Green Smoothies and Oxalates – How to Minimize Oxalates in Your Smoothies
Green smoothies are Hollywood's latest trend, but these nutritious drinks made by blending fruit and green leafy vegetables have also received a lot of criticism. The critics claim that green smoothies may cause health problems due to their high oxalate content. Oxalates, also known as oxalic acid, are naturally-occurring substances that are particularly abundant in certain green leafy vegetables such as spinach, parsley and purslane. It has been suggested that foods and drinks that contain oxalates, such as green smoothies featuring oxalate-rich greens, may be harmful to people who are susceptible to forming calcium-oxalate kidney stones. Furthermore, those who suffer from primary or enteric hyperoxaluria are usually advised to watch their oxalate intake. Finally, evidence suggests that a diet that is very high in oxalates but low in calcium may lead to problems associated with calcium deficiency as oxalates can hinder the body's ability to absorb calcium.
However, most health expert agree that, unless you suffer from one of the rare conditions that require oxalate restriction, there's no reason to avoid green smoothies. Made of a wide variety of fresh (and mainly raw) ingredients, green smoothies are loaded with health promoting nutrients and minerals. However, as with all good things in life, too much of a good thing may have some negative side effects. If you are concerned about the potential side effects of oxalates found in green smoothies, here are a few great tips for minimizing oxalates in your green smoothies:
1. Choose veg that are low in oxalic acid
Contrary to popular belief, not all green leafy vegetables are rich in oxalates. Kale, for example, is typically low in oxalates. According to data provided by the U.S. Department of Agriculture (USDA), 100-gram serving of kale contains only 20 milligrams of oxalates. This is only 2% of the oxalic acid content of an equal serving of spinach (see Oxalates in Kale vs Spinach).
Other green vegetables that are low in oxalates include broccoli, cabbage, iceberg lettuce, peas, bok choy, cucumber, endives, romaine lettuce and zucchini (based on oxalate values provided by the Department of Nutrition at the Harvard School of Public Health).
2. Use whole foods including the peel
Smoothies made using the entire fruit or vegetable, including the peel, provide a good source of dietary fiber. This fiber in turn reduces the absorption of oxalates from the smoothie. According to a study published in Scanning Microscopy in 1995, also increases in dietary calcium and magnesium help reduce the absorption of oxalates.
3. Rotate your greens
By rotating the greens and vegetables you use in your smoothies you will increase your chances of getting sufficient amounts of all the vitamins and minerals your body needs. In addition, rotating greens will help you minimize your exposure to any single anti-nutrient. Anti-nutrients, such as oxalates and phytates, are plant-based substances that can hinder the absorption of health promoting nutrients, and in large amounts, some anti-nutrients may also be toxic.
4. Moderation is key
You've heard it before, but you'll hear it again: too much of a good thing can be a bad thing! That's also the case with green smoothies. Small amounts of oxalates from green smoothies are unlikely to cause problems in healthy individuals; however, drinking green smoothies in excessive amounts may expose your body to very high amounts of oxalates.