Actually, there is human research. Below is a message Olaf Adam sent to myself and several others on September 5, 2021.

I refer to the very readable review by Philip Calder “A systematic review of the effects of increasing arachidonic acid intake on PUFA status, metabolism and health-related outcomes in humans.” His final statement is that an increase in arachidonic acid intake up to 1.5 grams per day does not significantly change the parameters associated with inflammation, blood clotting or atherogenesis. In this very interesting observation, I was astonished by the fact that the background diet was not taken into account. Although the intake of arachidonic acid with the background diet is reported several times, the resulting metabolic consequences are not discussed.
From the data provided, it can be concluded that the background diet in all studies included in the review was a Western diet, the proportion of arachidonic acid being estimated at 200 to 400 mg per day. Our studies on healthy volunteers were carried out with formula diets and allowed a precisely defined supply of arachidonic acid over a period of 6 weeks. These studies have shown that the exclusion of arachidonic acid from the diet (vegan diet) causes a progressive decrease of this fatty acid from 11 + 3% of the total fatty acids in the cholesterol esters of the plasma to 8 + 2% after 6 weeks. The later studies on patients with rheumatoid arthritis have shown that an intake of arachidonic acid amounting to not more than 80 mg/day does not increase the concentration of arachidonic acid in the phospholipids of the plasma and in the erythrocyte lipids. From these findings I have concluded that the body's own production of arachidonic acid is around 80 mg per day. This means that the Western Diet provides approximately 2.5 to 5 times the estimated need for arachidonic acid.
This intake that is higher than the requirement primarily has no negative consequences. We know from many studies that the "silent inflammation" characteristic for the prevalent diseases of western societies has a latency period of more than 10 years before the consequences such as arteriosclerosis and myocardial infarction become apparent. The body is evidently able to avert the consequences of an unfavorable diet for a long time. To do this, there are numerous regulatory options, such as substrate or product inhibition in the case of enzymes or the inhibition of transport to or incorporation into cells. Arachidonic acid has a very special metabolic pathway that offers possibilities for regulating absorption from the intestine, transport in the chylomicrons, metabolism via the enzymes involved and also for incorporation into the cells. For example, we have found a completely different efficiency for the uptake of arachidonic acid into the cell membrane for platelets compared to erythrocytes or granulocytes. It is therefore very likely that regulation options on the metabolic pathway of arachidonic acid can, to a certain extent, compensate for changes in intake.
Only when too much arachidonic acid is present in the food for a prolonged time do these protective mechanisms apparently fail and inflammation and the manifestation of lifestyle diseases is seen. This explains the long latency period with which the diseases of civilization occur. It is documented in the literature that unhealthy supplementation, such as megadoses of vitamin E, has no deleterious effects on health-related outcomes for humans in the short term. Only long-term observations and meta-analyzes have been able to prove the increased overall mortality. These protective functions with which our body is endowed are very important, because our body is often confronted with megadoses of vitamins or other food stuff or unreasonable diets. Otherwise humans would already be extinct.
In summary, I would like to note that the human metabolism has many opportunities to compensate for unreasonable interventions for a limited time. The studies available so far relate to arachidonic acid intake with the Western Diet. This condition may already have provoked defense mechanisms that delay the occurrence of Western Diet diseases. We all agree that the Western Diet is too meat-based. The studies included in the review gave me the impression that an attempt had been made to further aggravate an already bad situation, present in Western civilizations. The negative result of these studies is reassuring for me, but does not mean that this supplementation has to be harmless and without long-term effects.
From my point of view, it would have been more productive from the experimental approach if vegans had been given the doses of arachidonic acid employed in the studies that are included in the review. This would come closer to the desired goal of the effects of arachidonic acid on PUFA status, metabolism and health-related outcomes in humans. Then one could also come to a result for the desirable intake of arachidonic acid, which I estimate for patients with inflammatory rheumatic diseases at 80 mg per day, corresponding to 560 mg per week. This corresponds to a diet with 5 vegan days and 2 days with consumption of animal products per week.