There seems to be a massive debate in the paleo community about whether low carb diets or high carb diets are better for the thyroid.
Paul Jaminet has touched on this: http://perfecthealthdiet.com/?p=4383
As has Danny Roddy http://www.dannyroddy.com/main/2011/8/16/why-im-not-a-fan-of-high-fat-diets-part-i.html http://www.dannyroddy.com/main/2011/8/22/why-im-not-a-fan-of-high-fat-diets-part-ii.html
Anthony Colpo also has replies that are linked in the Jaminet posts.
There are also several personal anectodes for both high fat and high carb increases libido, thyroid. Many of the carb ones tend to be from those who went low carb for awhile and found these things crashed. Many seem to be from those in the reproductive ages. Danny, myself, and some testimonies from Matt Stone's site ( http://180degreehealth.blogspot.com/2011/03/natural-testosterone-enhancement.html and here http://180degreehealth.blogspot.com/2011/06/paleo-fail.html ) Although not too sure how legit these anectodes are
We have anectodes for high fat here on paleo hacks.
So we've got both sides with postives and negatives, but we are still left with alot of questions. What works long term and what is optimal for long term? Does it change for age, genetics, dietary history?
This is what I posted on Paul's blog and explains why I think this topic is very important:
"It would be great if some long term low carbers could get their hormones tested and evaluted agaisnt their diet and activity level. I think that would shed some serious light on this issue. What we have is many younger paleos coming forth with these sex hormone and thyroid issues all of a sudden, and some of them seem to be fixing these with high carb paleo diets. On the other hand, I know much of the consensus of young people at AHS was that we were not impressed by the physiques of some of the older, long term low carb guru’s such as Cordain and Eades physiques. Sure, activity levels play a major role in leaness, but so do sex and thyroid hormones.
Personally, higher carbs seems to improve these things for me like Danny, but I dont have evidence for it yet. Fats also help, I definitely can’t be too low in these. But more fat doesn’t do it for me the way more carbs does.
That said, Jeff pointed out something that I;ve been on to for a while as well… HDL and Testosterone are always postively correlated. Saturated Fats raise HDL, so higher fat should = higher T. But for some reason this isn’t the case for some? Also, Paul noted in his HDL post that higher potassium excretion was correlated with high HDL, so tubers such as potatoes and sweet potatoes, which are to my knowledge the highest dietary sources of potassium around, also should help HDL and testosterone and this is certainly true in my case going off of symptoms.
We have all these short term studies but no long ones. We have anectodes from both sides of the board, but what are the variables? Are these folks with good thyroid and sex hormones on high fat doing something different that those whose dropped arent? I think we will continue to have these questions until we really dig digger with the evidence we have in long term long carb dieters."
Not to call anyone out but I would like to add Fred Hahn to the long term low carbers who look like their thyroids might not be optimal... he has even reported a high LDL and hairloss online which is usually seen with hypothyroidism, as well as the red skin that Melissa has pointed out.