Flaxseed is one of the oldest and most affordable sources of fibre in our kitchens. In this guide you will learn how much fibre, omega-3 fatty acids and lignans it contains, why it is better ground, how much to eat per day and how to make a traditional flaxseed drink.
Flaxseed is nothing new in Lithuania: our grandmothers cooked it into a thick drink called kisielius and added it to bread and porridge. Today it is popular again, because this tiny seed is rich in fibre, a plant-based omega-3 fatty acid and lignans. With its popularity come questions: do you need to grind flaxseed, how much can you eat, and is raw flaxseed safe?
In this article we draw on food composition data from the U.S. Department of Agriculture (USDA), scientific assessments by the European Food Safety Authority (EFSA), EU legislation, and information from the U.S. National Center for Complementary and Integrative Health (NCCIH), Mayo Clinic and Cleveland Clinic. You will find the sources at the end of the article, and they are marked with numbers in the text, for example [1]. If fibre is a new topic for you, start with our guide “Fibre: what it is and where to find it”. A comparison of flaxseed and chia seeds follows below.
What is flaxseed?
Flaxseed (also called linseed) is the seed of the flax plant (Linum usitatissimum). The same plant gives us linen fabric and flaxseed oil. The seeds are brown or golden, and their nutritional value is similar.
In shops you will usually find three forms:
- Whole seeds. They keep the longest, but intact seeds can pass through the digestive tract undigested [4].
- Ground flaxseed. Easier to digest, which is why most nutrition experts recommend it [4]. Ground seeds should be used up sooner.
- Flaxseed oil. Rich in the omega-3 fatty acid, but contains no fibre. The oil spoils even faster than ground seeds [5].
Flaxseed benefits: what does it contain?
According to USDA data, 100 g of flaxseed contains 27.3 g of fibre, 22.8 g of alpha-linolenic acid (ALA), a plant-based omega-3 fatty acid, and 18.3 g of protein [1]. It is an energy-dense food: 100 g provides 534 kcal, because almost half of the seed's weight is fat [1]. That is why we eat flaxseed by the spoonful, not by the bowl.
| Nutrient | 100 g flaxseed | 1 tbsp ground flaxseed (about 7 g) |
|---|---|---|
| Energy | 534 kcal | about 37 kcal |
| Fibre | 27.3 g | about 1.9 g |
| ALA (omega-3) | 22.8 g | about 1.6 g |
| Protein | 18.3 g | about 1.3 g |
| Total fat | 42.2 g | about 3 g |
| Magnesium | 392 mg | about 27 mg |
| Calcium | 255 mg | about 18 mg |
| Lignans | about 335 mg | about 23 mg |
Fibre
Flaxseed contains both soluble and insoluble fibre. The soluble part forms a slippery gel with water, which is why a flaxseed drink turns thick [5]. We explain the difference between these fibres in our article “Soluble and insoluble fibre: what are their benefits?”. EFSA considers 25 g of fibre per day an adequate intake for normal bowel function in adults [11], and one tablespoon of ground flaxseed adds almost 2 g.
ALA, a plant-based omega-3 fatty acid
ALA is an essential fatty acid: the body cannot make it, so we need to get it from food. EFSA has set an adequate intake for adults of 0.5% of daily energy [10], which is about 1.1 g if you eat 2,000 kcal a day. In the EU it may be stated that ALA contributes to the maintenance of normal blood cholesterol levels, with the beneficial effect obtained from a daily intake of 2 g of ALA [9]. That amount of ALA is found in roughly 9 g of ground flaxseed [1]. This is a statement about a nutrient, not a promise that any specific product will replace medical treatment.
Lignans
Lignans are plant compounds found in very small amounts in most foods. Flaxseed is the exception: it contains about 335 mg of lignans per 100 g, roughly a hundred times more than other common dietary sources [3]. How lignans affect human health is still being studied, and their absorption varies widely between people [3].
Why is ground flaxseed better?
The hull of a whole flaxseed is hard, so an intact seed can pass through the intestine undigested and some of its nutrients will not be absorbed [4]. Mayo Clinic notes that most nutrition experts recommend ground flaxseed because it is easier to digest [4].
- Grind it yourself. A coffee grinder or food processor does the job in seconds [4, 5].
- Grind small batches. Ideally grind only what you will use within a few days or a week, because ground seeds spoil faster [5].
- Buying it ground? Check the date. Choose an airtight package and keep it in the fridge once opened.
How much flaxseed can you eat per day?
There is no official daily amount for flaxseed. A Cleveland Clinic dietitian suggests starting with a teaspoon a day and gradually working up to about 2 tablespoons [5]. NCCIH notes that larger amounts of flaxseed can cause bloating, a feeling of fullness or diarrhoea [6].
What you should know about cyanogenic glycosides
Flaxseed naturally contains cyanogenic glycosides. These are plant compounds that can release hydrogen cyanide (hydrocyanic acid) when the seed is crushed and chewed [7, 8]. In 2019 EFSA assessed the risks of these substances and applied an acute reference dose of 20 µg of cyanide per kilogram of body weight [7]. EU legislation notes that eating large amounts of linseed, almonds or cassava with high levels of these compounds could exceed this dose [8].
For this reason, maximum levels of hydrocyanic acid in linseed have applied in the EU since 2023 [8]:
| Product | Maximum level |
|---|---|
| Unprocessed linseed (whole, ground, milled, cracked) sold to the final consumer | 150 mg/kg |
| Other unprocessed linseed | 250 mg/kg |
| Small packs labelled “Only to be used for cooking and baking. Do not consume raw!” | 250 mg/kg |
What does this mean in practice? Flaxseed sold in shops must meet these limits, and a normal amount such as a tablespoon or two a day is an ordinary part of the diet. Still, do not eat flaxseed by the handful, and read the label carefully: if the pack says the seeds are only for cooking or baking, do not eat them raw [8]. NCCIH also reminds us that raw or unripe seeds may contain potentially toxic compounds [6].
How to use flaxseed
Ground flaxseed has a mild, nutty taste, so it is easy to stir into everyday meals. The key rule: as with other sources of fibre, drink plenty of fluids and do not take flaxseed at the same time as oral medication [4].
- In porridge. Stir a tablespoon of ground flaxseed into oat or buckwheat porridge [4]. For more breakfast ideas, see our article “Healthy breakfasts: recipes”.
- In yoghurt or kefir. A tablespoon of ground flaxseed in a pot of yoghurt, a few berries, and your snack is ready [4].
- In baking. Replace some of the flour in bread, buns or cookies with ground flaxseed [4]. In our snacks article we use it in oat energy balls.
- As an egg substitute. Mix a tablespoon of ground flaxseed with 3 tablespoons of water and let it sit until it thickens [5]. It works for pancakes, muffins and patties.
- In a smoothie. Stir in a tablespoon of ground flaxseed and drink it straight away, before it thickens.
Flaxseed drink (kisielius): recipe
Kisielius is the traditional Lithuanian way of using whole flaxseed. When cooked, the seeds release mucilage and the liquid becomes thick.
You will need: 1 tablespoon (about 10 g) of whole flaxseed, 250 ml of water.
Method: cover the seeds with the water and bring to the boil. Simmer over a low heat for about 10 minutes, stirring now and then. Take it off the heat, leave for 15–20 minutes to thicken, then strain. Drink it warm. If you like, add a squeeze of lemon juice. It is best to drink it the same day.
How to store flaxseed
- Whole seeds: keep them in an airtight container in a cool, dark place. This form keeps the longest [5].
- Ground seeds: keep them in an airtight container in the fridge, or freeze them if you will not use them soon [5].
- Flaxseed oil: keep it in the fridge and watch the use-by date [5].
- Spot spoiled seeds. Rancid flaxseed smells sour and tastes bitter [5]. Throw it away.
Flaxseed or chia seeds?
Both are good sources of fibre and ALA; they simply work differently in the kitchen. We write more about chia in our article “Chia seeds: how to use them and how much fibre they contain”.
| Flaxseed | Chia seeds | |
|---|---|---|
| Fibre per 100 g | 27.3 g | 34.4 g |
| ALA (omega-3) per 100 g | 22.8 g | 17.8 g |
| Energy per 100 g | 534 kcal | 486 kcal |
| Calcium per 100 g | 255 mg | 631 mg |
| Lignans | very high, about 335 mg per 100 g [3] | much lower |
| Need to grind? | Yes, ground is better [4] | Not necessary, but must be soaked |
| How to use | Porridge, yoghurt, baking, flaxseed drink | Pudding, yoghurt, smoothies, baking |
| Storage | Ground seeds in the fridge | In a dry, cool place |
There is no need to choose just one: you can alternate them depending on what you are cooking that day.
When should you talk to a doctor?
Flaxseed is an ordinary food, but in some cases it is worth talking to a doctor or pharmacist before eating it regularly:
- You take medication. Flaxseed could theoretically interact with blood-thinning medicines [6], and fibre can interfere with the absorption of oral medication, so do not take flaxseed at the same time as your medicines [4].
- You are pregnant or breastfeeding. NCCIH notes that evidence on the safety of flaxseed supplements during pregnancy is inconclusive, and little is known about breastfeeding [6].
- You have kidney disease. Flaxseed is high in potassium [5].
- You are being treated for a hormone-sensitive condition. Cleveland Clinic advises checking with your doctor, because flaxseed contains phytoestrogens [5].
- You have diverticula or difficulty swallowing. Your doctor can advise which form and amount suit you [5].
- You want to give flaxseed to children. Discuss the amount with your child’s doctor.
Important: these data are about flaxseed and nutrition in general. They do not describe the effects of the fruttberry product and do not replace a doctor’s advice.
When you don’t always have seeds at hand: the fruttberry fibre blend
Flaxseed is great for home cooking, but it is not always convenient to grind it, keep it in the fridge or take it to work. The fruttberry blend contains no flaxseed or chia seeds. It is a different, convenient additional source of fibre alongside them, for days when you get too little fibre from food.
Ingredients
- Psyllium husk (psyllium) is the base of the blend.
- Agave inulin is a soluble fibre that is fermented in the gut.
- Freeze-dried strawberries (12%) and blackcurrants (8%) give flavour and colour from real berries, not from flavourings.
- Glucomannan from konjac (Amorphophallus) tubers is another soluble fibre.
How much fibre is in one teaspoon?
100 g of the blend contains 77 g of fibre. In an independent test by the KTU Food Institute, a sample of our blend contained as much as 84.4 g of fibre per 100 g. One teaspoon (5 g) provides about 3.86 g of fibre and only 11 kcal. The blend contains no added sugar, gluten, lactose or preservatives, and it is suitable for vegans.
Stir one teaspoon into 200–250 ml of water and drink it straight away, increasing the amount every 3–4 days. Psyllium and glucomannan swell, so always take the blend with enough water: drinking too little liquid can cause a choking risk. If you have difficulty swallowing, do not take fibres of this kind.
For home, the most practical choice is the 250 g pack, and for work and travel the 30 single servings of 5 g.
All fruttberry dietary fibre products in one place.
Frequently asked questions about flaxseed
Do I have to grind flaxseed?
Not necessarily, but it is recommended. Whole seeds can pass through the gut undigested, while ground ones are easier to digest [4]. The exception is the flaxseed drink, which uses whole seeds.
How much flaxseed can I eat per day?
There is no official amount. A common suggestion is to start with a teaspoon and gradually work up to about 2 tablespoons a day [5]. Always follow the manufacturer’s instructions on the pack as well.
Does flaxseed contain omega-3?
Yes. 100 g of flaxseed contains 22.8 g of ALA, a plant-based omega-3 fatty acid [1]. About 9 g of ground flaxseed provides 2 g of ALA.
How do I use ground flaxseed?
Stir a tablespoon into porridge, yoghurt or a smoothie, add it to baking or use it as an egg substitute [4, 5]. Drink enough water and do not take it together with medication [4].
Is flaxseed safe during pregnancy?
Evidence on flaxseed supplements during pregnancy is inconclusive [6], so talk to your doctor before using it regularly.
Sources
- U.S. Department of Agriculture, Agricultural Research Service. Seeds, flaxseed (FDC ID 169414). FoodData Central, SR Legacy, 2018.
- U.S. Department of Agriculture, Agricultural Research Service. Seeds, chia seeds, dried (FDC ID 170554). FoodData Central, SR Legacy, 2018.
- Peterson J, Dwyer J, Adlercreutz H, Scalbert A, Jacques P, McCullough ML. Dietary lignans: physiology and potential for cardiovascular disease risk reduction. Nutrition Reviews. 2010;68(10):571–603.
- Mayo Clinic. Flaxseed: Is ground better than whole? 2023.
- Cleveland Clinic. Flaxseed: A Little Seed With Big Health Benefits. 2024.
- National Center for Complementary and Integrative Health (NCCIH). Flaxseed and Flaxseed Oil: Usefulness and Safety. Updated 2025.
- EFSA Panel on Contaminants in the Food Chain (CONTAM). Evaluation of the health risks related to the presence of cyanogenic glycosides in foods other than raw apricot kernels. EFSA Journal. 2019;17(4):5662.
- European Commission. Commission Regulation (EU) 2022/1364 amending Regulation (EC) No 1881/2006 as regards maximum levels of hydrocyanic acid in certain foodstuffs. 4 August 2022.
- European Commission. Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. OJ L 136, 25 May 2012, pp. 1–40.
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol. EFSA Journal. 2010;8(3):1461.
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre. EFSA Journal. 2010;8(3):1462.
The information provided is general in nature and does not replace advice from a doctor or dietitian. The scientific data refer to fibre and nutrition in general and do not describe the properties of any specific product. If you have a chronic condition, take medication, are pregnant or breastfeeding, talk to a healthcare professional before starting any food supplement. A food supplement is not a substitute for a varied and balanced diet.
