Oily fish, omega-3s and health
The heart of the matter
One of the main reasons oily fish is promoted is because EFAs can lower the risk of heart disease. They got the nutritional thumbs up when it was seen that Japanese and Inuit (Eskimo) people who eat lots of fish had much lower rates of heart disease. Research showed that EPA and DHA from fish helped reduce blood-clotting and lowered blood pressure, cholesterol and fat levels – all factors in reducing heart disease. What the research ignored was that EPA and DHA can be formed from plant omega-3 (ALA).
Since then, numerous studies have looked at the role of ALA, EPA and DHA in reducing heart disease with three studies in particular most usually being quoted – DART, GISSI and LYON.
The DART and GISSI trials showed how fish oils could reduce death rates in people
who already have heart disease. Plenty of other studies showed that plant-based oils did the same thing – but without harmful toxins – particularly the LYON study.
DART – fish to fight heart disease
The DART trial set out to find if oily fish or fish oil supplements could help prevent a second heart attack in people who had already had one attack. It showed that those on fish oils were a third less likely to die from heart failure in the two years after their first heart attack compared to those not taking fish oils. The improvement was thought to come from a normalising of heartbeat rhythms where heartbeats were irregular (arrhythmia).While the DART trial showed a reduced number of deaths it didn’t show a reduction in heart attacks – fewer deaths but the same number of painful attacks.
A large body of evidence shows that plantbased diets can be used to both prevent and even reverse heart disease (see the Viva!Health guide Have a Heart for further information).Those taking blood-thinning medication such as daily aspirin or warfarin should speak to their GP before eating lots of food with added omega-3 or fish oil supplements, as these can also reduce blood-clotting.
GISSI – fish oil and heart disease
The GISSI trial also looked at the effect of EPA and DHA omega-3s on people who had recently survived a heart attack. Some were given a daily supplement of fish oil capsules while others weren’t.
After three-and-a-half years, it showed a 20 per cent reduction in death rates for those on fish oil but, like the DART trial, the number of non-fatal heart attacks was unchanged. The daily one gram of fish oil taken was the equivalent to eating 100 grams of oily fish a day – exceeding the Food Standards Agency’s ‘safe’ levels (see page 8).
These two studies showed that fish oils may reduce the risk of death in people who have already had a heart attack but a review of many more studies showed that fish and fish oils do not reduce the risk for people with no history of heart problems. So, those with healthy lifestyles don’t protect their heart by eating fish. There is now even doubt that fish oils offer protection to people with existing heart disease.
No long-term protection
Over a decade after the DART trial started, researchers went back to the fish and nonfish groups and found, to their surprise, that the death rate was almost identical in
both groups. So, there was no evidence of long-term protection even for those with a heart condition.
Another study looked at whether advising men with angina to eat oily fish or fish oil
supplements would help their condition. It found an increased death rate of 20 per
cent and 45 per cent respectively! Health organisations and the government should
perhaps rethink their promotion of fish and fish oils.
The British Medical Journal drew all the evidence together in a major review which looked at 89 studies on omega-3 fats and found no clear evidence that people’s health benefited from them. Surprising, considering the benefits previously shown for omega-3s. What could it be about fish omega-3s that was negating these positive effects?
A possible explanation was provided by one large study in their review that showed
a significant increase in deaths from heart attack in men taking fish oil capsules. This
trial had the longest follow-up period of all the studies. It was thought that the
mercury in fish oil could build up over time and that early protective effects might later
become harmful. In other words, pollutants cancel out the beneficial effects of fish omega-3s in the long term!
LYON – plants on trial
The LYON study investigated whether a healthier, Mediterranean-type diet could
reduce the risk of a second heart attack.
Patients were given either a Mediterranean diet or a low-fat ‘prudent’ Western diet.
The Mediterranean diet was largely plant-based with butter and cream being replaced with olive oil and rapeseed oil margarine. The diet did contain some fish but less red meat and was lower in animal fat. It had much less cholesterol but was higher in the plant omega-3 ALA.
This diet increased levels of ALA in the blood by 70 per cent and EPA by 40 per
cent. Their fish intake was only seven grams a day more than the group on the ‘prudent’ Western diet so the higherEPA levels were due to plant ALA rather
After almost four years, patients following the Mediterranean-style diet had a 50-70 per cent lower risk of recurrent heart disease compared to those on the ‘prudent’ Western diet.
An important difference between this and previous studies with fish oils was that
the number of non-fatal heart attacks was reduced. Secondly, the diet’s protective effect was associated with the parent omega-3 ALA rather than the converted EPA as in previous studies. In fact there was no link between the converted EPA and DHA omega-3s and a reduction in heart attacks.
The LYON study showed that plant ALA is extremely effective in reducing the risks of
secondary heart disease, that it was superior to fish-derived EPA and DHA in reducing the risk of a second heart attack and that it protects the heart in the long-term.
The bonus is that the Mediterranean diet is rich in disease-busting antioxidants that can help reduce the build up of fatty deposits in the arteries that lead to heart disease and reduce the risk of cholesterol becoming ‘oxidised’ – the body’s equivalent of rust. When oxidised, ‘bad’ cholesterol can harm the walls of arteries, increasing the risk of heart disease.
The problem is – this research does not appear to have reached health professionals! Around 300,000 people in Britain have a heart attack every year and many of those who survive receive little or no dietary advice. Many scientists agree that survivors should be advised to follow a diet similar to that used in the LYON study.
Plant omega-3s and heart disease
There is a wealth of science showing that plant-based omega-3s protect against heart disease. The Health Professionals’ Study found that a one per cent increase in ALA intake lowered the risk of heart attack by 59 per cent.
The Nurses’ Health Study found that those who ate the most ALA had a 45 per cent lower risk of fatal heart disease.In 2003, a WHO/UN FAO report supported the fact that ALA protected against heart
disease and listed flaxseed, rapeseed and soya bean oils as being beneficial.
In 2008, a study in the journal Circulation (the journal of the American Heart Association) reported that when ALA intake was just 0.65 per cent of daily energy intake (compared to 0.24 per cent), non-fatal heart attacks reduced by a staggering 57 per cent. In weight, this amounts to just 1.79 grams per day – two teaspoons of soya bean or rapeseed oil, 1-2ml (1tsp = 5ml) of flaxseed oil, or 6-10 walnuts a
day would do the trick.
Interestingly, neither fish nor EPA and DHA intake altered the heart attack-lowering effect of ALA, indicating that it is the parent ALA rather than the converted EPA or DHA that lowers the risk.
veggie diets...THE RIGHT PRESCRIPTION
Changing your diet can change – and save – your life! Meat, poultry, fish, eggs and dairy products all contain cholesterol while a plant-based diet contains little or no cholesterol so, not surprisingly, vegans have lower cholesterol levels than vegetarians – fish and meat-eaters tend to have the highest. As a result, vegetarians and
vegans have a much lower risk of heart disease than meat-eaters – and a 25 per cent lower risk of dying from heart disease! If people throughout Britain went vegetarian, there would be some 40,000 fewer deaths from heart disease every year.
And it’s never too late to change. Plantbased diets can not only prevent heart disease, they can reverse the damage. Dr Dean Ornish, Clinical Professor of Medicine at the University of California in San Francisco, is known for his Lifestyle
Heart Trial in which he treated severe heart disease patients by changing their lifestyle and nothing else. They ate a low-fat, wholegrain, plant-based diet containing lots of fruit, vegetables and pulses, took exercise and managed their stress. A ‘control’ group of similar patients received conventional treatment.
After one year, the control group experienced a 165 per cent increase in the frequency of chest pain, cholesterol was higher and artery blockages had worsened. Conversely, 82 per cent of the patients following Ornish’s lifestyle changes had improved with a 91 per cent reduction in chest pain and reduced cholesterol levels.
For more information on heart disease see the Health!Viva fact sheet Plant-based Diets
and Cardiovascular Disease.
The conclusion of the study was that vegetable oils rich in ALA could provide important protection against heart disease. The National Heart, Lung and Blood Institute Family Heart Study showed that men eating the most ALA had a 40 per cent lower risk and women, a whopping 50-70 per cent reduction.