A compound found in broccoli and other cruciferous vegetables has been found to hinder the replication of coronaviruses in human cells and live rodents. When everyone from your parents to nutritionists told you to eat your greens, they may have been more right than they knew.
Whether it will do the same in human trials is still undetermined, but if you insist on taking unproven medications, biting into a brassica is probably a lot better for you than Ivermectin or hydroxychloroquine, let alone bleach.
Sulforaphane is a phytochemical found in vegetables such as Brussel sprouts, kale, and broccoli – what many consider diverse vegetables that are all actually the same species, Brassica oleracea. It has already been identified as a likely cause of the healthy effects of a diet rich in leafy green vegetables, offering suspected protection against cancer, schizophrenia, and, perhaps more relevantly, lung damage from acute respiratory distress syndrome.
Researchers have been investigating sulforaphane's use against viruses in cultured human cells – and in the journal Communications Biology, a team has announced encouraging results. Molecules that work against pathogens in cells in the lab are common, as XKCD reminds us, but this study goes further, demonstrating the benefits in mice.
"When the COVID-19 pandemic started, our multidisciplinary research teams switched our investigations of other viruses and bacteria to focus on a potential treatment for what was then a challenging new virus for us," senior study author Dr Lori Jones-Brando of Johns Hopkins University said in a statement. "I was screening multiple compounds for anti-coronavirus activity and decided to try sulforaphane since it has shown modest activity against other microbial agents that we study."
Jones-Brando and colleagues exposed tissue cultures to sulforaphane then infected them with either SARS-CoV-s or another coronavirus, HcoV-OC43, one cause of the common cold. Even at a few parts per million, sulforaphane exposure reduced viral replication by about 50 percent. The results were similar to exposure to remdesivir, the first medication approved for COVID-19, but at a fraction of the cost.
Low doses of the two together worked better than higher concentrations of either on their own. Even when the virus was applied first, the sulforaphane reduced replication rates.
Importantly, these findings applied to six COVID-19 strains, including both delta and omicron. If – and it remains a big if – the results translate to living humans, they would indicate broad-spectrum protection likely to apply to future variants which may evade existing vaccines and medications.
The authors think this is because sulforaphane is a “host-directed therapy” that alters mechanisms in cells that allow viruses to infect them and replicate, rather than a direct attack on aspects of the virus. Sulforaphane's antioxidant effects are probably also beneficial when viruses often increase reactive oxygen species.
Mice pretreated with sulforaphane had lower viral loads and lost less weight when infected with SARS-CoV-2 – and most importantly, suffered less lung damage. Nevertheless, the results here were less dramatic than in human cells.
Sulforaphane's benefits for other conditions have been known for long enough that supplements are widely available. The authors caution that people shouldn't rush to buy these in the absence of further study. They certainly shouldn't think popping supplements is grounds for abandoning other COVID-avoidance strategies like vaccination, mask-wearing, or social distancing.
The work has parallels with recent evidence carnosic acid, found in rosemary, could be protective against COVID-19. Carnosic acid is under investigation for controlling Alzheimer's disease. In both cases, the slow cautious approach taken by the scientists conducting the investigation stands in contrast to the frantic boosterism of quack cure advocates.
The research team are hoping to conduct clinical trials of sulforaphane in humans. In the meantime, eating more broccoli may or may not save you from COVID-19, but it will certainly do you good in other ways, and the side effects are mild.