Flaxseed is emerging as one of the most effective nutritional medicines for lowering a high blood pressure. Also known as linseed, flaxseed are a rich source of antioxidant polyphenols known as lignans. They are also a good source of beneficial omega-3 fatty acids and fibre.
How does flaxseed lower blood pressure?
Flaxseeds are one of the richest sources of lignans, antioxidant polyphenols which are best known for their oestrogen-like action. Flaxseed provide eight times more lignans than the other main dietary source, sesame seed, and must be ground or crushed to release the maximum amount of lignans for absorption.
Lignans have a variety of beneficial effects on the circulation, improving cholesterol and glucose control. The blood pressure lowering effect of flaxseed is thought to result from their high levels of omega-3 alpha-linolenic acid, however. This omega-3 was found to block an enzyme called epoxide hydrolase which would otherwise generate substances known as oxylipins which are associated with a rise in blood pressure.
In a study known as FlaxPAD, which involved 110 people with peripheral arterial disease, eating 30g of ground flaxseed per day, for 6 months, was associated with significant blood pressure reductions of 10/7 mm Hg blood pressure compared with placebo.
In those with hypertension at the start of the trial (systolic blood pressure 140 mmHg or over) blood pressure improvements were even greater at 15/7 mmHg in those taking flaxseed. These results are astonishing, given that participants had significant hardening and furring up of the arteries, and the researchers concluded that flaxseed ‘induced one of the most potent antihypertensive effects achieved by a dietary intervention’.
Another recent study showed that flaxseed can also lower central blood pressure in the aorta – the largest artery in the body. In patients with high blood pressure, the average decrease in central blood pressures was 10/6 mm Hg compared with placebo.
When the results from 14 earlier trials, involving 1004 people, were analysed, the overall result showed that flaxseed supplements reduced blood pressure by an average of 1.77/1.58 mm Hg. This seems a lot less dramatic, although a 2 mm Hg reduction in systolic blood pressure can lower the risk of stroke mortality by 10% and the mortality from ischemic heart disease by 7%.
However, not all these studies used all the components of flaxseed. Six used flaxseed oil and 3 used flaxseed extracts containing concentrated lignans in capsule form, rather than ground or whole flaxseed which are recognised as producing the most pronounced reductions in blood pressure. Another factor was that some studies only lasted 3, 4 or 6 weeks, and trials of longer durations, of at least 12 weeks, were shown to have the best response.
How to add flaxseed to your diet
Although flaxseed oil supplements are widely available, you will gain the best blood pressure lowering effect by eating ground or whole flaxseeds. Milling releases significantly more omega-3 and lignans for absorption than when eating the seeds whole.
Sprinkle the flaxseed on any meal, add to muesli, smoothies, deserts, and use in baking, too. Regular daily use of 30g was the dose used in clinical trials, with best results seen after 12 weeks.
If you have high blood pressure, then following the so-called DASH diet – which is essentially a low-salt version of the Mediterranean diet, will also produce good results.
Image credits: HealthAliciousness.com/flickr;