High Cholesterol

NOTE: THESE SUMMARIES ARE OF HISTORICAL INTEREST ONLY AS THE COCHRANE REVIEWS ARE OUTDATED

Studies

Cardiovascular Disease  

Cardiovascular disease remains the leading cause of death in developed countries. The main underlying problem is atherosclerosis, a process that is characterised by thickening of the wall of blood vessels and the formation of fatty plaques. Blood clots can form on the damaged areas of a blood vessel wall and fragments break off to block narrower blood vessels – which can result in a heart attack or a stroke.

Lack of physical activity, poor diet, smoking and stress can speed up clogging of the blood vessels, particularly the arteries, and also make the blood more likely to clot. High blood pressure and narrowing and hardening of major heart blood vessels (coronary arteries) increases the stress within blood vessels hastening atherosclerosis and making blood clots more likely, so increasing the risk of a heart attack and stroke. People also get pain on exertion or stress (angina), which occurs when a vessel is narrowed so that not enough blood (and oxygen) can reach the heart muscle when it is working. The pain is a warning sign to slow down and reduce the risk of the heart being starved of oxygen.

Too much cholesterol in the blood adds to cholesterol deposits on the walls of the arteries. Lipoproteins carry the cholesterol in the blood to the body tissues. Low density lipoproteins (LDL), ‘bad lipoproteins’, can be reduced by losing weight, cutting down on saturated fat, and statin drugs. High density lipoproteins (HDL), ‘good lipoproteins’, can be boosted by smoking cessation and physical activity. HDLs carry cholesterol to the liver to be removed from the body. Complementary therapies may reduce the need for drug treatment.

For young people with no other risk factors for cardiovascular disease, a total blood cholesterol level above 7.5 millimoles per litre (mmol/L) or LDL cholesterol above 4.9 mmol/L may be considered ‘high’, but in people with other risk factors much lower cholesterol levels are considered risky.

We present some of the evidence from Cochrane systematic reviews about complementary and alternative treatments related to high cholesterol. This evidence comes from carefully researched reviews of information about clinical trials done to evaluate medical treatments. Studies are only included in these reviews if they meet pre-defined criteria.

DIET FOR INHERITED FAMILIAL HIGH CHOLESTEROL  

Special cholesterol-lowering diets are useful for children and adults from families with a history of high cholesterol. Drug treatment is available for adults but two existing drugs did not appear to be effective in children and statins are being investigated. Treatment for children could be important because cholesterol deposits and coronary heart disease can be detected in people as early as 20 years of age.

What the synthesised research says

There are too few trials, including too few participants, to know whether cholesterol-lowering diets for children and adults with familial hyperlipidaemia do reduce fasting levels of cholesterol, trigylcerides, and lipoproteins compared to otherdiets or no dietary guidance. In the short-term, six trials reported results and found no difference between fasting levels when the results of a cholesterol- lowering diet were compared to diets containing either fish oils, soy products, plant cholesterols, high protein, dietary cholesterols, or with no dietary guidance.

How it was tested

The researchers thoroughly searched the medical literature and were able to find seven controlled trials including only 162 participants in total. These were children in three trials (65 children) and adults in the other three trials, all with familial hyperlipidaemia who were randomly assigned to a cholesterol-lowering diet during half of the trial (for four to eight weeks) and to the other intervention during the other half of the trial (for a further four to eight weeks). All of the trials were very small (ranging from five to 41 participants).

* The cholesterol-lowering diet was compared to no dietary guidance in one trial and an alternative diet in the other five trials. These alternative diets assessed the benefits of fish oils, soy products, plant cholesterols, high protein diet, and dietary cholesterol.

Side effects and general limitations

The trials were too short and included too few participants to be able to make any conclusions about the effectiveness of dietary interventions for children and adults with genetic high cholesterol levels. The risk of heart and vascular disease could not be looked at in this time period.

Wellbeing and quality of life were not measured.

Several larger trials have looked at the effect of a cholesterol-lowering diet in people with both familial and non-familial high cholesterol. The information could not be used in this review because it was not possible to separate out the information on participants with familial high cholesterol.

Source

Poustie VJ, Rutherford P. Dietary treatment for familial hypercholesterolaemia. The Cochrane Database of Systematic Reviews 2001, Issue 2. Art. No.: CD001918. DOI: 10.1002/14651858.CD001918.

ARTICHOKE LEAF EXTRACT FOR TREATING RAISED CHOLESTEROL LEVELS 

Too much cholesterol in the blood can lead to cholesterol deposits on the walls of the arteries that clog up and harden the blood vessels. With high levels of cholesterol, fatty deposits can form in the tendons, skin and blood vessels (arteries), and people are more likely to have heart disease and strokes. LDL is sometimes referred to as the ‘bad cholesterol’ because it is associated with increased risk of heart disease. By contrast, high-density lipoprotein (HDL) is referred to as ‘good cholesterol’ because it helps remove cholesterol from the body.

LDL (‘bad’) cholesterol can be lowered by weight loss and eating less saturated fats, while HDL or ‘good’ cholesterol can be raised by quitting smoking and exercise. A number of herbs and natural supplements are used to lower total and LDL cholesterol levels. Artichoke leaf extract is an over-the-counter herbal remedy sold for this purpose.

What the synthesised research says

Taking an herbal preparation containing artichoke leaf extract may have a modest reducing effect on total blood cholesterol levels but there are too few trials to know for certain.

In one trial (143 men and women), total cholesterol and low density lipoprotein levels (LDL or ‘bad cholesterol’) were lowered without any change in triglycerides (a type of fat) and high-density lipoprotein (HDL or ’good cholesterol’).  

How it was tested

The researchers thoroughly searched the medical literature and were able to find two controlled trials involving a total of 187 people who were randomly assigned to receive the artichoke leaf extract or a non-active treatment (placebo).

One trial included 143 participants (96 women, 47 men) aged between 18 and 70 years with a total cholesterol level of greater than 7.3 mmol/l (equivalent to 280 mg/dl). In that trial, the amount of artichoke leaf extract taken was 900 mg, twice daily for six weeks. Both artichoke leaf extract and placebo reduced total cholesterol levels but the artichoke leaf extract more so (from 7.7 mmol/l to 6.3 mmol/l compared with 7.7 mmol/l to 7.0 mmol/l).

In the other trial, which was not reported in full, 44 participants between the ages of 20 and 49 years took 640 mg three times daily for 12 weeks. Artichoke leaf extract may have decreased total cholesterol only for people with high cholesterol levels.

Side effects and general limitations

Overall, evidence from the reviewed trials and post-marketing surveillance studies indicates that artichoke leaf extract is relatively well tolerated in the short-term, six to twelve weeks in these trials. Side effects were mild, temporary, and infrequent.

With only two trials the evidence is not clear and better trials including more participants over longer periods are needed to understand the effects of artichoke leaf extract.

The larger trial had mostly over-weight people but diet was not rigorously taken into account. This makes it hard to determine whether the results could have been influenced by diet as well as the artichoke leaf extract. The size of the effect reported is moderate and similar to that found in studies using garlic and dietary advice as a way of lowering cholesterol levels.

Source

Pittler MH, Thompson Coon J, Ernst E. Artichoke leaf extract for treating hypercholesterolaemia. The Cochrane Database of Systematic Reviews 2002, Issue 3. Art. No.: CD003335. DOI: 10.1002/14651858.CD003335.

OMEGA 3 FATTY ACIDS FOR PREVENTION AND TREATMENT OF CARDIOVASCULAR DISEASE

Greenland Eskimos used to have a low incidence of heart disease and ate large quantities of marine unsaturated fats, omega 3 fatty acids, from oily fish and marine mammals. This led to speculation that marine unsaturated fats may have a protective role and benefit our health. Some plant oils are also rich in omega 3 fatty acids, including flax (linseed) and rapeseed (canola) oils.

Some studies have found that omega 3 fats have lowered some risk factors for cardiovascular disease (e.g. triglycerides, blood pressure) but there is also concern that the most widely consumed sources of omega 3 fats, oily fish or fish oil capsules, could have harmful effects over the long-term because they may contain high levels of toxic compounds (mercury, dioxins, polychlorinated biphenyls (PCBs)) which can accumulate in the body over time and may increase the risk of cancers or neurological difficulties.

What the synthesised research says

Omega 3 fats (whether fish-based or plant-based, as part of the diet or as supplement) did not reduce the overall risk of death or cardiovascular events. Cardiovascular events include a cardiovascular death; heart attack (myocardial infarction); stroke; angina; heart failure; a peripheral vascular event; and unplanned coronary artery bypass grafting or angioplasty.

Omega 3 fats reduced blood triglyceride levels and increased LDL cholesterol a little but had no clear effects on weight, total cholesterol, HDL cholesterol, or blood pressure.

This conclusion is based on 48 randomised controlled trials each lasting for at least 6 months and involving 36,913 people overall and 41 studies of populations (cohort studies).

Omega 3 fats did not increase the risk of cancer.

How it was tested

The researchers thoroughly searched the medical literature and were able to identify 48 controlled trials. These lasted a minimum of six months to over six years and involved people aged in their 30s to their 80s (in one trial only). The participants were given omega 3 fat supplements or advised to eat more oily fish (four trials, one with supplement too) and compared with people who were given a non-active supplement (placebo) or no supplement or ate their usual diet. Amounts of fish-based omega 3 fatty acids varied from 0.4 to 7g per day.

The trials included 36,913 participants who were either at high risk (21 trials), moderate risk (10 trials) or low risk (17 trials) of cardiovascular disease. Participants were predominantly male in 24 trials, male and female in 17 trials, and predominantly women in five trials (not reported in two trials).

Combining the results of the three relevant observational studies that followed groups of people (cohorts) suggested a protective effect of higher omega 3 intakes on total mortality, the relative risk was 0.65. These types of studies were investigated as they may have shown up any ill effects from the toxins in fish-based omega 3 fats. People’s intake of omega 3 was assessed.

Only ten trials reported cancer outcomes, two of which reported no cancers. Overall 391 cancer diagnoses or deaths were reported from 17,433 participants. Most trials provided information on deaths from cancer, rather than diagnosis of cancer, so that we are unlikely to be seeing sufficient build up of body toxins leading to cancer in a trial.

Side effects and general limitations

Results were significantly affected by the inclusion of a large trial of 3114 men with angina. If that trial was excluded (because it was in a very specific population), results would have been more consistent with an earlier systematic review which found that omega 3 fats had protective effects on fatal heart attacks and overall mortality in trial participants with coronary heart disease.

Some people experienced a bad fishy taste, belching, nausea and gastrointestinal side effects with omega 3 intake.

One trial found that girls consuming more omega 3 fats were more likely to begin their menstrual periods before 12.5 years of age (relative risk 2.4).

Independent analyses of the levels of toxins in named brands of fish oil supplements and oily fish sold for food should be more widely available.

Source

Hooper L, Thompson RL, Harrison RA, Summerbell CD, Moore H, Worthington HV, Durrington PN, Ness AR, Capps NE, Davey Smith G, Riemersma RA, Ebrahim SBJ. Omega 3 fatty acids for prevention and treatment of cardiovascular disease. The Cochrane Database of Systematic Reviews 2004, Issue 4. Art. No.: CD003177.pub2. DOI: 10.1002/14651858.CD003177.pub2.

Bucher HC, Hengstler P, Schindler C, Meier G. N-3 polyunsaturated fatty acids in coronary heart disease: a meta-analysis of randomized controlled trials. American Journal of Medicine 2002;112:298-304.

CHELATION THERAPY FOR HEART DISEASE 

Chelation has been found to be effective in removing toxic metals from the blood. Proponents believe that it can also reduce plaque (fatty deposits and other substances) in arteries and thereby restore blood flow to clogged or blocked arteries. This could potentially prevent symptoms of heart and circulatory disease including chest pain, heart attacks, strokes, and fatigue or pain in the calf muscles that people experience after walking short distances (claudication).

Chelation therapy consists of a series of intravenous infusions into the bloodstream (that is, a solution slowly injected into the blood stream over a period of time). The infusions contained a chemical called EDTA (disodium ethylene diamine tetraacetic acid) in combination with other substances.

What the synthesised research says

No controlled trials were found looking at any benefits of chelation therapy on heart disease or strokes.

No clear benefits were seen for people with peripheral arterial disease (intermittent claudication).

Of the five trials that evaluated people with peripheral arterial disease, four of them, involving a total of 250 participants, did not show any benefit from chelation therapy. Chelation therapy was evaluated by measuring blood pressure at the ankle compared to the arm, computer assisted x-rays, the distance a person could walk, cholesterol levels, and how the person felt. One very small study (10 participants) found some improvement with chelation therapy.

How it was tested

The researchers thoroughly searched the medical literature but could not find any controlled trials of chelation therapy involving people with blocked or clogged arteries that supply the heart or brain.

They did find five trials that evaluated the use of chelation therapy on people with restricted blood flow to the legs (peripheral arterial disease) who experienced cramping, pain, fatigue on and off while walking or exercising (intermittent claudication).

The trials were small, ranging from 30 to 153 people. Participants were randomly assigned to receive 20 infusions of chelation therapy or non-active (placebo) infusions over 5 to 10 weeks. The follow-ups and number of infusions varied but in general, there were 10 to 20 infusions and follow ups ranged from 3 to 12 months after treatment.

Side effects and general limitations

One trial reported some possible side effects from chelation therapy including pain and inflammation at the site of the infusion, faintness, gastrointestinal symptoms, protein in urine, and low blood calcium.

Source

Villarruz MV, Dans A, Tan F. Chelation therapy for atherosclerotic cardiovascular disease. The Cochrane Database of Systematic Reviews 2002, Issue 4. Art. No.: CD002785. DOI: 10.1002/14651858.CD002785

WHOLEGRAIN CEREALS FOR PREVENTING CORONARY HEART DISEASE

Coronary heart disease (CHD) is the major cause of death in western societies. Major risk factors include being overweight, a family history of the disease, high blood pressure, raised blood levels of low density lipoproteins (LDL) cholesterol, triglycerides or total cholesterol, abnormal blood clotting factors and diabetes.

Wholegrain contains the entire edible parts of a natural grain kernel, including the bran and germ, and is rich in dietary fibre, anti-oxidants, resistant starch, phyto-oestrogens and other important micronutrients such as vitamins and folic acid. Wholemeal foods are made from milled wholegrains. Food made with white flour does not contain a high level of fibre and micronutrients because most of the bran is removed in the refining process. Eating wholegrains may be beneficial to health.

What the synthesised research says

Randomised controlled trials provide evidence that wholegrain oats lower LDL- and total cholesterol levels - in people with pre-existing risk factors for CHD. The reduced total cholesterol was seen as early as after four weeks of eating wholegrain oats. There is a lack of evidence on other risk factors.

None of the studies looked at effects on coronary heart disease or deaths and did not follow the participants long enough to show any such benefit. Nine trials were carried out in the USA and one in Finland, over 4 to 12 weeks. One trial examined the effects of a varied diet containing wholegrain breakfast cereal, bread, rice, pasta, muffins, cookies and grain-based snacks. Another investigated the effects of wholegrain rye bread as part of the usual diet. In the eight other studies oatmeal foods were the source of wholegrain. Many of the trials were short-term, conducted on small numbers and of poor quality and most were wholly or partly funded by commercial sources with interests in cereal products.

How it was tested

This review is based on 10 trials involving 914 adults with risk factors for coronary heart disease. The main risk factors were raised cholesterol (seven trials), high blood pressure (two trials) and being overweight (one trial).

Nine trials were carried out in the USA and one in Finland, over 4 to 12 weeks. One trial examined the effects of a varied diet containing wholegrain breakfast cereal, bread, rice, pasta, muffins, cookies and grain-based snacks and one study investigated the effects of wholegrain rye bread as part of the usual diet. In the eight other studies oatmeal foods were the source of wholegrain.

Side effects and general limitations

None of the studies looked at effects on coronary heart disease itself, or deaths.

Many of the trials were of poor quality, conducted over a short time perion and involved only small numbers of people. Most of the included trials were wholly or partly funded by commercial sources with interests in cereal products.

Source

SAM Kelly, A Brynes, G Frost, R Lang, V Whittaker, CD Summerbell. Wholegrain cereals for coronary heart disease. Cochrane Database of Systematic Reviews 2004, Issue 4. Art. No.: CD005051. DOI: 10.1002/14651858.CD005051.