A recent 2021 study has found that spermidine promotes melanin production. The aging process causes melanocytes to decrease, leading to gray hairs. Although, implementing spermidine allows the melanocytes to function more effectively, leading to an increase in melanin production and a decrease in gray hairs.

Polyamines spermine, spermidine, and putrescine and their effects on the cellular function and the expression of adhesion molecules on human peripheral blood mononuclear cells, or PBMCs, were studied from healthy volunteers.

An article written by authors at the prestigious National Institute of Health (NIH) in the United States suggested increasing dietary and supplemental spermidine:

"Thus, it could be relatively easy for most people to get the benefits of spermidine through dietary modifications or by supplementation, and thus validate its potential as a new therapeutic approach for cardioprotection against aging."

The longevity effects of spermidine were explored in this study. It reported that the administration of spermidine extends the lifespan of yeast, flies, worms, and human immune cells.

A recent Viewpoint published in Microbial Cell, highlights the role that virophagy (a subform of autophagy that directly eliminates viruses) plays with respect to coronaviruses. Autophagy is the cellular process whereby defective, unwanted, or superfluous components of the cell are eliminated or recycled via a fusion with the lysosome.

A 2018 study published in the American Journal of Clinical Nutrition found that higher dietary intake of spermidine is associated with a lower risk of mortality. This was a prospective, population based study of 829 participants, aged 40-79 years, which looked at 118 item food frequency questionnaires.

Oral supplementation of the natural polyamine spermidine extends the lifespan of mice and exerts cardioprotective effects, reducing cardiac hypertrophy and preserving diastolic function in old mice.

Conducted by Frank Madeo, Maria A. Bauer, Didac Carmona-Gutierrez, and Guido Kroemer, this article discusses nutritional and other possible routes to counteract the age-mediated decline of spermidine levels.

Researchers have found that calorie restriction is one way to increase lifespan. However, the levels of caloric restriction necessary to achieve this are often unrealistic for the average person, and may lead to nutrient deficiencies or other negative effects throughout the body.

A 2020 cross-sectional study published in NeuroImage, looked at the association between dietary intakes of spermidine and brain structure in older adults, finding that those with the highest intakes of spermidine had significantly greater hippocampal volume, and both greater mean cortical thickness and cortical thickness in regions vulnerable to Alzheimer’s disease.

The purpose of this epidemiological study, conducted by the Jichi Medical University, was to examine the contribution of dietary polyamines including spermidine toward preventing cardiovascular disease (CVD). The results showed that polyamines including spermidine had significantly negative associations with CVD.

In this randomized controlled trial, cognitively intact participants with subjective cognitive decline were included in this three-month, placebo-controlled trial with a spermidine-rich plant extract supplement.

This study concluded that spermidine reduces lipid accumulation and neurotic core formation in atherosclerotic plaques in mice. Additionally, spermidine reduces lipid accumulation in vascular smooth muscle cells and also mediates cholesterol efflux in vascular smooth muscle cells by the induction of autophagy.

In this study, neuronal cell injury was induced by treating PC12 cells and cortical neurons with 1 μM staurosporine (STS). They found that STS-induced cell injury could be efficiently attenuated by pretreatment with 1 mM spermidine.

A 2015 study in the Simon Lab at Oxford University establishes how spermidine makes memory T-cells recognize foreign invaders like flu, virus and bacteria, and protects the body against them.

An Oxford University team has demonstrated that spermidine induces autophagy and boosts older immune systems. This study shows that when elderly mice (corresponding to 90-year-old humans) are given spermidine and a vaccine together, the older mice have a better immune response than younger mice (corresponding to 20-year-old humans) who are also given a spermidine and vaccine cocktail.

A team at the Charite Hospital in Berlin has reported that human cells exposed in vitro (meaning 'outside the body') to spermidine and Covid-19 at the same time were better able to withstand infection and spread than human cells exposed only to Covid-19.