Liver injury due to green tea supplements typically manifests within 3 mo of chronic ingestion; however, the latency to onset of symptoms can range from 10 d to 7 mo . Most cases present symptoms of acute hepatitis accompanied by marked hepatocellular enzyme elevations. Under specific conditions such as fasting, higher doses and repeated administration of green tea extract result in systemic plasma catechin concentrations that are substantially higher than when ingested under fed conditions and/or low single doses. Damage to the liver can occur through the first- and second-phase metabolism of catechins when saturation of drug metabolizing enzymes occurs. In several animal toxicity studies, EGCG has been shown to accumulate in the liver causing dose-dependent liver necrosis resulting in the primary cause-of-death in test animals . Toxicity worsened when EGCG was administered as a high-dose supplement to animals under fasting conditions. Other reported adverse effects of flavan-3- ol preparations include gastrointestinal distress , dizziness, and muscle fatigue . In animal models, absorbed EGCG damaged the gastrointestinal tract in a dose-dependent manner . The Expert Panel also considered several assessments and opinions by authoritative scientific bodies that provided guidance around the safety of green tea extracts or EGCG including the US Pharmacopeia , Health Canada , EFSA , and Norwegian Institute of Public Health . Each has provided cautionary guidance around the use of high-dose supplemental green tea extracts or EGCG. For example,gutter berries the recent scientific opinion from EFSA regarding the safety of green tea catechins concluded that there is evidence from clinical trials that intake of doses ≥800 mg EGCG/d taken in supplemental form can increase serum transaminases.

Similarly, the Chinese Nutrition Society has proposed a 800 mg/d tolerable upper intake level for proanthocyanidins . As such, foods including tea, cocoa,cinnamon, apples, and berries should be prioritized over supplementation when seeking potential cardiometabolic benefits from flavan-3-ols.In order to assess the health equity of the guideline, it must be acknowledged that mean dietary intake of flavan- 3-ols varies greatly among the general adult population. For example, in the United States, the mean intake is 223 mg/d compared with 793 mg/d in Ireland . Across the globe, the greatest food sources of flavan-3-ols include tea, apples, pears, berries, and chocolate/cocoa products . Despite the variety of flavan-3-ol sources, intake analysis from the NHANES 2007–2016 shows tea accounting for 35– 94% of dietary flavan-3-ol intake in the United States . Among tea consumers, consumption was highest in older adults, non-Hispanic Whites, Asians, and individuals with higher education and socioeconomic status . Thus, these results suggest that the equity of health benefits derived from flavan-3-ols might not be achieved equally across all populations. Regarding acceptability and feasibility, the key question is how stakeholders accept or agree with the conferred effects including benefits or harms as well as cost associated with adopting the guideline. First, given the pervasiveness of cardiometabolic diseases in the general adult population, individual awareness of these diseases has increased, especially among women . Thus, practical approaches to reduce risk are warranted. Acknowledging the high benefit-to-risk ratio when flavan-3-ols are consumed in the recommended range of 400–600 mg/d, it is advantageous that foods rich in flavan-3-ols are among the most highly consumed flavonoids by the general population . Further, the fact that each can be consumed in many forms at a variety of cost points extends the feasibility of the guideline. To highlight feasibility, estimated flavan-3-ol contents of primary food sources are provided in Table 4 along with standard serving sizes . Practically speaking, a combination of foods listed allows for intake in the range of the guideline recommendation for cardiometabolic health benefits. Finally, it should be noted that foods in this list with greatest alignment to the Dietary Guidelines for Americans 2020–2025 should comprise the majority of sources for bolstering flavan-3-ol intake .

The health efficacy of this bio-active guideline recommendation is dependent upon the bio-activity of flavan-3-ols. Thus, special populations such as those with autoimmune, cancer, and kidney or liver diseases can have altered absorption, distribution, metabolism, and excretion, thus affecting the bio-availability and subsequent effectiveness of phenolic compounds in food . Similarly, specific life stages, such as pregnancy, can also affect the bioactivity of phenolic compounds. For example, some clinical trials evaluating flavan-3-ol intake from berries and cocoa/chocolate products on health outcomes in pregnancy showed improvement in maternal weight gain, glycemic control, inflammation, and placental function .Although this bio-active can be consumed in supplement form, it should be noted that a supplement is intended to complement or enhance the diet. By the very definition, a supplement is defined as a dietary substance to supplement the diet by increasing the total dietary intake . Because toxicity is more commonly associated with high-dose single nutrient supplementation than with foods , a food first approach to flavan-3-ol intake could capitalize on the potential synergy of this bio-active with other nutrients in the food matrix while also minimizing risks associated with intake of supraphysiological doses of individual compounds from extracts or supplements. Furthermore, this guideline is a food-based guideline and not a recommendation for flavan- 3-ol supplements. Lastly, as foods provide an assortment of nutrients and bio-active compounds with benefits for health, the Dietary Guidelines for Americans 2020–2025 and Canada’s Dietary Guidelines recognize that nutrition requirements should be met primarily through foods .A guideline recommendation for a plant bio-active such as flavan-3-ols is a departure from previous recommendations as it is not based on deficiencies but rather improvement in health outcomes. The Expert Panel found moderate evidence supporting cardiometabolic protection resulting from flavan-3-ol intake such that we are proposing the first dietary recommendation for a bio-active compound.

The recommendation of 400–600 mg/d for flavan-3-ols to improve cardiometabolic health is based on beneficial effects observed across a range of disease biomarkers and endpoints. This recommendation is higher than the recent health claim of 200 mg/d for cocoa-flavanols by EFSA . The main reason for this discrepancy is that the EFSA health claim is only based on vasodilation as an endpoint and no other cardiometabolic disease markers. Regarding upper intake limits for flavan-3-ols, risk assessments of green tea catechins by EFSA concluded that no adverse effects are expected for intakes <800 mg/d . It must be acknowledged that challenges were encountered in establishing this guideline, such as limitations from lack of homogeneity in protocols. For example, studies included in the Raman et al. systematic review/meta-analysis reported large discrepancies in quality as well as lack of consensus in population description, duration of supplementation, form of bio-active/food/extract, and statistical methods . Implementing methodological consensus in executing and describing randomized clinical trials would allow for more rigorous assessment of study findings for comparison and pooling of data. Other limitations include the following: inclusion of more men than women in randomized clinical trials, different biomarkers used to assess prevention and development of cardiometabolic disease, and heterogeneity in dosages examined along with metabolism and assessment of circulating concentrations, which was not routinely evaluated. Additionally, it should be noted that cohort studies often relied on self-reported dietary intake, often at one time point, to assess benefit, which could contribute to information bias compromising internal validity; furthermore, the estimates of flavan-3-ol exposure were calculated from different food composition databases,strawberry gutter system which could preclude precise comparability. Although FFQ data can clearly differentiate between extremes of intake, this assessment method does not account for the extensive interindividual metabolism that these compounds undergo after ingestion, which could impact effectiveness. As such, future studies should integrate biomarker, genetic, and dietary assessment methods to assess the effect of flavan-3-ols and their metabolites on cardiometabolic health. Considering a lack of homogeneity among studies, several research considerations would improve the generalizability of results from randomized clinical trials. For example, dose-dependent trials are warranted to assess minimal and maximal dose effects along with identifying potential negative effects from higher doses. Additional repository databases should be developed not only to report studies, but also to archive raw data and results to allow future ancillary analyses. This would allow for comparison and merging of results, thus increasing the total sample size,thereby increasing statistical power. Further, standardization in biomarkers of intake and exposure to flavan-3-ols is warranted. For example, γ -valerolactones, a flavan-3-ol metabolite formed by the colonic microbiome, can be used as markers of chronic flavan-3-ol intake . Future research should also include more diverse populations to assess interindividual variability for optimizing dietary recommendations and food product development, especially for specific population subgroups.

Further, although this guideline was developed from research on the general adult population, additional research evaluating flavan-3-ol intake earlier in the lifespan is warranted because dietary habits adopted earlier in life can contribute to the magnitude of effect of flavan-3-ols on cardiometabolic health. In conclusion, when quality evidence is available to make an evidence-based intake guideline, such a recommendation can inform multiple stakeholders including clinicians, policymakers, public health entities, and consumers. Evidence gaps identified in the review process can inform scientists, thereby guiding future randomized clinical trials. In summary, upon review of data from human studies reporting effects of foods rich in flavon-3-ols, the Expert Panel found moderate evidence supporting cardiometabolic protection resulting from flavan-3-ol intake in the range of 400–600 mg/d. It should be noted that the beneficial effects were observed across a range of disease biomarkers and endpoints; furthermore, this is a food-based guideline and not a recommendation for flavan-3-ol supplements.

Surface mulches are widely used in the production of strawberries and certain high value vegetable crops. Polyethylene mulch is used on virtually all tomato and strawberry production in Florida and is also widely used in the production of other crops such as peppers, eggplant, and melons throughout much of the southern United States. Researchers at the University of Florida estimate that more than 100,000 acres of vegetable crops in that state currently use plastic mulches annually, making Florida the national leader in this production system . In California, the majority of strawberry and staked tomato production uses polyethylene mulch. Peppers, eggplant, and melons also use mulches in certain situations, especially when earliness is desired. Field management and research related to plastic mulches in these production regions is now quite developed. Potential benefits as well as drawbacks of polyethylene mulches for vegetable crop production are given in table 1. The use of inter crop cover crop residues as surface mulches is a more recent and far less widely used production practice. It has recently gained considerable interest in a number of commercial vegetable crop production regions in the United States. Potential advantages and disadvantages of this vegetable crop production technique are summarized in table 2. Reflective plastic and some cover crop mulches share similar features relative to crop production: insect and disease management, weed management, fertilizer availability, and water conservation. In order for production practices using either polyethylene or cover crop mulches to be successfully adopted in California, specific production goals must be carefully matched with specialized management know how and experience.Plastic mulches have been commonly used for commercial vegetable crop production for more than 30 years. Excellent sources of information on specific characteristics and applications of plastic mulches are available on the World Wide Web, and several of these are provided in the references to this publication. Most plastic mulch materials are made of either high- or low-density polyethylene, ranging from 0.30 to 0.79 inches in thickness, are 5 to 6 feet wide, and are available on rolls 555 to 1,338 yards long, depending on the thickness of the mulch . The color of mulch is an important determinant of the microclimate around a crop plant. Black, white, and clear plastic mulches are most commonly used in commercial production, with black being the dominant color used for vegetables. Black plastic mulch is typically used for spring-seeded crops because it increases soil temperatures about 5ºF at a depth of 2 inches and 3ºF at 4 inches , compared to those of bare soil . Recently, a mulch has been introduced that consists of a strip of black plastic 30 cm wide down the center that is flanked on either side by metalized reflective plastic. This plastic combines the advantages of black plastic over the seed row, to help heat the soil, with the reflective characteristics of metalized plastic for insect and disease management. Black mulches have also recently been shown to reduce weed growth.