Exercise helps to prevent heart attacks, but exercise does not prevent plaques from forming in arteries. What you eat is far more important in determining how much plaque you have in your arteries, so even competitive master athletes should follow a heart-healthy diet. A recent study showed that lifelong male athletes older than 40 had increased markers that doctors use to predict a future heart attack (European Heart Journal, July 2021;42(28):2737–2744):
• very high Coronary Artery Calcium Scores (>300 Agatston units)
• increased plaques in the heart arteries
• scarring around the heart muscle

Another study of 798 asymptomatic and apparently healthy master athletes (runners, cyclists, triathletes, rowers and hockey players), 35+ years old, who exercised fairly vigorously 3-7 days a week, found that 10 percent had greater than 70 percent blockage of the arteries leading to their hearts (BMJ Open Sport & Exercise Medicine, 2018;4 (1):e000370).

A group of men over 60 who had ran marathons for 26-34 years and completed 27-171 marathons had plaques in their arteries in amounts that were related to their own risk factors for heart attacks and not to the number of miles or marathons they had run (Med & Sci in Sports & Ex, July 17, 2017). This suggests that plaques in arteries are not related to the amount of endurance training, but are caused by other factors such as a pro-inflammatory diet, high blood pressure, high cholesterol or tobacco use.

Heart Attacks are Occur When Plaques Break Off from Arteries Leading to the Heart
Heart attacks are not caused by narrowed arteries. They are caused by plaques suddenly breaking off from a heart artery, followed by bleeding, and then a clot forms that suddenly and completely blocks all blood flow to a part of the heart muscle. The part of the heart muscle suddenly deprived of oxygen then dies, which is a heart attack. Exercise helps to prevent heart attacks by making plaques more stable so they do not break off as easily. However, a healthful diet, not exercise, prevents plaques from forming. Everyone should follow a heart-healthy diet, especially if you have risk factors for a heart attack such as:
• a family history of heart attacks
• chest pain
• irregular heartbeats
• a big belly (particularly if you also have small buttocks)
• high blood pressure
• high cholesterol
• high blood sugar

A Diet to Prevent Plaques
Master athletes burn a lot of calories, so they can be expected to eat more food than sedentary people do. If they eat a lot of sugar or a lot of meat, they can expect to have plaques in their arteries. A diet that is high in vegetables, fruits, whole grains, legumes and nuts is associated with reduced risk for cardiovascular disease, while less healthful diets that are high in sweets, refined grains, juices, red meats and processed meats are associated with increased risk (Journal of the American College of Cardiology, July 2017; 70(4)).

How Doctors Measure Plaque Stability
A CT scan can show how stable plaques are (American Journal of Roentgenology, March 2015;204(3):W249-W260). X rays and sonograms can also show the difference between stable plaques that are safe and those that are unstable and more likely to break off to cause heart attacks. Stable plaques contain more calcium and are smoother and more homogeneous than unstable plaques. The radiologist estimates plaque stability by looking for an extensive calcification cap on the inner lining of plaques that prevent them from breaking off, less fat content inside the plaque, increased fibrous areas and less structural change. See Exercisers Have More Stable Plaques

My Recommendations
• To help prevent or reduce plaque formation, follow a heart-attack-preventing diet that is high in anti-inflammatory foods and low in pro-inflammatory foods. This means that you should eat plenty of plants and restrict red meat, processed meats, sugar-added foods, all sugared drinks and fried foods.
• Avoid overweight
• Do not smoke
• Limit or avoid alcohol
• To stabilize existing plaques and widen your coronary arteries, try to exercise every day for at least a half hour a day. Exercising more than that may be even more protective.