Thymus aging mitigation strategies
OK time to start thinking about the thymus. First start with this blog post by Josh Mitteldorf (an aging theorist) which is a good introduction to the thymus and aging. The short answer is the Thymus generates memory T-cells ('memory' meaning they remember past exposure to viruses, and T meaning "thymus"). The Thymus gets smaller with age, and we also generate fewer T-cells. From the post, we don't know why the Thymus shrinks, except that it is not from typical aging senescence.
One way to increase its size (presuming that larger = better) is possibly through human growth hormone (HGH). Supplementing with GH comes with a host of other problems - at the moment it's best not to attempt this. In the comments the author, who is a friend of Greg Fahy's, discusses Gregs 1 year experiment with HGH. At the end he did have a larger thymus
So AFAIK we don't know yet how to fix the root cause of aging thymus degeneration, but we do know (clinically verified in many studies) how to mitigate the result which is poor T-cell function. In this way we can address the effect, if not the cause, similar to addressing failing adrenal function by hormone supplementation. This is something I've mentioned here several times, because it surprises me that it's not bigger in the aging community, bu which is 3+ day water only fasting. There's a lot of top drawer research behind this, the most approachable is to read The Longevity Diet by Valter Longo who is one of the primary researchers, working at UCLA. No he's not trying to make a buck, I think all the money goes to a research foundation, he's reporting on his work which started as a PhD student working for Roy Walford.
Roy believed that long term calorie restriction prolonged life, but now we know that unfortunately it does not. Aubrey DeGrey frequently cites this, it turns out that chronic calorie restriction in long lived species does not confer the same benefit it does in short lived species. We can hypothesize about this from an evolutionary standpoint, but regardless it's an established fact. Now Valter continued Roy's work and has found that instead of chronic restriction intermittent calorie restriction does have tremendous benefits. Far more that what many of us are doing here via pharmaceuticals and nutraceuticals.
It's spelled out in that book, but back to the topic at hand, at around 3-4 days of a water only fast what happens is about half of our T-cells are killed off. These are old programmed T-cells hanging around, after a lifetime of exposure we have this old programming still around. But what happens is when you re-feed (start eating again), your stem cells (which enjoy a rejuvenating effect) regenerate those T-cells, but now they're baby unprogrammed cells. So - stem cell therapy, simply by not eating for a few days.
If anybody is interested we can discuss why's and how's. I do it - been doing water only fasts for years, twice a year which coincidentally what Valter recommends for those with 'elite health'. Anecdotal evidence of it's benefits; since I started I haven't gotten sick. Not once. Used to get sick every year, but no longer. I attribute this to probable T-cell rejuvenation which is more responsive to infection. Note there are many, many other benefits too, which Bill Faloon recently reiterated in lecture.
I would recommend for everybody here to deeply consider adding multi-day water only fasting to their regime. It's the cheapest, simplest, easiest, strongest with no side effect way to improve longevity.