What I Changed in the Calculator (and Why)
Glucosamine out, sauna demoted, olive oil in, and the bottom tier retired.
Since the last update on the calculator, I've made a few changes. Let's delve... Ahem. Let's take a look!
Glucosamine removed
As part of my research on effects of supplements, I realized that healthy user bias is real and affected the recommendations for Vitamin E in the 1990s. Under that same criteria, the small minority who consistently take glucosamine for their joints is also likely to be a health motivated small group. In any case, the effect was not large, and I've removed it from the calculator as not worth recommending.
Sauna no longer stacks with aerobic exercise
Saunas are popular among longevity influencers, and I'm afraid I was pulled along with the hype. I recently reviewed the studies on them with a more critical eye, and two things stood out. One is that while additional weekly sessions, from one up to four to seven weekly, do appear to show more benefit, longer time per session (from under 11 to more than 19 minutes) does not show statistically improved longevity.[1] To guess why, it seems that cardiovascular issues continue to improve with longer sauna sessions, but other factors may not.
(Spot the typo! In Table 3 of the sauna study,[2] All-Cause Mortality for taking sauna baths for longer than 19 minutes is listed as having a Hazard Ratio (HR) of 0.83, but the 95% confidence interval is 0.87-1.20. It's impossible for the HR to be outside the confidence interval! The correct HR is probably 1.03, which then matches the confidence interval, the p-value, and is closer to the age-only HR.)
The bigger point, though, is that sauna adds nothing for people who are already fit. A Finnish study followed 2,277 men for 26 years, sorting them by both cardiorespiratory fitness and sauna habit.[3] Unfit men who took saunas often came in at a hazard ratio of 0.78 for all-cause mortality, compared with those who did neither. Fit men who took saunas often came in at 0.60, against 0.63 for fit men who rarely used one. Since the confidence intervals overlap, adding saunas for someone who is already fit doesn't provide statistically significant additional longevity. I've updated the calculator to only add longevity for people who are not currently doing aerobic exercise, and to not recommend saunas for people who are.
Nuts is now "Nuts or Olive Oil"
In looking at the dose-response curves for nuts and olive oil, they are strikingly similar. Both show a significant benefit at low daily doses: 20g of nuts or 10g of olive oil, with little additional benefit after that. In fact, the PREDIMED trial of the Mediterranean diet supplemented one group with extra-virgin olive oil and another with nuts, and found a similar reduction in cardiovascular disease in each, providing a randomized controlled test to confirm the benefits of both.[4]
There aren't that many commonalities between nuts and olive oil, so I assume the benefit is driven by the high amount of unsaturated fats in each. It's likely that avocados have a similar benefit, but no study has yet tested avocados against mortality.
Removed Tier D and No Effect Interventions
The focus of this longevity blog post is to identify and quantify the interventions that materially affect longevity. When I categorized interventions into tiers, the S-tier intervention of walking could add 7 years of expected life. A-Tier interventions like High Intensity Interval Training or Strength Training can provide over 2 years extra expected life. In comparison, the D-tier interventions are less than half a year each. Eating fruits and vegetables falls into this category, as well as brushing your teeth, drinking decaffeinated tea or coffee, or eating hot peppers at least once a month. Marginally useful, but if you capitalize on the more powerful interventions, these won't significantly change longevity further.
Also in this category is chicken and refined grains, neither of which appear to have a positive or negative benefit on overall lifespan. Replace where you can with healthier foods, but eat them guilt-free if that's what's available.