To Microwave or not to Microwave? Fish Thrives, While Extra Virgin Olive Oil Deteriorates in the Microwave Oven

The effect of microwave steaming, i.e. steaming with the microwave by the means of one of those microwave steaming bags has not been tested in the study at hand, but it should be relatively harmless... assuming your steaming bag is BPA free.

I know that people all around the world still argue that microwaving your foods would modify them in ways that render them at least less, if not simply downright unhealthy. In reality, however, the safety of microwaving is well established; and there's evidence suggesting that it is rather the way of heating you should prefer than the way to heat you should avoid.

With the latest study from the Unidad de Investigación y Desarrollo de Alimentos the previously discussed and often (falsely) ignored formation of oxysterols, i.e. oxidized cholesterol that's bad for your metabolic and cardiovascular health microwave (MW) foods or I should say fish just got even more attractive.

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As Leal-Castañeda et al. point out in the introduction to their paper, "cholesterol oxidation products (COPs) formation depends on the conditions of MW heating and the composition of the food matrix" (Leal-Castañeda. 2016).

It is thus only logical that the Mexican researchers compared different oils / foods, namely palm, extra virgin olive, soybean and fish oils. All oils were heated in a two different microwaves:

• a Panasonic, Model NN-6653, 900 W, operating at in multimode
• Thermo CEM DISCOVER series SP-D, operating in monomode

But wait, where's the cholesterol in palm, olive ad soybean oils? Obviously, there is none. Accordingly, the scientists added a standardized amount of 2.5 mg of cholesterol/g of oil to all four test oils before MW heating them.

Table 1: Temperature reached by in lipid systems made of oils and cholesterol during heating in multimode MW oven; the monomode MW was set to heat until the temperature was 180°C  (Leal-Castañeda. 2016).

Next to the temperature and oxysterol formation, the scientists also monitored the changes in peroxide value and fatty acid (FA) profiles.

"MW heating of edible oils may cause its degradation by oxidation, hydrolysis and polymerization. It has been suggested that the unsaturated components of the oils are usually the most susceptible to these degradation processes, altering their physicochemical properties and FA profile. However, it has been reported that heating time and temperature, and the presence of natural antioxidants (tocopherols, chlorophylls, carotenoids and phenolic compounds) have a significant influence on the extent of the oxidative processes. [In the study at hand, the] most relevant change was the decrease of PUFAs presen[t] in fish oil (Figure 1)" (Leal-Castañeda. 2016).).

As Leal-Castañeda, et al point out (2016), the significant decrease of PUFAs in fish oil heated in MW (both unimode and multimode) and conventional oven is in agreement with Weber et al. (2008) and Zhang, et al. (2013), who observed a slight decrease in the PUFA content in silver catfish fillets and grass carp (ctenopharynyodon idellus) fillet (this is important, because this is a whole food) baked in conventional oven, and a greater reduction when MW oven was employed.

• Overall, the maximum total COPs contents "largely varied (46.4-250.4 μg/g lipids), depending on the type of heating system and oil matrix" (Leal-Castañeda. 2016).
• In that, the multimode MW heating caused greater COPs formation than the unimode MW. 
• On the other hand, the COP formation in the allegedly healthier was significantly higher - albeit only for fish oil - than during either of the two microwaving treatments.

If you scrutinize the data in Figure 1 you will see that another not exactly expected result of the study at hand was that that "soybean oil, compared with the other oils tested, did not promote cholesterol oxidation during MW heating" (Leal-Castañeda. 2016).

The contents of vitamin C and total carotenoids, aliphatic and indole glucosinolate in broccoli cooked by different methods Effects of  cooking methods (1. raw; 2. boiled; 3. steamed; 4. microwaved; 5. stir-fried; 6. stir-fried/boiled | Yuan. 2016).

Steaming and microwaving have been repeatedly shown to produce the least oxidative damage / detorioration of vitamins and other healthy molecules to cholesterol- and non-cholesterol containing food products, such potatoes (Tian. 2016), broccoli and cauliflower (Yuan. 2009; Mansour. 2016), other legumes and vegetables (Fabbri. 2016).

In that, the effects may differ not just based on the macronutrient composition of the food, it may also differ for individual micronutrients such as vitamins or indoles.

That's much in contrast to the allegedly healthier extra-virgin olive oil and palm oil, where the formation of oxysterols skyrocketed, in spite of the presence of natural antioxidants during MW heating.

Figure 1: Oxid. of cholesterol in lipid systems made of oils and cholesterol after 20 min of heating in unimode (UMO), multimode MW (MMO) oven and conventional (CO) oven (Leal-Castañeda. 2016) - 5,6α-CE, 5,6α-epoxycholesterol; 5,6β-CE, 5,6β-epoxycholesterol; 7α-HC, 7α hydroxycholesterol; 7β-HC, 7β-hydroxycholesterol; 7-KC, 7-ketocholesterol

In view of these important differences, it should be obvious that "the type and composition of the lipid medium should be considered for formulation of food products to be cooked in MW for long time periods (>10 min)" (Leal-Castañeda. 2016) - with high PUFA oils being more susceptible to oxidative damage than low PUFA oils and a suspicious lack of effect of natural anti-oxidants on the extents of oxidative degradation, and thus the overall nutritional quality and safety of food products.

After being absorbed in the gut, exogenous oxysterols are incorporated into cyclomicrons and will subsequently have the same ill (heart-)health effects as their endogenously produced (by inflammation) cousins (Otaegui-Arrazola. 2010)

It's not just about fish... If you revisit the data in Figure 1 you will realize that the likewise relatively PUFA rich extra-virgin olive oil showed a highly significant increase in oxysterols, especially 7α hydroxycholesterol, when it was heated in a classic (older technology) multimode microwave with its characteristically random temperature differences in different part of whatever it is you are cooking.

Whether and why the local temperature distribution is highly relevant for olive oil, but neither palm, soy or fish oil is something future studies will have to determine... in fact, we'd even have to confirm that it is the temperature difference, nothing else that explains the significant differences.

But do you even care? Well, it depends. Oftentimes you may not even have cholesterol in your EVOO. "Often", however, is "not always" and whenever you microwave animal products in EVOO, you will end up having sign. amounts of oxidizable cholesterol around - cholesterol that has been shown to be absorbed and "could represent a significant health risk" (Leal-Castañeda. 2016 | cf. Sottero, 2009 & Staprans, 2003). Comment on Facebook!

References:

• Fabbri, Adriana DT, and Guy A. Crosby. "A Review of the Impact of Preparation and Cooking on the Nutritional Quality of Vegetables and Legumes." International Journal of Gastronomy and Food Science 3 (2016): 2-11.
• Mansour, Abd Allah, et al. "Effect of Domestic Processing Methods on the Chemical Composition and Organoleptic Properties of Broccoli and Cauliflower." American Journal of Food and Nutrition 3.5 (2016): 125-130.
• Otaegui-Arrazola, Ana, et al. "Oxysterols: a world to explore." Food and Chemical Toxicology 48.12 (2010): 3289-3303.
• Sottero, Barbara, et al. "Cholesterol oxidation products and disease: an emerging topic of interest in medicinal chemistry." Current medicinal chemistry 16.6 (2009): 685-705.
• Staprans, Ilona, et al. "Oxidized cholesterol in the diet is a source of oxidized lipoproteins in human serum." Journal of lipid research 44.4 (2003): 705-715.
• Tian, Jinhu, et al. "Domestic cooking methods affect the phytochemical composition and antioxidant activity of purple-fleshed potatoes." Food chemistry 197 (2016): 1264-1270.
• Yuan, Gao-feng, et al. "Effects of different cooking methods on health-promoting compounds of broccoli." Journal of Zhejiang University Science B 10.8 (2009): 580-588.
• Zhang, Jinjie, et al. "Effect of cooking styles on the lipid oxidation and fatty acid composition of grass carp (ctenopharynyodon idellus) fillet." Journal of Food Biochemistry 37.2 (2013): 212-219.

Fishing for Muscle: Cod Protein Promotes Muscle Repair After Injury More than Casein or Peanut Protein

Image 1: There are obviously more nutritionally valuable parts to cod than just its liver.

On Wednesday, you have learned that diet-deoptimization with rice instead of casein protein is a possible way to gain less weight. Today, we are going to tackle what appears to be a way more promising alternative to the dairy-based top-dogs among the protein supplements: Cod protein! Within the health and fitness community, the cold(er) water fish is hitherto, above all, known for its vitamin-laden liver and the oil humans have been producing from it and consuming for centuries, now. That the arginine-, glycine- and taurine-rich protein of its tasty white flesh could soon replace - or at least complement - dairy proteins (casein, whey) as the physical culturists' go-to protein for muscle building and regeneration will yet probably be news to most of you, right?

COD - Canned or dried? Probably doesn't matter as long as you eat it.

In a recently published paper on yet another rodent protein feeding trial (Dort. 2012), Junio Dort and his colleagues from the Laval University and the Research Center of CHUQ, CHUL in Quebec, Canada, report that the artificially injured tibialis muscle of rodents that were kept on cod-protein based diets for 21-days healed significantly faster than the skeletal muscle of the peanut or casein protein control groups.

Figure 1: Amino acid profile of casein, peanut and cod protein source on which the otherwise identical rodent diets were based (based on Dort. 2012)

For the smart SuppVersity student you are, it should not take more than just a brief glance at the amino acid profiles of the three protein sources to identify cod protein and casein as superior and peanut (as it was to be expected) inferior protein source. With -24% and -30% less branched-chain (BCAA) and total essential amino acids (EAA), peanut protein would certainly not be the first choice of any non-vegan physical culturist, let alone bodybuilder, who is interested in opti- and not deoptimizing his his/her diet (on an unrelated not: Don't you Americans never refer to the ladies, first? I always read "his/her" - that would not exactly be gentleman-like here, in Germany!).

118 neutrophils and still counting: Cod protein (not oil, in this case) tames the inflammation

In order to assess how peanut, casein and cod-based diets would modulate the rodents' response to muscular injury the animals were treated with bupivacaine, a substance that is myotoxic ("kills" muscle cells, but - and this is a specialty of bupicacaine - not satellite cells) at higher doses (here 100µL). The drug was injected into one of the animals' tibialis muscles, while the contra-lateral side was sham-injected (saline injection) to serve as a control. At days 3, 14, and 24 post-injury, both the injured and sham-injected tibialis muscles were "collected" (8 animals per dietary group) and the neutrophil count, and macrophage infiltration - both measures of ongoing inflammation and thusly incomplete healing subsequent to prior muscle damage - were assessed.

Figure 2: Neutrophil count and EDI+ macrophage count in bupivacaine injected tibialis muscle 3 and 14 days and 14 and 24 days after the injection; data expressed relative to sham control (data calculated based on Dort. 2012)

As the data in figure 2 goes to show, the cod protein group showed a markedly faster reduction in neutrophil and EDI+ macrophage count than the casein group, which - in a separate experiment - had already been found to sustain the healing process better than the nutritionally inferior peanut proteins, which also exhibited a -19% lower feeding efficacy (meaning that similar to the rice protein in Wednesday's newspost, it lead reduced weight gain; again, not necessarily desirable, specifically in injured rats) and, "in results previously published, [...] lower skeletal muscle mass than those fed casein [even] before injury" (Dort. 2012).

The anti-inflammatory effects of cod protein reach beyond skeletal muscle

Though muscle is, as my friend Carl Lanore likes to say, "metabolic currency" and it's protection and repair should be on everyone's, man and women top list of health priorities, the benefits of cod protein extend beyond skeletal muscle. A brief review of the literature revealed among others ...

• increases in HDL, decreasse in VLDL with cod over casein and soy (Jacques. 1995)
• restoration of GLUT-4 activity in skeletal muscle of HFD obese rodents (Trembley. 2003)
• lower hepatic triglyceride production vs. beef or casein (Demonti. 2003)
• lowest insulin / glucose ratio (vs. soy or casein), when given as part of complex test meal (Post-Skagegard. 2006)
• improvements in insulin sensitivity and reductions in C-reactive protein vs. diet containing beef, pork, veil, eggs and dairy in insulin resistant men and women (Ouellet. 2007; Ouellet. 2008)

Just as the improved healing of the muscoskeletal injury in the rodent study at hand, most of the aforementioned effects are probably attributable to the modulatory the homemade cod protein (the scientists simply used frozen cod fillets to prepare their protein powder) exerts on the immune system. In this context, it is particularly important to mention that

[...] an impairment of insulin-stimulated glucose uptake and a reduction of protein synthesis, combined with an increase of muscle protein degradation, are the main adverse metabolic changes induced by injuries in skeletal muscle.

In previous studies, the researchers were also able to show that the profound impairment of the AKT /PKB pathway, which is one of the key mechanisms behind the nutrient induced increase of protein synthesis, is protected from the impairments of "high fat diets" (the researcher variety, which is more akin to the standard American than to "low carb" diet), if the latter contains cod, instead of soy- or casein-protein (Tremblay. 2003).

Arginine for repair, EAA for growth: It may be of interest that Dort et al. attribute the muscle building and muscle repairing effects of cod protein to different amino acid in the cod protein. While they believe that its high arginine content suffices as NO precursor to drive and accelerate the repair process, they hold the high essential amino acid (EAA) content responsible for its pro-anabolic effects which are comparable to those of casein (and probably even whey) proteins.

Image 2: Fish is not for you? Maybe you just don't know how to prepare it properly? It's not really difficult to grill a fillet, trust me - even I can do that.

It stands to reason, that both the restoration and / or maintenance of skeletal muscle mass and insulin sensitivity, as well as the general anti-inflammatory properties of cod protein (remember: the protein in the study was derived directly from frozen fillets and contained almost no fat!) come handy for everyone who wants to live a healthy and active live into the old age. In this regard the study result do not only underline the importance and multifaceted benefits of regular fish consumption (fatty or not) as part of a healthy diet, they also support my repeatedly proffered believe that the latter should not be defined by macronutrient ratios, let alone calories, but must be build around concrete meal and food suggestions, as well as general and flexible recommendations regarding the frequency and combinations in which these can be consumed.