Lupins and toxicity

Once primarily an animal food source, lupins are increasingly entering human diets. As a high-protein legume the beans, interestingly, do not contain starch and they are particularly useful in gluten-free formulations.

However, while lupins have been a source of human and animal nutrition for thousands of years, they can come with a sting in the tail. So called ‘bitter lupin’ varieties contain toxic alkaloids that can affect the nervous, circulatory and digestive systems in humans. These bitter lupin beans are preferred by many Mediterranean cultures, but if not prepared properly the anticholinergic alkaloids can remain in the beans and cause poisoning. Traditional means of removing the toxins is by leaching in water.

‘Australian Sweet Lupins’ (L. angustifolius) lack any bitter taste and do not need any ‘debittering’. However, recognising the dangers of cross-pollination between the sweet, low-alkaloid variety and the wild bitter plant, the presence of one bitter bean per hundred sweet beans is considered unacceptable and a wide quarantine zone is maintained around lupin-growing croplands to prevent wind-blown wild pollen from having a large influence on crop toxicity.

In Germany there have been isolated reports of poisoning caused by bitter lupin seeds with the Federal Institute for Risk Assessment (BfR) receiving data from the Poison Information Centres on around 30 instances between 2010 and 2016. Most of these cases were attributable to the inadequate debittering of the bitter lupin seeds in private kitchens.

The BfR is now recommending to the producers of foods containing lupin seeds that they only market lupin seeds which can be consumed without the need for any further debittering processes at home. These can be sweet lupin seeds, which have naturally low alkaloid levels, or bitter lupin seeds, which have already been sufficiently debittered by the manufacturer. Where flour made from lupin seeds is sold to consumers, the manufacturers should ensure that it was made from lupin seeds which were low in alkaloids or sufficiently debittered.

The BfR has published a detailed risk assessment of alkaloid levels in lupin seeds in its Opinion No. 003/2017.