Where did this claim come from?
I have no idea precisely where the claim that oat milk is pro-inflammatory comes from. Perhaps based on the “toxins” it supposedly has, or perhaps (as I have noticed lately) being pro-inflammatory is just a non-specific accusation of being bad. (Most people don’t really understand inflammation anyway).
In any case a randomized clinical trial of oat-enriched diet for people with type 2 diabetes showed that increased consumption of oats was associated with fewer markers of inflammation12. Overall, studies investigating oats and inflammation have found either mild anti-inflammatory effects, or no effects.
Let’s break this down
Glycemic index
Oat milk does have a higher glycemic index than other diary or diary substitutes, even though it is made of oats, which have a low glycemic index. This is because the oats are ground, and thus making the sugars in it more quickly absorbable. The real concern here is when commercial sources of oat milk add extra sugars to the oat milk13,14.
Lectins
Oat milk does have lectins in it, as all plants have lectins. Lectins are proteins that can have a variety of effects on cells, including negative effects, depending on the type of lectin. The food group with the highest concentration of lections are the seeds of beans. It needs to be said that the beans we eat are not the ones, such as castor beans, that high lectin content. Lectins are destroyed by cooking, so cooked beans are “safe”. In oats, the levels of lectins are too small to have consequences for health15 and are typically cooked first also.
Nutrition facts
It is also true that oat milk lacks the important nutrients that dairy contains, but this is true of all of the dairy substitutes14. Commercial dairy alternatives are typically supplemented with vitamins, minerals and/or protein to bring them more in line with dairy nutrition.
Overall, we’re OK with oatmilk!
So, the grain of truth is that pure oat milk (that does not have added nutrients) is less nutritious than dairy milk. This should not be a serious concern unless the oat milk is the major food source being consumed.
The claims of “lectins”, “toxins”, and “inflammation” are hooey!