"Healthy" fatty acids and other dietary myths

Sofia Dolotovskaya, N+1 

Recently, American doctors have shown that fish oil and omega-3 fatty acids contained in it, contrary to popular belief, do not protect the brain from aging and mental decline in old age. In this regard, we decided to recall several dietary and medical myths that were very popular at the time, but eventually debunked by science.

Omega-3 polyunsaturated fatty acids are found in fatty fish and seafood, linseed and mustard oil and some other vegetable oils. The name "omega-3" indicates the position of the double carbon-carbon bond – at the third carbon atom relative to the omega atom, which is located at the end of the fatty acid chain. These fatty acids are essential – that is, such acids that the body really needs, but, not being able to synthesize them independently, must be obtained with food.

Over the past ten years, it has been assumed that omega-3 fatty acids protect the brain from aging. This seems to be indicated by studies demonstrating a correlation between fish consumption and mental abilities in older people. It seems like – because when making adjustments to the level of education and the psychological state of the subjects, this correlation turns out to be not so convincing at all, and no one has conducted randomized clinical trials that helped you find out whether this correlation is random or based on a causal relationship. The same story is with senile dementia, or dementia: on the one hand, it has been shown that people with Alzheimer's disease have lowered the level of one of the omega-3 acids in brain cells, on the other – none of the numerous clinical studies have been able to prove that omega-3 acids are effective in the treatment of dementia.

Equally implicit evidence points to the effectiveness of omega-3 fatty acids to prevent cardiovascular diseases: there is definitely some correlation there, but direct evidence that it is omega-3 that reduces the likelihood of diseases has not been found. Nevertheless, since the importance of omega-3 fatty acids for the normal functioning of the brain and blood vessels is obvious, and no one has died from an overdose of fish oil, omega-3 fatty acids continue to be recommended and sold for the prevention of brain aging and cardiovascular diseases (and at the same time cancer, rheumatoid arthritis and depression).

Scientists from the National Institute of Vision in the USA decided to analyze the effect of omega-3 fatty acids on cognitive functions in the elderly. The analysis was carried out as part of a large-scale double–blind randomized placebo–controlled clinical trial (that is, one where neither patients nor doctors know what the patient is receiving - the investigational drug or placebo - and patients are randomly assigned to control and experimental groups). More than 4 thousand elderly people with an increased risk of developing degenerative retinal diseases participated in it. 

The study used a mixture of vitamins, beta-carotene and zinc, which, as previously shown in another group of subjects, slowed the destruction of the retina. The authors of the study tried to improve this mixture by adding omega-3 fatty acids to it. For 6 years, from 2006 to 2012, scientists monitored changes in the retina and assessed the cognitive functions of study participants who took an improved mixture (or took a placebo).

The results, adjusted for age, gender, level of education, depression and other factors, showed that omega-3 fatty acids had no effect on the cognitive functions of the participants and did not prevent the deterioration of memory and mental acuity. They had no effect on the aging of the retina.

Similar results were obtained for the second supplement tested in this study: a mixture of lutein and zeaxanthin, a popular remedy for preventing aging of the eyes and brain. Lutein and zeaxanthin are carotenoid pigments that give a yellow color, for example, to corn, egg yolk or peaches. They are necessary for the normal operation of the eyes, because, firstly, they function as antioxidants, protecting the eye from free radicals formed in direct light, and, secondly, they absorb the most aggressive part of the spectrum – blue-violet. The human body does not know how to synthesize these pigments, so they must come with food.

As the study showed, lutein and zeaxanthin do not affect brain aging in any way. The majority of the subjects did not have any effect on the aging of the retina. The only thing that was found is that lutein and zeaxanthin reduce the risk of developing degenerative retinal diseases in two small subgroups of subjects: people whose daily diet contains very few of these pigments, and those study participants who received a therapeutic mixture without beta–carotene - another pigment–carotenoid, from which vitamin A is formed, very important for the eyes.

In conclusion, the authors try to explain the discrepancy between the indirect evidence of the benefits of omega-3 and carotenoids and the results of clinical studies. Perhaps, they suggest, it matters how these substances enter the body: simply with food or in the form of special additives. After all, we cannot know about the thousands of possible interactions that food components enter into and that ultimately affect the final effect. Therefore, it is likely that fish oil in the composition of fish and fish oil in capsules can really affect the body in different ways. Anyway, today the conclusion is clear: taking fish oil and other supplements with omega-3 fatty acids, as well as taking lutein and zeaxanthin, does not benefit anyone except pharmaceutical companies. But fish and carrots may still help you to escape from senile dementia and blindness. Or they won't help. No one knows for sure yet.

Another dietary myth is associated with spinach and is reflected in the cartoons about Popeye the Sailor, which the New York animation studio Fleischer Studios began shooting in 1933. 

Popeye the sailor has great power, and the source of this power is spinach: as soon as the hero eats a can of spinach, his biceps immediately grow several times, and he goes to perform feats. 

The popularity of the cartoon caused a rapid increase in spinach sales, for which its producers expressed their gratitude by installing Popeye monuments in Texas and Arkansas. 

Thanks to the sailor Popeye, the consumption of not only spinach increased, but also vegetables in general: a 2010 study conducted by scientists from Bangkok University showed that children who watched cartoons about Popeye began to eat more vegetables.

Why did the creator of Popeye the sailor, the cartoonist Elzie Chrysler Segar, make spinach the source of his hero's strength? 

This is usually explained by a typo in an 1870 publication, the author of which accidentally put the wrong dot in the decimal number denoting the iron content in spinach - which is why the value turned out to be ten times more than the real one. 

The mistake spread to other scientific publications, eventually giving rise to a popular myth that spinach contains an incredible amount of iron – even more than in red meat. Despite the fact that in the 1930s some biochemists discovered a typo and pointed it out in print, the myth lived until the 80s, until a fairly authoritative physician T. Hamblin published an article exposing the error.

However, as it turned out recently, the story of exposing the myth itself was a myth. In 2010, criminologist Mike Sutton published an article in the Internet Journal of Criminology with the results of his own investigation. It turned out, firstly, that the error in the publication of 1870 was not a typo, but the result of incorrect measurements. Secondly, in fact, these measurements were almost never quoted anywhere, and in the publications of the 30s, biochemists did not talk about this old mistake at all, but about their own, made in an earlier article, where they accidentally overestimated the iron content in spinach by 20 times, confusing dried spinach with fresh. And finally, the "disclosure" published by Hamblin, upon closer examination, was not confirmed by any facts and, it seems, turned out to be a fiction based on far-fetched facts.

As for Popeye the sailor, the reason why the creator of the hero Segar forced him to eat spinach was the high content of vitamin A. Which, by the way, is true: spinach is really rich in vitamins A, C, B2, folic acid and other useful things. So you can and should eat it, the main thing is not to count on the same miracle effect as in the cartoon about Popeye.

Another myth concerns ascorbic acid and is associated with the name of the famous American chemist, winner of two Nobel Prizes Linus Pauling. A great scientist who discovered the secondary structure of protein, described the disease at the molecular level for the first time (showing that the cause of sickle cell anemia is a violation of the structure of the hemoglobin protein) and actually founded structural chemistry, at the end of his life Pauling became interested in medicine and aging and began to promote the intake of vitamin C. Pauling believed that ultra-high doses of ascorbic acid (from 2 g per day at the accepted rate of about 90 mg) are effective for the prevention and treatment of viral and oncological diseases, and can also prevent aging by protecting the body from free radicals (which, according to one of the theories of aging, accumulate in the body with age and damage mitochondria). For himself and his wife, he prescribed a daily dose of vitamin C in 10 g and claimed that he began to catch colds much less often and generally felt healthier.

In 1970, Pauling published Vitamin C and the Common Cold, which immediately became a bestseller. Millions of people, first in the United States, and then in other countries, began to take high doses of vitamin C for the treatment and prevention of everything in a row. Later, Pauling formulated the theory of orthomolecular medicine ("the right molecules in the right quantities"), the idea of which is to treat and prevent various diseases with vitamins, amino acids and nutrients in the form of biologically active additives (dietary supplements), and even founded the Institute of Orthomolecular Medicine in California. In 1979, Pauling, together with his like-minded British surgeon Evan Cameron, wrote the book "Cancer and vitamin C", which, like the book about the common cold, was very popular among non-professionals, but caused a lot of criticism in the scientific community.

Initially, Pauling's theory was based on theoretical reasoning, but in the late 1970s, he, together with faithful Cameron, published two articles with the results of their clinical study. The study involved 100 patients with terminal-stage malignant tumors who received high doses of vitamin C, and 1,000 of the same patients who did not receive vitamin C. As stated in the articles, the survival rate in the group receiving ascorbic acid increased by as much as 4 times compared with the control group.

However, a few years later it turned out that the comparison of the two groups was incorrect: patients receiving vitamin C were initially "less ill", and the severity of their disease was assessed as terminal at an earlier stage compared to the other group. Later, one of the most reputable medical centers in the world – the American Mayo Clinic – conducted several control clinical studies performed according to all the rules of modern evidence-based medicine. Studies have shown that ascorbic acid treats malignant tumors no better than placebo. Theories that vitamin C is effective for the prevention and treatment of colds, too, have not yet been confirmed in any clinical study.

Although Pauling tried to defend his theories for a long time, accusing opponents of incompetence and falsification of data (to which they responded in kind), to date, the benefits of vitamin C remain unproven. However, the authority of Pauling – who, despite his mistakes, was certainly a great scientist – turned out to be so great that many people still continue to take vitamin C "for prevention" and swallow shock doses at the first signs of a cold.

This does not mean, of course, that vitamin C is not needed at all. No one disputes that it is necessary for the normal functioning of connective tissue, blood vessels and bones, and the lack of it in the body leads to the development of scurvy. Since the human body does not know how to synthesize vitamin C, we must get it from food – from fruits and vegetables. At the same time, most animals and plants can synthesize ascorbic acid from glucose themselves. The exception is humans and other dry-nosed primates, guinea pigs, capybaras and bats. Therefore, for example, cats and dogs do not need to eat vegetables and fruits: they can only eat meat, and a person from such a diet will develop scurvy very quickly.

And finally, a myth that has not yet been fully exposed, but, apparently, has every chance of eventually turning out to be a myth. We are talking about antioxidants, which, as is commonly believed, protect the body from aging, malignant tumors, cardiovascular diseases and other ills. Antioxidants are substances that resist the oxidation of important components of the cell: proteins, DNA, and so on. They usually act as traps, "easy prey" for molecular oxygen and its radicals. Antioxidants include vitamin C, vitamin A (retinol), vitamin E, beta-carotene and many other substances found mainly in fruits, vegetables and berries, as well as, for example, in cocoa, red wine and green tea.

There has long been a link between consuming large amounts of fresh plant foods and reducing the risk of cardiovascular, neurological and oncological diseases. Hence arose the very popular theory that antioxidants slow down aging and prevent the appearance of malignant tumors and other diseases, protecting the body from free radicals. Antioxidants have become very popular as dietary supplements: they are taken "for the general health of the body" and the prevention of almost all diseases traditionally associated with aging.

As for the "general health", numerous clinical studies in which antioxidants were tested both individually and in various combinations, not only did not prove their benefits, but also in some cases demonstrated their harm. Thus, a large-scale clinical study involving 242 thousand people aged 18 to 103 years showed that beta-carotene and vitamin E in doses exceeding the recommended daily norm significantly increases overall mortality.

However, the most interesting discoveries relate to the role of antioxidants in the prevention of malignant tumors. Since the 1980s, several clinical studies have been conducted that have shown that smokers taking beta-carotene and vitamin A are significantly more likely to develop lung cancer than smokers who do not take any antioxidant supplements. It was also found that taking antioxidants increases the risk of prostate cancer and rectal cancer.

In 2014, scientists from the University of Gothenburg in Sweden in a line of mice with an increased risk of lung cancer showed how the mechanism by which antioxidants stimulate the development of tumors can work. It turned out that antioxidants (in this case, vitamin E and N-acetylcysteine) inhibit the work of the tumor suppressor p53 – a protein that normally regulates the cell cycle and prevents tumor transformation of cells.

In the same year, James Watson, the Nobel Prize winner for the discovery of the structure of DNA, put forward a whole theory explaining why antioxidants can act as carcinogens. Watson himself, commenting on his article, called it "one of his most important works since the double helix." Watson's main idea is that the tumor itself is struggling to protect itself from reactive oxygen species that cause the death of its cells. Most of the means of antitumor therapy – ionizing radiation, many types of chemotherapy – are based precisely on the effects of reactive oxygen species that block the cell cycle of tumor cells.  As they evolve, tumor cells learn to fight reactive oxygen species, producing antioxidants that make them virtually invulnerable to many types of therapy. Therefore, according to Watson, taking antioxidants, we are essentially rendering a service to the tumor, helping it fight for its life.

Despite the fact that Watson's theory has yet to be proven, it is already clear today that it is not worth getting too carried away with antioxidants, especially for people with an increased risk of cancer – for example, smokers – or those who have already detected a malignant tumor at an early stage. And in general, as Watson himself said, "it's worth eating blueberries because they're delicious, not because they protect against cancer." Similarly, fish, spinach and fruits and other useful things.

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14.10.2015