Is soluble fiber a miracle dietary component?

Question

I was out to breakfast with a friend today and he's started on the "Karen Hurd diet." I've heard of this dietitian before in my circles and several follow her like a savior. In fact, when my wife was pregnant with our first, she was told that Karen Hurd had a "cure" for morning sickness: soluble fiber.

This morning I found out that Karen also has a cure for high cholesterol (drum roll): soluble fiber.

I've looked into this a bit before, particularly when my wife was nauseous. She brought home a writeup of Karen Hurd's theory and I didn't buy it (this was about 3.5 years ago).

Bile is a digestive enzyme designed to break down the fatty acids that we eat. When we have no fatty acids in our duodenum (the first part of the small intestine and what most people commonly call “the stomach”), there is nothing to digest but YOU! This causes us to feel nauseous.

It seems to make sense that if the bile is meant to digest fatty acids, all we need to do is give the bile the fatty acids it wants to digest. Then the bile will not bother our intestinal lining making us feel nauseous. But, when we eat foods with fats in them, it actually causes a further release of bile. Now we have the original bile making us feel queasy PLUS a new onslaught of this same nauseous-causing substance.

Soluble fiber and bile (or any fatty acid) have a great affinity toward one another. In fact, they will bind so tightly together that they cannot be parted. As no fiber (soluble or insoluble) can cross the intestinal barrier, all the bile that has been bound together with the soluble fiber will exit the body through a bowel movement. That means the bile will not recycle. That means the bile will not grow nasty with accumulating debris. That means you will feel less nauseous.

The story is quite similar in her writeup on high cholesterol:

Our Creator designed our bodies to use cholesterol in the making of bile. Bile is a digestive enzyme that aids in the breaking down of fats in the intestinal tract. If a person can produce a regular supply of bile, then cholesterol levels will drop as this raw material is converted into a useful digestive enzyme.

Soluble fiber binds tightly with bile in the intestinal tract, in fact, so tightly that the bile cannot be reabsorbed through the intestinal tract and return to the liver...Over the course of time, levels will fall to the point of a total cholesterol of 150 or below.

...it is this author’s hypothesis that the liver releases an enzyme at this point of 150 and below that literally melts the hardened plaque off the interior of the blood vessel walls, so that the oxidized cholesterol is then available in the bloodstream for the liver to utilize in the making of bile.

Is there any evidence to support these claims about the interaction between bile, cholesterol, hormones, and soluble fiber? I became suspicious when I read the writeup on morning sickness many years ago, but to hear such a similar hypothesis (bile, etc.) being proposed re. high cholesterol really struck me as odd.

Oddly enough, check out THIS google search for the word "bile" on her site. Quite a few of her writeups mention it. I've never heard of bile being so destructive or such an integral component to various health issues before hearing about this dietitian and want to investigate.

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Sources

• Karen Hurd site (LINK)
• Writeup on morning sickness (LINK)
• Writeup on cholesterol (LINK)

Answer 1

Holy cow! Apparently, soluble fiber has been shown to reduce cholesterol and reduce risk of various heart issues!

• Fernandez, "Soluble fiber and nondigestible carbohydrate effects on plasma lipids and cardiovascular risk," 2001 (SOURCE):

Several large-scale cohort studies have documented that dietary fiber lowers the risk for coronary heart disease. In addition, there is substantial evidence from randomized controlled clinical trials that a mean reduction of 9% in LDL-cholesterol can be achieved by intake of different sources of soluble fiber.

• Bell et al., "Cholesterol-lowering effects of soluble-fiber cereals as part of a prudent diet for patients with mild to moderate hypercholesterolemia," 1990 (SOURCE):

Soluble-fiber breakfast cereals were examined for their cholesterol- lowering ability in 58 male patients with mild to moderate hypercholesterolemia in a randomized, double-blind, placebo-controlled study...During the cereal-plus-diet phase, total and LDL cholesterol values of the pectin-enriched cereal group dropped an additional 2.1% (P = 0.243) and 3.9% (P = 0.16), respectively, and they dropped 5.9% (P = 0.005) and 5.7% (P = 0.034), respectively, in the psyllium-enriched cereal group. During the cereal-plus-diet phase, no significant effects on HDL cholesterol, triglyceride, or body weight were found within or between any cereal groups. These results support use of soluble-fiber cereals as an effective and well-tolerated part of a prudent diet in the treatment of mild to moderate hypercholesterolemia.

• Jenkens et al., "Combined effect of vegetable protein (soy) and soluble fiber added to a standard cholesterol-lowering diet," 1999 (SOURCE):

Compared with the low-fat control diet, the test diet [vegetable protein and soluble fiber) decreased total cholesterol, low-density lipoprotein (LDL) cholesterol, apolipoprotein B, and the ratios of LDL to high-density lipoprotein (HDL) cholesterol and apolipoprotein B to A-I. A combination of vegetable protein and soluble fiber significantly improved the lipid-lowering effect of a low-saturated-fat diet. The results support expanding the current dietary advice to include increased vegetable protein and soluble fiber intake so that the gap in effectiveness between a good diet and drug therapy is reduced.

I had no idea. I guess that the recommendations about soluble fiber and cholesterol are true, after all.

Even more, I found these:

• Jenkins, "Effect on blood lipids of very high intakes of fiber in diets low in saturated fat and cholesterol," 1993 (SOURCE):

The loss of fecal bile acids was 83 +/- 14 percent greater during the soluble-fiber period than during the insoluble-fiber period (P < 0.001) and was related to the differences in total and LDL cholesterol and apolipoprotein B levels...

Incredible! Bile really does seem to have had an increase in excretion rates when soluble fiber was consumed. Whether this is due to Hurd's binding theory or not, I'm not sure -- but at the least, bile is being expelled at a greater rate.

• Lia et al., "Oat beta-glucan increases bile acid excretion and a fiber-rich barley fraction increases cholesterol excretion in ileostomy subjects," 1995 (SOURCE):

The 24-h excretion of bile acids was 53% higher in the [oat bran] diet period than in the [oat bran with beta beta-glucanase] diet period and also was significantly higher than in the [barley] and [wheat] diet periods (P < 0.05). Median (range) bile acid excretion was 851, and 606 mg/d in the [oat bran], [oat bran with beta-glucanase], [barley], and [wheat] diet periods, respectively. The excretion of cholesterol was significantly higher in the [barley] diet period than in the [oat bran with beta-glucanase] and [wheat] diet periods (P < 0.05), but the mechanism behind this effect of barley fiber is unknown. In oat bran, however, beta-glucan mediates an increase in bile acid excretion, which most probably explains the effect of oat fiber in lowering serum lipids.

So, again, bile acid increased with test diets, but it appears that the mechanism is unknown.

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I still have no evidence for soluble fiber binding with Human chorionic gonadotropin (hCG) and/or bile to reduce morning sickness. It's also undetermined exactly how soluble fiber is dealing with cholesterol or bile, at least from my survey. So... it's unclear as to whether Hurd is just speculating or has any basis for her claims.

At the very least, I can say that my research surprised me a great deal (due to finding the positive connection with soluble fiber, cholesterol decreases, and increase in bile expulsion rates), but I'm still skeptical about mechanisms and morning sickness. This is all I've found for now.

Answer 2

In summary:

The intake of soluble fiber:

• may worsen morning sickness and irritable bowel syndrome
• (from foods, less likely from supplements) may be associated with increased satiety and a small reduction in blood pressure, cholesterol and blood glucose levels
• may not be associated with lower risk of constipation, diabetes type 2, cardiovascular disease and most cancers

Morning sickness

In the study: Nausea and vomiting in early pregnancy: Effects on food intake and diet quality (Maternal & Child Nutrition, 2017), pregnant women with severe nausea tended to eat less foods high in soluble fiber (beans/pulses):

Increasing severity of nausea was associated with changes in intake of a range of foods, most notably reduced consumption of vegetables, tea/coffee, rice/pasta, breakfast cereals, beans/pulses and citrus fruits/fruit juices

According to Nausea: a review of pathophysiology and therapeutics (Therapeutic Advances in Gastroenterology, 2016):

With respect to dietary recommendations in the management of nausea and vomiting, a low-fat, low-fiber diet with small frequent meals is typically recommended if patients are able to tolerate oral intake.

Cholesterol levels

According to the following review of 162 studies, intake of soluble fiber (psyllium, oats, pectin, guar gum) has been associated with a small reduction of cholesterol levels.

Cholesterol-lowering effects of dietary fiber: a meta-analysis (THe America Journal of Clinical Nutrition, 1999):

Various soluble fibers reduce total and LDL cholesterol by similar amounts. The effect is small within the practical range of intake. For example, 3 g soluble fiber from oats (3 servings of oatmeal, 28 g each) can decrease total and LDL cholesterol by <0.13 mmol/L. Increasing soluble fiber can make only a small contribution to dietary therapy to lower cholesterol.

The mechanism by which fiber lowers blood cholesterol remains undefined. Evidence suggests that some soluble fibers bind bile acids or cholesterol during the intraluminal formation of micelles...The resulting reduction in the cholesterol content of liver cells leads to an up-regulation of the LDL receptors and thus increased clearance of LDL cholesterol.

Other suggested mechanisms include inhibition of hepatic fatty acid synthesis by products of fermentation (production of short-chain fatty acids such as acetate, butyrate, propionate)...; changes in intestinal motility...; fibers with high viscosity causing slowed absorption of macronutrients, leading to increased insulin sensitivity...; and increased satiety, leading to lower overall energy intake.

Cardiovascular disease

The authors of a 2016 Cochrane review Dietary fibre to prevent cardiovascular disease did not make any conclusions about the effect of dietary fiber on heart disease:

Studies were short term and therefore did not report on our primary outcomes, CVD clinical events. The pooled analyses for CVD risk factors suggest reductions in total cholesterol and LDL cholesterol with increased fibre intake, and reductions in diastolic blood pressure. There were no obvious effects of subgroup analyses by type of intervention or fibre type but the number of studies included in each of these analyses were small. Risk of bias was unclear in the majority of studies and high for some quality domains so results need to be interpreted cautiously. There is a need for longer term, well-conducted RCTs to determine the effects of fibre type (soluble versus insoluble) and administration (supplements versus foods) on CVD events and risk factors for the primary prevention of CVD.

Other

According to a comprehensive review of dietary fiber by Linus Pauling Institute, soluble fiber (from foods, but less likely from supplements) was associated with:

• A small reduction in systolic blood pressure (1.59 mm Hg)
• Better control of blood glucose in individuals with diabetes type 2
• Reduced risk of colorectal cancer
• Increased satiety (by beta-glucan from oats or barley)

There was no association between the intake of soluble fiber and consipation relief, reduced risk of diverticulitis and dibetes type 2 or all-cause mortality.

High intake of foods high in soluble fiber (legumes, barley, oats, apples, pears) can cause significant abdominal bloating and flatulence.

Answer 3

Soluble fiber binds to bile.

FactDr lists many sources.

Karen Hurd repeats her claim in this video.