High dietary fiber intake may prevent strokes. The belief that dietary fiber intake is protectively associated with some diseases was postulated 40 years ago, and then enormously fueled and kept alive by a great body of science since. Today, it is therefore generally believed that eating lots of fiber helps prevent obesity, diabetes, and cardiovascular diseases such as stroke. Strokes are the second most common cause of death worldwide. Moreover, stroke is a leading cause of disability, and so preventing strokes in the first place–what’s called primary prevention–should therefore be a key public health priority. All best studies to date found that fiber appears to significantly protect against the risk of stroke. Different strokes for different folks, depending, evidently, on how much fiber they ate. Notably, increasing fiber just seven grams a day was associated with a significant 7% reduction in stroke risk. And seven grams is easy, like a small serving of whole grain pasta with tomato sauce, and an apple.
What’s the mechanism? Well, fiber helps lower cholesterol and blood sugar levels. Or could just be we’re just eating more vegetables, or fewer calories, or less meat and fat, or improving digestion, slimming us down, lowering our blood pressure and the amount of inflammation within our bodies. Does it really matter though? As Dr. Burkitt commented on the biblical passage that reads, “A man scatters seed on the land—the seed sprouts and opens—how, he does not know.” But, he doesn’t wait to find out. Had the farmer postponed his sowing until he understood seed germination, he would not have lasted very long. So yes, let’s keep trying to figure out why fiber is protective, but in the meanwhile we should be increasing our intake of fiber, which is to say whole plant foods.
And it’s never too early. Strokes are one of many complications of arterial stiffness. Though our first stroke might not happen until our 50s, our arteries may have been already stiffening for decades leading up to it. Hundreds of kids were followed for 24 years, from age 13 in junior high through age 36, and they found that the lower intake of fiber during young age is associated with stiffening of the arteries leading up to the brain, and so we need to promote consumption of fiber-rich foods among the young. In fact, even by age 13 they could see differences in arterial stiffness depending on diet. This emphasizes the view that increases in fiber intake should be pursued already among young children.
And again, it doesn’t take much. One extra apple a day, or an extra quarter cup of broccoli, might translate to meaningful differences in arterial stiffness in adulthood. But if you really don’t want a stroke, we should try to get 25 grams a day of soluble fiber, which is found in beans, oats, nuts, and berries, and 47 grams a day of insoluble fiber, found primarily in whole grains. One would have to eat an extraordinarily healthy diet to get that much, yet these cut-off values could be considered as the minimum recommended daily intake of soluble and insoluble fiber, to prevent stroke. They admit these are higher than those commonly and arbitrarily proposed as “adequate” levels by scientific societies, but do we want to be patronized as to what authorities think is practical, or do we want them to just tell us what the science says, like the researchers did here?
Someone funded by Kellogg’s wrote in to complain that in practice such fiber intakes are unachievable. Rather the message should just be the more, the better, ya know, just have a bowl of cereal or something. Wink, wink.
The real Dr. Kellogg, who was actually one of our most famous physicians, credited for being one of the first to sound the alarm about smoking, may have been the first American physician to have recognized the field of nutrition as a science, and would today be rolling in his grave if he knew what his company had become.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
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