Author: Qin Huiji Source: Medical Journal / University Journal
【Key words】 Cardiovascular disease
Summary
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Key words polyunsaturated fatty acids; cardiovascular disease; tumors; mental illness; asthma; children; growth and development
The role of fat (including polyunsaturated fatty acids) in nutrition is well known. Although eating a high-fat diet can increase triglycerides and cholesterol in the blood, it is easy to cause cardiovascular and cerebrovascular diseases. But polyunsaturated fatty acids in fat cannot be avoided because they are necessary for the human body. It is not only effective for the brain and retina development of infants and young children, but also can reduce blood cholesterol and triglycerides. Therefore, it is a good health food for preventing and treating cardiovascular and cerebrovascular diseases. In recent years, epidemiological and biochemical studies on polyunsaturated fatty acids (PUFAs) have increased rapidly. Both animal and human studies have shown that PUFAs are of great value in the clinical field.
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1 Cardiovascular effects of PUFAs
1.1 Fish oil's β-blocking effect against ventricular arrhythmias PUFAs have been clinically noted to have an effect against ischemic heart disease (IHD) for more than 20 years. Animal studies have shown that PUFAs have a beneficial effect on ventricular arrhythmias that cause cardiac arrest. Danish researchers used a controlled, double-blind method to study the effect of fish oil on the risk of arrhythmias after myocardial infarction and found that fish oil increased the threshold of ventricular fibrillation and protected the myocardium from ventricular arrhythmias. Fish oil has a β-blocking or angiotensin-converting enzyme (ACE) inhibitory effect, thereby reducing the mortality rate of patients after myocardial infarction [1].
1.2 PUFAs reduce the incidence of premature ventricular contractions in heart patients by 70%. Sellmayer studied 68 heart disease patients and found that the incidence of complex premature ventricular contractions was 70% lower in the group that supplemented with PUFAs than in the control group that took a placebo. This type of arrhythmia is a clear indicator of potential cardiac arrest. Therefore, adding PUFAs to the diet can not only help the general population prevent heart disease, but also improve the prognosis of patients who already have heart disease [2].
1.3 PUFAs reduce the risk of cardiac arrest by half American scholars found that people who ate more fish had a 50% lower risk of cardiac arrest than those who ate very little fish. The research subjects were 334 patients (aged 25 to 74 years) who had experienced cardiac arrest and compared them with a matched general population. The results showed that the reduction in the risk of cardiac arrest was positively correlated with the amount of fish consumed. Intake of 5.5 g of polyunsaturated fatty acids per month was enough to reduce the risk of cardiac arrest by half [3].
1.4 Eating fish protects the intima of the coronary arteries. Research by American scholars has found that eating fish twice or more a week can reduce the incidence of damage to the intima of the coronary arteries, thereby reducing the incidence of coronary heart disease. The Honolulu Heart Study Project autopsied 120 Japanese American men and found that the greatest protective effect was in patients without hypertension, and was not affected by weight, exercise, and alcohol consumption, but smoking history was important [4].
1.5 The protective effect of fish consumption on the heart German scholars studied 272 elderly people born before 1907 and found that those who ate a small amount of fish were 50% less likely to suffer from heart disease than those who did not eat fish at all. They also found that the protective effect of fish consumption was because fish was a source of PUFAs. Fish oil supplements can reduce the level of special fatty acids in the blood that are related to heart disease. Eating fish oil supplements containing polyunsaturated fatty acids can reduce the risk of heart disease in menopausal women by 27%. The compounds in fish oil can inhibit the production of specific fatty acids in the liver and reduce the rate of secretion of other fatty acids into the blood.
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2. The preventive and therapeutic effects of PUFAs on cancer
2.1 PUFAs and cancer risk in middle-aged men In the past 30 years, the incidence of coronary heart disease in Americans has dropped significantly, which may be related to their increased consumption of PUFAs. On average, PUFAs in the American diet account for 6% of total energy intake (in the 1950s, it was only 3%). Some doctors even recommend a higher proportion of 10%. However, safety issues have also been raised, especially whether it will increase the risk of cancer incidence. So far, there have been only animal experiments and very few human studies. A prospective study of more than 3,000 middle-aged French men over a period of 12 years found that only 59 deaths were related to cancer, and most deaths were closely related to smoking and alcoholism [5]. Zureik et al. [6] found that there was a negative correlation between PUFA intake and the risk of death from cancer, but the authors lacked a reasonable explanation for this protective effect, believing that the fatty acid ratio of cholesterol esters was a predictor of death in the study subjects and that PUFAs did not increase the risk of cancer.
2.2 Treatment of advanced gastrointestinal cancer There is a clear benefit in treating patients with various types of advanced gastrointestinal cancer (stomach, liver, pancreas and rectum) with PUFAs. In addition to standard radiotherapy and chemotherapy, 50 such patients were treated with 300 mg of natural PUFAs per day, and their survival rate was significantly improved compared with the placebo group. Clinicians believe that the importance of this finding is that the standard treatment for advanced gastrointestinal cancer, even the latest surgery, radiotherapy, chemotherapy and immunotherapy, is disappointing. The role of PUFAs is not to destroy tumor cells, but to protect normal cells and counteract the toxic side effects of conventional anticancer therapies [7].
2.3 Olive oil reduces the risk of breast cancer. British scholars reported that fat does not play any role in increasing the risk of breast cancer in women. In recent years, Italian researchers have found that there is a negative correlation between increased fat intake and the risk of breast cancer. Analysis of the types of fats that play a role found that PUFAs intake is associated with a reduced risk, while saturated fatty acids have a neutral effect, neither increasing nor decreasing the risk. French scientists have found that the effect of PUFAs may be due to eating more olive oil and plants [8].
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3 Anti-inflammatory effects of PUFAs
3.1 Fish oil capsules help reduce the onset of Crohn's disease Fish oil has anti-inflammatory properties, so it has been used in patients with some inflammatory diseases, including patients with intestinal inflammatory diseases. Due to the unpleasant taste and gastrointestinal irritation side effects of fish oil, patients often find it difficult to accept; using internally coated fish oil preparations can solve this problem. 78 patients with Crohn's disease, all of whom are high-risk patients prone to relapse, were divided into two groups: one group took 9 fish oil capsules per day (total polyunsaturated fatty acids 2.7 g); the other group took a placebo. A double-blind study lasting one year was conducted. The capsule coating is designed to resist gastric acid and protect for at least 30 minutes. Each capsule contains 500 mg of deep-sea lipids concentrated in a desaturated form, 40% of which is EPA, 20% is DHA, and of the remaining 40%, 17% is n7, 16% is n9, and 7% is a mixture of n6 fatty acids. The daily dose of EPA is 1.8 g and DHA is 0.9 g. Journal of Guangdong Pharmaceutical College (ACAD J GCP) 2000, 16(4) No. 4 Qin Huiji: The role of polyunsaturated fatty acids in disease prevention and treatment After one year of treatment, 23 of the 39 patients (59%) in the fish oil capsule group remained in remission, while only 10 of the 39 patients (26%) in the control group remained in remission. In addition, laboratory tests found that all inflammatory markers in the treatment group were significantly lower than those in the control group, with very few gastrointestinal side effects and occasional diarrhea. Patients had good medication compliance, and polyunsaturated fatty acids were highly absorbed and bound to phospholipid membranes [7].
3.2 Protective effect of fish consumption on women with rheumatoid arthritis Rheumatoid arthritis (RA) is rare among Eskimos, whose diet is richer in polyunsaturated fatty acids than Europeans. In Europe, researchers reported that people in the Faroe Islands, who eat more fish, have milder symptoms of RA and a shorter course of disease. This supports the hypothesis that polyunsaturated fatty acid synthesis in cells can inhibit the biochemical pathways that lead to the formation of lipid mediators of inflammation.
Research by scholars from Greece and Finland indicates that increasing fish and olive oil in the diet can reduce the incidence of RA.
Shapiro et al. from the University of Washington in the United States studied 324 women with RA and 1,245 normal controls, investigating their diet for one year and found that eating more grilled or baked fish, rather than tuna, reduced the risk of RA. These fish contain the most polyunsaturated fatty acids[9].
3.3 Eating oily fish can reduce the risk of childhood asthma. The increasing incidence of childhood asthma in urban and rural areas is one of the public health problems that has not been solved so far. Environmental allergies and pollution are important, but more and more evidence shows that dietary patterns also play an important role. In developed countries, the consumption of fish, fruits and vegetables has been declining, which has reduced the intake of β-carotene and vitamins A, E and C that help with antioxidant effects, and has a certain impact on the increase in the incidence of childhood asthma. Australian scholars have pointed out that school-age children who eat fish more than once a week have a one-third lower risk of asthma than children who do not eat fish frequently. Studies on children aged 8 to 11 have also shown that the incidence of asthma is closely related to diet. Hodge et al. [10] studied 574 children, including children with airway hyperresponsiveness (AHR), children who had asthma in the past 12 months and children with normal airways (i.e., no AHR or recent asthma). The results showed that 84% of children with normal airways and 70% of children with recent asthma ate fresh fish. When fresh fish was divided into oily (>20% fat) and non-oily (<20% fat), 30.8% of children with normal airways ate oily fish, while only 15.5% of children with recent asthma ate oily fish, which was significantly less. After adjusting for other risk factors, it was still clear that eating fish, especially oily fish, reduced the risk of asthma [10].
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4 Application of PUFAs in mental illness
Dietary supplementation of PUFAs can alleviate symptoms of schizophrenia. Studies have shown that phospholipid A2 enzymes in schizophrenia patients are overactive in releasing arachidonic acid (AA) from cell membranes; therefore, these patients have very low AA levels. Postmortem studies of brain cells from schizophrenia patients treated with medication have shown that levels of n3 and n6 PUFAs in red blood cell membranes are reduced. WHO experts found that schizophrenia patients in countries that eat more fish and vegetables as fat sources have better prognosis than those in countries that eat more animal fat. Therefore, dietary supplementation of PUFAs can improve symptoms of schizophrenia. Adding 10 g of concentrated fish oil to the diet daily for 6 weeks significantly alleviated the patient's positive and negative symptoms, although only the negative symptoms were statistically significant. At this time, red blood cell membrane EPA increased significantly, other n3 fatty acids entered the metabolic chain, and total n3 fatty acids also increased. On the other hand, during the addition period, n6 fatty acids decreased significantly. It is likely that the functional state of the cell membrane is more closely related to the ratio of n6:n3 than the absolute number of any fatty acid [11]. Therefore, schizophrenia is not only affected by genetic and environmental factors, but is also closely related to diet. Increased total n3 fatty acids, especially EPA, are associated with symptom relief.
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5 Applications for diabetes
Diabetic patients are associated with a decline in the essential fatty acid desaturation mechanism. In experimental diabetic animal models, peripheral nerve conduction velocity and blood flow velocity are significantly reduced. The problem of n6 desaturation deficiency can be solved by adding gamma-linolenic acid (GLA) to the feed, thereby correcting diabetic neuropathy[12].
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6 Impact on children’s growth and development
6.1 PUFA status and behavioral dysfunction in children There is increasing evidence of a relationship between PUFA levels and behavioral problems in children. Animal studies have shown that PUFA deficiency causes abnormal electroretinograms and reduced learning ability in new environments, and even vision loss. In 1981, ethical issues meant that experiments could not be conducted on children, but there were a few studies on patients receiving total parenteral nutrition or gastric feeding. Stevans et al. [13] conducted a comparative study on the behavior, learning ability, and health status of 96 children aged 6 to 12 years. Children with PUFA deficiency had low levels of plasma phospholipid n3 or n6 fatty acids, and clinical symptoms included thirst, frequent urination, dry skin, susceptibility to colds, frequent antibiotic use, oversensitivity, difficulty falling asleep and waking up early. Teachers evaluated these children as having significantly lower overall learning ability, especially math scores. A study of 53 children with attention deficit hyperactivity disorder (ADHD) found that compared with the control group, the levels of plasma PUFAs (AA, EPA, and DHA) in the affected group were significantly lower, and the AA in total red blood cell lipids, namely 22:4 (n6), was also significantly lower [13].
6.2 Adding PUFAs to artificially fed infants improves development. Several recent studies have found that if artificially fed infants do not have sufficient PUFAs in their diet, their neurological development will be significantly inhibited. Clinically, this is reflected in a variety of behavioral problems and decreased vision. For example, a group of Italian researchers found that infants who ate a standard liquid formula plus a mixture of three PUFAs had significantly better neurological development and significantly higher scores on behavioral development scores than 28 other infants who ate the same formula without PUFAs. In addition, there was no significant difference between the 30 infants in the supplement group and the breast-fed group.
6.3 DHA helps infant vision. Eilecn Birch of the Retina Foundation of Southwest Texas found that infants and young children who were fed formula supplemented with DHA had significantly better vision after one year old than those who were fed formula supplemented with DHA. Although it is well known that the addition of DHA to precocious infants is important for the normal development of vision, there is still no research on the need for full-term infants. Birch found that at least 1/3 of the liquid formulas for artificial feeding of American infants do not contain DHA. PUFAs are required for the development of nerve fibers that transmit visual information from the retina to the brain. PUFAs are particularly important in the first 3 months of pregnancy and the first 6 months after birth.
Wuhan Enwang Bioengineering Company in my country uses fermentation to produce arachidonic acid (AA) series products. AA is one of the PUFAs and belongs to the n6 series. Adding AA to milk powder, beverages, and cooking oil not only increases the nutritional value of the product, but also has health care and disease prevention effects.
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Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China