There’s no shortage of nutritional advice, but many experts say whole food groups are bad for you. Vegans advise avoiding animal products, while carnivores warn against grains and legumes. However, leafy greens seem to be widely praised. When it comes to vegetables, the more you eat, the healthier you will be, right?
Not necessarily. a compound called oxalate The foods found in leafy greens and other foods may make us think twice about how much we eat.
What is oxalate?
Oxalate (oxalic acid) is a natural compound found in many plant foods, but it is also produced by the human body as a waste product. Our bodies can produce 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 deter predators from eating them. These compounds also protect against viruses and bacteria. However, eating foods high in oxalate or foods rich in oxalate precursors can increase oxalate levels.
When consumed as part of a meal, the human body typically absorbs only 2-5% of dietary oxalate. On the other hand, up to 12% of oxalate can be absorbed from oxalate-rich foods and drinks on an empty stomach.
The majority of oxalate is excreted via the kidneys in the urine. However, when oxalate levels build up to the point that they overwhelm the kidneys, crystals can form. When these crystals build up in your tissues, they can cause kidney stones and other problems.
Are oxalates found in foods? Really Big deal?
The effects of oxalate depend on how it binds to food. In vegetables, oxalate is often combined with minerals such as calcium. The ratio of minerals to oxalate in these foods determines how much of a problem oxalate is.
However, certain conditions can increase oxalate absorption. In people with impaired fat absorption, fat binds calcium, making more free oxalate available for absorption. As a result, these people are able to absorb more than 30% of the oxalate they ingest.
People with the following symptoms are especially at 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 oxalate in the body comes from food. The rest can come from a variety of other situations.
Health concerns related to high oxalate levels
Although harmless in small amounts, excess oxalate can be harmful, especially if it is not properly broken down and excreted. Here are some possible consequences of high oxalate.
kidney stones
Oxalate produced by the body or absorbed from food can combine with minerals to form oxalate crystals. Calcium salts and oxalate crystals may combine to form calcium oxalate kidney stones. Approximately 80% of kidney stones are made of calcium oxalate.
nutritional deficiencies
Most leafy vegetables are rich in minerals, but these minerals are often bound with oxalates, making them less bioavailable. Like phytate, free oxalate is an antinutrient that binds to minerals and reduces absorption. Because oxalate is negatively charged, it easily binds to positively charged minerals such as calcium, magnesium, and iron.
Ingested oxalates can bind to these minerals in the intestines and be excreted in the stool rather than being absorbed and used by the body. Calcium deficiency can lead to osteopenia and osteoporosis. Iron deficiency can cause anemia.
However, when it is balanced with calcium, it is less likely to steal nutritional minerals from food.
Pain and urinary tract infection-like symptoms
High oxalate does not necessarily cause kidney stones, but the presence of crystals anywhere in the urinary tract can cause problems. In some women, it causes vulvodynia or pain in the vulva. Approximately one in four women with vulvodynia find that their symptoms improve significantly when they consume a low-oxalate diet.
Increased oxalate in the urine can also cause urinary tract infections. It may cause frequent urination, bladder pain, and a strong urge to urinate. Women who have recurring urinary tract infections often have high oxalate levels in their urine. Of course, urinary tract infections can also occur from the use of antibiotics, which can kill off healthy bacteria.
Possible toxicity if ingested in large quantities
Some case reports indicate that ingesting 4 to 5 grams of oxalate can be fatal in adults. In one case, a 56-year-old man developed kidney failure after drinking 16 cups of black tea every day for years. In another case report, a man died after ingesting 500 grams of sorrel (containing 6 to 8 grams of oxalate) in soup. It is difficult to determine whether these deaths were caused by oxalates or other ingredients or toxins in the food. However, the potential harm is worth considering.
May contribute to other diseases
Oxalates can contribute to extraurinary symptoms. Dr. Isabella Wentz thinks oxalates may contribute to hypothyroidism in some people. It can also contribute to joint pain, general pain, and depression.
Oxalate injections cause breast cancer in mice, and breast cancer cells contain calcium oxalate salts.
high oxalate foods
Certain leafy vegetables, tubers, seeds, and unfortunately even chocolate are high in oxalates. The oxalate to calcium ratio plays an important role in determining health effects. Many leafy vegetables are high in oxalates and low in calcium.
The ratio of oxalate to calcium in common foods (per 100 g) is as follows:
- spinach: Oxalate 890-1100 mg, oxalate to calcium ratio approximately 4-5:1
- rhubarb: Oxalate 275-1336 mg ~ 8-9:1
- Purslane: Oxalate 910-1679 mg, ~5:1
- Beet leaves: Oxalate 300-450 mg, approximately 2.5:1
Many tubers and seeds also contain high levels of oxalates, including:
- Beats: Oxalate 121-450 mg, ~5:1
- Taro: Oxalate 278-574 mg, ~10-20:1
- Sweet potato: Oxalate 470 mg, ~30:1
- Sesame: Oxalate 350-1750 mg, ~ 0.3-2:1
- Cacao: Oxalate 500-800 mg, ~4-6:1
For sensitive people, experts recommend avoiding foods containing more than 50 mg of oxalate per 100 grams. Other high-oxalate foods to avoid include collards, okra, corn grits, wheat germ, soybeans, blackberries, and oranges.
Benefits of high oxalate foods
Oxalates can be toxic in extremely high doses. However, in moderation, it can promote good health.
Activation of hormesis
Small amounts of toxins such as oxalates can induce hormesisthe process by which mild stress promotes healing and strength. This is much like weightlifting damages muscles but builds them stronger. Consuming oxalates activates the body’s defense mechanisms and increases recovery.
Providing essential nutrients
Foods high in oxalates, such as spinach, sweet potatoes, and cacao, contain essential vitamins and minerals. For example, spinach is a good source of vitamin K, folate, and iron. Sweet potatoes are a good source of beta-carotene, which is converted to vitamin A in the body. Cacao is rich in magnesium, iron, and flavonoids.
Nuts and seeds are rich in omega-3s and monounsaturated fatty acids, and beets contain nitrates. These nutrients are essential for bone health, vision, cardiovascular health, and the immune system.
Providing antioxidant support
Many high-oxalate foods are rich in antioxidants that fight free radicals. Spinach and beet greens contain lutein and zeaxanthin, which protect the eyes. Flavonoids in cocoa may lower blood pressure and support heart health. Raspberries and blackberries contain vitamin C and anthocyanins that support your immune response.
Fiber and resistant starch supply
Seeds, legumes, and tubers such as taro and sweet potato contain dietary fiber that supports gut health. Taro root provides resistant starch that feeds beneficial gut bacteria and supports metabolism.
cancer prevention
Some high-oxalate foods contain bioactive compounds that may reduce cancer risk. Cruciferous vegetables like kale contain glucosinolates, which have anti-cancer 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 consume high oxalate foods in moderation. However, you may want to try a low oxalate diet if you have the following symptoms:
- kidney stone disease
- Vulvodynia (vulvodynia) or pain during intercourse
- Frequent urination
- Frequent urinary tract infections (UTI)
- joint pain
- hypothyroidism
- Mineral deficiencies (calcium or iron causing osteopenia, osteoporosis, or iron deficiency anemia)
If you have digestive problems that interfere with fat absorption, you should also keep an eye on your oxalate levels. This is especially true if there is floating feces or fat in the stool.
If you wonder if your oxalate levels are high, it may be worth getting tested through your health care provider. In addition, the organic acid test (offered 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 oxalate levels. Many (but not all) patients experience significant relief of symptoms when they consume a low oxalate diet.
If you have high oxalate levels and symptoms of oxalate excess, you may want to avoid oxalate-rich vegetables like spinach. Some people follow a carnivorous diet to reduce 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 oxalate-rich foods, other sources of exposure can include:
- Yeast overgrowth because some yeast strains can produce oxalate in the body.
- Genetic conditions that increase oxalate production or decrease oxalate breakdown. Examples include primary hyperoxaluria and cystic fibrosis.
- Decrease in intestinal bacteria that degrade oxalate (Oxalobacter formigenes).
- Dehydration increases oxalate in the urine, increasing the chance of developing kidney stones.
- Vitamin C supplementation, as vitamin C is converted to oxalate in the body.
- A diet low in minerals such as calcium, magnesium, and iron. These minerals bind to oxalates in the intestines and prevent absorption.
A vegetarian diet increases the risk factor for oxalate problems, especially for women, who naturally require more calcium in their diets.
low oxalate vegetables
Low oxalate vegetables to enjoy on a low oxalate diet include:
- arugula
- broccoli
- Brussels sprouts
- cabbage
- cauliflower
- cucumber (peeled)
- summer squash
- Turnip (root)
- zucchini
Moderate oxalate vegetables can be consumed in small amounts. Leeks are moderately oxalate, as are parsnips. Lentils are a low oxalate legume and can be used in place of other (higher oxalate) beans in soups.
How to lower oxalate levels
You can reduce oxalate in your diet without eliminating whole food groups. Here’s how to lower the amount of oxalate absorbed from foods.
- Let’s cook the vegetables: Boiling leafy vegetables high in oxalate can significantly lower oxalate levels. The oxalates are leached into the water, which is then poured out.
- Soak and germinate: For grains, nuts, and seeds, soaking, sprouting, or blanching reduces oxalate.
- Add fermentation. Fermentation is also effective. Sourdough bread has less oxalates than regular bread.
- Soak and boil legumes: For legumes, soaking them in lemon juice or vinegar and cooking them well is also effective.
- Pair oxalate and calcium: Eat calcium-rich foods and oxalate-rich foods together to reduce oxalate absorption in the intestines. For example: oatmeal and yogurt or nuts and cheese. However, calcium supplements are not recommended.
- Stay hydrated: Drinking enough water dilutes oxalates in your urine, which can lower your risk of kidney stones and kidney disease.
If dietary changes are not sufficient, potassium citrate supplements are often used. Citrate helps prevent kidney stones by directly increasing citrate levels in the urine.
My thoughts on oxalates
Foods high in oxalates tend to include nutritious and delicious side dishes. If you’re healthy, you probably only absorb small amounts of oxalate from food, so it’s unlikely to be a problem. In such cases, enjoy moderate amounts of leafy vegetables, wild vegetables, tea, and chocolate.
Have you changed your diet to avoid oxalates? Has your health improved as a result? Share below!
