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Hypertension and Essential Fatty Acids

Read more about Essential Fatty Acids.

Overview

Fish oil is recommended for a number of cardiovascular conditions, including congestive heart failure (CHF) and heart attacks. It appears that fish oil may also help treat hypertension.

Effect of Essential Fatty Acids on Hypertension

Fish oil has a number of effects on the cardiovascular system. It may help lower blood pressure by acting as a blood thinner and slightly reducing the heart rate, among other actions.

Research Evidence on Essential Fatty Acids

Although the research record is mixed,15-21,104,137 it appears that fish oil may reduce blood pressure at least slightly.56 Fish oil contains two major active ingredients, DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). A 6-week, double-blind, placebo-controlled study of 59 overweight men suggests that the DHA in fish oil, but not the EPA, is responsible for this benefit.57

How to Use Essential Fatty Acids

Typical dosages of fish oil are 3 g to 9 g daily, but this is not the upper limit. In one study, participants ingested 60 g daily.

The most important omega-3 fatty acids found in fish oil are called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In order to match the dosage used in several major studies, you should take enough fish oil to supply about 2 g to 3 g of EPA (2,000 mg to 3,500 mg) and about 1.0 g to 2.5 g of DHA daily (1,000 mg to 2,500 mg). Far higher doses have been used in some studies; conversely, one study found blood-pressure lowering effects with a very low daily dosage of DHA—0.7 g.238

DHA and EPA are not identical and might not have identical effects. Some evidence hints that DHA may be more effective than EPA for thinning the blood 176 and reducing blood pressure.105 The reverse may be true for reducing triglyceride levels, but study results are conflicting.160-165,235

Some manufacturers add vitamin E to fish oil capsules to keep the oil from becoming rancid. Another method is to remove all the oxygen from the capsule.

If possible, purchase fish oil products certified as free of significant levels of mercury, toxic organochlorines, and PCBs (see Safety Issues).

Flaxseed oil also contains omega-3 fatty acids, although of a different kind. It has been suggested as a less smelly substitute for fish oil. However, it is far from clear whether flaxseed oil is therapeutically equivalent to fish oil.1,200

Types of Professionals That Would Be Involved with This Treatment

  • Clinical nutritionist or registered dietitian
  • Integrative MD
  • Naturopathic doctor

Side Effects and Warnings

#Safety Issues

Fish oil appears to be generally safe. The most common problem is fishy burps. However, there are some safety concerns to consider.

For example, it has been suggested that some fish oil products contain excessive levels of toxic substances such as organochlorines and PCBs. ^[1] If possible, try to purchase fish oil products certified not to contain significant levels of these contaminants. Note:Various types of fish contain mercury, but this has not been a problem with fish oil supplements, according to reports on Consumerlab.com.

Fish oil has a mild blood-thinning effect; ^[2] in one case report, it increased the effect of the blood-thinning medication warfarin (Coumadin). ^[3] Fish oil does not seem to cause bleeding problems when it is taken by itself ^[4] or with aspirin. ^[5] Nonetheless, people who are at risk of bleeding complications for any reason should consult a physician before taking fish oil.

Fish oil does not appear to raise blood sugar levels in people with diabetes. ^[6] Nonetheless, if you have diabetes, you should not take any supplement except on the advice of a physician.

Fish oil may modestly increase weight and lower total cholesterol and HDL (“good”) cholesterol levels. ^[7] It may also raise the level of LDL ("bad") cholesterol; however, this effect may be short-lived. ^[8] If you decide to use cod liver oil as your fish oil supplement, make sure you do not exceed the safe maximum intake of vitamin A and vitamin D . These vitamins are fat soluble, which means that excess amounts tend to build up in your body, possibly reaching toxic levels. The official maximum daily intake of vitamin A is 3,000 mcg for pregnant women as well as other adults. Look at the bottle label to determine how much vitamin A you are receiving. (It is less likely that you will get enough vitamin D to produce toxic effects.)

#Interactions You Should Know About

If you are taking warfarin (Coumadin) or heparin , do not take fish oil except on the advice of a physician.

References

  1. Harris WS. N-3 fatty acids and serum lipoproteins: human studies. Am J Clin Nutr. 1997;65(suppl 5 ):S1645-S1654.
  2. Lungershausen YK, Abbey M, Nestel PJ, et al. Reduction of blood pressure and plasma triglycerides by omega-3 fatty acids in treated hypertensives. J Hypertens. 1994;12:1041-1045.
  3. Radack K, Deck C, Huster G. The effects of low doses of n-3 fatty acid supplementation on blood pressure in hypertensive subjects. A randomized controlled trial. Arch Intern Med. 1991;151:1173-1180.
  4. Singer P, Jaeger W, Wirth M, et al. Lipid and blood-pressure-lowering effect of mackerel diet in man. Atherosclerosis. 1983;49:99-108.
  5. Singer P, Melzer S, Goschel M, et al. Fish oil amplifies the effect of propranolol in mild essential hypertension. Hypertension. 1990;16:682-691.
  6. Appel LJ, Miller ER III, Seidler AJ, et al. Does supplementation of diet with 'fish oil' reduce blood pressure? A meta-analysis of controlled clinical trials. Arch Intern Med. 1993;153:1429-1438.
  7. Whelton PK, Kumanyika SK, Cook NR, et al. Efficacy of nonpharmacologic interventions in adults with high-normal blood pressure: results from phase 1 of the Trials of Hypertension Prevention. Trials of Hypertension Prevention Collaborative Research Group. Am J Clin Nutr. 1997;65(suppl 2):S652-S660.
  8. Mori TA, Bao DQ, Burke V, et al. Docosahexaenoic acid but not eicosapentaenoic acid lowers ambulatory blood pressure and heart rate in humans. Hypertension. 1999; 34:253-260.
  9. Geleijnse JM, Giltay EJ, Grobbee DE, et al. Blood pressure response to fish oil supplementation: metaregression analysis of randomized trials. J Hypertens. 2002;20:1493-1499.
  10. Mori TA, Bao DQ, Burke V, et al. Docosahexaenoic acid but not eicosapentaenoic acid lowers ambulatory blood pressure and heart rate in humans. Hypertension. 1999;34:253-260.
  11. Theobald HE, Goodall AH, Sattar N, et al. Low-dose docosahexaenoic acid lowers diastolic blood pressure in middle-aged men and women. J Nutr. 2007;137:973-978.
  12. Mori TA, Bao DQ, Burke V, et al. Docosahexaenoic acid but not eicosapentaenoic acid lowers ambulatory blood pressure and heart rate in humans. Hypertension. 1999;34:253-260.
  13. Erkkila AT, Schwab US, de Mello VD, et al. Effects of fatty and lean fish intake on blood pressure in subjects with coronary heart disease using multiple medications. Eur J Nutr. 2008 Jul 29.
  14. Mori TA, Burke V, Puddey IB, et al. Purified eicosapentaenoic and docosahexaenoic acids have differential effects on serum lipids and lipoproteins, LDL particle size, glucose, and insulin in mildly hyperlipidemic men. Am J Clin Nutr. 2000;71:1085-1094.
  15. Rambjor GS, Walen AI, Windsor SL Eicosapentaenoic acid is primarily responsible for hypotriglyceridemic effect of fish oil in humans. Lipids. 1996;31(suppl):45-49.
  16. Agren JJ, Hanninen O, Julkunen A, et al. Fish diet, fish oil and docosahexaenoic acid rich oil lower fasting and postprandial plasma lipid levels. Eur J Clin Nutr. 1996;50:765-771.
  17. Childs MT, King IB, Knopp RH. Divergent lipoprotein responses to fish oils with various ratios of eicosapentaenoic acid and docosahexaenoic acid. Am J Clin Nutr. 1990;52:632-639.
  18. Davidson MH, Maki KC, Kalkowski J, et al. Effects of docosahexaenoic acid on serum lipoproteins in patients with combined hyperlipidemia: a randomized, double-blind, placebo-controlled trial. J Am Coll Nutr. 1997;16:236-243.
  19. Leigh-Firbank EC, Minihane AM, Minihane AM, et al. Eicosapentaenoic acid and docosahexaenoic acid from fish oils: differential associations with lipid responses. Br J Nutr. 2002;87:435-445.
  20. Harper CR, Edwards MJ, Defilipis AP, et al. Flaxseed Oil Increases the Plasma Concentrations of Cardioprotective (n-3) Fatty Acids in Humans. J Nutr. 2005;136:83-87.
  21. Theobald HE, Goodall AH, Sattar N, et al. Low-dose docosahexaenoic acid lowers diastolic blood pressure in middle-aged men and women. J Nutr. 2007;137:973-978.

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