When Fish Oil Won’t Lower Your Blood Pressure

Perhaps one of the most studied dietary substances used for treating high blood pressure is fish oil.

Many animal studies show fish oil lowers blood pressure significantly.

Fish oil even lowers the blood pressure of animals bred to develop the condition by up to 20 mmHg.

But there are rare situations where fish oil won’t lower blood pressure.

It appears that the reason fish oils lower your blood pressure is at least in part due to how they change the way calcium operates in the interior of cells. This causes the blood vessels to relax and dilate. It is the same mechanism that calcium channel blockers affect. But instead of drug-induced side effects, the “side effects” of fish oils are beneficial.

Just as with medication therapy, I have found that not all patients will respond to every natural therapy for hypertension. This is certainly true for fish oils. Some will respond very nicely to fish oils, but there are also many patients who will show no response at all. One reason is that many people simply don’t take enough.

Deficiencies of the two important fats that are found in fish oil, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are all too common. Some scientists recently suggested that the total daily intake of EPA and DHA should be at least 650 mg. But the average intake of these fatty acids is often less than 100 mg per day. Vegans (those who eat no animal derived foods at all) are at particular risk for deficiency of these vital oils. However, I don’t think 650 mg is nearly enough. Here’s why:

In one study, researchers followed 16 patients with essential hypertension and 16 patients with normal blood pressure. The researchers randomly gave the participants either a rather large four gram dose of highly purified EPA and DHA or a placebo. The study lasted for four months. The effect of the oils on blood pressure was highest after two months. It lowered the systolic pressure by an average of 6 mmHg and the diastolic by 5 mmHg. This study is a good example of what other studies have found; it takes a fairly high dose of fish oil taken for at least three to four months to see results.

But even high doses don’t work for everyone.

You can see this in another study where the authors followed 156 men and women. All of them had previously untreated stable, mild essential hypertension. They examined the effect of taking 5 grams per day of EPA/DHA for 10 weeks. Although many individual responses were much better, the mean systolic blood pressure fell by 4.6 mmHg and diastolic pressure by 3.0 mmHg. But the important message in this study had more to do with those who did not respond than with those who did.

The non-responders all had one of two things in common. They either ate fish regularly – three or more times a week – as part of their usual diet, or they had a blood level of EPA/DHA above 175.1 mg per liter. In other words, fish oils are only going to be effective in those patients with lower body levels of these oils. So if you are already eating fish three or more times per week, or if your blood EPA/DHA levels are greater than 175.1 mg per liter, don’t waste your time trying to lower your blood pressure with fish oils.

But if you don’t eat fish three or more times a week or have high blood levels of EPA/DHA, then I highly recommend you take fish oils. Fish oils are now available in a super concentrated, highly purified form, which is the only form you should use. Other forms often contain impurities, impart an unpleasant fish oil taste and smell, and require taking way too many capsules to get the proper dosage.

A good starting dose is to take 1,000 mg of combined EPA/DHA twice a day. Do this for two to three months. Then, if your blood pressure has not normalized, double the dose for an additional two to three months. Diabetics, particularly those on insulin, should carefully monitor their blood sugars while on the higher doses. Occasionally, these doses can interfere with optimal blood sugar control.