Tag Archives: cardiovascular disease

Alcohol, blood pressure, and hypertension

Alcohol intake and blood pressure

Many studies have shown a direct, dose-dependent relationship between alcohol intake and blood pressure, particularly for intake above two drinks per day.
This relationship is independent of:

  • age;
  • salt intake;
  • obesity;
  • finally, it persists regardless of beverage type.

Furthermore, heavy consumption of alcoholic beverages for long periods of time is one of the factors predisposing to hypertension: from 5 to 7% of hypertension cases is due to an excessive alcohol consumption.
A meta-analysis of 15 randomized controlled trials has shown that decreasing alcoholic beverage intake intake has therapeutic benefit to hypertensive and normotensive with similar systolic and diastolic blood pressure reductions (in hypertensive reduction occurs within weeks).

Alcohol intake and prevention of hypertension

Alcohol
Fig. 1 – Glass of Red Wine

Guidelines on the primary prevention of hypertension recommend that alcohol (ethanol) consumption in most men, in absence of other contra, should be less than 28 g/day, the limit in which it may reduce coronary heart disease risk.
The consumption limited to these quantities must be obtained by intake of drinks with low ethanol content, preferably at meals (drinking even lightly to moderately outside of meals increases the probability to have hypertension). This means no more than 680 ml or 24 oz of regular beer or 280 ml or 10 oz of wine (12% ethanol), especially in hypertension; for women and thinner subjects consumption should be halved1.
To avoid intake of drinks with high ethanol content even though the total ethanol content not exceeding 28 g/day.

Relationship between alcohol intake and blood pressure

Anyway, uncertainty remains regarding benefits or risks attributable to light-to-moderate alcoholic beverage intake on the risk of hypertension.
In a study published on April 2008, the authors examined the association between ethanol intake and the risk of developing hypertension in 28848 women from “The Women’s Health Study” and 13455 men from the “Physicians’ Health Study”, (the follow-up lasted respectively for 10.9 and 21.8 years). The study confirms that heavy ethanol intake (exceeding 2 drinks/day) increases hypertension risk in both men and women but, surprisingly, found that the association between light-to-moderate alcohol intake (up to 2 drinks/day) and the risk of developing hypertension is different in women and men. Women have a potential reduced risk of hypertension from a light-to-moderate ethanol consumption with a J-shaped association2; men have no benefits of light-to-moderate ethanol consumption but an increased risk of hypertension.
However, guidelines for the primary prevention of hypertension limit alcohol consumption to less 2 drinks/day in men and less 1 drink/day in thinner subjects and women.

1. A standard drink contains approximately 14 g of ethanol i.e. a 340 ml or 12 oz of regular beer, 140 ml or 5 oz wine (12% alcohol), or 42 ml or 1,5 oz of distilled spirits (inadvisable).

2. Many studies have shown a J-shaped relationship between ethanol intake and blood pressure. Light drinker (no more than 28 g of ethanol/day) have lower blood pressure than teetotalers; instead, who consumes more than 28 g ethanol/day have higher blood pressure than non drinker. So alcohol is a vasodilator at low doses but a vasoconstrictor at higher doses.

References

Pickering T.G. New Guidelines on Diet and Blood Pressure. Hypertension 2006;47:135-6 [Full text]

Sesso H.D., Cook N.R., Buring J.E., Manson J.E. and Gaziano J.M. Alcohol consumption and the risk of hypertension in women and men. Hypertension 2008;51:1080-87 [Abstract]

Writing Group of the PREMIER Collaborative Research Group. Effects of Comprehensive Lifestyle Modification on Blood Pressure Control: Main Results of the PREMIER Clinical Trial. JAMA 2003;289:2083-2093 [Abstract]

World Health Organization, International Society of Hypertension Writing Group. 2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension. Guidelines and recommendations. J Hyperten 2003;21:1983-92. [Abstract]


Dietary trans fatty acids: industrial and natural sources

Industrial and natural sources of dietary trans fatty acids

Dietary trans fatty acids come from different sources:

  • they can come from industrial processing, being the by-product of partial hydrogenation of unsaturated vegetable oils;
  • they can be produced naturally by plants and animals.

Dietary trans fatty acids from partial hydrogenation of vegetable oils

Dietary Trans Fatty Acids: Hydrogenation Process
Fig. 1 – Hydrogenation of Oleic Acid

In industrialized countries, greater part of the consumed trans fatty acids are produced industrially (in USA about 80%), in varying amounts, during partial hydrogenation of edible oils containing unsaturated fatty acids.
Hydrogenate means to add hydrogen atoms to unsaturated sites (that is, on a double bond) on the carbon chains of fatty acids by heating vegetable oils in presence of metal catalyst and hydrogen.
During the partial hydrogenation, an incomplete saturation of the unsaturated sites on the carbon chains of unsaturated fatty acids occurs: some double bonds remain, but they may be moved in their positions on the carbon chain, producing geometrical and positional isomers (double bonds are modified in both conformation and position).
Notably, with regard to fish oil, trans fatty acid content in non-hydrogenated oils and in highly hydrogenated oils is 0,5 and 3,6%, whereas in partially hydrogenated oils is 30%.
Hydrogenation converts vegetable oils into semisolid fats for use in:

  • margarines and shortenings;
  • commercial cooking;
  • manufacturing processes.

It should be noted that partial hydrogenation largely destroys alpha-linolenic acid, the plant-based omega-3-fatty acid.
Industrial trans fatty acids (ITFA) have adverse effects on:

  • serum lipid levels (total and LDL-cholesterol);
  • endothelial cells;
  • systemic inflammation;
  • other risk factors for cardiovascular disease;
  • moreover, they are positively associated with the risk of coronary heart disease (CHD), and sudden death from cardiac causes and diabetes.

Industrial trans fatty acids are an independent cardiovascular risk factor.
Their adverse effects are seen at low level of intake: for a person consuming 2000 kcal/d, 20-60 kcal from industrial trans fatty acids, equivalent to about 2-7 g or 1-3% of the total energy intake, is enough.
So, avoidance of industrial trans fatty acids, or a consumption of less 0,5% of total daily energy intake is necessary to avoid their adverse effects (these are far stronger, on average, than those of food contaminants or pesticide residues!).

Dietary trans fatty acids from deodorization of vegetable oils

Very small amounts of trans fatty acids (less than 2 percent) are formed during deodorization of vegetable oils, a process unrelated to partial hydrogenation and necessary in the refining of edible oils. During this process trans fatty acids with more than one double bond are formed in small amounts (if the isomer contains 18 carbon atoms it is marked C18:2). These isomers are also present in fried foods and in considerable amounts in partially hydrogenated vegetable oils (e.g. soybean oil).

Dietary trans fatty acids from animals

A natural source comes from bacterial transformation of a proportion of the relatively small amounts of unsaturated fatty acids ingested by ruminants in their rumen.
They are present at low levels in meat and full fat dairy products from cows, sheep, and other ruminants (typically <5% of total fatty acids).

Dietary trans fatty acids from vegetables

Another natural source is represented by some plant species, and plant-derived foods as:

  • leeks, peas, lettuce and spinach, that contain trans-3-hexadecenoic acid;
  • rapeseed oil, that contains brassidic acid and gondoic acid.

In these sources trans fatty acids are present in small amounts.

“Homemade”dietary trans fatty acids

They are produced at home during frying with vegetable oils.

Isomers of dietary trans fatty acids

Dietary Trans Fatty Acids: ITFA
Fig. 2 – ITFA

The most important cluster of trans fatty acids both animal and industrial origin is isomers containing 18 carbon atoms  plus one double bond (C18:1) whose position varies between the Δ6 and Δ16 carbon atoms of molecule.
Even if the same trans fatty acids are largely present in industrial trans fatty acids and in trans fatty acids from ruminants, there is a considerable quantitative difference between individual molecules in the two different sources.
The most common isomers in both sources are those with double bond in position between Δ9 and Δ11, but Δ11-C18:1 or vaccenic acid represents over 60% of the trans C18:1 isomers in ruminant trans fatty acids, whereas in industrial ones  Δ9-C18:1 or elaidic acid comprises 15-20%, and Δ10-C18:1 and Δ11-C18:1 over 20% each others.

References

Akoh C.C. and Min D.B. “Food lipids: chemistry, nutrition, and biotechnology” 3th ed. 2008

Chow Ching K. “Fatty acids in foods and their health implication” 3th ed. 2008

Lemaitre R.N., King I.B., Raghunathan T.E. et al. Cell membrane trans-fatty acids and the risk of primary cardiac arrest. Circulation 2002;105:697-01 [Abstract]

Lichtenstein A. H., Ausman L., Jalbert S.M , Schaefer E.J. Effect of different forms of dietary hydrogenated fats on serum lipoprotein cholesterol levels. N Engl J Med 1999;340:1933-40 [Abstract]

Lopez-Garcia E., Schulze M.B., Meigs J.B., Manson JA.E, Rifai N., Stampfer M.J., Willett W.C. and Hu F.B. Consumption of trans fatty acids is related to plasma biomarkers of inflammation and endothelial dysfunction. J Nutr 2005;135:562-66 [Abstract]

Mozaffarian D. Commentary: Ruminant trans fatty acids and coronary heart disease-cause for concern? Int J Epidemiol 2008;37:182-84 [Extract]

Mozaffarian D., Katan M.B., Ascherio A., Stampfer M.J., Willett W.C. Trans fatty acids and cardiovascular disease. N Engl J Med 2006;354:1601-13 [Abstract]

Oomen C.M., Ocke M.C., Feskens E.J., van Erp-Baart M.A., Kok F.J., Kromhout D. Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study: a prospective population-based study. The Lancet 2001;357:746-51 [Abstract]

Willett W. and Mozaffarian D. Ruminant or industrial sources of trans fatty acids: public health issue or food label skirmish? Am J Clin Nutr 2008;87:515-6 [PDF]

Green tea: definition, processing, properties, polyphenols

What is green tea?

Green tea is an infusion of processed leaves of tea plant, Camellia sinensis, a member of the Theaceae family.
It is the most consumed beverages in Asia, particularly in China and Japan.
Western populations consume black tea more frequently than green tea. However, in recent years, thanks to its health benefits, it has been gaining their attention.
Currently, it accounts for 20% of the tea consumed worldwide.

“You can never get a cup of tea large enough or a book long enough to suit me.”C.S. Lewis

Processing and properties of green tea

Green Tea
Fig. 1 – Camellia sinensis

As all other types of tea, it is produced from fresh leaves of Camellia sinensis.
The peculiar properties of the beverage depend on the type of processing that the leaves undergo. In fact, they are processed in such a way as to minimize both enzymatic and chemical oxidation processes of the substances contained in them, in particular catechins.
Therefore, among the different types of tea, it undergoes the lowest degree of oxidation during processing.
At the end of the processing, tea leaves retain their green color, thanks to the little chemical modifications/oxidations they have undergone. The infusion shows off a yellow-gold color.
Finally, the processing of tea leaves ensures that green tea flavor is more delicate and lighter than black tea.

The three main steps in the processing of green tea

After harvesting, tea leaves are exposed to the sun for 2-3 hours and withered/dried; then, the real processing starts.
It consists of three main steps: heat treatment, rolling and drying.

Heat treatment

Heat treatment, short and gentle, is the crucial step for the quality and properties of the beverage.
It occurs with steam (the traditional Japanese method) or by dry cooking in hot pans (a large wok, the traditional Chinese method). Heat treatment has the purpose of:

  • inactivate the enzymes present in the tissues of the leaves, thus stopping enzymatic oxidation processes, particularly of polyphenols;
  • eliminate the grassy smell in order to stand out tea flavor;
  • evaporate part of the water present in the fresh leaf (water constitutes about 75% of the weight of the leaf), making it softer, so as to make the next step easier.

Rolling

The rolling step follows the heat treatment of the leaves; this step has the purpose of:

  • facilitate the next stage of drying;
  • destroy the tissues of the leaves in order to favor, later, the release of aromas, thus improving the quality of the product.

Drying

The drying is the last step, which also leads to the production of new compounds and improves the appearance of the product.

Green tea polyphenols

Gree Tea
Fig. 2 – EGCG

All types of tea are rich in polyphenols, compounds that are also present in fruits, vegetables, extra virgin olive oil, and red wine.
Fresh tea leaves are rich in water-soluble polyphenols, especially catechins (or flavanols) and glycosylated catechins (both belonging to the class of flavonoids), molecules which are believed to be the responsibles of the benefits of green tea.
The major catechins in green tea are epigallocatechin-3-gallate (EGCG), epigallocatechin, epicatechin-3-gallate, epicatechin, epicatechin, but also catechin, gallocatechin, catechin gallate, and gallocatechin gallate are present, even if in lower amount. These polyphenols account for 30%-42% of the dry leaf weight (but only 3%–10% of the solid content of black tea).
Green tea caffeine accounts for 1,5-4,5% of the dry leaf weight.

How to maximize the absorption of green tea catechins

In vitro studies have shown the high antioxidant power of catechins, greater than that of vitamin C and vitamin E. In vitro, EGCG is generally considered the most biologically active catechin.
In vivo studies and several epidemiologic studies have shown the possible preventive effects of green tea catechins, especially EGCG, in preventing the development of:

  • cardiovascular disease, such as hypertension and stroke;
  • some cancers, such as lung cancer (but not among smokers) and oral and digestive tract cancers.

For these reasons, it is essential to maximize the intestinal absorption of catechins.
Catechins are stable in acidic environment, but not in non-acidic environment, as in the small intestine; also for this reason, after digestion, less than 20% of the total remains.
Studies with models of the digestive tract of rat and man, that simulate digestion in stomach and small intestine, have shown that the addition of citrus juice or vitamin C to green tea significantly increases the absorption of catechins.
Among tested citrus juices, lemon juice is the best, followed by orange, lime and grapefruit juices. Citrus juices seem to have a stabilizing effect on catechins that goes beyond what would be predicted solely based on their ascorbic acid content.

References

Clifford M.N., van der Hooft J.J.J., and Crozier A. Human studies on the absorption, distribution, metabolism, and excretion of tea polyphenols. Am J Clin Nutr 2013;98:1619S-1630S [Abstract]

Dwyer J.T. and Peterson J. Tea and flavonoids: where we are, where to go next. Am J Clin Nutr 2013;98:1611S-1618S [Abstract]

Green R.J., Murphy A.S., Schulz B., Watkins B.A. and Ferruzzi M.G. Common tea formulations modulate in vitro digestive recovery of green tea catechins. Mol Nutr Food Res 2007;51(9):1152-1162 [Abstract]

Huang W-Y., Lin Y-R., Ho R-F., Liu H-Y., and Lin Y-S. Effects of water solutions on extracting green tea leaves. ScientificWorldJournal 2013;Article ID 368350 [Abstract]

Sharma V.K., Bhattacharya A., Kumar A. and Sharma H.K. Health benefits of tea consumption. Trop J Pharm Res 2007;6(3):785-792 [Abstract]

Green tea benefits for health

Benefits of green tea: science and myths

Green Tea Benefits
Fig. 1 – Green Tea Benefits

Tea drinking, particularly green tea, has always been associated, at least in East Asia cultures (mainly in China and Japan) with health benefits. Only recently, the scientific community has begun to study the health benefits of tea consumption, recognizing its preventive value in many diseases.

Green tea benefits in preventing cancer

Several epidemiological and laboratory studies have shown encouraging results with respect to possible preventive role of tea, particularly green tea and its catechins, a subgroup of flavonoids (the most abundant polyphenols in human diet) against the development of some cancers like:

  • oral and digestive tract cancers;
  • lung cancer among those who have never smoked, not among smokers.

Tea polyphenols, the most active of which is epigallocatechin-3-gallate (EGCG), seem to act not only as antioxidants, but also as molecules that, directly, may influence gene expression and diverse metabolic pathways.

Green tea benefits in cardiovascular disease

Cardiovascular disease is the main cause of deaths worldwide, particularly in low- and middle-income countries, with an estimate of about 17 million deaths in 2008 that will increase up to 23.3 million by 2030.
Daily tea consumption, especially green tea, seems to be associated with a reduced risk of developing cardiovascular disease, such as hypertension and stroke.
Among the proposed mechanisms, the improved bioactivity of the endothelium-derived vasodilator nitric oxide (NO), due to the action of tea polyphenols that enhance nitric oxide synthesis, and/or decrease superoxide-mediated nitric oxide breakdown seem to be important.

Drinking a daily cup of tea will surely starve the apothecary.” Chinese proverb

Green tea benefits and antioxidant properties

Tea polyphenols may act, in vitro, as free radical scavengers.
Since radical damage plays a pivotal role in the development of many diseases such as atherosclerosis, rheumatoid arthritis, cancer, or in ischemia-reoxygenation injury, tea polyphenols, particularly green tea catechins, may have a preventive role.

Green tea benefits in weight loss and weight maintenance

Green tea, but also oolong tea, that is, catechins and caffeine rich teas, has a potential thermogenic effect. This has made them a potential tool for:

  • weight loss, by increasing energy expenditure and fat oxidation;
  • weight maintenance, ensuring a high energy expenditure during the maintenance of weight loss.

Indeed, it has been shown that green tea and green tea extracts are not an aid in weight loss and weight maintenance, since:

  • they are not able to induce a significant weight loss in overweight and obese adults;
  • they are not helpful in the maintenance of weight loss.

Green tea benefits in preventing dental decay

Animal and in vitro studies have shown that tea, and in particular its polyphenols, seems to possess:

  • antibacterial properties against pathogenic action of cariogenic bacteria, as Streptococcus mutans, particularly green tea EGCG;
  • inhibitory action on salivary and bacterial amylase (it seems that black tea thearubigins and theaflavins are more effective than green tea catechins);
  • it is able to inhibit acid production in the oral cavity.

All these properties make green tea and black tea, beverages with potential anticariogenic activity.

References

Human health and carotenoids

Benefits of carotenoids for human health

Carotenoids belong to the category of bioactive compounds taken up with diet, that is, molecules able to provide protection against many diseases such as cardiovascular diseases, cancer and macular degeneration. They are also important for the proper functioning of the immune system.
Among the mechanisms that seem to be at the basis of their human health-promoting effects have been reported (Olson, 1999, see References):

  • the capability to quench singlet oxygen (see above);
  • the scavenging of peroxyl radicals and reactive nitrogen species;
  • the modulation of carcinogen metabolism;
  • the inhibition of cell proliferation;
  • the enhancement of the immune response;
  • a filtering action of blue light;
  • the enhancement of cell differentiation;
  • stimulation of cell-to-cell communication

Carotenoids, antioxidant activity and human health

Human Health and Carotenoids
Fig. 1 – Free Radical

Carotenoids, with the adaptation of organisms to aerobic environment, and therefore to the presence of oxygen, have offered protection against oxidative damage from free radicals, particularly by singlet oxygen, a powerful oxidizing agent (see also below).
Carotenoids stabilize singlet oxygen acting both chemical and physical point of view:

  • chemical action involves the union between the two molecules;
  • in physical action, the radical transfers its excitation energy to the carotenoid. The result is a low energy free radical and an excited carotenoid; later, the energy acquired by the carotenoid is released as heat to the environment, and the molecule, that remains intact, is ready to carry out another cycle of stabilization of singlet oxygen, and so on.

The capability of carotenoids to quench singlet oxygen is due to the conjugated double-bond system present in the molecule, and the maximum protection is given by those molecules that have nine or more double bonds (moreover, the presence of oxygen in the molecule, as in xanthophylls, seems to have a role).
Carotenoids are involved not only in singlet oxygen quenching, but also in the scavenging of other reactive species both of oxygen, as peroxyl radicals (therefore contributing to the reduction of lipid peroxidation) and nitrogen. These reactive molecules are generated during the aerobic metabolism but also in the pathological processes.

Lycopene, xanthophylls and human health

Lycopene, a carotene, canthaxanthin and astaxanthin, two xanthophylls present in foods of animal origin, are better antioxidants than beta-carotene but also than zeaxanthin that, with lutein, is involved in prevention of age-related macular degeneration.
Lycopene, in addition to act on oxygen free radicals, acts as antioxidant also on the radicals of vitamin C and vitamin E, that are generated during the antioxidant processes in which these vitamins are involved, “repairing them”.
Finally, lycopene exerts its antioxidant action also indirectly, inducing the synthesis of enzymes involved in the protection against the action of oxygen free radicals and other electrophilic species; these enzymes are quinone reductase, glutathione S-transferase and superoxide dismutase (they are part of the enzymatic antioxidant system).

Vitamin A and human health

Human Health and Vitamin A
Fig. 2 – Provitamin A Activity

Vitamin A, whose deficiency affects annually more than 100 million children worldwide, causing more than a million deaths and half million cases of blindness, is a well-known carotenoid derivative with many biological actions, being essential for reproduction, growth, vision, immune function and general human health.
In the human diet, the major sources of vitamin A are the preformed vitamin, which is found in foods of animal origins (meat, milk, eggs, etc), and provitamin A carotenoids, present in fruits and vegetables. In economically deprived countries, fruits and vegetables are the main source of vitamin A being less expensive than food of animal origin.
Of the more than 750 different carotenoids identified in natural sources, only about 50 have provitamin A activity, and among these, beta-carotene (precisely, all-trans-beta-carotene isomer) is the main precursor of the vitamin A.
Among the other carotenoids precursors of vitamin A, alpha-carotene, gamma-carotene, beta-cryptoxanthin, alpha-cryptoxanthin, and beta-carotene-5,6-epoxide have about half the bioactivity of beta-carotene.
Spinach, carrots, pumpkins, sweet potatoes (yellow) are example of vegetables rich in beta-carotene and other provitamin A carotenoids.
Acyclic carotenes, such as lycopene (the main carotenoid in the human diet), and xanthophylls, except those mentioned above (beta-cryptoxanthin, alpha-cryptoxanthin, and beta-carotene-5,6-epoxide), cannot be converted to vitamin A.

References

de la Rosa L.A., Alvarez-Parrilla E., Gonzàlez-Aguilar G.A. Fruit and vegetable phytochemicals: chemistry, nutritional value, and stability. 1th Edition. Wiley J. & Sons, Inc., Publication, 2010

Johnson E.J. The role of carotenoids in human health. Nutr Clin Care 2002;5(2):56-65 [Abstract]

Olson, J.A. 1999. Carotenoids. p. 525-541. In: Shils M.E., Olson J.A., Shike M., Ross A.C. “Modern nutrition in health and disease” 9th ed., by Lippincott, Williams & Wilkins, 1999

Ross A.B., Thuy Vuong L., Ruckle J., Synal H.A., Schulze-König T., Wertz K., Rümbeli R., Liberman R.G., Skipper P.L., Tannenbaum S.R., Bourgeois A., Guy P.A., Enslen M., Nielsen I.L.F., Kochhar S., Richelle M., Fay L.B., and Williamson G. Lycopene bioavailability and metabolism in humans: an accelerator mass spectrometry study. Am J Clin Nutr 2011;93:1263-73 [Abstract]

 

Omega-3 fatty acid supplements in the secondary prevention of CVD

Omega-3 fatty acids and prevention of CVD

Omega-3 Fatty Acid Supplements: DHA-Docosahexaenoic acid
Fig. 1 – DHA

Studies conducted on Greenland Eskimos, which consume large amount of fish or marine mammals rich in omega-3 fatty acids and have a low incidence of cardiovascular disease or CVD, have suggested a protective effects of such fatty acids against these disease. Results of other epidemiological studies, randomized trials and animal investigations, have also suggested that omega-3 fats, and in particular long-chain omega-3 fatty acids, eicosapentaenoic aci or EPA and docosahexaenoic acid or DHA have cardiovascular effects. These studies indicate that they have anti-inflammatory, antiatherogenic, and antiarrhythmic effects, which are considered plausible mechanisms for reducing the risk of cardiovascular disease.

Omega-3 fatty acid supplements and secondary prevention of CVD

In a study published on Archives of Internal Medicine a research team, using a meta-analysis of randomized, double-blind, placebo-controlled trials, has evaluated the preventive effect of omega-3 fatty acid supplements (omega-3 fatty acid supplements for at least 1 year, with a daily dose of EPA or DHA ranged from 0.4 to 4.8 g/d, and a follow-up period ranged from 1.0 to 4.7 years) in the secondary prevention of cardiovascular disease, i.e. among patients with a history of cardiovascular disease (not in healthy individuals).
The study involved 20485 patients, male or female aged ≥18 years, 10259 randomized to a placebo group and 10226 randomized to an intervention group. Placebo groups received vegetable oils (sunflower oil, olive oil, and corn oil), mixed fatty oil, and other “inert” or ill-defined substances (aluminum hydroxide and unspecified placebo).
The meta-analysis showed insufficient evidence of a secondary preventive effect of omega-3 fatty acid supplements against overall cardiovascular events, which include peripheral vascular disease, angina and unstable angina, transient ischemic attack and stroke, fatal and nonfatal myocardial infarction, sudden cardiac death, cardiovascular death, congestive heart failure, and nonscheduled cardiovascular interventions (i.e., coronary artery bypass surgery or angioplasty).
Moreover, no significant preventive effect was observed in subgroup analyses by the following: history of cardiovascular disease, concomitant medication use (lipid lowering agents, no lipid-lowering agents, or antiplatelet agents only), country location (Western Europe, Northern Europe, United States, or Asia), inland or coastal geographic area, methodological quality of the trial, duration of treatment, type of placebo material in the trial (oil vs nonoil), dosage of EPA or DHA, or use of fish oil supplementation only as treatment.

Conclusion

The study showed insufficient evidence of a secondary preventive effect of omega-3 fatty acid supplements against overall cardiovascular events among patients with a history of cardiovascular disease.

References

Kwak S.M., Myung S-K., Lee Y.J., Seo H.G., for the Korean Meta-analysis Study Group. Efficacy of omega-3 fatty acid supplements (eicosapentaenoic acid and docosahexaenoic acid) in the secondary prevention of cardiovascular disease. A meta-analysis of randomized, double-blind, placebo-controlled trials. Arch Intern Med 2012;172(9):686-694. doi:10.1001/archinternmed.2012.262

Potassium intake and cardiovascular risk factors

Potassium intake and health

In a study published on British Medical Journal a research team has conducted a systematic review of the literature and meta-analyses on potassium intake and health in apparently healthy adults and children without renal impairment that might compromise its handling.
Eleven cohort studies (127038 participants) reporting all cause mortality, stroke, cardiovascular disease, or coronary heart disease in adults and twenty-two randomized controlled trials (1606 participants) reporting blood lipids, blood pressure, renal function, and catecholamine concentrations were included in the study.
In adult with hypertension an increased potassium intake reduced systolic blood pressure by 3.49 mm Hg and diastolic blood pressure by 1.96 mm Hg.
No effect was seen in adult without hypertension (however, the studies were of relatively short duration and did not consider the effect that increased potassium intake may have over time) and in children (there is a lack of data in children: only three controlled studies with 156 partecipants).
There was no adverse effect of increased potassium intake on blood lipids, or catecholamine concentrations in adults whereas an inverse statistically significant association was seen between its intake and the risk of incident stroke (a 24% lower risk).
In healthy adult there was no significant adverse effect on renal function.
This study suggests that, in people without impaired renal function, increased potassium intake (at least 90 mmol/day) is potentially beneficial for the prevention and control of elevated blood pressure and stroke.

How to increase potassium intake

Potassium Intake: Fruits and Vegetables: Rich in Potassium
Fig. 1 – Fruits and Vegetables: Rich in Potassium

It should be noted that an increased potassium intake can be achieved following the largely plant-based Mediterranean Diet, which is characterized by the consumption of large quantities of fresh fruit, vegetable, legumes and unrefined cereals, all rich in potassium (that is also accompanied by a variety of other nutrients).

Aburto N.J., Hanson S., Gutierrez H., Hooper .L, Elliott P., Cappuccio F.P. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ 2013;346:f1378

Artificial trans fats: businness and health

The hydrogenation of vegetable oils

The process of hydrogenation was first discovered in 1897 by French Nobel prize in Chemistry (jointly with fellow Frenchman Victor Grignard) Paul Sabatier using a nickel catalyst.
Partially hydrogenated vegetable oils were developed in 1903 by a German chemist, Wilhelm Normann who files British patent on “Process for converting unsaturated fatty acids or their glycerides into saturated compounds” and the term trans fatty acids or trans fats (they are produced  during partial hydrogenation of edible oils containing monounsaturated and polyunsaturated fatty acids) appeared for the first time in the Remark column of the 5th edition of the “Standard Tables of Food Composition” in Japan.

Partially hydrogenated vegetable oils were developed as a cheaper alternative to animal fats.
Moreover, they:

  • contribute to the hardness of fat in which they are who can be semi-solids and solids (they are used to make margarine or shortening with a melting point, consistency and “mouth feel” similar to those of butter);
  • have a long shelf life at room temperature;
  • have flavor stability and be stable during frying.

Note: per year in USA 6-8 billion pounds of hydrogenated vegetable oil are produced.

The war on artificial trans fats

Trans Fats
Fig. 1 – Shortening

The first hydrogenated oil was cottonseed oil in USA in 1911 to produce vegetable shortening.
So, before this date, the only trans fats in human diet were those derived from ruminants.
In the 1930’s partial hydrogenation became popular with the development of margarine; through hydrogenation, oils such as soybean, safflower and cottonseed oil, which are rich in unsaturated fatty acids, are converted to margarines and vegetable shortenings.
Until 1985 no adverse effects of trans fats on human health was demonstrated and in 1975 Procter & Gamble study shows no effect of partially hydrogenated fats on cholesterol.
Their use in fast food preparation grow up from 1980’s when the role of dietary saturated fats in increasing cardiac risk began clear; it was led a successful campaign to get McDonald’s to switch from beef tallow to vegetable oil for frying its French fries. Meanwhile, studies began to raise concerns about their effects on health: on 1985 in USA Food and Drug Administration (FDA) concludes that trans fats and monounsaturated fat oleic acid affect serum cholesterol level similarly but from the second half of 1985 their harmful began clear and the final proof comes from both controlled feeding trials and prospective epidemiologic studies.
After June 1996 they were eliminated from margarine sold in Australia, which before contributed about 50% of the dietary intake of trans fatty acids in such country.
On March 11, 2003 the Danish government, after a debate started in 1994 and two new reports in 2001 and 2003, decided to phase out the use of industrially produced trans fats (ITFA) in food before the end of 2003; two years later, however, the European Commission asked Denmark to withdraw this law, which was not accepted on the EU level, unfortunately.
Canada is considering legislation to eliminate industrially produced trans fats from food supplies.
On 2003 FDA ruled that food labels (for conventional foods and supplements) show trans fat content beginning January 1, 2006. Notably, this ruling is the first substantive change to food labeling since the requirement for per-serving food labels information was added in 1990.
On 2005 the US Department of Agriculture made a minimized intake of trans fats a key recommendation of the new food-pyramid guidelines.
On 2006 American Heart Association recommends to limit their intake to 1% of daily calorie consumption and suggests food manufacturers and restaurants switch to other fats.
On 2006 New York City Board of Health announces trans fat ban in its 40.000 restaurants within July 1, 2008.

References

Akoh C.C. and Min D.B. “Food lipids: chemistry, nutrition, and biotechnology” 3th ed. 2008

Ascherio A., Katan M.B., Zock P.L., Stampfer M.J., Willett W.C. Trans fatty acids and coronary heart disease. N Engl J Med 1999;340:1994-8 [Abstract]

Chow Ching K. “Fatty acids in foods and their health implication” 3th ed. 2008

Eckel R.H., Borra S., Lichtenstein A.H., Yin-Piazza D.Y. Understanding the Complexity of Trans fatty acid reduction in the American diet. American Heart Association trans fat conference 2006 report of the trans fat conference planning group. Circulation 2007;115:2231-46; originally published online Apr 10, 2007 [Abstract]

Mozaffarian D., Jacobson M.F., Greenstein J.S. Food Reformulations to reduce trans fatty acids. N Eng J Med 2010;362:2037-39 [PDF]

Okie S. New York to trans fats: you’re out! N Engl J Med 2007;356:2017-21 [PDF]

Stender S., Astrup A., Dyerberg J. What went in when trans went out?. N Engl J Med 2009;361:314-16 [PDF]

Stender S., Dyerberg J. and Astrup A. Consumer protection through a legislative ban on industrially produced trans fatty acids in foods in Denmark. Scand J Food Nutr 2006;50:155-60 [Abstract]

Stender S., Dyerberg J. The influence of trans fatty acids on health. Fourth edition 2003 (from Danish Nutrition Council; publ. no. 34)