With its oblong purple body, there's no mistaking the appearance of a Kalamata. Its namesake is the same as that of a Greek city in southern Peloponnese. The extensive amounts of sunshine and mild Mediterranean climate make it an ideal environment for growing the Olea europaea. When sold in the European Union, they are required to be grown in this region in order to be labeled Kalamata. In the United States, the labeling laws are not as strict. For example, you will see products branded as California Kalamata when they are grown in that state.
Bottled/canned olives sold under the brand name Iliada (from Greece) were used for this test. This sample was purchased in Norway and while this particular brand is not very common in the United States, its parent company - Agrovim - is one of the largest olive exporters in Greece. Therefore, the same olives are likely being sold under other brand names in the U.S. and elsewhere.
How much antioxidants there are in Kalamata olives is significantly higher versus common black olives, but comparable when compared to some varieties of green. The types of antioxidants in them include:
Hydroxytyrosol - Represents approximately 50% of the phenolic compounds in olives. Studies show is has excellent bioavailability in humans. It has been shown to decrease levels of oxidized LDL "bad" cholesterol with just a small intake of about 10 mg per day, which would equate to around three Kalamata olives (1).
Luteolin - Primarily found in the leaves and bark of plants. Although in lower concentrations, a number of foods contain it including olives, broccoli, chamomile tea, and various herbs and spices like oregano and rosemary. In Chinese traditional medicine, food sources of luteolin have been used as an herbal remedy for inflammation and high blood pressure. Today, this flavonoid is being studied for potential anti-cancer properties (2).
Anthocyanins - These are the pigments which give them their signature purple color. It's the same potent antioxidant found in blueberries, acai, raspberries, and countless other superfoods. The color expressed whether it be blue, red, or purple is dependent on the fruit's pH value.
Oleuropein - This phenolic compound is extremely bitter and as a result, it's traditionally neutralized or removed (at least as much as possible) from Kalamata olives as well as other varieties through curing and fermentation processes. That's unfortunate because while the taste may not be appealing to most people, it is type of antioxidant which is believed to have numerous health benefits. In studies, it has demonstrated as being antiviral, anticancer, anti-inflammatory, antimicrobial, hypolipidemic (cholesterol lowering), and hypoglycemic (lowering blood sugar) (3). While most is removed during processing, inevitably trace amounts will be left behind, which one can argue is a benefit.
Can you eat too many olives?
Given their excellent nutritional value, you may wonder if it's even possible to eat too many Kalamata olives or other varieties like black and green. Yes, it is most definitely possible, but the danger is not caused by the fruit itself but rather the additives they are processed with. The brine they're soaked in often has extremely high sodium content.
For example the nutrition facts label for the popular brand name Pearls (Musco Family Olive Co.) lists a staggering 380 mg of sodium for a serving size of merely 4 kalamata olives. In excess, that's unhealthy for anyone, but especially those with hypertension. We recommend buying reduced or low sodium versions and also minimizing the brine. Rinsing the olives before eating would be ideal, but that may adversely affect their flavor, too.
Olives are also calorically denser than most fruits and vegetables, as the same serving size of 4 Kalamata contains 50 calories. Eating a couple servings is certainly no concern, but binging on an entire bottle of olives in one sitting would not only give you a disastrous sodium overdose, but also a high amount of calories. That being said, they're certainly much lower in calories than olive oil (or any type of oil for that matter) which all clock in at 118 to 120 calories per tablespoon. So if you want the olive taste with fewer calories, stick with the actual fruit versus the oil.
How long do olives last in fridge after opening?
While not specific to Kalamata, the California Olive Committee recommends you consume an opened can or bottle of olives within the first 10 days. Of course, refrigeration during that time is required.
While many people keep opened jars of olives in their fridge for weeks or even months, this is not a good idea as murkiness or milkiness can develop can develop which is bacterial growth. However please note that even unopened bottles can create milky solids, which is simply the hardening or clumping of substances due to the cold temperatures within a fridge.
Olives vs. other healthy foods
To put Kalamata's ORAC in perspective, it's actually slightly higher than fresh goji berries. Dried goji, which are of course the most common form, do have a higher value but that's only because the water content has been removed and hence, their concentration of antioxidants is increased. In terms of fresh produce, Kalamata are about double the value of lacinato kale. Blueberries and raspberries are each around 50% higher than Kalamata.
Research Support, Non-U.S. Gov't: Carlsen MH, Halvorsen BL, Holte K, et al. Nutrition Journal NIH Jan 2010