Fish oils recommended for heart disease prevention
DALLAS, TEXAS. The American Heart Association has reviewed the benefits of regular consumption of
fish and fish oils. The review concludes that fish and fish oils help prevent cardiovascular disease
including fatal and non-fatal heart attacks, strokes, sudden cardiac death, and coronary artery disease
(angina). The reviewers believe that the mechanisms by which fish oils exert their protective effect
include:
- Reduction in susceptibility to ventricular arrhythmia
- Decrease in platelet aggregation
- Reduction in triglyceride levels
- Retardation of atherosclerosis
- Lowering of blood pressure
- Promotion of nitric oxide induced endothelial relaxation
- Anti-inflammatory effects.
Fish and fish oils contain long-chain polyunsaturated omega-3 fatty acids, more specifically,
eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The average American diet contains
only about 100-200 mg/day of EPA and DHA. The diet also contains about 1.4 grams/day of alpha-
linolenic acid mainly from canola and soybean oils. Alpha-linolenic acid can be converted in the body to
EPA and DHA, but not in amounts sufficient to make a significant impact. Some studies have shown that
alpha-linolenic acid, on its own, may have heart-protective effects, but other studies have failed to confirm
this. NOTE: Flax seed oil is a particularly rich source of alpha-linolenic acid.
The American Heart Association recommends that people increase their intake of long-chain
polyunsaturated omega-3 oils from fish or directly from fish oil supplements. Healthy people should
consume oily fish at least twice a week. Patients with heart disease should eat enough oily fish on a daily
basis to obtain about 1 gram per day of EPA and DHA combined or take a fish oil supplement providing 1
gram per day of EPA + DHA. Patients with high triglyceride levels should receive 2-4 grams/day of
EPA+DHA under the care of a physician. The reviewers point out that many fish species contain
significant amounts of methylmercury, polychlorinated biphenyls (PCBs), dioxins, and other
environmental contaminants and therefore must be consumed in moderation, if at all, especially by
children and pregnant and lactating women. Poorer quality fish oils may also contain these contaminants,
so it is important to only supplement with highly purified, pharmaceutical grade oils.
Kris-Etherton, PM, et al. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation,
Vol. 106, November 19, 2002, pp. 2747-57
Fish consumption combats hypertension and obesity
PERTH, AUSTRALIA. Obesity in patients with high blood pressure is associated with high cholesterol
levels, poorer glucose control, and an increased risk of atherosclerosis and heart attacks. Researchers at
the University of Western Australia have just released the results of a study that clearly demonstrates that
a weight-loss diet combined with daily fish consumption is highly effective in reducing blood pressure,
lowering triglyceride levels while increasing "good" (HDL2) cholesterol levels and in improving glucose
tolerance.
The study involved 63 men and postmenopausal women who were overweight and being treated for
hypertension. The participants were randomly assigned to one of four groups. Group 1 included a daily
fish meal (turbot, sardines, tuna or salmon) in their diet; group 2 consumed a calorie-restricted diet; group
3 consumed a calorie-restricted diet including a daily fish meal; and group 4 served as a control. Blood
pressure, glucose tolerance, fatty acid profile, and cholesterol levels were measured at baseline and after
16 weeks on the diets.
The two calorie-restricted diets resulted in an average weight loss of 5.6 kg (12 lbs) during the first 12
weeks of the experiment. No significant weight loss was observed in the control group and the daily fish
meal group. Waking blood pressures decreased by 5.5 mm Hg (systolic) and 2.2 mm Hg (diastolic) in the
calorie-restricted group and by 13.0 mm Hg and 9.3 mm Hg in the group combining a daily fish meal with
a calorie-restricted diet. The combination of fish consumption and weight loss improved glucose and
insulin metabolism significantly and also resulted in a 38% reduction in triglyceride levels and a 24%
increase in the level of "good" cholesterol (HDL2). The researchers conclude that a combination of weight
loss and daily fish consumption significantly reduces the risk of cardiovascular disease among obese,
hypertensive patients.
Mori, Trevor A., et al. Dietary fish as a major component of a weight-loss diet: effect on serum lipids, glucose, and
insulin metabolism in overweight hypertensive subjects. American Journal of Clinical Nutrition, Vol. 70, November
1999, pp. 817-25 [57 references]
Fish oils benefit heart transplant patients
OSLO, NORWAY. Most heart transplant patients (60-100%) develop hypertension within six months
following their surgery. It is believed that the increase in blood pressure is caused by the anti-rejection
drug cyclosporine. Medical doctors at the University of Oslo now report that supplementation with fish oils
will prevent the development of hypertension. Their clinical trial involved 28 heart transplant patients
who, 4 days after surgery, were randomized to receive either 4 grams of fish oil (providing 1.9 g of
eicosapentaenoic acid [EPA] and 1.5 g of docosahexaenoic acid [DHA] as well as 14.8 mg of vitamin E)
or 4 grams of corn oil with vitamin E once a day for 6 months. The patients' blood pressure (24-hour
readings) were measured 12 days, 1 month, 2 months, 3 months, and 6 months after surgery. Blood
samples were also taken for analysis of EPA and DHA content.
The researchers found that the average (mean) systolic blood pressure in the placebo group had
increased by 17 mm Hg at the end of the 6-month supplementation period. In contrast, the average
systolic blood pressure in the fish oil group had decreased by 2 mm Hg. The average diastolic pressure
in the placebo group increased by 21 mm Hg as compared to an increase of only 10 mm Hg in the fish oil
group. The researchers also observed a clear inverse correlation between the blood serum levels of EPA
+ DHA and systolic blood pressure. They conclude that daily supplementation with 4 grams of fish oil can
markedly reduce the tendency to develop hypertension among cyclosporine-treated heart transplant
patients.
Andreassen, Arne K., et al. Hypertension prophylaxis with omega-3 fatty acids in heart transplant
recipients. Journal of the American College of Cardiology, Vol. 29, May 1997, pp. 1324-31
Fish oils recommended for diabetes and hypertension
TROMSO, NORWAY. Fish and fish oils help protect against the development of atherosclerosis and
heart disease. It is believed that fish oils exert their protective effect by lowering blood pressure and the
levels of triglycerides and very-low-density lipoprotein (VLDL). Fish oils are also believed to reduce
platelet aggregation and to suppress the growth of smooth-muscle cells in the arterial walls. Many people
with hypertension also suffer from diabetes and there has been concern that fish oil supplementation may
aggravate problems with glucose intolerance. Researchers at the University of Tromso now report that
fish oil supplementation lowers blood pressure significantly in people with hypertension and has no effect
on glucose control even in people with mild diabetes. The study involved 78 obese volunteers with
essential hypertension. The participants were randomly assigned to one of two equal-sized groups. The
fish oil group received four fish oil capsules a day (containing a total of 3.4 grams of a mixture of
eicosapentaenoic acid and docosahexaenoic acid) for a period of 16 weeks. The control group received
four corn oil capsules a day.
At the end of the test period the average (mean) systolic blood pressure had dropped by 4.4 mm Hg and
the diastolic pressure by 3.2 mm Hg in the fish oil group. The average blood pressure in the control
group did not change. The researchers also found that plasma triglyceride and VLDL levels in the fish oil
group decreased significantly (by about 9 per cent) while they increased significantly (by about 12 per
cent) in the control group. There were no changes in total or low-density-lipoprotein levels in either
group. Extensive tests (oral glucose tolerance, hyperglycemic and hyperinsulemic clamps) were done to
evaluate the effect of fish oil supplementation on glucose control. No adverse effects were found. An
editorial accompanying the research report concludes that fish or fish oil is useful in the prevention of
vascular disease in diabetics. Patients with diabetes should eat fish two to three times a week or, as an
alternative, supplement with two to three one gram capsules of fish oil per day.
Toft, Ingrid, et al. Effects of n-3 polyunsaturated fatty acids on glucose homeostasis and blood pressure
in essential hypertension. Annals of Internal Medicine, Vol. 123, No. 12, December 15, 1995, pp. 911-
18
Connor, William E. Diabetes, fish oil, and vascular disease. Annals of Internal Medicine, Vol. 123, No.
12, December 15, 1995, pp. 950-52
Controlled trials confirm blood pressure reduction with fish oils
BOSTON, MASSACHUSETTS. Numerous studies have concluded that fish oil consumption lowers blood
pressure, but a few have found no effect and others have been inconclusive. Researchers at the Harvard
Medical School have just completed a major evaluation of the results of 31 placebo-controlled trials
involving 1356 subjects. They found that fish oil supplementation (mean dose of 5.6 grams/day) lowers
systolic blood pressure (first [highest] reading of blood pressure measurement) by an average of 3.4 mm
Hg and diastolic pressure (second [lowest] reading) by an average of 2.0 mm Hg. The effect is highly
dose-dependent with 1 gram/day of fish oil lowering systolic pressure by an average of 0.66 mm Hg and
diastolic pressure by an average of 0.35 mm Hg. Fish oil supplementation does not affect blood pressure
in people with normal blood pressure, but relatively dramatic effects are seen in patients with high
cholesterol levels and in patients with atherosclerosis. Both eicosapentaenoic and docosahexaenoic
acids (the main components of fish oils) are effective in blood pressure reduction with docosahexaenoic
acid being slightly superior. The Harvard researchers conclude that supplementation with 7.7 to 9
grams/day of fish oils will reduce systolic blood pressure by 4 mm Hg and diastolic pressure by 3 mm Hg
in hypertensive individuals. Blood pressure reductions may be substantially larger among patients with
atherosclerosis or high cholesterol levels.
Morris, Martha Clare, et al. Does fish oil lower blood pressure? A meta-analysis of controlled trials.
Circulation, Vol. 88, No. 2, August 1993, pp. 523-33
Fish oils reduce blood pressure
BALTIMORE, MARYLAND. The daily consumption of fish oils (omega-3 polyunsaturated fatty acids) can
significantly lower blood pressure in people suffering from hypertension. The benefit of the fish oils is
comparable to that obtainable by sodium reduction and weight loss. A group of medical researchers at
the Johns Hopkins Medical School evaluated the results of 17 clinical trials involving supplementation
with fish oils for periods of three months or less. They found that the consumption of 3 grams per day of
fish oil (6-10 capsules) or more led to impressive reductions in the blood pressure of hypertensive
individuals. Systolic pressure was lowered by an average of 5.5 mm Hg and diastolic pressure was
lowered by 3.5 mm Hg. The effect was found to be more pronounced at higher blood pressures and no
significant effects were noted in people with normal blood pressure. Twenty-eight percent of the
participants in the trials reported side effects such as a fishy taste or belching. The doctors suggest that
fish oil supplementation may be a valuable therapy in patients with borderline hypertension who would
otherwise be candidates for conventional drug therapy. They point out that the effects of long term (> 3
months) supplementation are unknown and that lower dosages than 3 g/day may be desirable and
perhaps as effective. NOTE: Systolic pressure is the first (highest) reading given for a blood pressure
measurement, diastolic is the second (lowest) reading, i.e. 120/80.
Appel, Lawrence J., et al. Does supplementation of diet with "fish oil" reduce blood pressure? Archives
of Internal Medicine, Vol. 153, June 28, 1993, pp. 1429-38
Fish oil supplementation reduces blood pressure
CINCINNATI, OHIO. Conventional blood pressure lowering medications often have detrimental effects on
quality of life and may lead to unfavourable changes in cholesterol levels. Several studies have found
that supplementation with large amounts of fish oil (5-15 grams/day) lowers blood pressure significantly in
hypertensive individuals. Whether smaller amounts are equally effective has been open to question.
Researchers at the University of Cincinnati (Ohio) College of Medicine now report that daily
supplementation with low doses of fish oil is indeed effective in lowering blood pressure in mildly
hypertensive patients. Their study involved 33 patients (men and women) with a diastolic pressure
between 90 and 104 mm Hg. After a four-week wash-out period during which the participants
discontinued all medications the patients were randomly allocated to one of two groups. Group 1
supplemented with 2.04 grams/day of fish oil containing 410 mg of eicosapentaenoic acid and 285 mg of
docosahexaenoic acid. Group 2 was given a placebo capsule daily containing safflower oil (80% linoleic
acid). After 12 weeks and a four-week wash-out period the groups switched supplementation so that
group 1 now received the placebo. Blood pressure, heart rate, and body weight were recorded at two-
week intervals during the study and blood samples were collected and analyzed at the beginning and end
of each treatment period.
The researchers found that fish oil supplementation reduced diastolic pressure (sitting) by an average of
approximately 4.4 mm Hg and systolic pressure by an average of 6.5 mm Hg when compared to values
obtained prior to the start of treatment. There were no adverse effects on cholesterol levels. They
conclude that fish oil supplementation is a safe and effective way of lowering blood pressure in mildly
hypertensive subjects, but noted that the beneficial effects wear off relatively quickly once
supplementation is discontinued. NOTE: This study was funded by a grant from RP Scherer Ltd. a
manufacturer of fish oil products.
Radack, Kenneth, et al. The effects of low doses of n-3 fatty acid supplementation on blood pressure in
hypertensive subjects. Archives of Internal Medicine, Vol. 151, June 1991, pp. 1173-80
Salt restriction and fish oil supplementation lower blood pressure
ADELAIDE, AUSTRALIA. Salt (sodium) restriction can help lower blood pressure in people with
hypertension, but is less effective in people with normal pressure. Blood pressure tends to rise with age
and there is some evidence that sodium restriction may help reduce this age-related increase. Fish oil
supplementation is also effective in lowering blood pressure in hypertensive individuals, but its effect on
people with normal pressure is unclear.
Australian researchers report that a combination of fish oil supplementation and salt restriction is highly
effective in lowering both systolic and diastolic blood pressure in elderly people with normal pressures.
Their study involved 50 healthy volunteers aged 60 to 80 years whose mean initial systolic and diastolic
blood pressures were 133 and 77 mm Hg respectively. The participants were randomly assigned to one
of four groups. Group 1 supplemented with 8 fish oil capsules per day (providing 4.2 g of omega-3 fatty
acids) while maintaining a normal sodium intake. Group 2 supplemented with fish oil while consuming a
low-sodium diet. Group 3 supplemented with sunflower oil combined with normal sodium intake while
group 4 took sunflower oil while consuming a low-sodium diet. After 4 weeks the mean systolic blood
pressure in group 1 had decreased by 8.9 mm Hg and the diastolic pressure by 6.0 mm Hg. There were
no significant changes in blood pressure in the group supplementing with fish oil while maintaining a
normal sodium intake. The researchers conclude that sodium restriction combined with fish oil
supplementation effectively lowers blood pressure. They suggest that this finding may be of particular
relevance in the treatment of hypertension in the elderly.
Cobiac, Lynne, et al. Effects of dietary sodium restriction and fish oil supplements on blood pressure in
the elderly. Clinical and Experimental Pharmacology and Physiology, Vol. 18, 1991, pp. 265-68
