At what kind of doses would it be dangerous?
I know that menopausal women should take 3g from studies I've seen before
This is impossible to give a firm answer to because its entirely variable. Its an unstable result, possibly due to large numbers of hormonal and other influences. That is its subject to lots of interference including feedback loops, not all of which are probably identified yet ... just a guess, but I doubt we know enough even now to figure it out.
I would argue that any amount is dangerous, but its also an essential food ... omega-6 and omega-3 fats are called essential because without them you die. So small amounts are great.
So its about finding a balance, and its a moving target. There is no stable balance here. I tried to find an omega-6 balance in the mid 90s before I realised the issues with the biochemistry. A similar thing happens with omega-3s. Taking both together only has a slightly better reaction. I was probably one of the early ME patients who tried high dose omega-3 treatments, which gave initial benefit then failed. So did omega-6s.
I used to know a lot on this topic, but I have forgotten nearly all of it. It was my pet topic for many years. Keep in mind that I am very out of date, and the science would have changed
a lot. I could never keep up with the research as there was so very much, with new hormones being discovered almost every year.
There are two impacts of polyunsaturated fats that are important I think. Simpson was focusing on the cell membrane deformability. I am much more interested in cell hormone regulation. Both main types of polyunsaturated fats lead to hormone synthesis. Omega-6 leads to series one and series two eicosanoid synthesis, and omega-3 leads to series 3. Series 2 and 3 are predominantly inflammatory, both of them. So omega-3s are inflammatory, not anti-inflammatory ... so why is the other story so commonly claimed?
Series 1 leads to PGE1, which was the outcome I think Simpson wanted. I pointed out he should directly supplement with PGE1 and not try to get it from evening primrose oil as a source. He didn't like that. I made that suggestion to a vascular surgeon once as well, as this can restore blood flow and remove the need for some amputation.
We have at least one and maybe several issues with eicosanoid synthesis. There has a been a lot of debate on this, but not a lot of firm answers. Secondary evidence indicates we may over-produce series 2 eicosanoids, including the nitrosative stress findings. I certainly do ... if I consume rendered animal fat by accident, due to bad restaurant choices by the chefs, then I collapse in pain for many many hours, unable to move.
Eicosanoids are several families of hormones, including prostaglandins and several types of immune signalling molecules. Eicosanoids are critical for sleep, in particular you need PGED2 or sleep is impossible. These hormones frequently have a half-life of only seconds. So you have to keep making them. If you supply too much free substrate (its usually bound), especially arachidonic acid, you will rapidly make too much of these hormones, and this can induce a frightening sequence of hormonal disasters. Inject a rabbit with even tiny amounts of this stuff, not bound, and its a rapid screaming death. Alcohol poisoning most often kills this way, because alcohol releases free arachidonic acid and death from alcohol poisoning is reliably blocked by drugs that block eicosanoid synthesis.
Some series 2 eicosanoids are anti-inflammatory, but its the balance that matters. So far as I know we do not have any reliable means to direct which are made and which are not.
So the typical result of series 2 eicosanoids is a complex mix of inflammatory problems.
Series 3 have the same profile, but here is the important part ... they are much less active. Also, critical enzymes process both types of fat, with a preferential binding to omega-3. So omega-3 induces something called competitive inhibition. So less omega-6 eicosanoids are made. THIS is why it often has an anti-inflammatory effect.
If you are salicylate sensitive then there are a number of known factors, possibly more because I have not kept up to date. Glutathione is required to regulate the two critical desaturase enzymes, delta-5 and delta-6 desaturase. It also requires, I think, vitamin C and magnesium, but I would need to go back and check that to be sure. If for any reason you do not have enough of these enzymes, or not enough glutathione, they cannot make enough eicosanoid substrate to keep up with demand if they are challenged. Salicylates and similar substances inhibit these two enzymes, that has been known for 34 years now. Suddenly your supply of critical hormones at the cellular level is halving every few seconds. Instant symptoms. A lot of chemical intolerance is explained by this and similar substances and their impact on cellular hormones.
The short answer is if you are healthy then small amounts of both fats are great, with not too high a poly-6 to poly-3 ratio. If you are sick with issues involving oxidative and nitrosative stress then you may have very big problems. Its a gamble. Its also variable over time. I could say more but this post is already too long. There is lots more on oxidative stress and trans fats that are important here, much of which I have forgotten.