Mild cooling and chilling of the body without hypo¬thermia can lead to an increase in the total number and stickiness of platelets and may increase clotting. This may influence the incidence of coronary thrombosis in winter. During stress, or in early morning, adrenaline and other chemicals increase the number and stickiness of platelets, which may clump onto an atheromatous plaque and cause a coronary thrombosis and myocardial infarction
(MI). It is not surprising, therefore, that most fatal heart attacks occur in the early morning hours between 5 and 8 a.m. Certain foods, especially high-fat foods, increase the stickiness of platelets and influence other blood-clotting factors, but to a small extent.
Atheromatous plaques produce turbulence and slow the blood flow in the coronary artery. The force of blood and increases in blood pressure can cause fissures or rupture of plaques. Platelets stick to these areas on the plaque and can start clot formation. Prevention of clots will be achieved if the formation of atheromatous plaques and their rupture are prevented. Plaque rupture liberates highly thrombo-genic substances that rapidly cause clotting and blockage of arteries.
Nicotine and carbon monoxide, which are by-products of cigarette smoking, increase platelet stickiness and may be important factors. Carbon monoxide from cigarette smoke and exhaust of motor vehicles increase atheroma formation. Some foods have a high vitamin K content and increase the concentration of a clotting factor made in the liver (prothrombin). In addition, fibrinogen, the final protein involved in the formation of clots, is manufactured in the liver; it has been shown that the mean fibrinogen concentration and viscosity in the blood is increased in patients who have had heart attacks. Thus, it is important to recognize that certain foods other than those involved in elevating blood cholesterol may be important in increasing or decreasing clot formation. Some foods have properties that may prevent clot formation, albeit with a modest effect. (see Section VII in the chapter Cholesterol).

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