Red spinach extract has few recorded side effects: in the trials that tracked them, 1 to 2 grams a day for up to about 11 weeks produced no adverse events. The leaf you eat as a vegetable is a different story. It is high in oxalate, potassium and vitamin K, which matters if you have kidney stones, kidney disease, or take certain medicines.
So the honest answer to "is red spinach safe" depends on which form you mean. Below, we separate the food from the supplement, list who should talk to a doctor first, and show where the research runs out.
Red Spinach Is Amaranth, Not Regular Spinach
Red spinach is a leafy amaranth, Amaranthus tricolor, with red and green leaves. It is a different plant from the common spinach in a salad bag. People cook the leaves as a vegetable, and supplement makers dry and concentrate them into a powdered extract.
The two forms carry different compounds in different amounts. The leaf brings fiber, minerals and oxalate. The extract is made to deliver a measured dose of dietary nitrate. Your body converts that nitrate to nitric oxide, as a 2009 review in the American Journal of Clinical Nutrition explains. That split is why the side effects differ.
Red Spinach Leaf vs Extract at a Glance
You can read the safety picture in one table. Figures come from the sources linked in this article.
| Red spinach leaf (food) | Red spinach extract (supplement) | |
|---|---|---|
| Main safety concern | Oxalate, potassium and vitamin K | Nitrate, which affects blood vessels |
| Key amount | Raw leaves: 611 mg potassium and 1,140 mcg vitamin K per 100 g | About 90 mg nitrate per gram of extract |
| Oxalate | High in amaranth leaves | Described as devoid of oxalates in a 2017 trial |
| Adverse events in studies | Studied as a food, not as a treatment | None recorded at 1 to 2 g a day |
| Longest study length | Not applicable | About 11 weeks |
| Ask a doctor first if you | Have kidney stones or kidney disease, or take warfarin | Take nitrate drugs, PDE5 inhibitors or blood pressure medicine, or have low blood pressure |
What Are the Potential Side Effects of Taking Spinach Extract?
If you take red spinach extract at 1 to 2 grams a day, the trials recorded no adverse events at that dose. The main thing to know is that the extract is a nitrate source, and nitrate can lower blood pressure. That effect is the reason certain medicines and conditions call for a doctor's advice first.
What the trials recorded
A 2025 systematic review in Cureus looked at four spinach extract trials, three of them using red spinach at 1 to 2 grams a day. Three of the four reported on adverse events, and none were recorded. The longest red spinach trial ran about 11 weeks in 16 college baseball players.
The individual trials point the same way. A 2016 study in the European Journal of Applied Physiology gave 15 healthy adults 1,000 mg of extract, about 90 mg of nitrate. A 2021 trial in the Journal of Strength and Conditioning Research gave 17 active men and women 1 gram a day for 7 days. A 2021 study in Sports gave 10 trained men 2 grams a day for 7 days.
Nitrate and blood pressure
Dietary nitrate is studied for blood pressure because it relaxes blood vessels. A 2013 meta analysis in the Journal of Nutrition pooled 16 trials of inorganic nitrate and beet juice. Systolic blood pressure fell, and larger daily doses were linked to larger drops. For most people that is not a side effect. For someone already on blood pressure medicine, or with low blood pressure, it is worth a conversation with a doctor.
How one scoop compares with the nitrate limit
The European Food Safety Authority set an acceptable daily intake for nitrate of 3.7 mg per kilogram of body weight. By our math, that is about 259 mg a day for a 70 kg adult. One gram of red spinach extract supplies about 90 mg, roughly a third of that figure, before counting the nitrate in your vegetables.
The Cureus review notes that excessive nitrate can lead to methemoglobinemia, a condition where blood carries less oxygen. That warning is about excess, not the doses used in the trials. Staying within the label amount keeps you inside the research.
What Are the Potential Downsides of Consuming Red Spinach?
If you eat red spinach leaves, the downsides come from three nutrients: oxalate, potassium and vitamin K. None of them is a problem for most healthy adults. Each one matters for a specific group of people.
Oxalate
Amaranth leaves contain high amounts of oxalate, a compound that binds calcium. A 1978 study in the British Journal of Nutrition fed six adult men amaranth leaves with milk. Calcium absorption from the milk dropped when the leaves were cooked and the cooking water kept. When the water was drained, calcium absorption was unaffected.
The National Institute of Diabetes and Digestive and Kidney Diseases lists spinach among the high oxalate foods that people with calcium oxalate stones may want to avoid. Its advice is to talk with a health care professional about how much oxalate to eat.
Potassium
Raw amaranth leaves carry 611 mg of potassium per 100 grams, according to USDA FoodData Central. For a healthy person that is a plus. For someone with kidney disease, or taking medicines that raise potassium, the NIH Office of Dietary Supplements potassium fact sheet explains why intake may need to be watched.
Vitamin K
The same 100 grams of raw leaves carry 1,140 mcg of vitamin K. The NIH vitamin K fact sheet sets adequate intake at 120 mcg a day for men and 90 mcg for women. People on warfarin are advised to keep their vitamin K intake steady, so a sudden habit of eating large amounts of leafy greens is worth raising with a doctor.
Who Should Talk to a Doctor Before Taking Red Spinach
You should ask your doctor before taking red spinach extract if you take nitrate medicines, PDE5 inhibitors or blood pressure medicine, or have low blood pressure. The same goes for kidney disease, a kidney stone history, pregnancy and breastfeeding. This is general information, not medical advice.
Nitrate medicines and PDE5 inhibitors
PDE5 inhibitors are erectile dysfunction and pulmonary hypertension drugs such as sildenafil. The FDA prescribing label for sildenafil says it should not be taken with organic nitrates, such as nitroglycerin, because together they can drop blood pressure sharply. Dietary nitrate from food is a different compound from those drugs. No published study has tested red spinach extract alongside them, so ask your doctor.
Blood pressure medicine or low blood pressure
If you take blood pressure medicine, know that dietary nitrate can lower systolic blood pressure and may add to the effect of a blood pressure medicine. If you already run low, or feel dizzy when you stand up, check with your doctor before adding a nitrate supplement.
Kidney disease or a kidney stone history
If your kidneys are the worry, the leaf is the bigger concern, because of its oxalate and potassium. If you have kidney disease or have had stones, your doctor or dietitian can tell you how much leafy green is right for you.
Pregnancy and breastfeeding
The red spinach extract trials enrolled healthy adults. No published trial has studied the extract during pregnancy or breastfeeding, so talk to your doctor before taking it.
What Should You Not Mix With Spinach?
Do not mix red spinach extract with nitrate medicines or PDE5 inhibitors unless your doctor approves it. Be careful pairing it with blood pressure medicine. With the leaf, avoid big swings in how much you eat if you take warfarin.
Food pairings matter less than people think. The 1978 amaranth study found that keeping the cooking water lowered calcium absorption from milk, while draining it did not. If calcium matters to you, drain the water after cooking the leaves.
Is Red Spinach Good for the Kidneys?
No study shows that red spinach is good for the kidneys. The leaf is high in oxalate and potassium, two things people with kidney stones or kidney disease are often told to watch. The extract was described as devoid of oxalates in a 2017 trial in Sports, but it has not been studied in people with kidney disease.
For healthy kidneys, red spinach is one leafy green among many. For kidneys that are already struggling, it is a question for your doctor, not a supplement label.
How Much Long Term Safety Data Exists
If you want years of data, very little exists. The red spinach extract trials are small, short and mostly done in young, active adults. That is the limit of what anyone can say about safety today.
The concession, plainly: no red spinach extract trial has run longer than about 11 weeks, and the largest enrolled 17 people. The Cureus review itself says its short follow up prevented it from judging long term effects. "No adverse events recorded" means none were seen in those trials, not that the extract is proven safe for years of daily use.
The trials also excluded the groups most likely to run into trouble: people with kidney disease, low blood pressure, or on heart medicines. That is why the doctor list above exists.
Red Spinach Safety FAQ
What are the potential side effects of consuming red spinach?
Consuming red spinach has two different risk profiles depending on the form. The leaf is a food that is high in oxalate, potassium and vitamin K, which matters for kidney stones, kidney disease and blood thinners. The extract is a concentrated nitrate source, and trials at 1 to 2 grams a day recorded no adverse events.
Can I eat red spinach every day?
Most healthy adults can eat red spinach every day as part of a varied diet, the same way they eat other leafy greens. If you have had calcium oxalate kidney stones, have kidney disease, or take warfarin, ask your doctor first. For the extract, trials gave a daily dose for up to about 11 weeks, and no longer term data exists.
How much red spinach extract is safe per day?
The published trials used 1 to 2 grams of red spinach extract a day, about 90 to 180 mg of nitrate, and recorded no adverse events. A 2025 trial gave a larger single dose, about 4.4 grams of red spinach powder (about 400 mg of nitrate), but did not report on side effects. Staying within the amount on the label keeps you inside the range the research covers.
The Verdict
If you eat red spinach leaves, treat them like any other leafy green. Enjoy them in a varied diet, drain the cooking water, and ask your doctor first if you have kidney stones, kidney disease, or take warfarin.
If you take red spinach extract, stay within the 1 to 2 grams a day the trials used. Ask your doctor first if you take nitrate medicines, PDE5 inhibitors or blood pressure medicine, or if you are pregnant or breastfeeding.
BioHealth Nutrition makes Vitality, a red spinach extract powder with 1,000 mg of non GMO red spinach extract per scoop and no caffeine or stimulants. It is vegan, gluten free and stevia sweetened, in Cherry Lime with 30 servings. The label directs 1 to 2 scoops, 15 to 30 minutes before activity. Vitality is in stock now.
Browse our other greens and superfood supplements, or see our performance supplements.
Related reading: we compared red spinach vs beet root for nitric oxide, and covered the health benefits of red spinach.
Sources. Wen J. et al., Improved Effect of Spinach Extract on Physical Performance: A Systematic Review of Randomized Controlled Trials, Cureus, 2025. Haun CT. et al., Differential vascular reactivity responses acutely following ingestion of a nitrate rich red spinach extract, European Journal of Applied Physiology, 2016. Moore AN. et al., Red Spinach Extract Increases Ventilatory Threshold during Graded Exercise Testing, Sports, 2017. Gonzalez AM. et al., Red Spinach Extract Supplementation Improves Cycle Time Trial Performance in Recreationally Active Men and Women, Journal of Strength and Conditioning Research, 2021. Haynes JT. et al., Impact of Red Spinach Extract Supplementation on Bench Press Performance, Muscle Oxygenation, and Cognitive Function in Resistance Trained Males, Sports, 2021. Hord NG. et al., Food sources of nitrates and nitrites: the physiologic context for potential health benefits, American Journal of Clinical Nutrition, 2009. Siervo M. et al., Inorganic Nitrate and Beetroot Juice Supplementation Reduces Blood Pressure in Adults: A Systematic Review and Meta Analysis, Journal of Nutrition, 2013. European Food Safety Authority, Nitrate in vegetables: Scientific Opinion of the Panel on Contaminants in the Food Chain, EFSA Journal, 2008. Pingle U. and Ramasastri BV., Effect of water soluble oxalates in Amaranthus spp. leaves on the absorption of milk calcium, British Journal of Nutrition, 1978. USDA Agricultural Research Service, FoodData Central, Amaranth leaves, raw (FDC 168385). National Institute of Diabetes and Digestive and Kidney Diseases, Eating, Diet and Nutrition for Kidney Stones. NIH Office of Dietary Supplements, Potassium and Vitamin K fact sheets. US Food and Drug Administration, Viagra (sildenafil citrate) prescribing information.
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