Bioavailability of ALA from Different Forms of Flaxseed – what does the science say?

There is much confusion around the “bioavailability” of nutrients from various forms of flaxseed, in particular that of the essential omega-3 fatty acid – alpha linolenic acid. In the marketplace, flaxseed is most commonly found in forms including whole seed, ground milled seed and oil. Additionally, constituents from flaxseed such as lignans and fibre are extracted for use in dietary supplements or are added to functional foods.

The issue of bioavailability is particularly relevant when it comes to making “nutrient content claims” in the United and Canada. The US Food and Drug Administration permits nutrient content claims for ALA based upon a minimum recommended Daily Value for ALA of 1,600 mg per day.

In the U.S.¹, nutrient content claims can be made as follows:

Similar claims are allowed in Canada², however different amounts per serving are required and different statements of claim are permitted:

Many food companies (in my opinion) “cheat” when using flaxseed to make ALA omega 3 claims. Often times, whole (not milled) seed is used. Does it matter? Yes it does – and many of the consumers that I speak to recognize that whole seed “goes right though you” and has “great laxative effects”. The bioavailability of the nutrients in whole seed are recognized in these statements as being limited. Consumers are increasingly aware that flaxseed needs it be milled or roasted for use in foods. At home, many people (if they choose to buy whole flaxseed) will grind it in a coffee grinder prior to ingestion. Some foods (but not all) that are available in our stores use milled seed.

Recognizing that the issue of bioavailability is a controversial one, scientists at the St. Boniface Research Centre in Winnipeg, Canada undertook the first of its kind study to look at the issue in humans³. The bioavailability of ALA was determined when the flaxseed was ingested in the form of whole seed, milled seed or as flaxseed oil. The flaxseed components (30 g of seed or 6 g of ALA in the oil) were baked into muffins and fed to healthy male and female subjects. Flaxseed ingestion over a 1 month period resulted in significant increases in plasma ALA levels in the flaxseed oil and the milled flaxseed supplemented groups. The flaxseed oil group had significantly higher ALA levels than the milled flaxseed group. The subjects supplemented with whole flaxseed did not achieve a significant increase in plasma ALA levels. Symptoms of gastro-intestinal discomfort and hence compliance to the diet, was a problem in the whole flaxseed group.

The authors concluded that “ingestion of flax oil and milled flaxseed delivered significant levels of ALA to the plasma whereas whole flaxseed did not. No one withdrew from the group that ingested milled flaxseed and, therefore, milled seeds represents a good form of flaxseed to avoid side-effects and provide significant increases in ALA to the body”. Note that roasted flaxseed was not included in this study so no observations are available with regard to nutrient bioavailability from this form of flaxseed.

Using whole flaxseed for nutrient content claims appears (from these results) to be misleading to consumers. They in fact are not receiving the beneficial effects of omega 3 ALA in products that use this form of flaxseed. Food manufacturers that choose to use the “cheaper” forms of flax in whole seed form may be alienating groups of consumers through these practices.

References:

1. https://www.federalregister.gov/articles/2014/04/28/2014-09492/food-labeling-nutrient-content-claims-alpha-linolenic-acid-eicosapentaenoic-acid-and-docosahexaenoic
2. http://www.inspection.gc.ca/food/labelling/food-labelling-for-industry/nutrient-content/specific-claim-requirements/eng/1389907770176/1389907817577?chap=7
3. Austria JA, Richard MN, Chahine MN, Edel AL, Malcolmson LJ, Dupasquier CM, Pierce GN.
4. Bioavailability of alpha-linolenic acid in subjects after ingestion of three different forms of flaxseed. J Am Coll Nutr. 27(2):214-21.