The topic of rotating greens typically centres on the concept of avoiding accumulation of alkaloids eaten from the same plant frequently; with specific avoidance of too much oxalate being the hot topic. Oxalate is present in many foods and greens, particularly in spinach and Swiss chard. Oxalates however aren’t alkaloids. Alkaloids are nitrogen based substances that have pharmacological effects on humans and animals, such as nicotine, caffeine and quinine.
Oxalates, like nitrates and phytates, are categorised as ‘chelating poisons’. Chelation is a type of chemistry based bonding to minerals. Chelation is used therapeutically for heavy metal and radiation poisoning using substances like chlorophyll rich chlorella or EDTA. In these instances, the chelation removes the heavy metal acting as a poison to the body. Chelating poisons in the other hand, can bind to beneficial nutrients like zinc, iron, magnesium and calcium and remove them from the body via the urine.
Nitrates can accumulate in plants that are treated with nitrogen based fertilisers. Phytates primarily exist in the hulls of nuts, seeds and legumes. Oxalates are well known to be high in the leaves of rhubarb and we have been raised to believe they are extremely poisonous; however we would still need to eat a lot of them to make us sick. The unpleasant taste would limit that happening which is a perfect example of a plant defence mechanism.
Interestingly, lambs-quarters have up to 30 times more oxalate than rhubarb leaves. Other high oxalate foods include buckwheat, star fruit, purslane, spinach, cacao, sorrel, beets, oats, Swiss chard, celery, kale, collards, parsley, nuts and seeds especially sesame, dandelion greens, turnip greens, concord grapes, dried figs, kiwi fruit and citrus peel. Non green smoothie high oxalate foods include wheat, popcorn, spelt, chickpeas, lentils, soybeans, beer and tea.
Low oxalate foods include apples, avocados, melons, berries, lemon and lime juice, rice, rye, peas, coconut, meat and eggs.
The concern over oxalate is its nature to bind to minerals, particularly calcium, potentially resulting in calcium deficiency or the development of kidney stones. Many of the foods high in oxalate are also high in calcium, which may offset the deficiency concern. With regard to kidney stones, calcium oxalate is just one type of stone formation, with other factors of influence in the body including the body manufacturing its own calcium oxalate, and the association between stone formation and diets low in fibre, greens, complex carbs and water, and high in sugar, refine carbs and meat. The latter is an acid forming diet which fits with the observation of stone formation more frequently occurring in acidic urine. Calcium is an alkaline mineral after all, so perhaps it’s an unfortunate side effect of trying to regain pH balance?
With regard to the amount of oxalate in raw versus cooked food, there is every statement possible published touting higher or lower with either, and most appears to be simply opinion. The research shows minimal reduction with cooking, so overall it’s not worth worrying about. The oxalate argument may seem complex, however what we know, is oxalate is abundant in nature and not just in greens like spinach and Swiss chard. Oxalates will give you that ‘spinach teeth’ sensation when eating them and may cause some nausea if eaten too often. The bottom line is, a variety of greens, a mixture of high and low oxalate foods and a predominantly alkaline forming diet, is less likely to form kidney stones in the first place.