Blood Clot Prevention
Dietary Approaches to Reduce Thrombosis Risk
The successful nutritional approach to reduce thrombosis risk does not depend solely on a set of "antithrombotic nutrients." Rather, Life Extension supports a multifactorial approach that includes nutrition and lifestyle interventions to reduce the risk of thrombosis. These include abnormal blood lipids, chronic inflammation, hypertension, elevated plasma homocysteine, and obesity.
Reducing Platelet Activation and Aggregation
Platelet activation and aggregation occurs via a complex, multifactorial process. Several natural ingredients can target varying steps involved in clot formation, and a diversified regimen can provide multiple defenses against aberrant clotting.
Olive. Olive (Olea europaea) has a history of use against high blood pressure, atherosclerosis, and diabetes.95 The leaves contain the active iridoid compounds oleuropein and oleacein,96 which are thought to be responsible for its blood pressure-lowering and cholesterol-lowering properties demonstrated in recent human trials.97
In laboratory tests, olive leaf extract also demonstrated antiplatelet activity in blood isolated from healthy male volunteers.98 High-oleuropein extracts from olive tree wood also inhibit aggregation of human platelets in laboratory tests, especially those from type 2 diabetic patients.99 Hydroxytyrosol and hydroxytyrol acetate, two metabolites of oleuropein that are found in olive fruit and oil, have well-established anti-inflammatory and antiplatelet activities in laboratory tests and in animal models.100
Phenolic-rich olive oil preparations have demonstrated decreases in the production of proinflammatory and prothrombotic factors in human studies as well.101,102 Hydroxytyrosol acetate inhibits platelet aggregation with an efficacy similar to aspirin in vitro using whole blood samples from healthy volunteers.103 Hydroxytyrosol-rich extracts (25 mg/day) for four days reduced production of the prothrombotic factor thromboxane A2 in a pilot trial of five diabetic adults.104 High-fat diets rich in olive oil lowered the plasma levels of several clotting factors in a larger study of 20 healthy young adults.105
Tea. Tea consumption has established protective effects on cardiovascular health; reductions in risk of coronary heart disease and stroke from tea consumption have been confirmed through the analyses of several population studies.106 Purified green tea polyphenols, such as EGCG, increase clotting time in rats and reduce platelet aggregation in isolated human platelets.107
Human trials of tea consumption and thrombosis risk have had mixed results. While short-term consumption (two weeks) of green tea showed no measurable effect of platelet activity,108 longer-term studies showed modest improvements in platelet function.109 The most promising results have been observed in a randomized blinded trial of tea consumption; six weeks of black tea consumption (four cups/day) in 37 healthy volunteers significantly reduced platelet activation, as measured by the presence of platelet aggregates.110 Tea catechins and the flavonoid quercetin have demonstrated synergistic reductions in platelet adhesion, activation, and aggregation in vitro.111
Quercetin. Quercetin has demonstrated success inhibiting platelet aggregation. Single doses of quercetin glucosides, the naturally occurring form of quercetin (150 mg or 300 mg), from food sources and higher quality dietary supplements, were able to significantly inhibit collagen-induced platelet aggregation in one small human study.112 However, long-term supplementation with 1 gram/day of quercetin aglycone (the form typically found in lower quality dietary supplements) for 28 days had no significant effect on platelet aggregation in healthy human volunteers.113 It should be noted that the plasma concentrations of quercetin in the former study (successful) were significantly higher than in the latter at the time of aggregation measurements, suggesting that quercetin glucosides are absorbed more efficiently than quercetin aglycone. Quercetin from food sources (onions) have shown positive trends on platelet aggregation.114
Salvia. Salvia is a diverse genus of plants encompassing hundreds of species, many with ornamental, culinary, or medicinal importance. Salvia miltiorrhiza (red sage or danshen) is one of the most versatile Chinese herbal drugs, used for hundreds of years in the treatment of cardiovascular diseases115 and still widely used as standard thrombolytic treatment in Chinese hospitals.116 Salvianolic acids A and B, water soluble polyphenols from S. miltiorrhiza root, are responsible for its observed antiplatelet activity in animal models117 and in blood samples from healthy human volunteers.118
The seeds of Salvia hispanica (chia) are rich in protein and the omega-3 fatty acid α-linolenic acid. In a small study of 27 patients with type 2 diabetes, whole chia seed (15 grams/1,000 kcal of intake) for 12 weeks showed significant reductions in plasma fibrinogen and the platelet adhesion protein von Willebrand factor (vWF). Small reductions in additional cardiovascular risk factors (systolic blood pressure and hs-CRP) were also observed.119
Resveratrol. Resveratrol has several effects on blood platelets as determined in vitro (using human platelets) and in animal models, including inhibition of platelet adhesion and aggregation, reduction in secretion of clotting factors from platelets, and inhibition of cyclooxygenase, the proinflammatory enzyme involved in platelet activation.120,121 Plasma resveratrol from consumption of red or white wine increases the release of nitric oxide from platelets in healthy volunteers, inhibiting their activation.122 In an experimental study, resveratrol was able to suppress the detrimental effects of homocysteine on platelet aggregation and free radical generation.123
Grape seed extract. Grape seed extract contains oligomeric procyanidins that support cardiovascular health through vasodilation and an increase in nitric oxide production.124 They have significantly reduced blood pressure in human trials.125 Grape seed extract also exhibits antithrombotic activity in animals126 and in platelets isolated from healthy human volunteers.127 This may be related to an anti-inflammatory effect.128
In a small, 8-week study of 17 post-menopausal women taking 400 mg of flavonoid-rich grape seed extract/day, a significant (23%) lengthening of clotting time compared to the control was observed on day 1 of the study. (Increased clotting time indicates reduced platelet activation and aggregation.) After eight weeks, the difference in clotting time was not as significant, but trended higher in the test group.129 Similar short-term reductions in platelet activity also were observed in a study of 23 male smokers.130 When combined with grape skin polyphenols, grape seed extracts demonstrated better antiplatelet properties than either extract alone in animal models as well as human platelets.131
Tomatoes. Tomatoes contain several nutrients with established protective effects on the cardiovascular system. Lycopene has demonstrated hypotensive activity in humans,132 and several human trials indicate a cholesterol-lowering effect.133 One mechanism by which lycopene may limit platelet aggregation is by activating cyclic-GMP, a signaling molecule involved in vessel dilation.
Tomatoes also exert potent antiplatelet activity in laboratory tests.134 The antithrombotic compounds of tomato are small molecules found within its water-soluble fractions, which are also high in soluble sugar content. Removal of these sugars increases the concentration of tomato actives and stimulates their inhibition of platelet aggregation by up to 50 times.135
Two studies examined the effects of these standardized tomato extracts on platelet function in healthy human volunteers: High dose (18 grams, equivalent to six whole tomatoes) and low dose (equivalent to two tomatoes) standardized tomato extracts both exhibited significant reductions in platelet aggregation up to six hours after ingestion. Standardized bioactives from tomato suppress platelet adhesion and aggregation by reversibly inhibiting P-selectin and GPIIb/IIIa, two receptors necessary for clot formation.135
Pomegranate. Pomegranate contains several bioactive antioxidant polyphenols, including the unique tannins punicaligins. Pomegranate juice consumption has been associated with significant decreases in blood pressure in hypertensive subjects136,137 and decreases in LDL cholesterol oxidation.138 Pomegranate juice polyphenols also function as vasodilators by supporting endothelial function, and as inhibitors of angiotensin-converting enzyme, an enzyme associated with high blood pressure. Two weeks of pomegranate juice consumption (50 mL/day) reduced platelet aggregation by 11% in a small study of 13 healthy individuals.139 In a human clinical trial, pomegranate juice consumption was shown to prolong clotting time as little as six hours after consumption.140
Garlic. Garlic's (Allium sativum) promotion of cardiovascular health has been substantiated by several human trials, particularly its blood pressure-lowering activity141 and its ability to induce favorable blood lipid profiles.142 In cell models, garlic extracts inhibit platelet aggregation by reducing ion signaling involved in platelet activation, and by increasing synthesis of c-GMP, a vasodilator. Garlic bioactives also promote endothelial nitric oxide release and enhance fibrinolysis.143,144 Moreover, garlic inhibits the COX-1 and COX-2 enzymes, which suppress TXA2 levels.145
The antithrombotic activity of garlic has also been the subject of several human trials in both healthy subjects and patients with cardiovascular disease, using aged extracts,146 water extracts,147 or garlic oil.148 Garlic demonstrated reductions in platelet aggregation in each of the studies.
Fish oil. Fish oil is a source of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are essential for several metabolic processes. Studies of tens of thousands of moderate- and high-risk cardiovascular disease patients demonstrated the ability of fish oil to reduce plasma triglycerides, blood pressure, and the risk of cardiovascular mortality.149 Several human studies observed the antithrombotic activities of fish oil,150 due in part to its ability to reduce the production of the platelet aggregator thromboxane A2, a metabolite of the inflammatory omega-6 fatty acid arachidonic acid.
Fish oil consumption decreases platelet activation151 and aggregation,152 and plasma fibrinogen levels.153 In type 2 diabetic patients, the pooled data from three human trials of 159 participants demonstrated a reduction in plasma fibrinogen by 32 mg/dL, and platelet aggregation by more than 10%.154
Capsaicinoids. Capsaicinoids (capsaicin and dihydrocapsaicin) are the major pungent constituents of chili peppers from the genus Capsicum. Regular intake of chili peppers delays oxidation of serum lipids, and lowers and improves insulin and glucose profiles following a meal, both of which contribute to reducing the risk of cardiovascular disease.155 In animal models, capsaicin reduces platelet aggregation.156 An early study attributed the reduced plasma fibrinogen and increased fibrinolytic activity of native Thai individuals, compared to Americans living in Thailand, to the amounts of capsaicin in their diets.157 In laboratory tests, both capsaicin and dihydrocapsaicin reduced platelet aggregation and reduced the activity of clotting proteins in blood samples from six healthy patients.158
Ginger. Ginger has been shown to inhibit platelet aggregation and to decrease platelet thromboxane production in laboratory tests.159 Both raw and powdered preparations reduced platelet aggregation in small human trials.160 Five grams/day of fresh ginger for seven days inhibited thromboxane production in seven healthy volunteers,161 while two additional studies (a single dose of 2.5 grams dried powder in 10 healthy volunteers and 10 grams dried powder/day for three months in 30 patients with coronary artery disease) demonstrated inhibition of platelet aggregation.162,163 Doses lower than 2.5 grams had no effect in human trials.164
Curcumin. Curcumin has a variety of protective roles in cardiovascular health, reducing oxidative stress, inflammation, and the proliferation of vascular smooth muscle cells and monocytes (immune cells that contribute to atherosclerosis in the presence of oxidized LDL cholesterol). Human trials revealed the effects of curcumin on reducing lipid peroxidation165,166 and plasma fibrinogen,167 both factors in the progression of atherosclerosis.168 Another mechanism by which curcumin inhibits platelet aggregation is through dampening expression of P-selectin, an adhesion molecule expressed on both activated endothelial cells and platelets that mediates aggregation between these two cell types.32 P-selectin also recruits leukocytes to the forming thrombus.
In eight subjects with abnormally high plasma fibrinogen, 20 mg of curcumin for 15 days reduced fibrinogen levels by nearly 50%.167 Experiments using human platelets or whole blood have demonstrated curcumin's ability to inhibit platelet aggregation.169
French maritime pine bark extract. French maritime pink bark extract (commercially known as Pycnogenol), which has strong anti-inflammatory and free radical-scavenging effects, has been found to stabilize vascular collagen and prevent blood clots.170 In in vitro research, an extract from New Zealand pine bark reduced cytokine-related expression of adhesion molecules by endothelial cells, thereby reducing the likelihood of blood cell aggregation, in response to inflammatory signaling.171
Pine bark extract may help travelers avoid blood clots during and after long flights. One study compared the effect of pine bark extract to placebo in 198 long-haul air travelers with a high risk of blood clots. Travelers received 200 mg pine bark extract or placebo two to three hours before flight time and six hours later, and 100 mg the next day. Flights averaged 8.25 hours. No thrombotic events occurred in those given pine bark extract, but five occurred in the placebo group.172 In another trial, 186 travelers on 7‒8 hour flights received two tablets containing 150 mg of a proprietary blend of pine bark extract plus nattokinase or placebo two hours before travel and six hours later, and completed pre- and post-flight monitoring of edema and blood clots. No thrombotic events occurred in the treated group, but seven flight-related thrombotic events occurred in the placebo group. In addition, edema scores based on measurements taken before treatment and after air travel decreased by 15% in the pine bark-nattokinase combination group and increased 12% in those receiving placebo, with a significant difference between the two.173
One trial examined the effect of pine bark extract in 156 participants who experienced a single episode of DVT. Participants were assigned to one of three treatments: pine bark extract, compression stockings, or both. After one year, two new episodes of DVT occurred in participants using compression stockings versus none in either of the groups receiving pine bark extract. In addition, pine bark extract was more effective than compression stockings in reducing edema and as effective in improving microcirculation, while the combination of both was the most effective. This may be especially significant because compression stockings are historically associated with low compliance due to discomfort.174
Findings from a clinical trial suggest pine bark extract may help prevent thrombosis and other side effects in cancer patients undergoing chemotherapy and radiation therapy. The study included 46 cancer patients who began supplementing with three 50 mg pine bark extract or placebo after meals (total of 150 mg daily) after completing their first course of chemotherapy or radiation. After two months, the patients receiving pine bark extract had decreased frequencies of all investigated side effects, including thrombotic events, compared with those receiving placebo.175
Suppressing Fibrinogen Levels
Niacin/nicotinic acid. Niacin/nicotinic acid (vitamin B3) is an essential nutrient with important effects throughout human metabolism. At dosages substantially above the Recommended Dietary Intake (RDI), niacin reduces risk factors for cardiovascular disease, and reduces cardiovascular events and mortality.176 Some of this risk reduction is due to niacin's ability to significantly raise HDL cholesterol by up to 35%,177 and reduce the amount of small, dense low-density lipoprotein (LDL) particles, a risk factor for atherosclerosis.178
Niacin also lowers plasma fibrinogen levels, a risk factor for cardiovascular disease. In the multi-center Arterial Disease Multiple Intervention Trial (ADMIT), patients with peripheral arterial disease (PAD) who were randomized to niacin (initially 100 mg a day, raised to 3,000 mg/day over the 12-month study) saw an average reduction of fibrinogen by 48 mg/dL (~13.5%), as well as a reduction in prothrombin time, a measure of blood clotting.35 Similar reductions in plasma fibrinogen (-54 mg/dL, ~15%) were observed in a 6-week study of men with elevated triglycerides.36
Vitamin C. Vitamin C may possibly suppress fibrinogen levels, as suggested by some association studies. A study involving more than 3,200 men in the United Kingdom found those with the higher plasma levels of vitamin C also had lower levels of fibrinogen and superior endothelial function.38 Likewise, a study of 96 aging men and women found that an increase of dietary vitamin C of 60 mg daily, or the equivalent of about one orange, was associated with a reduction in fibrinogen that was estimated to cause a 10% reduction in risk of ischemic heart disease.37
In an animal model, vitamin C was shown to reduce levels of von Willebrand factor and fibrinogen, suggesting inhibition of platelet adhesion and aggregation. Moreover, vitamin C was able to reduce blood pressure in this study.179
An experimental study found that incubation of fibrinogen molecules with vitamin C in vitro caused functional changes to fibrinogen, which may be associated with an impaired capacity for binding the surface of platelets.180
Promoting Fibrinolysis (Clot Breakdown)
Nattokinase. Nattokinase is a fibrinolytic enzyme (an enzyme that breaks down fibrin clots) found in natto, a soy fermented by the bacteria Bacillus subtillis. The bacteria produce the enzyme—nattokinase is not a metabolite of soy. In laboratory tests it reduces platelet aggregation and blood viscosity,181 and enhances the fibrinolytic activity of plasma in animal models.40
At a dose of 4,000 fibrinolysis units (FUs) per day, nattokinase has been shown to reduce circulating fibrinogen and clotting factors (which are independent risk factors for cardiovascular disease) in patients undergoing dialysis or with cardiovascular disease, and in healthy volunteers.182 It was also able to reduce the frequency of DVT in 94 high-risk individuals on extended airline flights when combined with pine bark extract, or pycnogenol.173 Nattokinase also has been shown to reduce blood pressure in hypertensive individuals, which may be attributed to its ability to lower blood viscosity.183
Ethanol. Ethanol (drinking alcohol), in low doses, reduces thrombotic risk by modifying platelet function and reducing platelet aggregation. As little as a half glass of red wine daily provides enough ethanol to reduce thrombotic risk. However, higher doses of ethanol increase the risk for clotting substantially.184 All types of ethanol consumed in moderation (two drinks or less daily for men and one drink or less daily for women) should reduce thrombotic risk, but red wine also provides beneficial polyphenols such as quercetin.
Disclaimer and Safety Information
This information (and any accompanying material) is not intended to replace the attention or advice of a physician or other qualified health care professional. Anyone who wishes to embark on any dietary, drug, exercise, or other lifestyle change intended to prevent or treat a specific disease or condition should first consult with and seek clearance from a physician or other qualified health care professional. Pregnant women in particular should seek the advice of a physician before using any protocol listed on this website. The protocols described on this website are for adults only, unless otherwise specified. Product labels may contain important safety information and the most recent product information provided by the product manufacturers should be carefully reviewed prior to use to verify the dose, administration, and contraindications. National, state, and local laws may vary regarding the use and application of many of the treatments discussed. The reader assumes the risk of any injuries. The authors and publishers, their affiliates and assigns are not liable for any injury and/or damage to persons arising from this protocol and expressly disclaim responsibility for any adverse effects resulting from the use of the information contained herein.
The protocols raise many issues that are subject to change as new data emerge. None of our suggested protocol regimens can guarantee health benefits. The publisher has not performed independent verification of the data contained herein, and expressly disclaim responsibility for any error in literature.