Several more studies are required to assess the clinical efficacy of the various treatments, even though hundreds of nutraceuticals have been examined for their potential benefit or damage in hepatic or pancreatic disease. Despite the fact that studies have revealed that many nutraceuticals have potential therapeutic properties that can be measured at the cellular and/or molecular level, proving clinical efficacy can be significantly trickier. It is difficult to determine any real effect from nutraceuticals because of confounding factors like co-administered compounds (e.g., drugs, herbal remedies, other nutraceuticals), questionable nutraceutical purity, and a lack of useful control populations. Reports of positive clinical responses of veterinary patients to nutraceuticals are largely limited to anecdotal evidence or individual case reports.

Com­mercially available nutraceuticals frequently differ significantly in quality and content of active components between brands (and frequently between lots within a brand); many manufacturers consider their formulations “proprietary” and refuse to divulge contents; and researchers frequently use purified and/or extracts of individual nutraceutical constituents rather than the products as available for use, making it difficult to compare studies. Numerous nations have lax regulations on herbal, supplement, and nutraceutical items, putting the user at the whim of the producer in terms of product quality and safety.

In vitro-effective nutritional supplements may not be able to achieve the plasma concentrations needed for any therapeutic impact due to poor bioavailability or quick clearance. Due to physiochemical qualities  or the presence or lack of suitable transporter molecules, substances that reach good plasma levels may be unable to distribute to target tissues. Some dietary supplements could be toxic to specific bodily tissues while being healthy to others. For instance, silymarin, a hepatoprotective substance, has been demonstrated to increase the growth of breast cancers; similarly, silibinin possesses hepatoprotective qualities but when combined with ethanol can accelerate the advancement of ethanol-dependent hepatocellular carcinoma.

The acute injury caused by endogenous and exogenous hepatotoxic agents may be inhibited or minimised by nutraceuticals with antioxidant, anti-inflammatory, and/or antifibrotic activities in the liver. These nutraceuticals may also prevent or slow the progression of chronic liver disorders like hepatic lipidosis, chronic active hepatitis, liver storage diseases, and hepatic carcinogenesis. Potential negative effects of nutraceuticals need to be investigated and documented, though, as altered hepatic metabolic enzymes, diminished inflammatory/immune responses, and stimulation of hepatocellular proliferation can have unfavourable effects like interfering with therapeutic agents, lowered hepatic immune surveillance, or increased risk of hepatic neoplasia. 

The majority of dietary supplements lack information on long-term safety and carcinogenicity, as well as the regulatory necessity to monitor side effects. There have been reports of illnesses and fatalities in humans and animals linked to the accidental or deliberate addition of biotoxins, heavy metals, mycotoxins, pesticide residues, medications, toxic plants, and other potentially dangerous substances to nutraceuticals. Before it is possible to assess the safety and effectiveness of nutraceutical goods, these challenges need to be addressed through additional research.