Though spinach is among the healthiest of vegetables with a powerful nutritional profile, consuming it in excess may lead to issues. Hence, moderation is key. For instance, excess intake of spinach may lead to kidney stones as the vegetable was found to increase urinary calcium excretion (1).
In this post, we will discuss the side effects of excessive intake of spinach.
What Are The Major Side Effects Of Spinach?
Spinach is high in oxalates, and their excess intake over a period may lead to the formation of kidney stones. The vitamin” k> in spinach may also interfere with blood thinners and certain other medications.
1. May Increase Kidney Stone Risk
Spinach contains oxalates, which are compounds that can form stones in the human system if consumed in excess. These stones are formed by an increase in oxalate content in the urine. The most common types of kidney” stones> are calcium oxalate stones (1).
A hundred grams of spinach contains 970 milligrams of oxalates (2).
Boiling spinach may reduce the oxalate concentration to some extent. Combining a calcium-based food (like curd or cottage cheese) with spinach can also prevent stone formation (3). However, every individual’s condition is unique, and the reaction may differ from person to person. Hence, please check with your doctor if you can include spinach in your diet.
2. May Interfere With Blood Thinners
Spinach contains high levels of vitamin K, a mineral that reduces the effectiveness of blood thinners. Blood thinners are usually given to prevent the onset of stroke.” hence susceptible individuals must reduce their spinach intake target=”_blank” rel=”nofollow noopener”>4).
Warfarin is a blood thinner that is prescribed for individuals who are at risk of forming harmful blood clots. Vitamin K was found to reduce the effectiveness of Warfarin (5). This is because vitamin K plays a vital role in forming blood clots in your body.
While half a cup of cooked spinach contains 444 mcg of vitamin K, one cup of raw spinach contains 145 mcg of the nutrient (6). Cooked spinach has higher vitamin K levels as heat increases the absorption of the nutrient.
However, you should not eliminate vitamin K from your diet as foods rich in the nutrient, like spinach, contain other essential vitamins and minerals as well. Vitamin K also has a role to play in the prevention of arterial calcifications, coronary heart disease, cancer, and osteoporosis (7). It is best to consult your doctor, who may increase the dosage of your blood thinner.
Eating spinach occasionally, in moderation, could be a safer option (provided the person is stable and not in an acute phase of illness).
3. May Hinder Mineral Absorption
There is some research that the intake of oxalate-rich” foods> can inhibit mineral absorption. Oxalate is an antinutrient (8).
The oxalates in spinach may also hinder the absorption of minerals like calcium. Spinach contains both oxalates and calcium, and consuming it in large amounts may impair the absorption of calcium in your system (9).
Spinach didn’t seem to have this effect on calcium when it was taken along with milk (9). This is because though spinach contains calcium, the nutrient from the vegetable is absorbed only one-tenth as efficiently as milk calcium (10).
The oxalates in spinach can also react with iron and inhibit its absorption by forming crystals (11).
Spinach is also thought to compromise thyroid function as it contains certain compounds called goitrogens. However, research is mixed in this regard. If you have thyroid issues, please consult your doctor before including spinach in your diet.
4. May Aggravate Symptoms Of Gout
Spinach contains purines, chemical compounds that are thought to contribute to gout. However, there is a lack of a significant association between the intake of purine-rich” vegetables and gout target=”_blank” rel=”nofollow noopener”>12). Hence, further research is warranted before we can arrive at a definitive conclusion.
But it always is better to stay safe. If you are dealing with gout, please talk to your doctor about your spinach intake. Since the leafy green may also interfere with certain medications, be sure to talk to your doctor if you are on any.
Some anecdotal evidence suggests that excess intake of spinach may cause an individual’s blood pressure and blood” sugar levels to drop too low.> This could be an issue for those who are on medications for treating high” blood pressure> and high blood sugar. However, more research is needed to confirm these effects. If you are on blood sugar or blood pressure medication, make sure to consult your doctor before including spinach in your diet.
Spinach is among the most nutritious” foods> you can find in your kitchen. However, as is the case with any food, moderation is key.
If you have kidney stones, you may have to drastically reduce or even avoid spinach intake (along with other oxalate-containing foods).
Otherwise, spinach is a healthy vegetable, and if you are a generally healthy individual, you should not miss out on its goodness.
Expert’s Answers For Readers’ Questions
How much of spinach is too much?
The lethal oral dose of oxalate in humans is between 15 to 30 grams (13). This could be between 3 to 6 pounds of spinach. It is highly unlikely for anyone to consume so much spinach in a short span of time. However, there is less research to understand if this dose is enough to lead to kidney stone formation.
Can raw spinach be bad for you?
Spinach, raw or cooked, offers great benefits. But if you have kidney stones or are on certain medications (like blood thinners, etc.), you may want to avoid spinach.
Can you eat spinach and tomatoes together?
Like spinach, tomatoes also contain oxalates (14). Hence, if you are someone prone to kidney stones or any drug interactions, you may be required to limit your intake of tomatoes.
Can spinach make your stomach hurt?
Spinach, by itself, may not hurt your stomach. However, eating too much of spinach all too soon may mean a sudden increase in your fiber intake. This may lead to a temporary stomach upset.
On the other hand, pain in the stomach (especially on the side) could be a symptom of kidney stones. If you suspect this could be the case, please visit your doctor.
- Effect of dietary oxalate and calcium on urinary oxalate and risk of formation of calcium oxalate kidney stones. Journal of the American Dietetic Association, US National Library of Medicine, National Institutes of Health.
- Nutritional Management of Kidney Stones (Nephrolithiasis), Clinical Nutrition Research, US National Library of Medicine, National Institutes of Health.
- Effect of Cooking on Soluble and Insoluble Oxalate Contents in Selected Pakistani Vegetables and Beans, International Journal of Food Properties, Taylor & Francis Online.
- Medication Interactions: Food, Supplements and Other Drugs, American Heart Association.
- Warfarin (Coumadin®), Department of Public Health and Human Services, Montana.
- Why Vitamin K Can Be Dangerous If You Take Warfarin, Cleveland Clinic.
- The health benefits of vitamin K, OpenHeart, US National Library of Medicine, National Institutes of Health.
- Expression Analysis of Oxalate Metabolic Pathway Genes Reveals Oxalate Regulation Patterns in Spinach, Molecules, US National Library of Medicine, National Institutes of Health.
- Oxalate: effect on calcium absorbability, The American Journal of Clinical Nutrition, US National Library of Medicine, National Institutes of Health.
- Calcium, National Center for Biotechnology Information.
- Making Spinach with Low Oxalate Levels, United States Department of Agriculture.
- The Association of Dietary Intake of Purine-Rich Vegetables, Sugar-Sweetened Beverages and Dairy with Plasma Urate, in a Cross-Sectional Study, PLoS One, US National Library of Medicine, National Institutes of Health.
- Oxalic acid, Centers for Disease Control and Prevention.
- Determination of total oxalate contents of a great variety of foods commonly available in Southern China using an oxalate oxidase prepared from wheat bran, United States Department of Agriculture.
Ravi Teja Tadimalla is a Senior Content Writer who specializes in writing on Health and Wellness. He graduated from SRM University, Chennai, and has been in the field for well over 4 years now. His work involves extensive research on how one can maintain better health through natural foods and organic supplements. Ravi has written over 250 articles and is also a published author. Reading and theater are his other interests.