Chris Kresser's Take:
When it comes to fish oil, more is not better
Highlights:
“A 2004 Cochrane meta-analysis of trials lasting longer than six months suggests that the cardiovascular benefits of fish oil have been dramatically over-stated. They analyzed 79 trials overall, and pooled data from 48 trials that met their criteria. The only effect that could be distinguished from chance was a reduced risk of heart failure. Fish oil provided no reduction in total or cardiovascular mortality.”
“To be fair, at least one review suggests that fish oil supplementation is beneficial in the short and even intermediate term. A recent meta-analysis of 11 trials lasting more than one year found that fish oil reduced the relative risk of cardiovascular death by 13 percent and the relative risk of death from any cause by 8 percent.
But the effect seen in this review was mostly due to the GISSI and DART-1 trials. They found that fish oil may prevent arrhythmia in patients with chronic heart failure and patients who have recently survived a heart attack.”
Chris Masterjohn's take:
Precious Yet Perilous - Weston A Price Foundation
Highlights:
http://www.westonaprice.org/images/articleimages/fall10-masterjohnfigure2.jpg
“Despite a daily supplement of vitamin E, his blood and urine levels of malondialdehyde (MDA)—a product of the oxidative destruction of PUFA (see Figure 3d)—rose to fifty times the normal level. Although MDA causes birth defects, Sinclair was not worried about having “misshapen offspring” because his sperm had disappeared.”
“Trials lasting less than one year were most likely to show positive results, while the only trial lasting more than four years—the Diet and Reinfarction 2 (DART 2) trial—showed a 15 percent increase in total mortality and a 30 percent increase in cardiovascular mortality. DART 2 used dietary advice to increase fatty fish intake in addition to fish oil supplementation, so could not be placebo-controlled or double-blind, and unfortunately funding problems led to interruptions of the recruitment process in the middle of the trial. Nevertheless, with over three thousand participants it was one of the largest fish oil trials ever conducted and, with over four years follow-up, it was the longest fish oil trial ever conducted. Thus, we should not casually dismiss the findings of this trial.”
“The Italian GISSI-Prevenzione and GISSI-Heart Failure trials were the largest included in this meta-analysis and were responsible for most of the effect. These trials, together with the DART 1 trial, suggested that fish oil may prevent arrhythmia in patients with chronic heart failure and patients who have recently survived a heart attack. Researchers provided participants with roughly one gram of long-chain omega-3 fatty acids per day. The GISSI trials found a long-term benefit over the course of almost four years in heart failure patients but a much shorter-term benefit concentrated in the first year of the study in patients who had recently undergone a heart attack. The DART 1 trial similarly found an early benefit of fatty fish consumption and fish oil supplementation in patients who had recently suffered from a heart attack. Fish oil thus seems likely to prevent very specific types of heart failure rather than to prevent heart disease more generally.”
Ray Peat's take:
The Great Fish Oil Experiment
Highlights:
“The US government and the mass media selectively promote research that is favorable to the fish oil industry. The editorial boards of oil research journals often include industry representatives, and their editorial decisions favor research conclusions that promote the industry, in the way that editorial decisions in previous decades favored articles that denied the dangers of radiation and reported that estrogen cures almost everything. Marcia Angell, former editor of the NEJM, has observed that the "significant results" reported in published studies can be properly interpreted only by knowing how many studies reporting opposite results were rejected by the editors.”
“The belief that eating cholesterol causes heart disease was based mainly on old experiments with rabbits, and subsequent experiments have made it clear that it is oxidized cholesterol that damages the arteries (Stapran, et al., 1997). Since both fish oil and oxidized cholesterol damage rabbits' arteries, and since the lipid peroxides associated with fish oil attack a great variety of biological materials, including the LDL lipoproteins carrying cholesterol, the implications of the rabbit experiments now seem very different.”
Appendix:
Polyunsaturates-
I also realize that "Precious Yet Perilous" is a long article, so here are the biggest things to keep in mind:
"Arachidonic acid is found in liver, egg yolks, and other fats from land animals, and in small amounts in seafood. DHA is found in cod liver oil, fatty fish, and in smaller amounts in the organs and fats of land animals. "
"The requirement for essential fatty acids is likely to be well below 0.1 percent of calories on a diet that is devoid of refined sugar and rancid vegetable oils, low in polyunsaturated vegetable oils, adequate in protein and total energy, and rich in vitamin B6, biotin, calcium, magnesium, and fresh, whole foods abundant in natural antioxidants."
"Excess linoleic acid from vegetable oils can cause a deficiency in DHA. An excess of the omega-3 fatty acid EPA from fish and cod liver oil can cause a deficiency in arachidonic acid. For this reason, cod liver oil should be used in moderation and in combination with a diet rich in egg yolks and organ meats."
"Up until the 1930s, Americans consumed on average about 15 grams (one tablespoon) of PUFA per day. Since the 1930s, this value has more than doubled to over 35 grams per day as Americans have increased their intake of vegetable oils rich in the omega-6 linoleic acid"
"... it may be possible that the optimal amounts are much higher. Research, however, suggests quite the opposite: even though the medical establishment has recommended the consumption of vegetable oils to prevent heart disease for decades, randomized, controlled trials conducted in humans demonstrated conclusively that vegetable oils cannot decrease atherosclerosis and suggested that they probably cause cancer."
When it comes to fish oil, more is not better
Highlights:
“A 2004 Cochrane meta-analysis of trials lasting longer than six months suggests that the cardiovascular benefits of fish oil have been dramatically over-stated. They analyzed 79 trials overall, and pooled data from 48 trials that met their criteria. The only effect that could be distinguished from chance was a reduced risk of heart failure. Fish oil provided no reduction in total or cardiovascular mortality.”
“To be fair, at least one review suggests that fish oil supplementation is beneficial in the short and even intermediate term. A recent meta-analysis of 11 trials lasting more than one year found that fish oil reduced the relative risk of cardiovascular death by 13 percent and the relative risk of death from any cause by 8 percent.
But the effect seen in this review was mostly due to the GISSI and DART-1 trials. They found that fish oil may prevent arrhythmia in patients with chronic heart failure and patients who have recently survived a heart attack.”
Chris Masterjohn's take:
Precious Yet Perilous - Weston A Price Foundation
Highlights:
http://www.westonaprice.org/images/articleimages/fall10-masterjohnfigure2.jpg
“Despite a daily supplement of vitamin E, his blood and urine levels of malondialdehyde (MDA)—a product of the oxidative destruction of PUFA (see Figure 3d)—rose to fifty times the normal level. Although MDA causes birth defects, Sinclair was not worried about having “misshapen offspring” because his sperm had disappeared.”
“Trials lasting less than one year were most likely to show positive results, while the only trial lasting more than four years—the Diet and Reinfarction 2 (DART 2) trial—showed a 15 percent increase in total mortality and a 30 percent increase in cardiovascular mortality. DART 2 used dietary advice to increase fatty fish intake in addition to fish oil supplementation, so could not be placebo-controlled or double-blind, and unfortunately funding problems led to interruptions of the recruitment process in the middle of the trial. Nevertheless, with over three thousand participants it was one of the largest fish oil trials ever conducted and, with over four years follow-up, it was the longest fish oil trial ever conducted. Thus, we should not casually dismiss the findings of this trial.”
“The Italian GISSI-Prevenzione and GISSI-Heart Failure trials were the largest included in this meta-analysis and were responsible for most of the effect. These trials, together with the DART 1 trial, suggested that fish oil may prevent arrhythmia in patients with chronic heart failure and patients who have recently survived a heart attack. Researchers provided participants with roughly one gram of long-chain omega-3 fatty acids per day. The GISSI trials found a long-term benefit over the course of almost four years in heart failure patients but a much shorter-term benefit concentrated in the first year of the study in patients who had recently undergone a heart attack. The DART 1 trial similarly found an early benefit of fatty fish consumption and fish oil supplementation in patients who had recently suffered from a heart attack. Fish oil thus seems likely to prevent very specific types of heart failure rather than to prevent heart disease more generally.”
Ray Peat's take:
The Great Fish Oil Experiment
Highlights:
“The US government and the mass media selectively promote research that is favorable to the fish oil industry. The editorial boards of oil research journals often include industry representatives, and their editorial decisions favor research conclusions that promote the industry, in the way that editorial decisions in previous decades favored articles that denied the dangers of radiation and reported that estrogen cures almost everything. Marcia Angell, former editor of the NEJM, has observed that the "significant results" reported in published studies can be properly interpreted only by knowing how many studies reporting opposite results were rejected by the editors.”
“The belief that eating cholesterol causes heart disease was based mainly on old experiments with rabbits, and subsequent experiments have made it clear that it is oxidized cholesterol that damages the arteries (Stapran, et al., 1997). Since both fish oil and oxidized cholesterol damage rabbits' arteries, and since the lipid peroxides associated with fish oil attack a great variety of biological materials, including the LDL lipoproteins carrying cholesterol, the implications of the rabbit experiments now seem very different.”
Appendix:
Polyunsaturates-
I also realize that "Precious Yet Perilous" is a long article, so here are the biggest things to keep in mind:
"Arachidonic acid is found in liver, egg yolks, and other fats from land animals, and in small amounts in seafood. DHA is found in cod liver oil, fatty fish, and in smaller amounts in the organs and fats of land animals. "
"The requirement for essential fatty acids is likely to be well below 0.1 percent of calories on a diet that is devoid of refined sugar and rancid vegetable oils, low in polyunsaturated vegetable oils, adequate in protein and total energy, and rich in vitamin B6, biotin, calcium, magnesium, and fresh, whole foods abundant in natural antioxidants."
"Excess linoleic acid from vegetable oils can cause a deficiency in DHA. An excess of the omega-3 fatty acid EPA from fish and cod liver oil can cause a deficiency in arachidonic acid. For this reason, cod liver oil should be used in moderation and in combination with a diet rich in egg yolks and organ meats."
"Up until the 1930s, Americans consumed on average about 15 grams (one tablespoon) of PUFA per day. Since the 1930s, this value has more than doubled to over 35 grams per day as Americans have increased their intake of vegetable oils rich in the omega-6 linoleic acid"
"... it may be possible that the optimal amounts are much higher. Research, however, suggests quite the opposite: even though the medical establishment has recommended the consumption of vegetable oils to prevent heart disease for decades, randomized, controlled trials conducted in humans demonstrated conclusively that vegetable oils cannot decrease atherosclerosis and suggested that they probably cause cancer."
