Is spermidine from food just as good as a supplement?
There is no evidence that a spermidine supplement does the same thing as spermidine from food; supplements may be neutralised by the body and the effective dose in humans is unknown. If you want to increase your spermidine intake, opt for spermidine-rich foods.
Spermidine occurs naturally in many foods, and people who eat relatively large amounts of it live longer on average and have lower rates of cardiovascular disease. Centenarians have higher blood polyamine levels than their peers. That sounds encouraging, but these are associations drawn from dietary questionnaires: someone who eats a lot of spermidine-rich foods (such as fermented cheese, soy and wholegrains) probably also follows a healthier diet in general, and that alone could explain the difference.
The real question is whether a supplement does the same thing. That has not yet been demonstrated. A well-designed trial giving 40 mg per day of high-purity spermidine supplement to men aged fifty to seventy found that after 28 days the spermidine concentration in both blood and urine did not rise at all. The body apparently regulates its own polyamine balance strictly, allowing a supplement to pass straight through without changing anything. Two authors of this study are employed by the manufacturer, which makes the findings somewhat less informative, but the mechanism is consistent with broader physiological knowledge.
A randomised trial in one hundred older adults with memory complaints (aged 60 to 90, 12 months at 0.9 mg/day from wheat germ extract) found no measurable memory benefit compared with placebo. The researchers suggest the dose may have been too low, but nobody yet knows what dose would actually work.
In animal research the effects of spermidine supplements are impressive: mice live longer and their cardiac function improves. The mechanism of action via cellular cleaning is well described. But animal results have so far not translated into comparable findings in humans, and direct comparisons between dietary spermidine and supplements have not been carried out in people.
In short: the rating for all goals is 'not recommended'. The effective dose in humans is unknown, supplements appear to be partly neutralised by the body, and it has not been investigated whether a supplement has the same bioavailability as spermidine from food. If you want to increase your intake, spermidine-rich foods (aged cheese, soybeans, mushrooms, wholegrains) are the only approach for which any positive association in humans exists at all, even though cause and effect have not been proven by that evidence.
This answer rests on several layers of evidence. The association between dietary spermidine and longevity or blood pressure comes from studies in which people were followed over longer periods, which cannot prove cause and effect. The supplement studies in humans are small and short, with mixed outcomes: one study saw no rise in blood spermidine after 28 days of high-dose supplementation, and one study found no cognitive benefit after 12 months. The animal research is convincing but not translatable to humans. The researchers behind the SmartAge trial (cognition) themselves recommend higher doses for follow-up research, indicating that they regard their own study as insufficient evidence. A pilot study with five participants provides only exploratory indications.
Does spermidine actually do anything against ageing?
Spermidine shows a measurable effect on the immune system in a small study of older people. Whether it genuinely slows ageing will only become clear once the large ongoing studies are complete.
Does shilajit actually work as a supplement?
Shilajit has shown positive results for specific goals, such as testosterone in men aged 45 to 55 and bone healing, but it does not work for everyone or for everything. Do not use it during pregnancy.
Is taking a stack of supplements at the same time dangerous?
Whether a supplement stack is smart or dangerous depends on which substances you combine and whether you also take medicines. Always tell your doctor or pharmacist what you are taking, and be especially careful with St John's wort and goldenseal.
Is colostrum (beestings) a worthwhile supplement?
For now, colostrum has the strongest indications as an aid against respiratory tract infections in athletes; for most other claims the evidence is too thin or too contradictory to recommend anything.
Is rapamycin found in food, or can you get it naturally through your diet?
Rapamycin is not present in food and cannot be obtained naturally through eating. If you want to learn more about it in the context of health or ageing, discuss it with your doctor.
Which supplements are worthwhile after forty?
A few supplements have reasonably solid backing after forty: calcium plus vitamin D for bone protection, B vitamins and a daily multivitamin for cognitive maintenance, and adequate protein for muscle preservation. Collagen is worthwhile for skin.