Red meat, fiber and stroke risk

Stroke is a leading cause of disability and death in the United States. About 795,000 people in the U.S. have a stroke each year. A stroke occurs when blood flow to a portion of the brain is interrupted, preventing oxygen and nutrients from reaching brain tissue; ischemic strokes, the most common type, are usually caused by a blood clot obstructing an artery leading to the brain. Elevated blood pressure is the chief risk factor for stroke; elevated blood pressure accounts for 62% of strokes.1,2 There have been countless studies on dietary factors and their relationship to stroke risk; within the past few years, new meta-analyses have strengthened these dietary links to stroke. In particular, higher fiber intake is associated with reduced risk, and higher red and processed meat intake is associated with increased risk.

Fiber and stroke:

Beans

Fiber and fiber-rich foods are known to be beneficial for colon health and healthy blood glucose regulation. For stroke prevention, the blood pressure-lowering effects of fiber and fiber-rich foods are thought to be primarily responsible. Elevated blood pressure is the primary risk factor for stroke, and greater intake of high-fiber foods (like beans) is consistently linked to lower blood pressure.3   Foods that are higher in fiber tend to have a lower glycemic load, which limits the rise in insulin after a meal; elevated insulin levels contribute to elevated blood pressure. Also, high-fiber foods are usually rich in phytochemicals and minerals like potassium and magnesium, which help to keep blood pressure in a healthy range.4-10  In addition to reducing blood pressure, high fiber foods improve several factors relevant to atherosclerotic plaque formation, such as cholesterol and triglyceride levels.11-13

A recently published meta-analysis on fiber intake and risk of stroke analyzed data from six prospective studies, including over 300,000 subjects.14 In this analysis, for every 10 gram increase in daily fiber intake, there was a 12% reduction in risk. A previous analysis of data from ten studies found that each 10 gram/day increase in fiber intake was associated with a 24% decrease in risk of death from heart disease.15 Ten grams is the approximate amount of fiber contained in 2/3 cup of beans or lentils, 2 cups of cooked collard greens, or 2 ½ cups of blueberries. The average daily intake of fiber in the United States is a meager 16 grams,16 but a Nutritarian diet, depending on one’s calorie needs, provides about 60-80 grams of fiber daily.  I want to make it clear it is the use of high fiber, whole foods that enable this degree of protection against stroke, not adding fiber to a standard American diet.  It is more than just the fiber in fiber-rich foods that offers protection.

Red/processed meat and stroke:

Red and processed meats are calorie-dense, micronutrient-poor, saturated fat-rich foods. Another major concern regarding red and processed meats when it comes to heart disease and stroke is heme iron. The human body absorbs heme iron, the form of iron found in animal foods, more readily than nonheme iron from plant foods. Iron is an essential mineral that transports oxygen in the blood and has many other crucial functions, but can promote free radical damage, called oxidative stress when excess is present. .  As a result, high body iron stores are associated with increased risk of chronic diseases that have an oxidative stress component: for example, diabetes, heart disease, and dementia.17-21 When it comes to increasing stroke risk, heme iron promotes oxidation of LDL cholesterol and elevated blood pressure. Several previous studies have found that higher heme iron (or red and processed meat) intake was associated with higher blood pressure, and higher non-heme iron intake (or plant food intake) was associated with lower blood pressure.22-26  Again, it is not merely the high iron in meats, many other factors play a role including their hormonally-induced growth-promoting effects that promote atherosclerosis. 

Another recent meta-analysis reported on five studies of red and processed meat and stroke risk, and found substantial risk increases in ischemic stroke risk (the most common type of stroke):  for each 100 gram daily increment red meat eating daily, there was a 13% increase in risk, and a 13% increase in risk for every 50 grams daily of processed meat. Processed meats are nutrient-poor and high in heme iron like red meat, but have additional sodium, which is likely why the authors found a steeper association with stroke.27

These studies add to the already huge body of evidence showing that whole plant foods are health-promoting, while red and processed meats are disease-causing.

Between the excessive amounts of protein and heme iron, new findings on detrimental effects of red meat compounds Neu5GC28  and carnitine, and the volume of evidence linking red and processed meats to cancer and premature death,29-36 there is no question – these are dangerous foods. People who still desire to eat meat, should think of it as a condiment, only to be used a few times a week in small amounts.  

References:

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