A new clinical trial affirms the idea that diets rich in antioxidants aid blood sugar control.
Whole plant foods and drinks are rich in a class of antioxidants called polyphenols, and the new trial tested their blood-sugar effects.
Foods and drinks extra-rich in polyphenols include berries, dark leafy greens, dark chocolate, non-Dutched cocoa, green tea, coffee, and extra virgin olive oil.
There's already a small mountain of epidemiological evidence suggesting that diets rich in whole, antioxidant-rich plant foods exert anti-diabetes effects.
And as limited amount of high-quality clinical evidence supports these indications pretty strongly.
But there isn't as much good clinical evidence on this point as we need, so every new finding is welcome.
Clinical trial affirms the anti-diabetes effects of whole foods
A trial published last March found that diets rich in polyphenols improved people's blood fat profiles and reduced oxidative stress (“rusting” of your cells) from free radicals.
As the Italian scientists wrote, “… polyphenols may favorably affect cardiovascular disease risk”. (Annuzzi G et al. 2014)
Now, the same research group – from the University of Naples– recruited 45 people who were overweight or obese, with a body-mass index greater than 30, and therefore prone to diabetes (Bozzetto L 2014).
The Italian team assigned the volunteers to one of four eight-week diets:
  1. Diet rich in polyphenols
  2. Diet rich in omega-3 fatty acids
  3. Control diet low in omega-3 fatty acids and polyphenols.
  4. Diet with abundant omega-3 fatty acids and polyphenols.
Lead investigator Lutgardo Bozzetto said that they picked a variety of polyphenol-rich foods to produce diets that patients found relatively easy to maintain.
The polyphenol content of the polyphenol-enriched diet was slightly higher than that of the diet that included polyphenols and omega-3 fatty acids.
After eight weeks, the results were intriguing and encouraging:
  • The people on the omega-3-enriched diet (group 2) lost the most weight.
  • Only the polyphenol-enriched diet (group 1) enjoyed big improvements in blood sugar and insulin control.
  • Blood-sugar absorption improved in both groups who got polyphenols in their diet (groups 1 and 4).
  • The function of insulin producing beta-cells in the pancreas improved among those eating the diet rich in polyphenols (group 1).
Dr. Bozzetto noted that in general, polyphenols work in ways similar to drugs used to treat diabetes. (As may omega-3s … see “Drug May Help Prevent Diabetes but Omega-3s Offer Comparable Effects” and “Omega-3s Deter Diabetes Signs in Clinical Trial”.)
Accordingly, as she said, people prone to diabetes would be wise to adopt diets rich in whole plant foods (hence polyphenols) to help prevent this debilitating and potentially crippling disease.
Of course, their trial was small and short, so larger, longer trials are still needed to confirm these findings.
Why are whole, polyphenol-rich plant foods so healthful?
Much of what goes in our bodies is sparked and controlled by our so-called “working” genes.
Among thousands of other crucial functions, these bits genetic material control the immune system's inflammation and antioxidant functions.
Tight control over free radicals – via the body's own “antioxidant network” – and inflammation is one key to healthy aging.
Diet plays a big role in health in part because various nutrients and other factors in food and drink exert powerful “nutrigenomic” influences on our working genes.
In short, the “antioxidants” in whole plant foods influence our genes toward healthful, anti-inflammatory states that also aid the body's antioxidant network, moderate blood sugar and more.
Thus, the more whole plant foods you have in your diet, the more your genes will work to optimize and preserve your health.
In contrast, junky diets that lack whole plant foods exert bad influences on our genes, causing serious damage over time.
Plant-food “antioxidants” are actually beneficial gene tweakers
Whole plant foods abound in polyphenol compounds … which are commonly called antioxidants because they behave that way in test tube experiments.
But in general, they do not exert direct antioxidant effects in the body … at least not to a very substantial extent.
Instead, polyphenols exert mild-to-strong indirect effects on oxidation and inflammation via so-called “nutrigenomic” effects on gene switches (e.g., transcription factors) in our cells.
Polyphenols' nutrigenomic effects tend to moderate inflammation and stimulate the body's own antioxidant network … which includes enzymes, lipoic acid, CoQ10, melatonin, and vitamins C and E.
The richest known food source of polyphenols are raw (non-alkalized / non-“Dutched”) cocoa, berries, plums, prunes, tea, coffee, extra virgin olive oil, beans, and whole grains.
Highly beneficial procyanidin-type polyphenols abound in cocoa, dark-hued berries – e.g., blackberries, blueberries açaí berries – grapes, red wine, and tea.
Comparably beneficial anthocyanin-type polyphenols abound in cherries and most berries.
Extra virgin olive oil is uniquely rich in hydroxytyrosol, oleuropein, oleocanthal, and other tyrosol esters … a particularly potent class of polyphenols with clinically documented vascular and brain benefits.
  • Annuzzi G, Bozzetto L, Costabile G, Giacco R, Mangione A, Anniballi G, Vitale M, Vetrani C, Cipriano P, Della Corte G, Pasanisi F, Riccardi G, Rivellese AA. Diets naturally rich in polyphenols improve fasting and postprandial dyslipidemia and reduce oxidative stress: a randomized controlled trial. Am J Clin Nutr. 2014 Mar;99(3):463-71. doi: 10.3945/ajcn.113.073445. Epub 2013 Dec 24.
  • Bozzetto L. Diets naturally-rich in polyphenols improve glucose metabolism in people at high cardiovascular risk: A controlled randomized trial. EAS 2014; June 1, 2014; Madrid, Spain. Abstract M087.
  • Kominami M. Supplementation of olive and grape seed extracts improves vascular function in healthy humans: a randomized controlled study. EAS 2014; June 1, 2014; Madrid, Spain. Abstract M090.