Summary of Health Canada’s safety assessment of grape seed extract for use as a supplemental ingredient

Abstract

Health Canada's Food and Nutrition Directorate assessed grape seed extract (GSE) for safety, based on publicly available information. The Food and Nutrition Directorate concluded that there was sufficient information to establish conditions under which standardized GSE could be consumed safely as a supplemental ingredient in supplemented foods. Consequently, Health Canada will permit the use of grape seed extract (oligomeric proanthocyanidins)^{Footnote 1} as a supplemental ingredient in supplemented foods under certain conditions. The conditions are outlined in the Notice of Modification.

Introduction

Between 2004 and 2012, after the Natural Health Products Regulations were put in place, Health Canada approved a number of products that had characteristics of both foods and natural health products (NHPs) as NHPs. This inadvertently created confusion among consumers and in 2012, following extensive consultations, Health Canada began regulating products that look like foods and are consumed as foods, as foods, noting that this would allow Canadians to make more informed choices due to consistent nutrition information and labelling requirements.

During the transition between regulatory frameworks, certain herbal and non-herbal ingredients in these products were identified as not having a history of safe food use, or were being used in these products at a level that was inconsistent with food use. As an interim measure, Health Canada used Temporary Marketing Authorizations to permit the sale of products, on a case-by-case basis and under specific conditions, while regulations were being developed for these types of products (that is, supplemented foods containing supplemental ingredients). Supplemental ingredients have historically been marketed as providing specific physiological or generally beneficial health effects. However, they can pose health risks if overconsumed by the general population, or if consumed by certain vulnerable populations.

Some of these ingredients, including GSE, were listed in Appendix 2 of Health Canada's Category Specific Guidance for Temporary Marketing Authorization: Supplemented Food, for further assessment to determine conditions (for example, use levels, specifications, and/or labelling statements), if any, under which they would be safe for use as supplemental ingredients.

The scientific information/studies that serve as the basis of the safety assessments were obtained from a search of publicly available primary literature, web searches on specific topics, and citations noted in other articles. This document summarizes the safety considerations that informed Health Canada's decision to allow the use of grape seed extract (oligomeric proanthocyanidins) as a supplemental ingredient.

Approach

The acceptability of a food ingredient typically considers its safety for the general population, over a lifetime of exposure with no limits on consumption; however, the safety assessment approach for supplemental ingredients gave further consideration to the potential use of cautionary labels to mitigate risks, when unlimited consumption may not be safe.

Based on the Food and Nutrition Directorate's safety assessment approach, only limited cautionary labelling is considered appropriate for foods containing supplemental ingredients (such as GSE). This labelling is designed to mitigate potential risk(s) identified for sensitive subpopulations, and to help ensure that the intake of the supplemental ingredient, through the diet, remains within acceptable (that is, safe) levels. Ingredients that require more extensive cautionary labelling (such as contraindications) to protect the consumer are not considered appropriate for food use. More information about labelling of Supplemented Foods is available in the Guidance Document: Supplemented Foods Regulations.

Safety assessment

The safety assessment included a review of the available information on GSE for the purposes of evaluating toxicological, nutritional and allergenicity endpoints. Based on this information, and in consideration of the background dietary exposures, a Recommended Maximum Daily Intake (RMDI) was derived for the use of GSE as a supplemental ingredient.

Characterization/standardization of the supplemental ingredient

GSE composition can vary with grape cultivar, year of production (that is, climate conditions), production site, maturation state, and extraction process (for example, solvents used). This safety assessment applies to grape seed extracts derived from the seeds of grape (Vitis vinifera L.), containing an oligomeric proanthocyanidin (the primary constituent of GSE) content ranging between 70% (minimum) and 90% (maximum). Acceptable preparations include dry extracts, fluid extracts, tinctures, decoctions and infusions obtained via water and/or food grade organic solvent extraction techniques. This safety assessment does not apply to modified forms of GSE or those with special carrier systems that could alter its bioavailability, distribution, metabolism or excretion when ingested.

Dietary exposure

GSE has a history of use as a food flavouring. The main constituent of GSE, proanthocyanidins, are naturally present in a wide variety of foods, including fruits, nuts, cereals/grains, beans, chocolate and spices. The mean daily dietary intake of proanthocyanidins was estimated to be 95 mg/day (Wang et al., 2011). This value was determined using the United States Department of Agriculture's Database for Proanthocyanidin Content of Selected Foods, as well as adult consumption data from the Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey (1999-2002). These values are considered a suitable proxy for the Canadian population, given that Canadian data are not available. Estimated exposures to proanthocyanidins from the use of GSE as a food flavouring were much lower.

Requirements for complying with the Supplemented Food Regulations

As with any food, the onus is on the food manufacturer or distributor to ensure that a food offered for sale in Canada complies with all regulatory provisions, including but not limited to requirements under the Food and Drugs Act (FDA) and the Safe Food for Canadians Act, and the Regulations associated with these Acts. This includes, for example, ensuring compliance with food labelling requirements, provisions for the use of food additives, and the general prohibitions in section 4 of the FDA, which prohibits selling a food that contains a poisonous or harmful substance.

More information on other requirements for Supplemented Foods is available in theGuidance Document: Supplemented Foods Regulations. These requirements are independent from the safety review of GSE itself, as described in this document.

Toxicological safety

Absorption, distribution, metabolism and excretion studies

Proanthocyanidins are poorly absorbed in the intestine, due to their large molecular weight. They are either excreted in the faeces or metabolised by colonic microflora into phenolic acids, which may be subsequently absorbed into the systemic circulation.

There is contradictory information regarding the capacity of the gastric environment to metabolise the more highly-polymerised proanthocyanidins into smaller constituents (that is, monomers and dimers). There is consistent evidence to show that only monomers (and possibly dimers) are absorbed to any great extent in the small intestine.

The monomers (that is, catechin and epicatechin) are readily methylated in the intestine and/or conjugated into glucuronides or sulphates in the liver. They are distributed rapidly to the plasma within about 3 hours. Both the monomers and phenolic acids are excreted in the urine, generally within 24 hours. There is no evidence of significant bioaccumulation.

Toxicology studies

Acute, subchronic, chronic, carcinogenicity, genotoxicity, reproductive, and developmental endpoints were considered to determine the potential toxicity of GSE, where available. Other endpoints considered included the effects of GSE on enzymatic activity and platelet function. Clinical studies and trials were also reviewed for evidence of toxicity. Results are summarized below (N.B. studies cited below are not exhaustive, but rather represent the studies that are critical to the conclusions of the safety assessment of GSE).

Three well-conducted 90-day oral (dietary) toxicity studies in rats, testing well-characterized GSE formulations, showed no treatment-related effects for a standard battery of toxicological endpoints (e.g., clinical observations, body weight and food consumption, organ weights, haematology, clinical chemistry, histology, pathology), at their respective highest doses tested. These studies (Yamakoshi et al., 2002; Wren et al., 2002; Bentivegna and Whitney, 2002) were considered adequate for hazard characterization, and the most appropriate (the study testing the highest dose) was used as the critical study for derivation of the RMDI (discussed below).

No chronic toxicity studies, meeting international standards for toxicological testing, including the fulsome reporting of a standard battery of toxicological endpoints, were identified in the literature. Long-term oral (dietary) studies in rodents, designed to determine the potential beneficial effects of GSE exposures (for example, to counter chemical-induced injury) up to 500 milligrams (mg)/kilogram (kg) body weight (bw) per day for up to 12 months, reported no overt toxicity, including no significant differences in mortality or cancer development (at the highest doses tested for all experiments). These were insufficient for hazard characterization but provide support for the aforementioned 90-day studies.

GSE did not induce mutagenicity or chromosomal aberrations in vitro under a variety of exposure conditions. Nor did it induce micronuclei in vivo when administered orally.

No reproductive and developmental toxicity studies, meeting international standards for toxicological testing, including the fulsome reporting of a standard battery of reproductive and developmental endpoints, were identified in the literature. The three 90-day oral toxicity studies reported no changes to relative or absolute reproductive organ weights, and no abnormalities were observed during histological examination. One study (Arola-Arnal et al., 2013) that assessed the distribution of GSE in pregnant rats reported significant concentrations of monomers (that is, catechin and epicatechin) from GSE in placental tissue, but significantly lower concentrations, if any, in foetuses and amniotic fluid. This suggests that the placenta may act as a barrier, although trace amounts of GSE constituents did appear to cross the placental barrier. The lack of well-conducted developmental toxicity studies in animals, as well as the paucity of relevant clinical data (see Clinical studies, below), supports cautionary labelling for supplemental use of GSE for certain sensitive subpopulations (that is, children and adolescents under 18 years of age, pregnant/breastfeeding individuals).

GSE appears to be a consistent and strong inhibitor of cytochrome P450 (CYP450) activity (examining a variety of isozymes) in vitro; however, the available animal and clinical studies reported inconsistent effects (of unknown biological significance), and/or effects that were not statistically significant. A possible explanation for the difference between the in vitro and in vivo observations is the limited bioavailability of GSE constituents. ADME data suggest that catechin monomers are absorbed to some extent; however, they may not be present at high enough concentrations to affect CYP450 activity in vivo.

Similarly, GSE affects platelet function (for example, increases clotting time) in vitro; however, the available animal and clinical studies provide only minimal evidence that these effects could occur in vivo. Again, the limited bioavailability of GSE constituents may limit their potential for effects on platelet function in vivo.

Recommended maximum daily intake (RMDI) derivation

GSE was administered in the diet to Sprague-Dawley rats over a 3-month period at doses up to 1788 and 2167 mg GSE/kg bw per day, in males and females, respectively, with no treatment-related effects observed (Bentivegna and Whitney, 2002). The no observed adverse effect level (NOAEL) of 1788 mg GSE/kg bw per day was used to establish safety levels. This NOAEL is equivalent to 1462 mg/kg bw per day of proanthocyanidins (based on 81.78% total proanthocyanidin content [excluding monomers] of the GSE test article).

Applying an uncertainty factor of 100 to account for inter- and intra-species differences, and an uncertainty factor of 5 to account for the subchronic (rather than chronic) duration of the critical study, the resultant critical point-of-departure was determined to be 205 mg proanthocyanidins per day^{Footnote 2}. The estimated background dietary exposure of approximately 95 mg proanthocyanidins per day was subtracted from the aforementioned point-of-departure, resulting in an RMDI of 100 mg proanthocyanidins per day (rounded value) for supplemental use from GSE. The available toxicology data do not support consumption at levels higher than the RMDI, and therefore GSE requires cautionary labelling for its supplemental use to prevent overconsumption.

Clinical studies

Most clinical studies of GSE were conducted primarily to determine its ability to improve a variety of health conditions/disorders, and not for acquiring data on its safety. Only two clinical studies (Sano et al., 2007 and Sano, 2017) examined toxicological parameters of GSE consumed by participants, up to 555 mg/day for 12 weeks and 2500 mg/day for 4 weeks, respectively. These short-term studies were small-scale (testing only 53 and 29 volunteers, respectively). However, GSE was well-tolerated during the treatment period, and no significant adverse effects were identified for the clinical, haematological, and biochemical parameters examined. These studies provide additional support of the safety and tolerability of use of GSE, but on their own does not provide sufficient evidence of long-term safety for the general population (including sensitive subpopulations).

None of the available clinical studies addressed the safety of supplemental GSE in children or pregnant/breastfeeding individuals. The lack of well-conducted developmental toxicity studies in animals, as well as the paucity of relevant clinical data, supports cautionary labelling for supplemental use of GSE for these sensitive subpopulations (that is, children and adolescents under 18 years of age, pregnant/breastfeeding individuals).

Allergenicity

Based on a fulsome review of the literature, no evidence of allergenicity of GSE was identified.

Nutritional safety

Proanthocyanidins are condensed tannins and have anti-nutrient effects. They have an affinity for binding proteins, which may result in a lower digestibility. However, proline-rich salivary proteins have a high affinity for proanthocyanidins, and their secretion may counteract the biological action of complexation of proanthocyanidins with dietary proteins (Santos-Buelga and Scalbert, 2000). In addition, Canadians consume adequate amounts of protein (Statistics Canada, 2021); therefore, any affinity of proanthocyanidins to bind dietary proteins is not expected to pose a nutritional risk at the proposed level and conditions of use for GSE as a supplemental ingredient.

There is evidence that polyphenols, which include proanthocyanidins, can bind iron, consequently inhibiting iron absorption; however, polyphenols must be ingested together with iron in order to inhibit its digestion, and the presence of ascorbic acid has been shown to reverse the inhibitory effects of polyphenols. Clinical trials indicate that doses of GSE up to 4.5 g per day in women (for 4 weeks) did not affect iron bioavailability or serum ferritin levels (Delimont et al., 2017). Further, GSE supplementation up to 1.5 g per day in healthy adults (for 4 weeks) showed no significant changes in serum iron levels (Sano, 2017). These results indicate that at the proposed level and conditions of use for GSE as a supplemental ingredient, there would not be a significant effect on iron status in healthy individuals.

However, it is noted that subsets of the Canadian population are at a greater risk of having depleted iron stores. Due to the possibility of decreased iron absorption, it is advisable for population groups most susceptible to developing iron deficiency (that is, children, adolescents, pregnant individuals) to avoid supplemental consumption of polyphenol-rich beverages and foods. Cautionary labelling is supported as a mitigation measure in these sensitive subpopulations.

Overall, no nutritional safety concerns were identified at the proposed level and conditions of use for GSE as a supplemental ingredient.

Conclusion and decision

Health Canada's Food and Nutrition Directorate determined there to be sufficient information to establish conditions under which standardized GSE would be safe for use as a supplemental ingredient in supplemented foods. Consequently, Health Canada will permit the use of grape seed extract (oligomeric proanthocyanidins) as a supplemental ingredient in supplemented foods under certain conditions. These conditions are outlined in the Notice of Modification.

Supplemental ingredient submissions for GSE

To propose future, additional changes to the conditions of use for grape seed extract (oligomeric proanthocyanidins) as a supplemental ingredient, stakeholders can submit a pre-market request to the Food and Nutrition Directorate as described in the Guidance document: Pre-market submission process for supplemented foods. Manufacturers and distributors are encouraged to request a pre-submission consultation with the Directorate to seek additional guidance so that a complete submission can be filed at the outset, potentially reducing the number of requests to the applicant for clarification or additional information, or preventing the submission from being rejected for incompleteness. Pre-submission consultations on supplemental ingredients may be arranged by contacting the Submission Management and Information Unit (smiu-ugdi@hc-sc.gc.ca).

The information set out below is recommended to be included in the submission, if relevant to the nature of the request.

For requests to include GSE formulations outside of the current grape seed extract (oligomeric proanthocyanidins) characterization, the submission must characterize in detail the GSE that is requested for supplemental use. It must also clearly demonstrate that the safety information in the submission applies to the requested GSE. For example, the submission must explain why the results of toxicity testing of a particular GSE formulation apply to the GSE to be used as a supplemental ingredient.

In general, any submitted safety information should be of good quality (for example, GLP/GCP and OECD compliant), and contain full study reports, not summaries. The reports should provide clear, detailed characterization of the GSE test material, and a full description of the study design, including methods, the type and number of animals treated, the doses administered, and the toxicological endpoints measured. Studies should also provide a detailed documentation of the test results. Similarly, the submission of clinical studies should provide fulsome details of the study design, providing toxicologically focused endpoints that contribute information to the assessment of the safety of the ingredient.

Future requests to modify grape seed extract (oligomeric proanthocyanidins) conditions, such as the RMDI or labelling, may require addressing data gaps that were identified in the current toxicological and nutritional assessments, such as the following:

Toxicological data gaps/uncertainties

1. Long-term (chronic) toxicity
2. Reproductive and developmental toxicity
3. Potential effects of GSE on platelet activity
4. Potential effects of GSE on drug-metabolizing enzymes (for example, CYP450) and potential GSE/drug interactions

Nutritional data gaps/uncertainties

1. Information that would provide adequate evidence that GSE would not affect digestion or absorption of other nutrients, especially in the intestines, and/or information that it would not pose nutritional safety concerns if foods supplemented with GSE were to be consumed frequently over a long period of time in different food matrices.

Health Canada may ask for additional data or other information related to the safety of GSE for use as a supplemental ingredient after reviewing the above information.

References

• Arola-Arnal, A., Oms-Oliu, G., Crescenti, A., del Bas, J.M., Ras, M.R., Arola, L., Caimari, A. 2013. Distribution of grape seed flavanols and their metabolites in pregnant rats and their fetuses. Mol. Nutr. Food Res. 57(10): 1741-1752.
• Bentivegna, S.S. and Whitney, K.M. 2002. Subchronic 3-month oral toxicity study of grape seed and grape skin extracts. Food Chem. Toxicol. 40(12): 1731-1743.
• Delimont, N.M., Fiorentino, N.M., Kimmel, K.A., Haub, M.D., Rosenkranz, S.K., Lindshield, B.L. 2017. Long-Term Dose-Response Condensed Tannin Supplementation Does Not Affect Iron Status or Bioavailability. Curr. Dev. Nutr. 1(10): e001081. doi:10.3945/cdnd.117.001081
• Sano, A., Uchida, R., Saito, M., Shioya, N., Komori, Y., Tho, Y., Hashizume, N. 2007. Beneficial Effects of Grape Seed Extract on Malondialdehyde-Modified LDL. J. Nutr. Sci. Vitaminol. 53(2): 174-182.
• Sano, A. 2017. Safety assessment of 4-week oral intake of proanthocyanidin-rich grape seed extract in healthy subjects. Food Chem. Toxicol. 108(Pt B): 519-523.
• Santos-Buelga, C., Scalbert, A. 2000. Proanthocyanidins and tannin-like compounds – nature, occurrence, dietary intake and effects on nutrition and health. J. Sci. Food Agric. 80: 1094-1117.
• Statistics Canada. 2021. https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=1310077101 Table 13-10-0771-01. Percentage of total energy intake from protein, by dietary reference intake age-sex group, household population aged 1 and over, Canadian Community Health Survey (CCHS) - Nutrition, Canada and provinces. Available from: https://doi.org/10.25318/1310077101-eng
• Wang, Y., Chung, S-J., Song, W.O., Chun, O.K. 2011. Estimation of daily proanthocyanidin intake and major food sources in the U.S. diet. J. Nutr. 141(3): 447-452.
• Wren, A.F., Cleary, M., Frantz, C., Melton, S., Norris, L. 2002. 90-Day Oral Toxicity Study of a Grape Seed Extract (IH636) in Rats. J. Agric. Food Chem. 50(7): 2180-2192.
• Yamakoshi, J., Saito, M., Kataoka, S., Kikuchi, M. 2002. Safety evaluation of proanthocyanidin-rich extract from grape seeds. Food Chem. Toxicol. 40(5): 599-607.