Interesting article found on Catalyst Athletics site:
An acquaintance of mine had a similar experience. She went on a weight loss diet and, upon the advice of a popular diet program, started eating whole grain crackers and bread for snacks. As a result, she also developed insomnia, heart palpitations and anxiety problems, which all stopped as soon as she cut off the whole grain, high fiber diet and went back to a lower grain, lower carb diet. All of her symptoms are medical issues that have commonly been linked to deficiencies of magnesium, and there have been medical studies that show that high fiber, whole grain diets can lead to decreased absorption of magnesium and other important minerals. So the symptoms linked to her diet changes may have logically been attributed to her increased consumption of whole grains.
Personally, I’ve never noticed any problem with high fiber foods that were not whole grains. It’s only whole grains that my body seems to have a problems with. Fiber from cooked beans, fruit and vegetables seems to be fine.
Many medical web sites state that while foods like whole wheat have phytates that may bind with minerals and make them less absorbable, the amount of minerals contained in the food makes up for this. I would say this dogma does not correlate with my personal experiences nor those of my friend. So I checked PubMed to see if there have ever been any actual studies on this subject.
Interestingly, I found a study just on this subject from researchers at the Research Department of Human Nutrition, Royal Veterinary and Agricultural University, Frederiksberg, Denmark. The study abstract was entitled Zinc, copper and magnesium absorption from a fibre-rich diet. The researchers examined selected mineral absorption and retention from a high fiber and high phytate diet of conventional foods in 8 healthy subjects. At the end of their study, they concluded that absorption of zinc, copper and magnesium from the fiber rich diet was not sufficient to cover intestinal and urinary losses of these elements, resulting in negative balances.
“Because whole grains and milk maintain the next to the lowest nutrient density rankings, displacement of fruit, vegetables, lean meats, and seafood by these staple food groups lowers the overall micronutrient density in the diet.”
from Origins and evolution of the Western diet: health implications for the 21st century, American Journal of Clinical Nutrition.
So this study confirmed what my acquaintance and I had both suspected from high intakes of whole grain foods. Perhaps for some people who may not be at risk for mineral deficiencies, these negative mineral balances would not pose a problem. In fact, consuming whole grains have been shown to be a great way to lose weight. Whole grains contain enzyme inhibitors that interfere with metabolic efficiency, causing the body to burn extra calories just to digest and absorb whole-grain foods. If you are overweight and not nutritionally deficient, then maybe this type of food is ideal for you. However, for people like me who always seem to be on the cusp of nutritional deficiencies, especially those of zinc and magnesium, I’ve learned that high grain fiber, high phytate diets are not the best food choice.
http://www.ctds.info/high_fiber_diets.html
