According to UK researchers taking 0.7g docosahexaenoic acid (DHA) daily, compared with no DHA intake, has been found to lower the diastolic blood pressure (the bottom number in a blood pressure reading) among middle-aged healthy men and women.
Docosahexaenoic acid is an omega-3 essential fatty acid, which belongs to the class of long chain polyunsaturated fatty acids (LC PUFAs or LCPs). It is a major fatty acid in phospholipids, major constituents of all biological membranes, and major consituent of sperm and brain cells.
Other studies have shown that dietary DHA can reduce the level of blood triglycerides (fat in blood) in humans, which, in turn, may reduce the risk of heart disease. Growing body of evidence shows that DHA supplementation might play vital role in combating diseases like Attention-Deficit Hyperactivity Disorder (ADHD), Alzheimer’s disease and even depression.
Docosahexaenoic acid (DHA) is found in cold water fatty fish, including salmon, tuna (bluefin tuna have up to five times more DHA than other types of tuna), mackerel, sardines, shellfish, and herring. Most of the DHA in fish and other more complex organisms originates in microalgae of the genus Schizochytrium, and concentrates in higher organisms as it moves up the food chain. DHA is also derived from the dietary essential fatty acids in the human liver. All fats in food contain alpha-linolenic acid ( ALA), a type of fatty acids, which in the human liver is further converted into eicosapentaenoic acid (EPA). Eicosapentaenoic acid yields DHA via docosapentaenoic acid (DPA), an intermediate fatty acid.
The study subjects (healthy men and women, aged 45-65 yrs) took 3 capsules per day for an uninterrupted period of 3 months. There was a gap of 4 months between the two phases of the treatment. Each phase lasted for 3 months. Each capsule contained 500 mg of refined triglycerol derived from a marine microalga scientifically known as Crypthecodinium cohnii. The daily DHA supplement was .7g DHA per day, and less than .005g EPA. The treatment group was compared with a control group who took placebo capsules, each containing 500 mg of refined olive oil.
Blood pressure and heartbeat were measured in a temperature-controlled lab set-up after at least 15 min supine rest. The study results showed that blood counts and liver function tests remained normal during both treatments. Compared to placebo, the DHA treatment revved up the level of DHA in red blood cells phosphoglycerides (a type of lipid) by 58 per cent. Among DHA treatment group diastolic blood pressure was lowered by 3.3 Hg compared to placebo. Heart rate also dropped by 2.1 beats per min after DHA treatment than after placebo period.
Eicosapentaenoic acid (EPA ) content remained unchanged with lowering of DPA after DHA regimen than after placebo period. Responses of men and women were same to the treatment.
A joint team of Finnish and US researchers has also shown that DHA has been inversely linked with atherosclerosis (a disease caused due to formation of multiple plaques within the arteries) progression among postmenopausal women with established coronary artery disease (CAD).
Though the low dose of DHA did not alter endothelial (lining of blood vessels) function or arterial stiffness, the fall in diastolic blood pressure is important given the risk of future cardiovascular disease (CVD) in middle-aged subjects. According to Heart Disease and Stroke Statistics – 2005 Update released by American Heart Association, CVD caused 1 of every 2.6 deaths in the United States in 2002. Nearly 2,600 American die of CVD each day, an average of 1 death every 34 seconds. In 2005 the estimated direct and indirect cost of CVD was $393.5 billion.
The UK study was published in the Journal of Nutrition on the April 2007 edition.**
**1) Theobald, H. E, Alison H. Goodall, Naveed Sattar, Duncan C. S. Talbot, Philip J. Chowienczyk, and Thomas A. B. Sanders. Low-Dose Docosahexaenoic Acid Lowers Diastolic Blood Pressure in Middle-Aged Men and Women. Journal of Nutrition, April 2007; 137: 973–978.
2) Arja T. Erkkilä , Nirupa R. Matthan, David M. Herrington and Alice H. Lichtenstein. Higher plasma docosahexaenoic acid is associated with reduced progression of coronary atherosclerosis in women with CAD. Journal of Lipid Research, December 2006; Vol. 47, 2814-2819.
3) Heart Disease and Stroke Statistics – 2005 Update, released by American Heart Association.
4) Frits A. J. Muskiet, M. Rebecca Fokkema , Anne Schaafsma, E. Rudy Boersma and Michael A. Crawford.Is Docosahexaenoic Acid (DHA) Essential? Lessons from DHA Status Regulation, Our Ancient Diet, Epidemiology and Randomized Controlled Trials. The Journal of Nutrition. January 2004; Vol.134, 183-186.
5) Docosahexaenoic Acid (DHA)