Last updated by Dr Sarah Brewer on
Flax seeds are one of the most nutrient-dense foods you can eat. Ground flax seeds health benefits are due to their high content of antioxidant plant hormones known as lignans, while flaxseed oil benefits are due to their high content of omega 3. Flax seed is also an excellent source of vitamin E, calcium, magnesium, phosphorus and potassium. Flax seed can lower blood pressure, improve cholesterol levels and glucose control, improve skin quality, aid weight loss, and has a gentle laxative action.
- Flax seeds health benefits
- Flax seed oil health benefits
- Flax seed lignans
- Flaxseed and weight loss
- Flax seed and cholesterol
- Flax seed and blood pressure
- Flaxseed and flaxseed oil benefits for women
- Flaxseed benefits for men
- Flax seeds dose
- Flax seed oil dose
- Flax seed oil versus fish oil
- Flax seeds side effects
Flax seeds health benefits
Flax seeds are obtained from the lovely blue-flowering plant, Linum usitatissimum, whose fibres are used to make linen. Flax seeds are also known as flaxseed or linseed, and there are two main types, golden flax seed and brown flax seed, which have similar nutritional benefits.
Flax seeds are the richest known source of a type of antioxidant polyphenol known as lignans. In fact, flax seeds provide eight times more lignans than the other main dietary source, which is sesame seed.
Flax seed must by ground or crushed to release the maximum amount of lignans for absorption, however. If eaten whole, much of these beneficial lignans are lost as ‘roughage’.
Flax seeds are well-known for their gentle yet effective laxative action to ease constipation. This results from the presence of mucilage – a gum-like mixture of soluble fibre and polysaccharides, which bind water and slow the absorption of cholesterol, fats and glucose.
Flax seed oil is pressed from ripe flax seeds, and is a rich source of essential fatty acids which cannot be made in the body and must therefore come from the diet.
Flax seed oil health benefits
Flax seed oil provides an unusually high content of the essential omega-3, alpha-linolenic acid (ALA). Flax seed oil also provides omega-6s with a beneficial ration of 3:1 in favour of omega-3. Most of the rest of the flax seed oil consists of the same healthy monounsaturated fats found in olive oil, with only a small amount of saturated fats.
The composition of flax seed oil is typically:
- 73% polyunsaturated fatty acids
- – 57% omega-3 alpha linolenic acid
- – 16% omega-6 linoleic acid
- 18% monounsaturated oleic acid
- 9% saturated fatty acids (palmitic and stearic).
This unique composition makes flax seeds and their oil a healthy addition to your diet.
Flax seed lignans
Lignans are oestrogen-like plant hormones which, when eaten, are in an inactive form.
Once they reach the large bowel, they are activated by probiotic bacteria which convert them into unique mammalian enterolignans which provide the health benefits.
Similar lignans are found in sweet potatoes, pumpkins and their seeds, sesame seeds, kale, broccoli and apricots.
Flax seed typically provides 955mg antioxidant polyphenols per 100g weight, including over 280mg of lignans.
When milled and defatted, however, ground flax seeds provide as much as 2080 mg polyphenols per 100g making flax seeds one of the most nutritious foods available.
Flaxseed and weight loss
Ground flaxseed is an excellent source of protein, which makes up around a quarter of its weight (over half if the flax seed is ground and defatted). This protein, plus the mucilage, helps you feel fuller for longer after eating to aid weight loss. Some of the fatty acids in flaxseed oil are also converted into substances called ethanolamides that stimulate fat burning and satiety.
A study involving 44 people assessed the effects of flaxseed on appetite and food intake.
Those taking part were asked to have a 300ml flax drink or flax tablets, (each of which supplied 2.5g soluble fibre), or a control drink (no flax) after an overnight fast on separate occasions so that each drink and supplement was tested in everyone.
Their appetite sensation was assessed for 120 minutes afterwards, on each occasion, before the volunteers were allowed to eat as much as they wanted in an early lunch.
Both the flaxseed drink and flaxseed tablets increased satiety and fullness compared to the control, with a significant decrease in subsequent energy intake at the meal.
Overall, they ate around 66 kcals less two hours after taking the flax products compared with the control (699 kcals versus 765 kcals). The researchers concluded that a small dose of flaxseed fibre significantly suppresses appetite and energy intake, and that the fibre can be taken as drink or as tablets to produce similar results.
Flax seed and cholesterol
The results from 28 clinical trials show that whole flaxseed and flaxseed lignans can significantly lower total cholesterol by 0.21 mmol/L, and LDL cholesterol by 0.16 mmol/L but flaxseed oil does not have this effect.
The cholesterol lowering effects were more apparent in females (especially postmenopausal women) and those with the highest initial cholesterol concentrations.
Flax seed and blood pressure
Eating flax seed can significantly lower a high blood pressure. The results from 11 studies show that taking daily flaxseed supplements can lower blood pressure by an average of 1.77/1.58 mmHg within 12 weeks. This effect is believed to result from the high level of omega-3 alpha-linolenic acid present. Individual results can be even greater over longer intakes.
In a study involving 110 people with peripheral arterial disease, eating 30g of ground flaxseed per day, for six months, lowered blood pressure by as much as 10/7 mmHg compared with placebo. In those with hypertension, reductions of as high as 15/7 mmHg were seen in those eating flaxseed – even though they all had significant hardening and furring up of the arteries. The researchers concluded that flaxseed had ‘potent antihypertensive effects’.
Flaxseed and flaxseed oil benefits for women
Flaxseed lignans have a similar structure to human oestrogen, and can interact with oestrogen receptors to provide a useful anti-aging boost after the menopause, and to reduce the hot flushes associated with menopause.
Flax seeds and menopause
In a pilot study, 28 women who did not want to take hormone replacement therapy, took 40g crushed flaxseed per day for six weeks. They kept a daily hot flash diary and while taking flaxseed their frequency of hot flashes scores reduced by an average of 57% from 7.3 to 3.6 hot flushes per week. However, there was no placebo group with which to compare these results.
Flax seeds and female hair loss
Flax seed lignans inhibit the enzyme, 5-alpha-reductase, which converts testosterone to the stronger dihydrotestosterone (DHT) in hair follicles. DHT is linked with female thinning hair in later life. Eating flax seed may help to reduce hair thinning, especially when used with a caffeine shampoo which also blocks DHT in hair follicles.
Flax seeds and breast cancer
Flaxseed lignans block access to the stronger human oestrogens that are associated with some hormone-dependent cancers. As a result, like soy isoflavones, they help to protect against breast cancer. Studies using human breast cell cultures have shown that flaxseed lignans can suppress the growth of breast cancer cells.
When the effects of different diet modifications and drug treatments were assessed in women due to have breast cancer surgery, those taking 25 g flaxseed per day showed similar beneficial suppressive effects on breast cancer cells to those taking the anti-oestrogen breast cancer drug, tamoxifen.
Flax seed oil and skin
The essential omega 3 fatty acids in flaxseed oil are incorporated into cell membranes to make them more fluid and supple. Taking flaxseed oil (2.2g per day for 12 weeks) has beneficial effects on skin quality, improving hydration and reducing water loss across the skin by over 10% compared with placebo. This reduced visible skin roughness and scaling.
Flaxseed benefits for men
Flaxseed lignans inhibit the enzyme, 5-alpha reductase, which converts testosterone to the stronger dihydrotestosterone (DHT) in both the prostate gland and in hair follicles. Research suggests that increasing your intake of flax lignans can reduce the rate of hair loss and thinning in males.Effects were noticed after one to two months and there was a modest improvement in hair loss.
Lignans are widely advised as part of a prostate-friendly diet to help reduce symptoms associated with benign prostate enlargement (BPH). As enterolignans have a normalising effect on hormone balance, they may also protect against some hormone-dependent cancers such as prostate cancer.
A clinical trial involving 161 men due to undergo prostate cancer surgery at least 21 days later, asked one group to take flaxseed at a dose of 30 g per day, one group to follow a low-fat diet, one group to do both (ie a flaxseed-supplemented, low-fat diet) and one group to carry on with their normal diet.
The men followed these diets for an average of 30 days before surgery. When their prostate cancer cells were removed and studied, their rate of growth (proliferation) was significantly lower among the men taking flaxseed supplements compared with those in the control group or low-fat diet group. The researchers concluded that flaxseed is safe and may be protective against prostate cancer.
Flax seeds dose
Whole flax seeds: 1–2 tablespoons with water twice a day for a filling effect (and as a laxative)
Ground defatted flaxseeds: 1 – 2 tablespoons per day sprinkled on food.
Keep ground flaxseeds refrigerated and use them within 24 hours after grinding for maximum potency.
Flax seeds can be eaten whole and lightly toasted for extra crunch and flavour.
Add to cereals, salads, soups, or add to trail mix for a healthy snack.
Add ground flaxseeds to smoothies, sprinkled over cereals or use during baking.
Flax seed oil dose
Flaxseed oil: 1 teaspoon–1 tablespoon once or twice a day.
Flax seed oil degrades on exposure to light and if not processed and stored properly quickly turns rancid. Avoid oil that is past its use by date, or which has a strong odour.
Liquid flaxseed oil should be stored in the fridge in opaque bottles.
Flaxseed oil capsules are the most convenient way to obtain flax seeds health benefits.
Flax seed oil versus fish oil
Flaxseed oil is often used as an alternative source of omega-3 for those unable or unwilling to take fish oils. Originally it was thought that only 5% of the polyunsaturated omega-3 ALA in flax seed oil was converted on to the beneficial long-chain omega 3, EPA, and that less than 0.5% was converted on to DHA.
New findings show that this conversion of polyunsaturated fatty acids is much more efficient in people who do not eat fish, including vegans and vegetarians, which makes sense as these fatty acids are so important for health. As a result, blood levels of EPA and DHA in non-fish eaters are similar to those of fish eaters.
One teaspoon (15 ml) of flax seed oil provides 2,800 mg (2.8grams) omega-3 ALA
- 20% conversion of 2,800 mg of ALA provides 560 mg EPA
- 4% conversion of 2,800 mg of ALA provides 112 mg DHA
The combined EPA and DHA obtained from conversion of the ALA in one teaspoon of flaxseed oil is therefore around 672mg, and compares well with taking an EPA-enriched fish oil.
Interestingly, women appear to convert alpha-linolenic acid (ALA) to EPA at a rate that is 2.5 fold greater than for men, which is thought to be an effect of oestrogen.
Flax seeds side effects
In a study in which women took 40g crushed flaxseed per day, reported side effects included mild to moderate abdominal distension, mild diarrhoea (a known laxative effect) and flatulence.