Effects of coffee on serum cholesterol and lipoproteins: the Italian brewing method. Italian Group for the Study of Atherosclerosis and Dismetabolic Diseases, Rome II Center

The effects of foods on LDL cholesterol levels: A systematic review of the accumulated evidence from systematic reviews and meta-analyses of randomized controlled trials

AIMS

To systematically evaluate the evidence regarding the effects of foods on LDL cholesterol levels and to compare the findings with current guidelines.

DATA SYNTHESIS

From inception through June 2019, we searched PubMed, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials for guidelines, systematic reviews, and RCTs (for coffee intake only) of at least 13 days duration. Additionally, we searched Trip database for guidelines from 2009 through Oct 2019. Language was restricted to English. The strength of evidence was evaluated using The Grading of Recommendations Assessment, Development, and Evaluation (GRADE). A total of 37 guidelines, 108 systematic reviews, and 20 RCTs were included. With high evidence, foods high in unsaturated and low in saturated and trans fatty acids (e.g. rapeseed/canola oil), with added plant sterols/stanols, and high in soluble fiber (e.g. oats, barley, and psyllium) caused at least moderate (i.e. 0.20-0.40 mmol/L) reductions in LDL cholesterol. Unfiltered coffee caused a moderate to large increase. Soy protein, tomatoes, flaxseeds, and almonds caused small reductions. With moderate evidence, avocados and turmeric caused moderate to large reductions. Pulses, hazelnuts, walnuts, high-fiber/wholegrain foods, and green tea caused small to moderate reductions, whereas sugar caused a small increase. Other identified foods were either neutral or had low or very low evidence regarding their effects.

CONCLUSIONS

Several foods distinctly modify LDL cholesterol levels. The results may aid future guidelines and dietary advice for hypercholesterolemia.

Impact of Coffee Consumption on Physiological Markers of Cardiovascular Risk: A Systematic Review

BACKGROUND

Coffee is one of the most widely consumed beverages globally. A substantial number of observational data suggest an inverse relationship between coffee consumption and the risk for cardiovascular disease. The basis for this association is not clear. In this review, we specifically study the impact of coffee on inflammatory biomarkers as one potential mechanistic basis for this observation. Our objective was to systematically review randomized controlled trials that examined the effects of coffee consumption on selected cardiovascular biomarkers.

METHODS

We systematically reviewed bibliographic databases including PubMed (NCBI), Embase (Elsevier), CINAHL (EBSCO), Web of Science (Clarivate Analytics), Cochrane Central Register of Controlled Trials (EBSCO), and CAB Abstracts (Clarivate Analytics). We searched for randomized controlled trials that studied the effect of drinking coffee on inflammatory markers of cardiovascular risk.

RESULTS

The search of electronic databases returned 1631 records. After removing duplicate records and ineligible studies, we examined a total of 40 full-text documents, 17 of which were eligible for further analysis. In our review, boiled coffee, in particular, appeared to raise total and low-density lipoprotein cholesterol and apolipoprotein B, but evidence suggests no similar effect for filtered coffee. One study showed a significant increase in blood interleukin 6 levels among individuals who drank caffeinated coffee, compared with individuals consuming no coffee.

CONCLUSION

Based on our systematic review of randomized controlled studies, we cannot confidently conclude that an anti-inflammatory effect of coffee is a major contributing factor to the lower all-cause mortality reported in observational studies.

Coffee consumption and serum lipids: a meta-analysis of randomized controlled clinical trials

Coffee drinking has been associated with increased serum cholesterol levels in some, but not all, studies. A Medline search of the English-language literature published prior to December 1998, a bibliography review, and consultations with experts were performed to identify 14 published trials of coffee consumption. Information was abstracted independently by two reviewers using a standardized protocol. With a random-effects model, treatment effects were estimated by pooling results from individual trials after weighting the results by the inverse of total variance. A dose-response relation between coffee consumption and both total cholesterol and LDL cholesterol was identified (p < 0.01). Increases in serum lipids were greater in studies of patients with hyperlipidemia and in trials of caffeinated or boiled coffee. Trials using filtered coffee demonstrated very little increase in serum cholesterol. Consumption of unfiltered, but not filtered, coffee increases serum levels of total and LDL cholesterol.

Analysis of the content of the diterpenes cafestol and kahweol in coffee brews

The diterpenes cafestol and kahweol have been implicated as the components in boiled coffee responsible for its hypercholesterolaemic effects. These particular coffee constituents have also been shown to possess anticarcinogenic effects. A simple and sensitive reverse-phase HPLC method using solid-phase extraction has been developed for the analysis of cafestol and kahweol in coffee brews. This method was used to confirm that the method of coffee brewing is a major determinant of the cup content and hence level of consumption of these diterpenes. Scandinavian-style boiled coffee and Turkish-style coffee contained the highest amounts, equivalent to 7.2 and 5.3 mg cafestol per cup and 7.2 and 5.4 mg kahweol per cup, respectively. In contrast, instant and drip-filtered coffee brews contained negligible amounts of these diterpenes, and espresso coffee contained intermediate amounts, about 1 mg cafestol and 1 mg kahweol per cup. These findings provide an explanation for the hypercholesterolaemic effect previously observed for boiled coffee and Turkish-style coffee, and the lack of effect of instant or drip-filtered coffee brews. This methodology will be of value in more correctly assessing the human exposure to these diterpenes through the consumption of coffee, and hence the potential physiological effects of different brews.

The cholesterol-raising factor from coffee beans

Some coffee brewing techniques raise the serum concentration of total and low-density-lipoprotein cholesterol in humans, whereas others do not. The responsible factors are the diterpene lipids cafestol and kahweol, which make up about 1% (wt:wt) of coffee beans. Diterpenes are extracted by hot water but are retained by a paper filter. This explains why filtered coffee does not affect cholesterol, whereas Scandinavian "boiled," cafetiere, and Turkish coffees do. We describe the identification of the cholesterol-raising factors, their effects on blood levels of lipids and liver function enzymes, and their impact on public health, based on papers published up to December 1996.