 As we age, our arteries stiffen. These are measurements of the stiffness of our aorta, the main artery coming off the heart, as we get older and older. As our aorta stiffens, it leads to a range of pathological changes, such as exposing our brain and kidneys to greater pressure fluctuations, which may increase the risk of stroke and impairment of kidney function. Those who consume garlic, though, just less than a quarter teaspoon of garlic powder a day appear to have less stiffness in our aortas. We think this is because garlic seems to improve the function of the inner lining of our arteries, which helps our arteries relax. But the protective mechanisms of garlic against cardiovascular diseases are multiple and include a combination of anti-clotting, clot busting, antioxidant, and blood pressure and cholesterol lowering effects. The latest review suggests a long-term garlic intake may drop bad cholesterol levels about 10%, but the blood thinning effects are such that the American Society of Anesthesiology recommends garlic intake be stopped a week before elective surgery, or, presumably, you could just cook it to death. Unlike the anti-clotting components concentrated in the yellow fluid around tomato seeds, which are heat stable, the anti-platelet activity in garlic and onions is lost with cooking. Here's the platelet inhibition of raw garlic compared to boiled garlic, which is right down around raw onion. So garlic appears to be about 13 times more potent than onion, and eating garlic raw appears to be better than cooked, suggesting that garlic and onions could be more potent inhibitors of blood clotting if consumed in raw, rather than cooked or boiled form. So right before surgery it might be good to cook garlic, but what about the rest of the time when we're trying to suppress platelet overactivity to decrease the risk of heart attacks and stroke? As garlic and onion are normally consumed in cooked form, their efficacy at preventive herbs and cardiovascular disease may be in doubt. But look, we can put raw onion on our salads, or put raw garlic in salsa, or dressings, or dips, or pesto, or we can crush or chop it, wait 10 minutes, and then cook it. Here's the platelet inhibiting power of raw garlic. And if you cook it just a few minutes, it does fine, but after like five minutes the benefit is abolished. But if you pre-crush and wait, some of the anti-platelet activity is retained a bit longer. That's because the enzyme that makes the anti-platelet compounds is activated by crushing, but destroyed by heat faster than the compounds it creates. So by crushing first and letting the enzyme work its magic before cooking, one can delay the loss of function. Even better though, just like we can add broccoli enzymes in the form of raw radish or mustard powder to boost the benefits of broccoli, the addition of a little raw garlic juice to cooked garlic can restore the full complement of anti-platelet activity that was completely lost without the raw garlic addition. When onions are cooked, the anti-platelet activity is similarly abolished within 10 minutes, but then something strange happens. After 20 or 30 minutes of cooking, the effect on platelets is reversed and appears to make matters worse. Significant pro-platelet activation effects, suggesting that extensively cooked onions may stimulate rather than inhibit platelets. This was in a test tube, though, thankfully when tested in people. Even when onions are dropped in boiling water, fried for 10 minutes, and then left to simmer for 30, platelet activation drops within an hour and three hours after onion soup ingestion.