My recent column about the best way to soak beans to retain nutrients brought a response from Ana Carolina Fernandes, PhD nutritionist and professor at Federal University of Santa Catarina in Brazil. In 2010, her research team published an article in the International Journal of Food Science & Technology in which they reviewed the nutritional impact of various methods of bean soaking and cooking. (Volume 45, pages 2209-2218 if you're interested).
"According to our review," she wrote, "the best practice is soaking beans overnight in water but discarding the water, without boiling, before discarding it. This method not only decreases gas but increases the bioavailability of some nutrients, since some antinutritional factors are also discarded. In other words, although there is some loss of nutrients, the remaining contents are more digested and absorbed than the nutrients from non-soaked beans."
Here's what I gleaned from her informative article: Some compounds in beans are considered "anti-nutrients" because they can interfere with the absorption of some nutrients. Phytates, for example, may reduce the body's ability to absorb iron, calcium and other minerals. Fernandes' review found that dumping the soaking water before cooking was the most effective way to get rid of some of these phytates.
Other substances in beans called oligosaccharides contribute to the unpleasant flatulence most of us wish to avoid. Soaking before cooking and discarding the soaking water also seems to be an effective way to reduce these oligosaccharides, says Fernandes.
Beans are a good source of plant protein and cooking method does not seem to affect their protein content, research has found. And it's interesting that even though some calcium, magnesium and iron can be lost in the soaking water, the minerals that remain may be even more available for the body after cooking. One reason is that some of the substances that interfere with the digestion of these nutrients is tossed out with the soaking water as well.
My answer to comments from a reader on what he considered to be misleading information about dietary fiber on bread labels brought this response from him:
"Thanx. As I'm sure you know, adjusting both size of the loaf and thickness of the slice, are common ways in which bakers manipulate nutritional labels."
We certainly do see different sizes of servings on Nutrition Facts labels. That's because the food labeling law mandates that serving sizes be based on the amounts that people eat. In the case of the bread, the serving is "1 slice" and the size of that one slice varies from product to product.
Thanks for writing!
(Barbara Quinn is a registered dietitian and certified diabetes educator affiliated with Community Hospital of the Monterey Peninsula. She is the author of "Quinn-Essential Nutrition" (Westbow Press, 2015). Email her at to email@example.com.)
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