate cancer.

Over half a million news cases of prostate cancer are diagnosed every year worldwide, and the cancer is the direct cause of over 200,000 deaths. Most worryingly, the incidence of the disease is increasing with a rise of 1.7 per cent over 15 years.