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   Bill Harris, M.D. | Q&A

Intestinal Problems
Q&A with Bill Harris, M.D.

Q. I am a 49 yo female, been vegetarian for 2 years and vegan for the last 6 months. For the last 3 weeks I have had lose stools upon awakening in a.m. and sometimes about 8 p.m. too. When this started I was having a lot of gas but that has stopped. I also have some insomnia and have craved ice for the last 2 yrs. (CBC was normal). I lost (intentionally) 40 lbs. in the last 6 months and am close to my desired weight.


A. Congratulations on the weight loss.

I feel good and have plenty of energy. Should I be concerned about the lose stools?

The transition to a vegan diet may often cause these symptoms because of the high fiber content. As you know fiber is mostly cellulose. Higher animals, us included, lack the enzyme cellulase that splits glucose molecules off the ends of the cellulose polymer. The fiber also shortens intestinal transit time with the result that not too long after eating, a large bolus of poorly digested high fiber food will pass the ileo-cecal valve into the colon where there are bacteria that do have cellulase. The bacteria then digest and utilize your dinner with the evolution of large amounts of gas. Diarrhea follows.

There are various medical syndromes that can also cause these symptoms so it might be wise to get stool specimens for enteric pathogens and parasites such as Giardia lamblia. However, your history suggests that the problems are due to your vegan transition so I would suggest the following:

1. A week trial with no grain products. About 5% of the population has celiac syndrome (non tropical sprue) due to gluten intolerance. From my own experience I suspect that the vegan diet is likely to unmask this condition in a person who previously had no symptoms, since the pre-vegan transit time was long enough to hide it. If this seems to help, reintroduce grains slowly and in this order: white rice, oats, brown rice, corn, and (with caution) rye, barley, and wheat, the gluten sources most likely to cause the problem. Be aware that you can permanently exclude grains from the diet with no ill effects.

2. Understand that legumes such as beans are also notorious for causing gas and digestive problems since they contain two indigestible 5-carbon sugars, raffinose and stachyose.

3. Try frequent small feedings rather than three large meals every day. Although a vegan diet based on vegetables easily meets nutrient needs, vegans must eat ~ 1/3rd more food by volume than omnivores to meet Calorie requirements. Large vegan meals simply overwhelm digestive resources leading to the symptoms you describe. Chew your food thoroughly in a tranquil environment. I'm seldom in such an environment so I run it through a Vita-Mix.

4. For the insomnia problem consider not eating after 5:00 PM. Peristalsis can be a severe inhibitor of sleep, so it's good to give the GI tract time to settle down before you retire. You can reset your appestat easily by just skipping dinner one evening. In the morning you start eating earlier and have your food intake done 6 hours before bedtime and without nocturnal hunger pangs. In the event the insomnia doesn't respond to this you might try 50 mg of diphenhydramine (Benadryl) about an hour before you plan to retire. It's not as fast or as powerful as a prescription sedative but it works, has little addiction potential, and can be bought OTC.

I am a registered nurse and promote this way of eating to my patients and peers and would hate to have to give it up.

I hope you won't have to. Let me know if this advice helps or if you have more questions. Good luck.


-William Harris, M.D.

William Harris MD received a degree in physics from the University of California Berkeley, where he earned Phi Beta Kappa honors. He received his degree in medicine from the University of California at San Francisco, and received his postgraduate training at San Diego County Hospital. He holds a Medical License in the State of Hawaii. He has been an Emergency Department physican since 1963, and the Director of the Kaiser Permanente Vegan Lifestyle Clinic on Oahu until his retirement in 1998. Dr. Harris is the author of The Scientific Basis of Vegetarianism.

In addition, he was the 1950 Big Ten Trampoline Champion, is an accomplished hangglider and commercial pilot, and at age 70 became a skydiver with 108 jumps to date. Dr. Harris has been vegetarian since 1950, and vegan since 1963.

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