In 1943, seven brothers set out to ease a child's agonizing pain.
The family of Italian immigrants had been living in California, making their living as inventors. They designed everything from super-light World War I fighter planes to irrigation systems, water pumps, and swimming pool supplies.
Then the youngest brother Candido's 15-month-old son Kenneth was diagnosed with rheumatoid arthritis... a painful, progressive joint disease. Candido and his brothers set their sights on inventing a solution to this much more personal problem.
The brothers wanted to help Kenneth find relief from the chronic pain and stiffness. They turned to their knowledge of agricultural hydraulics to create a portable hydrotherapy pump.
This pump could attach to a bathtub at home to create a rejuvenating, massaging spa experience. They called it the J-300. And after some further tweaks, the brothers started selling these pumps in 1949.
Today, that invention is known worldwide by the family's last name: Jacuzzi.
The Jacuzzi brothers' invention helped popularize the hot tub we know today. And while pressurized water is great for achy joints, adding heat is what truly unlocks the longevity benefits we've been talking about.
In fact, after we published an issue on heat therapy earlier this spring, readers have filled our inbox with questions about harnessing the health benefits of hot tubs and saunas.
We'll tackle a collection of these questions in this week's Q&A... And as always, keep sending your comments, questions, and topic suggestions to feedback@healthandwealthbulletin.com. My team and I read every e-mail.
Your Heat-Therapy Questions Answered
Q: Are you talking about saunas or hot tubs? Saunas as I understand them don't have water in which you put your body, as hot tubs do. – L.M.
Q: Doc Eifrig talked about heat therapy using a sauna or a hot water bath. I would like to know if a hot tub would serve the same purpose? – L.H.
A: Thanks for writing in, L.M. and L.H. We're talking about both.
A sauna uses heated air – either dry heat from a stove or infrared light – to warm your body. You sit in there and sweat. With a hot tub or bath, you fully submerge your body in heated water.
But the ultimate goal is the same: to raise your core body temperature enough to trigger your body's built-in repair and survival systems.
In a hot tub or sauna, the heat stress stimulates production of heat-shock proteins ("HSPs"). These help protect your cells from damage... clear out dysfunctional proteins... and support healthier aging.
Hot-water immersion may even provide an extra benefit. A University of Oregon study uncovered value in hydrostatic pressure, or the physical pressure of water pressing against your body. That all-over pressure helps move blood back toward the heart, so your heart and the rest of your cardiovascular system get a good workout. You don't get that pressure from sitting in a traditional sauna.
Still, both a hot tub (or hot bath) and a sauna both work wonders for improving circulation, reducing inflammation, and supporting long-term health. The best option to use is the one you have easiest access to – and the one you'll use consistently.
Q: Doc... I was reading your article on the Fountain of Youth (bathroom) which was quite enlightening... my question regarding use of the hot water therapy is, would this be something that might help with rheumatoid arthritis in your opinion. Thanks in advance for your reply! – D.F.
A: Heat therapy has been a go-to remedy for aching joints for centuries. And it's all backed up beautifully by modern science.
Rheumatoid arthritis ("RA") is an autoimmune condition driven by chronic inflammation. In our issue, we talked about "inflammaging" and how regular heat exposure actively lowers levels of C-reactive protein ("CRP").
CRP is a major biomarker of all-over, or systemic, inflammation and doctors look to this blood test to measure the severity of RA inflammation.
Regular heat exposure helps boost anti-inflammatory molecules while reducing levels of pro-inflammatory ones.
What's more, a 2025 review found that sauna bathing helps alleviate pain, reduce stiffness, and improve mobility in patients. And since hot-water immersion raises core body temperature in a similar way, many of the same benefits likely apply to hot tubs and baths as well.
Of course, anyone with RA or another chronic condition should check in with their doctor before starting regular heat therapy. But for many folks, it may be a simple and relaxing tool worth trying.
Q: In the most recent edition you talked about the benefits of using a sauna. Do the portable saunas give the same results? Thanks. – S.A.
A: For readers unfamiliar with portable saunas, they're typically collapsible tents that use steam or infrared heat. And the short answer is yes, they should work just as well as a permanent sauna... as long as they can maintain hot-enough temperatures to raise your core body temperature.
Heat therapy uses hormesis: a small, controlled dose of a physical stressor that triggers your body's survival and repair processes. Whether you're basking in a $5,000 cedar-lined Finnish sauna or zipping yourself into a $200 portable sauna tent in your basement, your cells won't care.
But again, it truly depends on if those "pods" can get hot enough and are insulated enough to boost your core temperature. Some portable saunas may not maintain heat very well, and some fail to get hot enough to produce the same effect as a traditional sauna.
I'd say if you have a bath or access to a traditional sauna, I wouldn't turn to a temporary sauna. But if it's what you'll have the easiest time using, a good-quality portable home sauna in your budget is worth looking into.
Q: I have a steam bath installed in my home and have one at my Club and use one or the other almost daily (I shave in the steam also – the best shave!). Does an equal time in the steam equate to the sauna – my steam at home is set at 110 degrees. Thanks, and love your stuff. – L.H.
A: Thanks for your support, L.H. And good news: your 110-degree steam bath is just as effective as an even hotter sauna. Here's why...
A traditional Finnish sauna has air temperatures of around 180 degrees Fahrenheit. But it's typically bone dry at usually 5% to 20% relative humidity.
Because the air is dry, your sweat evaporates quickly. That's your body's natural "air conditioning" system that keeps your core temperature from rising too fast.
Your steam bath, however, sits at 100% humidity. So even at 110 degrees, your sweat can't evaporate into air that's already saturated with water. So without your cooling system working, your core body temperature can skyrocket.
That's exactly what you want for heat therapy.
So a 15-minute session in your steam bath can still provide the same biological stress to boot on the cellular-repair response. You get the same cardiovascular workout and the same rush of HSPs. So keep enjoying that daily steam (and the great shave).
What We're Reading...
- Did you miss it? Sit, relax, and reverse aging.
- Something different: FDA pulls proposed rule barring teens from using tanning beds.
Here's to our health, wealth, and a great retirement,
Dr. David Eifrig and the Health & Wealth Bulletin Research Team
May 8, 2026