Nuts & seeds
Chia seeds
17.8 g of ALA and 34.4 g of fibre per 100 g. But ALA converts to EPA at 5–8% and to DHA at under 1%.
Chia vs flaxseed: whether you have to grind it is the deciding line
Both are rich in plant omega-3 (ALA). The decisive difference is that whole flaxseed passes through undigested while chia does not need grinding.
Nuts & seeds
Flaxseed
19.4 g of omega-3 (ALA) and 23.1 g of fibre per 100 g. But swallowed whole, the hard hull means most of it passes through undigested.
Chia seeds — Leads on
- Fiber
- Manganese
- Phosphorus
Flaxseed — Leads on
- Protein
- Omega-3
- Magnesium
- Selenium
Nutrition side by side
Per 100 g edible portion. Only rows where both have a figure are shown, and no winner is marked for items like calories or sugars where more is not better.
Basis for these figures
- Chia seeds
- Per 100 g of dried chia seeds. A serving is one or two tablespoons (10–20 g), so what you eat is about a tenth of this table.
- Flaxseed
- Per 100 g of ground flaxseed. Whole seeds pass through largely undigested.
| Nutrition | Chia seeds | Flaxseed |
|---|---|---|
| Calories | 486 kcal | 545 kcal |
| Protein | 16.5 g | 18.0 g |
| Fat | 30.7 g | 37.3 g |
| Fiber | 34.4 g | 23.1 g |
| Omega-3 | 17.8 g | 19.4 g |
| Magnesium | 335 mg | 372 mg |
| Selenium | 55.2 µg | 136 µg |
| Manganese | 2.72 mg | 2.4 mg |
| Phosphorus | 860 mg | 556 mg |
Bottom line
On the table the two are near twins. Flaxseed edges ahead on omega-3, 19.4 g against 17.8 g, on selenium, 136 µg against 55.2 µg, and on magnesium, 372 mg against 335 mg. Chia leads on fibre at 34.4 g and calcium at 631 mg.
But the difference that actually matters is not on the table.
Whole flaxseed passes through mostly undigested. The hull is hard enough that digestive enzymes cannot get in. That is why the table above is for ground flaxseed. Scatter whole flax over a salad and expect nutrition from it, and the numbers stay on the plate rather than reaching you. Buy it ground, or grind it yourself.
Grinding creates a second problem. Polyunsaturated fat goes rancid with air and light. Keep ground flax sealed and refrigerated, and use it within a few weeks. Whole seed keeps far longer but is of little use as it is.
Chia needs no grinding. Its hull forms a gel on contact with water and swells, and it is digested whole. It also stores easily. The easier seed to handle is clearly chia.
Flax has something chia does not — lignans. These are plant oestrogens, and flax carries far more of them than any other food. If you have a hormone-related condition or take related medication, talk to your clinician before using large amounts.
Both are ALA, and that is the same for each. It is a different compound from the EPA and DHA in fish, and the body converts it at a low rate. Neither replaces fish.
Take chia with plenty of liquid. Swallowing a lot of it dry has been reported to cause oesophageal obstruction as it swells. The same caution appears in this site's psyllium entry.