Writing in the journal Scientific Reports, a team of Italian university researchers set out to determine whether a seaweed extract would first enhance crop growth and quality by increasing plant mineral uptake and then how daily consumption of bio-augmented lettuce would affect mineral homeostasis in healthy adults.
“The results are of interest in the context of dietary iron deficiency especially among populations that avoid meat-based diets,” the researchers reported. “This research could have broad implications for enhancing the nutritional value of plant-based foods to support dietary health by promoting the intersection of sustainable agriculture and human nutrition.”
The study also evaluated the influence of the lettuce-induced iron homeostasis on essential metabolic pathways, noting that the impact of consuming seaweed-stimulated plants on human health had not yet been explored.
An agronomic approach to mineral deficiency
Previous research shows that plant biostimulants like seaweed extracts may be used to reduce the use of chemicals and increase crop tolerance to abiotic stressors like nutrient deficiency, drought and salinity—ultimately improving crop yield and quality.
In the current study, the researchers used an extract of Ecklonia maxima, a kelp species typically found along the southern Atlantic coast of Africa, and chose lettuce as test subject since it is one of the most widely consumed vegetables worldwide across all seasons.
“Similar to humans, where minerals have different important functions (immune function, regulates fluid balance, enzyme function, energy production), minerals have numerous essential roles [in plants] such as providing osmotic [processes] for turgor and growth, structural components and enzyme activation,” the researchers wrote. “The analysis showed a significantly increase in iron concentration of lettuce with SwE application while no differences were observed for the other minerals analyzed among the control and biostimulant lettuce.”
Regarding the impact on humans, they noted that the growing population at risk of mineral deficiency includes older adults, people with chronic illnesses, pregnant women, growing children, athletes, vegans and vegetarians, and those on weight reduction regimes.
Evaluating the effects in humans
The randomized, placebo-controlled trial assigned a group of 48 healthy adults (15 males and 33 females) to consume either 100 g a day of control lettuce, the lettuce with a seaweed application (SwE) or an iron tablet (30 mg) for four weeks.
Blood samples were collected at baseline and at the end of the trial to assess differences in serum mineral concentrations, as well as iron homeostasis, lipid profile and fasting glucose and insulin.
“In lettuce, the seaweed extract biostimulant enhanced iron concentration by about 63%,” the researchers wrote. “The consumption of lettuce with SwE application increased serum iron by about 38%, transferrin saturation by about 47%, and reduced total cholesterol by about 19% and low-density lipoprotein by about 22%.”
No changes in blood mineral concentration were observed in the control lettuce group, and the consumption of the intervention lettuce did not affect serum concentrations of the other minerals (potassium, calcium, magnesium and phosphorus). Iron supplementation in tablet form showed similar effects to lettuce with SwE application but was accompanied by diarrhea or constipation, the researchers noted.
They called for further research in a larger group for a longer study period, investigation of long-term effects of seaweed extract-enriched crops and expanding the study to populations with iron deficiencies.
Source: Scientific Reports. doi: 10.1038/s41598-025-91380-7. “Consumption of lettuce with seaweed extract biostimulant application improved iron homeostasis in a randomized interventional trial of healthy individuals”. Authors: Francesca Di Gaudio et al.
