A recent Consumer Reports article highlights why consumers find it so difficult to navigate through all the misinformation in the nutrition science field.
On Sept. 17, 2017, Consumer Reports (CR) published the article "5 vegetables that are healthier cooked." CR tries to make the case that five vegetables: carrots, mushrooms, spinach, asparagus and tomatoes (which botanically is a fruit), are better for you if cooked vs. eaten raw. Is this true, or is it just another spin on an irrelevant issue? CR initially states that the tips they provide will "unleash their full potential in terms of nutrition. …" Is this statement true? Let's take a look.
Carrots: CR states "cooking ignites this veggie's cancer-fighting carotenoids," by increasing the "concentration of carotenoids by 14 percent." First, it is true that carotenoids are one of the many plant chemicals which are associated with reduced cancer rates among those who consume them. However, as I have explained, this is an association, not a cause-and-effect relationship. It is the synergistic effect of the many thousands of plant chemicals that appear to be responsible for this effect and not the isolation of any specific one. To state that just because cooking increases the concentrations of carotenoids from carrots, it will "ignite" carrots cancer-fighting potential, is a spin. Obtaining more of any plant chemical does not necessarily equate with improved health. The carrot already provides more than enough carotenoids in any state of ingestion. Just because you purportedly ingest 14 percent more is meaningless. More does not mean better, it's just more.
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Mushrooms: CR states "a cup of cooked white mushrooms has about twice as much muscle-building potassium, heart-healthy niacin, immune-boosting zinc, and bone-strengthening magnesium as a cup of raw ones." This statement can almost qualify as a bad riddle. Before you continue reading, stop for a moment and re-read what CR just stated. What is the glaring problem with this statement? It is related to one simple word: cup. Is CR really that naïve to compare the nutrient content of a cup of cooked mushrooms, which has likely four times the number of mushrooms per cup, to a cup of raw mushrooms? What CR should have done was compare the actual number of mushrooms cooked vs raw, not the volume of them. A mushroom is 92 percent water by weight, so when you cook them, the volume is significantly reduced – so of course a cup of cooked mushrooms will have substantially more nutrients. This is common sense.
CR also needs a food chemistry lesson. Potassium is concentrated inside the cell, so when you cook the mushroom and break down the cell wall, some of the potassium is leached out with the water. The same holds true for the niacin. Additionally, when Consumer Reports highlight the so-called positive role of the "bone-strengthening magnesium," they forgot to mention that vitamin D, which is responsible for the absorption of calcium, is greatly reduced during cooking. The last misstep CR makes is stating that mushrooms "sometimes contain small amounts of toxins, but they can be destroyed through cooking." This statement falls under the Principle of Toxicology – The Dose Makes the Poison, which I explained earlier here in WND.
Spinach: CR states, "The leafy green is packed with nutrients [true], but you'll absorb more calcium and iron if you eat it cooked." This is blamed on the oxalic acid in spinach. Oxalic acid is commonly believed to bind with both minerals and prevent their absorption. However, this would only apply to the two minerals contained in the spinach and not from other food sources you may be having with your meal, such as milk for the calcium and any meat item or beans for your iron. Additionally, there are some data indicating that the oxalic acid in spinach may not actually prevent the iron absorption. A study done in 2008, using iron isotope absorption in humans, concluded, "Our results strongly suggest that oxalic acid in plant foods does not inhibit iron absorption." This study was published in the European Journal of Clinical Nutrition and conducted at Institute of Food Science and Nutrition, ETH Zurich, Zurich, Switzerland.
Asparagus: CR states, "Cooking these stalks raised the level of six nutrients, including cancer-fighting antioxidants." The value of antioxidants individually has been over emphasized for well over a decade. They are important, but all plants contain them, and they are readily supplied by any plant-based diet, cooked or otherwise. Antioxidants are not some magical good-health compound consumers have been led to believe, even though they have become a very popular buzzword for marketing products. It is the mix of compounds, not a specific compound. You also increase the production of your own antioxidants when you exercise.
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CR also states cooking asparagus "more than doubled the level of two types of phenolic acid, which some studies linked [my emphasis] to lower cancer rates." A "link" has nothing to do with cause and effect, which I have stated many times. I can pick anyone of the thousands of chemical compounds found in produce or grains and state the same thing. CR should understand the obvious issue here. Diets high in phenolic acid simply means those individuals are consuming a plant-based diet, which of course will reduce their cancer rates. By the way, who eats uncooked asparagus anyway?
Tomatoes: Here we go again with the linked nonsense. CR states "heat increases a phytochemical, lycopene, that has been linked [my emphasis] to lower cancer rates and heart disease." I will not repeat myself again here. Simply see my comments above regarding such "links." You need no more lycopene than is already found in a fresh raw uncooked tomato. If you believe there is magic in lycopene, try some ketchup.
This standard bearer of consumer education receives an F grade on this report. Cooking does not "ignite" these vegetables into superfoods. They are excellent for you regardless how you consume them.