The subject of this article is about specific foods that lower bad cholesterol (also known as low-density lipoprotein, LDL). I mainly relied on an article published in January 2021 in journal “Nutrition, Metabolism and Cardiovascular Diseases” [1]. It is a systematic overview of systematic reviews and meta-analyzes of randomized controlled trials (RCTs). The main goals were to find out which foods lower bad cholesterol and to compare the results with the existing nutritional guidelines. I also analyzed a few articles about the food effects on triglycerides.
A total of 37 nutritional guidelines, 108 systematic reviews and 20 RCTs from 2009 to 2019 were included. A strong advantage of this work was that the strength of the evidence was assessed using “The Grading of Recommendations for Assessment, Development, and Evaluation” (GRADE). The target population were adults without lipid lowering drugs.
Elevated bad cholesterol is a causal and cumulative risk factor for cardiovascular disease, and lowering it is the primary goal of reducing the risk [2].
Triglycerides are considered a lower risk factor and should only be treated when levels are high. Foods that lower bad cholesterol don’t necessarily work on triglycerides and vice versa.
What products do guidelines recommend to lower cholesterol and what are the with these guidelines associated problems?
- Most guidelines recommend:
- Switching saturated and trans fatty acids to unsaturated ones;
- Reducing sugar consumption;
- Restricting processed and red meats;
- Limiting dietary cholesterol to 300 mg/day;
- Consuming fruits, vegetables, nuts;
- Consuming non-tropical oils, legumes, whole grains and high fiber products, as well as fish.
- Only a few guidelines recommend:
- Avoiding simple and processed carbohydrates;
- Restricting alcohol consumption;
- Avoiding salt;
- Consuming plant sterols and soy products.
- Only one guideline recommend avoiding unfiltered coffee.
- The main problems with the food guidelines are that it is not clear what specific foods lower cholesterol, and how much evidence (and level of safety) it provides. It is also unclear what type of cholesterol each product lowers and often by what mechanism.
Tables for different food groups and their effects on bad cholesterol with the level (no effect evidence according to GRAVE will be provided below.
How do fatty acids affect bad cholesterol?
There are monounsaturated (MUFAs) und polyunsaturated fatty acids (PUFAs). It remains unclear what ratio of omega-3 and -6 should be in PUFAs [2].
Fish has no effect on the lipid profile. According to another study, eating fish (at least 2x/week) and vegetable short-chain omega-3 fatty acids (e.g. alpha-linolenic acid (ALA)) reduce cardiovascular mortality, but has no relevant effect on the lipid profile [3].
Marine oils contain long-chain omega-3 fatty acids (e.g. eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) and may even slightly increase LDL cholesterol.
The strength study with the fish oil product “Epanova” (EPA/DHA mixture) was terminated prematurely due to its ineffectiveness [4]. For this reason and due to environmental issues, fish oil capsules are not recommended.
So far, only the REDUCE-IT study [5] has shown a significant reduction in cardiovascular mortality and a reduction in triglycerides under the high-dose EPA preparation “Vascepa”. However, with side effects such as atrial fibrillation, swelling, heavy bleeding. This product is currently only available in the US.
Dairy products (both high- and low-fat) and have no effect on bad cholesterol, although the evidence is very low.
Dietary intake of fat should be <30%, of which <10% is saturated fat [2].
How do fiber and whole-grain products affect bad cholesterol?
Plant sterols, stanols and soluble fibers compete with cholesterol for absorption in the intestines. Consumption of at least 2 g of phytosterols per day can lower LDL cholesterol to 10% and this dosage has no side effects [6].
Resistant starch also acts as dietary fiber and may slightly lower LDL cholesterol, although evidence is low. 30 g fiber per day is recommended, of which about 10 g should be soluble fiber [2].
How do sugar, carbohydrates, and sweeteners affect bad cholesterol?
How do fruits, vegetables, and berries affect bad cholesterol?
Red rice was not analyzed in this study due to insufficient criteria. According to the 2019 ESC/EAS guidelines, monocholine in red rice acts similarly to statins (blocks HMG-CoA reductase), but safety (potential contamination and statin-like side effects) has not been studied enough [2] and different concentrations of monocholine in products must be taken into account [10].
With a daily dose of 5-10 mg monocholine, a reduction in LDL cholesterol of up to 20% has been observed [11].
How do nuts and seeds affect bad cholesterol?
How do spices affect bad cholesterol?
How do eggs affect bad cholesterol?
How do probiotics, prebiotics and synbiotics affect bad cholesterol?
How do coffee, tea, alcohol and chocolate affect bad cholesterol?
However, alcohol is known to greatly increase triglyceride levels [2].
Discussion
- Existing dietary guidelines should be viewed more critically. They provide general instructions for a healthy diet, but do not necessarily specific advices to lower bad cholesterol;
- It is not clear from this study alone how these foods affect triglycerides;
- Only one guideline did not recommend filter coffee, although the evidence is high. However, it should be noted that most coffee research were conducted 20-30 years ago with an average of 4-6 cups of coffee per day. This is a high dose and does not accurately reflect coffee consumption in the general population;
- Although the GRADE criteria are good for classifying levels of evidence, many large and high quality studies were excluded;
- Mechanisms of action have not been analyzed;
- Although some products have a definite positive or negative effects on cholesterol, no other properties of them have been discussed.
Summary of foods lowering bad cholesterol
According to this article, there was strong evidence that food high in unsaturated and low in saturated and trans fatty acids, with added plant sterols/stenols, and high in soluble fiber reduce bad cholesterol at least moderate. Unfiltered coffee can increase it moderate to large.
There was also moderate evidence that avocados and turmeric can reduce bad cholesterol moderate to large, high-fiber/whole-grain foods, pulses, hazelnuts, walnuts, and green tea – small to moderate reduction. Sugar can cause a small increase in bad cholesterol.
According to other articles, carbohydrates and alcohol increase triglycerides.
How diet and weight loss, exercise and smoking cessation affect bad and good cholesterol and triglycerides? [2]
References
- Schoeneck, Malin, and David Iggman. “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.” Nutrition, Metabolism and Cardiovascular Diseases (2021).
- Mach, François, et al. “2019 ESC/EAS Guidelines for the management of dyslipidaemias: lipid modification to reduce cardiovascular risk. The Task Force for the Management of Dyslipidaemias of the European Society of Cardiology (ESC) and European Atherosclerosis Society (EAS).” European heart journal 41.1 (2019).
- Sacks, Frank M., et al. “Dietary fats and cardiovascular disease: a presidential advisory from the American Heart Association.” Circulation 136.3 (2017): e1-e23.
- Kemp III, A. “Update on Phase III STRENGTH trial for Epanova in mixed dyslipidaemia.” (2020).
- Bhatt, Deepak L., et al. “Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia.” New England Journal of Medicine 380.1 (2019): 11-22.
- Musa-Veloso, Kathy, et al. “A comparison of the LDL-cholesterol lowering efficacy of plant stanols and plant sterols over a continuous dose range: results of a meta-analysis of randomized, placebo-controlled trials.” Prostaglandins, Leukotrienes and Essential Fatty Acids 85.1 (2011): 9-28.
- Te Morenga, Lisa A., et al. “Dietary sugars and cardiometabolic risk: systematic review and meta-analyses of randomized controlled trials of the effects on blood pressure and lipids.” The American journal of clinical nutrition 100.1 (2014): 65-79.
- Mensink, Ronald P., et al. “Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials.” The American journal of clinical nutrition 77.5 (2003): 1146-1155.
- Cheng, Ho Ming, et al. “Tomato and lycopene supplementation and cardiovascular risk factors: A systematic review and meta-analysis.” Atherosclerosis 257 (2017): 100-108.
- Gordon, Ram Y., et al. “Marked variability of monacolin levels in commercial red yeast rice products: buyer beware!.” Archives of internal medicine 170.19 (2010): 1722-1727.
- Li, Yinhua, et al. “A meta-analysis of red yeast rice: an effective and relatively safe alternative approach for dyslipidemia.” PloS one 9.6 (2014): e98611.
- Pan, An, et al. “Meta-analysis of the effects of flaxseed interventions on blood lipids.” The American journal of clinical nutrition 90.2 (2009): 288-297.
- Hadi, Amir, et al. “Cumin (Cuminum cyminum L.) is a safe approach for management of lipid parameters: A systematic review and meta‐analysis of randomized controlled trials.” Phytotherapy Research 32.11 (2018): 2146-2154.
- Pourmasoumi, Makan, et al. “The effect of ginger supplementation on lipid profile: A systematic review and meta-analysis of clinical trials.” Phytomedicine 43 (2018): 28-36.
