Breast cancer rates differ greatly between countries. They are 5 times higher in the United States than in Japan and twice as high in France as in neighboring Spain. Differences in overall fat consumption in these countries have been extensively studied, but no link to breast cancer incidence has been detected so far. A large team of researchers from the Netherlands, Ireland, Spain, Finland, Switzerland, Germany and the United States now report that, while overall fat consumption may not be significant, the make-up of the fats could be.
As part of the large EURAMIC Study the researchers investigated the link between the content of polyunsaturated fats in adipose (fat) tissue of postmenopausal women and breast cancer incidence. A total of 291 women with breast cancer and 351 controls were included in the study which involved 5 European medical centers. The women all had samples of adipose tissue taken (from the buttocks) and analyzed to determine the concentration of the main polyunsaturated fatty acids: the omega-3 acids - alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the omega-6 acids - linoleic acid (LA) and its metabolite arachidonic acid (AA).
The study found no significant correlation between omega-3 fatty acid levels and breast cancer incidence, but did find a trend to higher incidences with increasing levels of omega-6 fatty acids in the adipose tissue samples. The researchers also found a significant association between the ratio of EPA and DHA to LA levels and breast cancer incidence in 4 out of 5 of the medical centers involved in the study. Pooling all results showed that women with the highest ratio had a 35% lower breast cancer incidence than women with the lowest ratio. In other words, women with a relatively high adipose tissue level of EPA and DHA (the main components of fish oils) and a relatively low level of LA and its metabolites had a lower breast cancer risk. The researchers note that LA (linoleic acid) is the precursor of certain eicosanoids which may promote tumour growth. EPA and DHA inhibit the production of these harmful compounds and may also, on their own, inhibit tumour growth. The researchers also point out that several epidemiological studies have found an inverse correlation between fish consumption and breast cancer incidence and urge further studies to determine the relationship between the dietary intake of specific fatty acids and breast cancer risk.
Several major epidemiologic studies have found a clear association between a high dietary fat intake and the risk of developing breast and colon cancer. The correlation is particularly strong in the case of animal fats. One study found that a high fish or fish oil consumption is protective against later stage colon cancer in men but has no effect on mortality from breast cancer. British medical researchers now report that fish and fish oils not only protect against colon cancer in men, but also against colon and breast cancer in women. This protective effect, however, is only apparent in countries where the intake of animal fats is high. In other words, a high intake of fish or fish oils counteracts the detrimental effects of a high animal fat consumption.
The study compared cancer mortality rates in 24 European countries, Canada and the USA with fish consumption and the intake of animal fats. In countries where the animal fat intake was high the researchers found a clear inverse correlation between the ratio of fish fat to animal fat and the risk of developing breast cancer in women and colon cancer in both men and women. A similar correlation was found between cancer risk and the ratio of fish fat to total fat intake.
The researchers conclude that a 15% decrease in animal fat intake combined with a 3-fold increase in fish oil intake could possibly reduce male colon cancer risk by as much as 30% in countries with a high animal fat intake. A 3-fold increase in fish oil intake could be achieved by eating fish three times a week or by taking two standard fish oil capsules daily.
Studies indicate the following:
Feeding omega 3 has slowed the growth of the tumour and made it less likely that the cancer would spread.
-Galli, Claudia, Butrum, Simopoulos et al, eds 1991, Karger, Basel, p462-476
A study of 12, 866 American men determined that those eating high amounts of omega 3 and low amounts of omega 6 had a 33% lower risk of dying from cancer.
-Dolecek, There and Grandits, World Review Nutr. Diet, Karger, 1991, 66: 205-216
Tissues taken from 100 skin cancer patients were compared with skin from 100 healthy individuals and it was found that the more omega 6 found in a person's tissues, the more likely they were to have cancer.
- MacKie, MacKie and Bourne, Nutr and Cancer, 1987 9, 205-216
A comparison of cancerous brain tumours with healthy tissue revealed that omega 6 was 4x more prevalent in the cancerous tissues.
-Martin, Robbins and Hussy, Lipids, 1996, 31: 1238-1288
Incidence of breast cancer increased as Greenland and Icelandic women abandoned their traditional diets of marine life (mainly seal which is very high in omega 3)
- Bjarnason, Int. J., Cancer, 1974, 13: 689-696
In a 8 year study of 846 men, those given a diet high in omega 6 were twice as likely to die of cancer as those eating a diet low in omega 6.
- Pearce and Dayton, The Lancet, 1971, 464-467.
"For breast cancer, omega 6 fatty acids appear to have the greater cancer promoting effects and omega 3 fatty acids are the most protective."
- C.L. Williams, M., Bollella, Laura Boccia and Arlene Spark, "Dietary Fat and Children" Nutrition today, vol 33, no 4: July/Aug 1998
In animal experiments, dietary corn oil very high in omega 6 has been shown to stimulate lung cancer of the adenocarcinoma type.
- Okuyama, Kobayashi and Watanabe. p.415
How does Omega 3 Reduce Cancer or The Risk Of Cancer?
Research indicates the following: Consuming more omega 3 makes the omega 6 linolenic acid that promote tumor growth less available. Omega 3 makes the cancer cells more vulnerable to free-radical attack by rendering the membranes less saturated. Omega 3 seems to promote the self-destruction of cancer cells thereby slowing tumor growth.
The International Arteriosclerosis Project (1992)
Since 1990, researchers from the Louisiana State University have analyzed the coronary arteries of 23,000 deceased persons from 16 countries. The interim results reveal that the Greenlanders have the lowest rate of arteriosclerosis among all those tested.
Some of the fascinating early results are as follows:
1) The Inuit who ate a modern diet had the same rate of this disease as ordinary Europeans and therefore the results were not based on heredity.
2) The Inuit who lived on a traditional diet of marine mammals (mainly seal) had, at the age of seventy, the same coronary artery elasticity as a 20 year old European.
3) Some European countries may eat more fish than is found in the traditional Greenland diet, but have a far higher incidence of arteriosclerosis and, in general, higher levels of cholesterol.
At the National Hospital in Nuuk, a person with very high cholesterol was given various diets and medicines without major impact. When he was placed on a traditional Greenland diet (mostly of seal), his cholesterol level fell dramatically in one month.
The Orsoq Study
Dr. E. Jorgenson of the Center of Arctic Environmental Medicine in Denmark recently presented the initial results of the Orsoq Seal Research Project, a pilot study on the effect of seal oil on human health. These preliminary findings indicate that the general population of Denmark, fed on a modern diet, was ten times more likely to develop cardiovascular and inflammatory diseases that Greenlanders on their traditional diet of seal, a food high in omega 3
"Inuit Whaling", Inuit Circumpolar Conference, June 1992, special issue. Gerth Mulved and Henning Sloth Pederson, Doctors of Medicine Dronning Ingrids Hospital.
Numerous studies show that increased long term intake of marine oils, rich in EPA and DHA, reduces the morbidity and mortality associated with cardiovascular disorders in middle-aged men. Conflicting data exist as to whether it is EPA or DHA, or the combination which is responsible for the various beneficial effects. In any event, it is known that there may be limits to the elongation and desaturation of EPA to DHA, whereas the retroconversion of DHA to EPA occurs.
-Harris et al., Grimsgaard et al., 1995
It is generally agreed that omega-3 fatty acids moderate hyperlipidemia, particularly hypertriglyceridemia, very rapidly in a dose dependent manner. Omega-3 fatty acids reduce the triglyceride levels in the blood by a reduced synthesis and secretion of VLDL particles from the liver and enhances the in vivo liposysis of the VLDL-particles. An improved balance between LDL-cholesterol and HDL-cholesterol is also normally found, whereas the effect on total cholesterol is marginal. A large number of studies report such findings. Omega-3 fatty acids influence on platelet aggregability at rather low doses (50-350mg), whereas significant effects on blood lipids and blood pressure can be achieved at higher doses (2 g/day).
-Christensen et al, 1995
Recent data (from a parallel group study) show that 3g pure DHA (95% DHA, ethyl ester) produce a 30-40% greater reduction in triglyceride levels in plasma than a corresponding amount of EPA (90% EPA, ethyl ester). DHA also seems to have a more marked effect on increasing HDL-cholesterol, whereas EPA was found to slightly decrease both total cholesterol and APO-1 in normal subjects
-Grimsgaard et al, 1995.
This study suggests that DHA might be more beneficial than EPA in terms of effects on blood lipids. Others have reported that DHA-rich oils (4g/day, 42% DHA) are less active than EPA-rich oils and fish diet on both fasting and postprandial triglyceride levels.
A positive correlation has been observed between supplementation with EPA and DHA (85% ethyl ester) and improvements in blood pressure and heart rate in subjects suffering from mild hypertension. Recently published studies showed that DHA (EE), not EPA (EE), lowered the heart rate in healthy humans.
-Bönaa el al, 1995
Even short time supplementation with large amounts (19g/day) of a combination of EPA and DHA (as ethyl esters) has shown to have long-lasting effects on the human platelet aggregation, an effect suggested by inhibition on TXA2/PGH2 receptor by EPA and/or DHA-sensitive mechanisms.
-Di Minno et al,1995
Studies on cardiac arrhythmias do not give any clear evidence on the efficacy of omega-3 fatty acids. However, a trend towards reduction in ventricular extracystoles in patients with ventricular tachyarrhythmias has been observed after supplementation with omega-3 fatty acids
-Christiansen et al,1995.
Animal studies show that DHA may inhibit ventricular tachyarrhytmias more significantly than EPA
and also increases the cardiac contractibility.
-Grynberg et al, 1995
Recent data also show that DHA has more pronounced inhibitory effect on the expression of cytokines in endothelial cells, which clearly downregulate the inflammatory process and may inhibit the progression of arteriosclerosis.
-DeCaterina & Libby, 1995
Epidemiological and clinical research have shown that omega-3 fatty acids intervene in the arteriosclerotic process at all steps, and that there probably are synergistic effects of EPA and DHA at many levels.
Crohn's disease is an inflammatory disease involving intestinal pain, diarrhea, and malabsorption of nutrients. The disease is characterized by periods of active disease interspersed with periods of remission. Elemental diet (ED) therapy is the preferred treatment in Japan. Conventional treatment with prednisone and salycylates has been only marginally successful in extending the periods of remission. The ED therapy involves tube feeding (enteral nutrition) a mixture of free amino acids, short-chain maltodextrins, and low levels of fat in the form of soybean oil. Not surprisingly, compliance with this diet is poor resulting in shorter periods of remission.
Researchers at the University of Bologna report that fish oils can prevent relapses. Their experiment involved 78 patients with Crohn's disease who had been classified as having a high risk of relapse. Half the patients were randomized to receive nine fish oil capsules daily, the other half received nine placebo capsules daily. The fish oil capsules contained 500 mg of a marine lipid concentrate each (40 per cent eicosapentaenoic acid and 20 per cent docosahexaenoic acid) and provided a total of 2.7 grams of n-3 fatty acids per day. The capsules were enteric-coated so as to ensure that they dissolved in the small intestine instead of in the stomach and to minimize unpleasant side effects such as flatulence, heartburn, belching, and diarrhea. The results of the fish oil therapy were spectacular. While 69% of the patients in the control group had a relapse during the one-year study period, only 28% in the therapy group did. At the end of the one-year period 59% of the patients in the fish oil group were still in remission as compared to only 26% in the placebo group. The researchers conclude that fish oil therapy (with enteric-coated capsules) is effective in preventing relapses in patients with Crohn's disease in remission.
Seriously ill Cystic Fibrosis (CF) patients cannot absorb fats and other nutrients properly and therefore often need infusions of essential fatty acids. These infusions are most often based on linoleic acid as many CF patients have been found to have a deficiency of this omega-6 fatty acid. There is now substantial evidence that long-chain omega-3 fatty acids found in fish oils can suppress inflammatory processes such as those involved in CF.
A team of American, Finnish, and German researchers completed a small clinical trial aimed at determining if it would be safe and effective to use a fish oil fortified emulsion in the intravenous feeding of CF patients. The trial involved 12 patients; 6 were given infusions of a lipid emulsion enriched with fish oils while the remaining 6 (control group) were given infusions of the standard linoleic acid-based emulsion. The fish oil emulsion contained 18.3% eicosapentaenoic acid (EPA), 27.6% docosahexaenoic acid (DHA), 12.7% oleic acid, and 2.5% linoleic acid. The standard emulsion contained 54.5% linoleic acid, 22.4% oleic acid, and 0% EPA and DHA. Both emulsions were administered daily (over a 4-hour period) for 1 month at a dose of 150 mg/kg of body weight. The researchers found no adverse effects on liver function or coagulation parameters and no toxic or allergic reactions in the patients receiving the fish oil emulsion. There was a tendency to improved lung function in the fish oil group and a tendency towards a worsening in the control group during the trial; however, these effects were not statistically significant.
The researchers conclude that intravenous infusions of lipid emulsions containing fish oils are safe for CF patients. They urge additional, longer-term studies to determine if such infusions would be of clinical benefit.