There’s no shortage of nutritional advice, with many experts saying entire food groups are bad. Vegans warn against animal products, while meat eaters warn against grains and legumes. But leafy greens seem to be universally praised. The more vegetables you eat, the better your health, right?
Not necessarily. called a compound oxalate Eating leafy greens and other foods may make us rethink how much we eat.
What is oxalate?
Oxalate (oxalic acid) is a natural compound found in many plant foods, but is also produced as a waste product in the body. Our bodies can make vitamin C from excess vitamin C, certain amino acids (glycine and hydroxyproline), and glyoxylic acid.
Plants produce oxalates and alkaloids as a defense mechanism to prevent predators from eating them. This compound also protects against viruses and bacteria. However, eating foods high in oxalate or foods rich in oxalate precursors can increase your oxalate levels.
The body typically absorbs only 2 to 5 percent of dietary oxalate when consumed as part of a diet. On the other hand, up to 12% of oxalate can be absorbed from foods high in oxalate or drinks taken on an empty stomach.
Most of the oxalate is excreted through the kidneys and into the urine. However, if oxalate levels build up to the point that they overwhelm the kidneys, crystals can form. If these crystals build up in your tissues, they can cause kidney stones or other problems.
Do foods contain oxalate? really Big deal?
The effects of oxalate depend on how it is bound to food. In vegetables, oxalates are often combined with minerals such as calcium. The mineral-to-oxalate ratio of these foods determines how problematic the oxalates can be.
However, under certain conditions, oxalate absorption may increase. In people with impaired fat absorption, fat binds calcium, making more free oxalate available for absorption. As a result, these people can absorb more than 30% of the oxalate they consume.
People with the following conditions are particularly at higher risk:
- Irritable Bowel Syndrome (IBS)
- Inflammatory Bowel Disease (IBD – Crohn’s Disease and Colitis)
- celiac disease
- short bowel syndrome
- bariatric surgery
- Drugs that block fat absorption, such as orlistat (Alli)
However, only about 20% of the body’s oxalate comes from food. The rest can occur in a variety of different situations.
Health problems associated with high oxalate levels
Although harmless in small amounts, excess oxalate can be harmful, especially if it is not broken down and excreted properly. Some consequences that can occur due to high oxalate include:
kidney stones
Oxalate produced internally or absorbed from food can combine with minerals to form oxalate crystals. Calcium salts and oxalate crystals can combine to form calcium oxalate kidney stones. About 80% of kidney stones are made up of calcium oxalate.
nutritional deficiencies
Most leafy vegetables are rich in minerals, but these minerals are often bound to oxalate, making them less bioavailable. Like phytate, free oxalate is an anti-nutrient that can bind to minerals and reduce their absorption. The negative charge of oxalate makes it easily combined with positively charged forms of minerals such as calcium, magnesium, and iron.
Ingested oxalate binds these minerals in the intestines, allowing them to be excreted in the feces rather than being absorbed and used by the body. Calcium deficiency can cause osteopenia and osteoporosis. Iron deficiency can cause anemia.
However, when balanced with calcium, you are less likely to steal nutritional minerals from your food.
Pain and UTI-like symptoms
High oxalate does not necessarily cause kidney stones, but crystals anywhere in the urinary tract can be problematic. In some women, it causes vulvodynia or pain in the vulva. About one in four women with vulvodynia see significant improvement in their symptoms when they eat a low-oxalate diet.
Increased oxalate in the urine can also cause urinary tract infections. It may cause frequent urination, bladder pain, and an intense urge to urinate. Women with recurrent UTIs often have high levels of oxalate in their urine. Of course, UTIs can also be caused by antibiotic use, which can kill healthy bacteria.
Highly toxic potential
According to several case reports, ingestion of 4 to 5 grams of oxalate can cause death in adults. In one case, a 56-year-old man who drank 16 cups of black tea daily for several years developed kidney failure. In another case report, a man died after consuming 500 grams of sorrel in soup (6 to 8 grams of oxalate) in one sitting. It is difficult to say whether these deaths were caused by oxalates or other ingredients or toxins in the food. However, it is worth considering the potential harm.
May cause other diseases
Oxalates can cause diseases outside the urinary tract. Dr. Isabella Wentz suspects oxalate contributes to hypothyroidism in some people. It can also cause joint pain, body pain, and depression.
Oxalate injections cause breast cancer in rats, and oxalate calcium salts are found in breast cancer cells.
Foods high in oxalic acid
Certain leafy vegetables, tubers, seeds, and, unfortunately, chocolate are also high in oxalates. The oxalate to calcium ratio plays an important role in determining health effects. Many leafy vegetables are high in oxalate and low in calcium.
The ratio of oxalate to calcium in common foods is as follows (per 100 g):
- spinach: Oxalate 890-1100 mg, oxalate to calcium ratio ~4-5:1
- rhubarb: 275-1336 mg oxalate ~ 8-9:1
- purslane: 910-1679 mg oxalate, ~ 5:1
- Beet greens: 300-450 mg oxalate, ~2.5:1
Many tubers and seeds contain high levels of oxalates, including:
- Beetroot: 121-450 mg oxalate, ~ 5:1
- Tarot: 278-574 mg oxalate, ~ 10-20:1
- sweet potato: Oxalate 470 mg, ~ 30:1
- sesame: 350-1750 mg oxalate, ~ 0.3-2:1
- Kakao: 500-800 mg oxalate, ~ 4-6:1
For sensitive individuals, experts recommend avoiding foods containing more than 50 mg of oxalate per 100 g. Other high-oxalate foods to avoid include collards, okra, cornmeal, wheat germ, beans, blackberries, and oranges.
Benefits of foods high in oxalic acid
At extremely high doses, oxalate can be toxic. However, eating it in moderation can improve your health.
Inducing hormesis
Small amounts of toxins such as oxalate may cause it. hormesisMild stress is a process that promotes healing and strength. It’s similar to lifting weights, which damages your muscles but makes them stronger. Consuming some oxalates may activate your body’s defense mechanisms and improve resilience.
Provides essential nutrients
Foods high in oxalate, such as spinach, sweet potatoes, and cacao, contain essential vitamins and minerals. For example, spinach is a great source of vitamin K, folate, and iron. Sweet potatoes are an excellent source of beta-carotene, which the body converts to vitamin A. Cacao is rich in magnesium, iron, and flavonoids.
Nuts and seeds are rich in omega-3 and monounsaturated fatty acids, and beets contain nitrates. These nutrients are essential for bone health, vision, cardiovascular health, and immune system.
Provides antioxidant support
Many foods high in oxalate are rich in antioxidants that fight free radicals. Spinach and beet greens contain lutein and zeaxanthin, which protect your eyes. Flavonoids in cacao may lower blood pressure and support heart health. Raspberries and blackberries contain vitamin C and anthocyanins, which support the immune response.
Supply of fiber and resistant starch
Seeds, legumes, taro, and tubers such as sweet potatoes provide dietary fiber that supports gut health. Taro root provides resistant starch that nourishes beneficial gut bacteria and supports metabolism.
cancer prevention
Some high-oxalate foods contain bioactive compounds that may reduce cancer risk. Cruciferous vegetables, such as kale, contain glucosinolates, which have anticancer properties. Rhubarb contains anthraquinones, compounds known to reduce inflammation and potentially fight cancer.
Should I go on a low-oxalate diet?
Most people can safely enjoy foods high in oxalic acid in moderation. However, people with the following conditions may want to try a low-oxalate diet:
- kidney stone disease
- Pain in the vulva (vulvodynia) or pain during intercourse
- frequent urination
- Frequent urinary tract infections (UTIs)
- joint pain
- hypothyroidism
- Mineral deficiencies (calcium or iron, leading to osteopenia, osteoporosis, or iron deficiency anemia)
You should also pay attention to your oxalate levels if you have digestive issues that prevent fat absorption. This is especially true if you see floating feces or fat in your stool.
If you’re wondering if you have high oxalate levels, it’s a good idea to get tested by your health care provider. The organic acids test (available through Genova or mosaic) also includes urinary oxalate levels.
If you are sensitive to oxalate, eating a low-oxalate diet may be a good way to manage your levels. Many (but not all) patients find that their symptoms are significantly relieved when they eat a low-oxalate diet.
If you have a high oxalate content and have symptoms of oxalate overload, you may want to avoid vegetables with a high oxalate content, such as spinach. Some people follow a carnivore diet to lower oxalate intake and promote oxalate excretion from tissues.
Other factors that can increase oxalate levels in the body
In addition to leafy greens, chocolate, and other foods high in oxalate, other sources of exposure may include:
- Some strains of yeast can produce oxalate in the body, which is an overgrowth of yeast.
- Genetic conditions that increase oxalate production or decrease oxalate breakdown. Examples include primary hyperoxaluria and cystic fibrosis.
- Reduction of intestinal bacteria that break down oxalate (Oxalobacter formigenes).
- Dehydration increases oxalate in the urine, increasing the likelihood of developing kidney stones.
- Vitamin C supplementation (vitamin C can be converted to oxalate in the body)
- Low dietary minerals such as calcium, magnesium and iron. This mineral binds to oxalate in the intestines, preventing its absorption.
A vegetarian diet increases your risk for oxalate problems, especially for women who need more calcium in their diet.
low oxalic acid vegetables
Low-oxalate vegetables that can be enjoyed on a low-oxalate diet include:
- arugula
- broccoli
- Brussels Sprouts
- cabbage
- cauliflower
- Cucumber (peeled)
- summer squash
- Turnip (root)
- zucchini
Medium oxalate vegetables can be consumed in small amounts. Leeks, like parsnips, are medium oxalates. Lentils are a low-oxalate legume that can replace other (high-oxalate) beans in soups.
How to Lower Oxalate Levels
You can reduce oxalates in your diet without eliminating entire food groups. Here are some ways to lower oxalate absorption from food:
- Cook your vegetables: Boiling leafy greens, which are high in oxalate, can significantly reduce oxalate levels. Oxalates leach into water and then pour out.
- Soaking and Sprouting: For grains, nuts, and seeds, soaking, sprouting, or blanching reduces oxalates.
- Add fermentation: Fermentation also helps. Sourdough bread has lower oxalate content than regular bread.
- Soak and Boil Legumes: For legumes, it is also helpful to soak them in lemon juice or vinegar and cook them thoroughly.
- Combination of Oxalate and Calcium: Reduce oxalate absorption from the intestines by eating calcium-rich foods along with oxalate-rich foods. Examples: oatmeal with yogurt or nuts with cheese. Although I do not recommend calcium supplements!
- Stay hydrated: Drinking enough water dilutes oxalates in your urine, which helps lower your risk of kidney stones and kidney disease.
Potassium citrate supplements are often used when dietary changes are not sufficient. Citrate may help prevent kidney stones by directly increasing citrate levels in the urine.
My thoughts on oxalate
Foods high in oxalates tend to make nutritious and delicious side dishes. If you are healthy, you will probably only absorb small amounts of oxalate from your food and this will not be a problem. In this case, consume leafy vegetables, wild vegetables, tea, chocolate, etc. in appropriate amounts.
Have you changed your diet to avoid oxalates? Has your health improved as a result? Please share below!
