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There are heaps of websites and food packs out there that try to compare this super food to that one. Depending on which testing method is used, you'll see sites and ads proclaiming that blueberries have more antioxidants than red wine; that goji has more than blueberries; that pomegranate juice has more than tea; and that dark chocolate is up there with all of them.
Generally I don't pay too much attention to these comparisons for a couple of reasons.
1. The tests vary in what they measure. Results depend on which test is used e.g. ORAC, FRAP, Folin. Also there will be a wide variation in natural antioxidant levels from season to season and variety to variety (red grapefruit vs yellow grapefruit). Nonetheless the same foods appear at the top of each test method - the usual suspects of berries, spices, herbs, tea, cocoa and wine.
2. New European research has identified the top 100 foods for polyphenols. This is a new listing based on the polyphenol content as measured by the Folin assay method which will supercede the rest. You can find all the details on the Phenol-Explorer database.
What are polyphenols?
Many antioxidants are polyphenols so it's worth knowing a little about them.
Polyphenols are a large class of chemical compounds found in plants. They are characterised by the presence of more than one phenol unit or building block per molecule. A phenol unit consists of a six-membered aromatic hydrocarbon ring, bonded directly to a hydroxyl group (-OH). The simplest of the class is phenol (C6H5OH) which has long been used as an antiseptic. See diagram.
They are also called phenolics. Poly means many, which refers to the large number of groupings of the basic phenol rings. There are over 4,000 polyphenol compounds. Many are powerful antioxidants and can neutralise free radicals, reduce inflammation and slow the growth of tumours.
Here's the chemical structure of resveratrol which is found in red wine:
Examples of polyphenols like resveratrol
Polyphenols add astringency and bite to foods. You'll notice it in tea that's brewed too strong (once called tannins) and in the "greenish" flavour of extra-virgin olive oil or the back palate of red wine. Anything that makes your mouth pucker generally contains polyphenols.
In plants, polyphenols help defend against attack by insects and give plants their colour (anthocyanins).
Examples: resveratrol in red wine, capsaicin in chilli and paprika, thymol in thyme, cinnamic acid in cinnamon, rosmarinic acid found in rosemary, thyme, oregano, sage and peppermint.
What are the top 100
This new research gives you two lists – the first list is the richest 100 foods by concentration, (ie. the number of mg per 100g) while the second comes up with 89 foods ranked by their content per serve. It shows you the best foods and beverages that provide more than 1mg of total polyphenols per serving.
The foods range from 15,000mg per 100 grams for cloves down to a tiny 10mg per 100ml for rosé wine. Many spices and dried herbs appear on this list but not on the Per serve list as their serve size is so small (usually less than a gram or a pinch) that they were excluded.
Think of it this way – while herbs are very concentrated, we use so little that they don't contribute much in a meal. Although at times we can eat generous amounts of some – think of the amount of parsley you eat in tabbouli salad. Tea on the other hand is ranked only No 52 (black) and No 54 (green) on the Per 100g list but makes it to Nos 16 and 17 in the Per serve list as we drink sizeable quantities (200ml/7oz in a cup).
Best overall foods for polyphenols
By combining the two lists I've come up with this general list of the best food sources of polyphenols for each category of foodstuff. I've also linked to my Top 20 Super Foods so you can see the commonalities:
Peppermint, oregano, sage, rosemary, thyme, basil, lemon verbena, parsley, marjoram
Black chokeberry, black elderberry, low bush blueberry, plum, cherry, blackcurrant, blackberry, strawberry, raspberry, prune, black grapes.
Flaxseed, celery seeds
Chestnuts, hazelnuts, pecans, almonds, walnuts
Black olives, green olives
Fruit other than berries
Apples, apple juice, pomegranate juice, peach, blood orange juice, lemon juice, apricot, quince.
Extra-virgin olive oil, rapeseed (canola) oil
Reference: Perez-Jimenez J, Neveu V, Vos Fm Scalbert A. Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database. Eur J Clin Nutr 2010; 64(S3):S112-S120.
A word of caution
1. The researchers noted that the Folin method over-estimates the quantity of antioxidant present so these figures look greater than say the ORAC test from the US FDA which has been the biggest database until now. What this means is what I said at the outset - don't follow the numbers slavishly or base your decision on which fruit or herb to buy by this list. It doesn't matter whether there's 20 per cent more or less. It's the overall ranking that matters.
2. In addition, not all foods with a high antioxidant content have been analysed at this point in time. The authors note the following lack analyses (most are spices or dried herbs) but we'd assume they similar high levels to the ones on the reported list:
dried oregano, dried summer savoury, dried bay leaves, dried camomile, dried coriander, fenugreek, dried winter savoury, pistachio, hyssop, red swiss chard leaves, dried dill, raisin, black pepper, fresh peppermint, fig, fresh lemon balm, fenugreek seed, tarragon, lentils.
Spices in the news
Antioxidant spices reduces triglycerides and insulin response to a high-fat meal
Eating a diet rich in spices, like turmeric and cinnamon, reduces the body's negative responses to eating high-fat meals, according to US researchers. The researchers added two tablespoons of culinary spices to each test meal, which consisted of chicken curry, Italian herb bread, and a cinnamon biscuit. Spices tested were rosemary, oregano, cinnamon, turmeric, black pepper, cloves, garlic powder and paprika, which were selected because of their potent antioxidant activity. The spiced meal raised the antioxidant activity of the blood by 13 per cent and decreased insulin response by about 20 per cent. Published in the Journal of Nutrition.