I'll say this now. I find it difficult getting to the bottom of what food is good to eat and how it's best to prepare it.
I hear so much contradictory advice that often I don't know what to believe. Part of the problem is that food studies are not as straight forward as we might think; There are so many genetic, environmental and lifestyle factors that effect how people react to food.
Sometimes I want to bury my head in the sand and just feed my family the status quo diet based on the "healthy" food pyramid. But I push on because I'd like to think my family is better off for my efforts to feed them well.
You may recall that recently I posted a link to The Healthy Home Economist's article where she states that eating raw spinach, silverbeet and kale is bad for you because of its oxalic acid content. Her suggestion is to lightly boil or steam spinach and then discard the water to reduce the oxalic acid content. I've posted my technique for doing that here.
However, my friend Jessica Eccles saw my article and as she has access to medical journals through her university, was able to investigate this topic a little further.
What she discovered is cause for celebration. Here's what she says:
"I was just catching up on your blog when I read that you had stopped eating raw spinach because of what the Healthy Home Economist (HHE) said about oxalic acid. I looked at her blog to read more about it and look at her references. She references Dr. William Shaw and the book Nourishing Traditions. Shaw's assertion that, "Virtually everybody who eats a large spinach salad every day is going to succumb to kidney stones" seems to be based solely on anecdotal evidence; a search of the pubmed database did not come up with any research articles by him on the topic. Unfortunately, I don't have access to Nourishing Traditions, so I wasn't able to see how well-researched that book is.
"Therefore, I decided to have a look at the current research myself.
"The research articles I found support some of the HHE's claims but do not support others and overall it looks like we can continue eating spinach (raw or cooked) without much danger that we will develop kidney stones or reduce our iron or calcium stores.
"The HHE says "[oxalic acid] also blocks iron and calcium absorption". Contrary to this, Bonsmann et al. found that oxalic acid did not influence iron absorption in humans. Weaver et al. found that oxalic acid decreases calcium absorption in rats but they also mention that "most of the human balance studies have indicated that spinach does not adversely affect calcium balances". Also, while oxalic acid inhibits calcium absorbtion it appears that calcium inhibits oxalic acid absorption.
"The HHE says "[oxalic acid] may contribute to the formation of kidney stones." However, a large prospective study by Taylor and Curhan found "Oxalate intake and spinach were not associated with [kidney stone] risk in younger women. These data do not implicate dietary oxalate as a major risk factor for nephrolithiasis [kidney stones]."
"I also found a study about the effect of probiotics on oxalic acid absorption. In this study it was found that probiotics reduced oxalic acid absorption markedly in people who naturally absorbed high amounts of this acid, and slightly reduced absorption in other people.
"From my reading, this all means that spinach won't affect your iron or calcium levels by much, and eating raw spinach probably won't increase your risk of developing kidney stones.
"Even if you happen to be a high oxalic acid absorber, and therefore perhaps at a higher risk for developing kidney stones, it's still probably OK because the probiotics that you eat anyway from kefir, yoghurt, etc. will markedly reduce the absorption."
[this reference is here so that you can see for yourself that his research is not well referenced]
I've linked this post up to Healthy 2day Wednesdays.