Study Puts "?" Behind Beneficial Health Effects of Veggies! Is There No Correlation Between Antioxidant Content & Beneficial Health Effects of Cucumber, Lotus & Rape!?

Don't obsess about "optimal" antioxidant contents, just eat your veggies!

Over the past couple of weeks, ... no actually over the past years I have repeatedly written about the concept of (mito-)hormesis and its consequences for the well-established, but not necessarily accurate free radical theory of aging (and for some people everything else). ROS, i.e. reactive oxygen species, have been established as an important signalling molecule that is - among other things - heavily involved in the insulin sensitizing effects of exercise. "Inflammation" makes muscles grow and burns body fat and the "what doesn't kill me makes me strong" principle appears to reign everywhere you look.

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That being said, the latest study from the Institute of Health and Environmental Medicine in Tianjin, China, opens another "anti-antioxidant" Box of Pandora. One that puts a huge questionmark behind the implications of hundreds of thousands of scientific studies, when it says in it's title, already: "No correlation is found for vegetables between antioxidant capacity and potential benefits in improving antioxidant function in aged rats"

"Skin of Grape Tomatoes Contains Max. Amount of Antioxidants" - You can find this and dozens of other daily updated SuppVersity Science News on www.facebook.com/SuppVersity

This is a title that may in fact change the way we look at study results like those of a recent study by Valdez-Morales, et al. (2014) investigating the "best" = highest antioxidant tomato, the results of which you are about to find among the ~20/day SuppVersity Facebook News @ www.facebook.com/SuppVersity - don't forget to like it, or you'll miss out on the latest science news!

If the results of the study can be confirmed by an independent team for vegetables other than lotus root, rape or cucumber and if there is an identical mismatch between the in-vivo anti-oxidant capacity and the potential benefits in improving antioxidant function in (aged) humans.

This would be big and highly consequential news for nutrition experts, scientists and average Joes and Janes like you and me. Why? Well,...

• any ranking of "superfoods" that was based even partly on in vitro data derived with the good old ferric reducing antioxidant power (FRAP) assay would be invalid, ...
• every scientist who has been following up on "promising" data from FRAP assays would have been wasting his time, ...
• and you may have been eating all the wrong foods for years...

... hell no, as long as you ate your veggies over the past years, I wouldn't worry if you may have made a "suboptimal" selection (which would be different based on whatever new criteria you select).

Figure 1: FRAP value, vitamin C and vitamin E content and total amount phenolics in the powdered vegetables that were added to the rodent diets in the study at hand (Ji. 2014)

Honestly, I'd hope that you didn't select your foods only based on the orthorexic principle of maximal antioxidant content, anyways. 

Never forget the three principles of veggie eating: Variety, seasonality, colorfulness

Against that background I'd recommend you keep eating your lotus roots, if you like them, although, they have a significantly lower beneficial effect on SuperOxide Dismutase (SOD, a group of antioxidant enzymes) than rape and cucumber.

Figure 2: Serum markers of anti-oxidant status / oxidative damage after 6 weeks on the three experimental diets (Ji. 2014)

Moreover, if you look closely at the data in Figure 1+2, you will realize that lotus may suck at SOD and its ability to reduce hemolysis (the destruction of red blood cells), but will have the most profound beneficial effects on the levels of malondealdehyde (MDA), a marker of lipid oxidation, and the amount of plasma carbonyls, which have - just as in cellular regulation, aging, and disease (Levine. 2002). Just like their similarly radical cousins, carbonyls will thus play a dual role so that in the end, their reduction may not be beneficial in each and every case.

Figure 3: Blood mononuclear cell DNA damage expressed as total injury rate (%) and total tails low (% of all) in male Wistar rats on control and experimental diets (Ji. 2014)

The Take Away: Whatever the role of carbonyls, MDA & co may be and no matter what you believe which of the three tested vegetables may be the "best" one, if there is one definite message you can take home from today's SuppVersity article, it's not to overly rely on the abstract data from chemical tests the reliability of which appears to be inversely proportional to their accuracy.

Trust your instincts and go for a broad variety of vegetables. Eat seasonal! Eat colorful! And most importantly eat plenty. Optimal or not, none of the vegetables in the study at hand would harm you - all of them would help you defy diabesity and slow the aging process as best mother nature allows.

Reference: 

• Ji, Linlin, et al. "No correlation is found for vegetables between antioxidant capacity and potential benefits in improving antioxidant function in aged rats." Journal of Clinical Biochemistry and Nutrition 54.3 (2014): 198-203.
• Levine, Rodney L. "Carbonyl modified proteins in cellular regulation, aging, and disease^{2, 3}." Free Radical Biology and Medicine 32.9 (2002): 790-796.
• Valdez-Morales, Maribel, et al. "Phenolic content, and antioxidant and antimutagenic activities in tomato peel and seeds, and tomato by-products." Journal of Agricultural and Food Chemistry (2014). Accepted Manuscript.

Fruit Olympics: Study Analyses Antioxidant and Total Phenolic Content of 62 Fruits

Did you ever want to know how your favorite fruit would perform in the most prestigious disciplines of the "Fruit Olympics", i.e. antioxidant capacity and phenolic content? Yes? Well, I guess a group of researchers from China has just done you a favor...

Xu et al. (Xu. 2011) analysed the antioxidant capacity by Ferric-reducing antioxidant power (FRAP) assays and the free radical scavenging capacities by Trolox equivalent antioxidant capacity assays (TEAC) and found:

Seven fruits had the strongest antioxidant activities among 62 tested fruits [...] they were Chinese date, pomegranate, guava, sweetsop, persimmon, Chinese wampee and plum (sanhua). In addition, olive showed the strongest free radical scavenging ability, and cherry and pineapple also had high antioxidant capacities. Because of their high antioxidant activities, it could be speculated that these fruits will be beneficial for the diseases caused by oxidative stress.

An interesting observation is that the total antioxidant capacity measured by FRAP and the radical scavenging capacities directly assessed by Trolox show only a weak correlation of R² = 0.0337 (0<1; R = 1 would indicate 100% correlated), which would "suggest that the compounds capable of reducing oxidants could be different from those scavenging free radicals in these fruits". By removing the four fruits with the highest antioxidant capacity, however, the correlation increases to R²=0.7169, which makes me think that the lack of correlation might be explained by artifices of the measuring process at high antioxidant concentrations. It is nevertheless an interesting thought that, after all, the amount of antioxidants (measured by FRAP) would only partly explain the free-radical scavenging capability of a certain food.

Figure 1: The Chinese or red date (also known as Jujuba), an antioxidant powerhouse with an abundance of polyphenols (photo by Marco Schmidt, Wikipedia)

Next to antioxidants, the "perfomance" in terms of total phenolic content, constitutes the second most prestigious discipline of the "Fruit Olympics". Xu et al. used the Folin–Ciocalteu method, "which relie[s] on the transfer of electrons from phenolic compounds to the Folin–Ciocalteu reagent in alkaline medium, and is a simple and widely used method" and found that

[...] the total phenolic contents varied from 11.88 to 585.52mg GAE/100 g with the difference of 49-fold, and the mean value was 71.80 mg GAE/100 g for 62 fruits.Chinese date (585.52    +/-18.59 mg GAE/100 g) had the highest total phenolic content, followed by sweetsop (405.41 +/-16.70 mg GAE/100 g), guava (194.11+/-7.01 mg GAE/100 g), pomegranate (146.94+/-0.04 mg GAE/100 g), Chinese wampee (116.10+/-7.48 mg GAE/100 g), cherries (114.56+/-4.72 mg GAE/100 g), persimmon (112.09+/-4.60 mg GAE/100 g) and plum (sanhua) (102.43    2.83 mg GAE/100 g), but pear (honey) had the lowest total phenolic content (11.88    0.11 mg GAE/100 g) among the tested fruits.

Another result is that olive oil had the highest content of gallic acid (50.25 ± 4.87 mg/100g), followed by wax apple and Chinese date. The latter also had the highest content of cyanidin-3-O-galacoside (13.5 ± 0.11 mg/100g, while one of my personal favorites, the pomegranate, outperformed the competition in terms of  quercetin-3-glucoside (11.1 ± 0.60 mg/100g). If you are looking for hesperitin, a natural COX-2 inhibitor (anti-inflammatory), lemons should be your "fruit athlete" of choice.

Figure 2: Although he is not among the "top athletes", a recent study has shown that "an apple a day [in fact] keeps the doctor away" (photo by Firr2000)

In view of all this data, don't forget the motto of the original Olympic Games: "Its taking part that counts!" Or, in other word, get your daily serving of healthy fruits and if you cannot stand Chinese dates, or Jujuba's as they are commonly called, as well, eat something less exotic - remember: A recent study validated the old saying "an apple a day will keep the doctor away".