Spinach is a widely beloved vegetable and it has been ever since it was first planted in Europe in the 11th century. It was first planted in Spain and hence became known as the “Spanish vegetable” in England, which eventually got shortened to form spinach.
These days the average US citizen eats roughly 2.5 pounds of spinach per year and consumption is heaviest in the west and northeast of the country. Spinach is most heavily eaten by women over 40 and least frequently eaten by women under 18. Interestingly, Americans now eat 4 times more spinach than they did 40 years ago.
However spinach is most famous for supposedly triggering a shocking explosion of muscle growth. It all started when German scientist Emil von Wolff misplaced a decimal point and accidently gave spinach an iron content ten times higher than it actually had.
Hence, cartoonists picked up on it and created Popeye the Sailor, who got his bulging forearms from eating tons of spinach. Thanks to Popeye, US spinach farmers in the 1930s credited the cartoon with a 33% increase in national spinach consumption. Later, the prominent spinach growing town of Crystal City, Texas erected a full-sized statue of Popeye to show their gratitude.
Because of all this, spinach has a reputation in the public mind of being a highly nutritious, leafy green vegetable, like kale. However, the stats are all misleading.
Indeed, the initial muscle building reputation was built on a scientific mistake in the first place. In reality, spinach is not as nutritious for acne or for health as it first appears.
A notorious source of mineral-binding oxalates
On the face of it, spinach is an excellent source of acne nutrients.
100 grams of raw spinach contains 20% of the recommended daily allowance for magnesium, a mineral which aids sleep and boosts glutathione production. There’s 47% of the RDA for vitamin C, which increases collagen production, and a giant 188% for vitamin A, which lowers sebum and keratin production.
However spinach has one major complication. Spinach is the cruciferous vegetable highest in oxalic acid, a potent mineral-binder that inhibits the absorption of dietary minerals including calcium, zinc, magnesium and iron.
Oxalic acid is found in a wide variety of plant foods, at low levels. Strawberries have 34mg per half cup, celery has 35mg per half cup, acne-friendly green veggies such as broccoli and brussel sprouts have 1.8mg and 37mg respectively.
In most foods, oxalates are so insignificant that their impact is barely felt. Spinach, however, looms over the competition with 750mg per half cup. Only rhubarb, pursiane, and beet greens beat spinach, with 860mg, 910mg, and 916mg per half cup respectively.
What’s the problem then? In short, the 20% magnesium content of spinach looks stellar on paper, as there are very few rich and simultaneously acne-friendly sources of magnesium. However, the magnesium isn’t actually absorbed into the bloodstream via the gastrointestinal tract properly, because humans lack the necessary gut bacteria to break down oxalates without assistance.
This study conducted in 2004 confirmed the problem by analysing the bioavailability of minerals from spinach versus those of kale. Curly kale itself is a food that’s very similar to kale – it contains plenty of magnesium. However kale only contains about 15% of the oxalates of spinach, with 110mg per 100 grams.
Scientists in the study gathered 9 completely healthy volunteers and fed them either white bread with 300 grams of spinach or white bread with 300 grams of curly kale. The results showed clearly that the bioavailability for magnesium from spinach was significantly lower than that from kale; 26.7% versus 36.5%, or a 27% lower absorption rate. The scientists concluded that “the difference in Mg absorption observed in the present study is attributed to the difference in oxalic acid content between the two vegetables”.
Kale wasn’t amazing itself; 110mg of oxalates is way higher than broccoli or brussel sprouts. With spinach though, you’re only absorbing 5% of the RDA for magnesium when it actually contains 20%. If you have compromised gut function, as many acne patients do, then the absorption into the blood will be even poorer.
More nutrient depletion due to cooking
Next there’s the vitamin C question. The good news is that oxalic acid only binds to minerals, not vitamins. However oxalic acid has health effects that mean you need to cook spinach more than the average cruciferous vegetable.
Firstly, oxalic acid is a major player in kidney stone formation. Oxalic acid has a strong tendency to bind with dietary calcium intake and form calcium oxalate molecules. These accumulate around the body and in the kidneys. Thus kidney stones are often little more than calcium oxalate build-ups. Doctors routinely prescribe low-oxalate diets to kidney stone patients, and spinach is one food they insist their patients avoid.
Secondly, there’s preliminary evidence that excessive oxalates roaming around the bloodstream can increase chronic inflammation too. Patients with oxalate overload suffer from classic inflammatory symptoms such as painful joints, aching muscles, depression, and a clouded mind.
Simply put, it isn’t good for calcium crystals to be floating around your bloodstream. There’s evidence that oxalates can deplete glutathione levels as well, and increase oxidative stress.
For normal people both of those risks from oxalates are relatively low; in healthy people only 5% of dietary oxalates are absorbed, versus 50% in those with compromised gut function. The problem is that acne patients have a disproportionately higher rate of gut problems, particularly increased intestinal permeability (leaky gut syndrome), where the absorption of unhealthy toxins is poorly regulated.
Hence, I recommend that all acne patients give spinach a thorough cooking to deactivate the oxalates…
…and here’s where the problem kicks in: all cruciferous vegetables are vulnerable to nutritional depletion when cooked, including spinach. This 2000 study found that boiling spinach led to 46.5% drop in vitamin C content, higher than other vegetables tested like peas (25.2%) and green beans (18.2%).
This study found that spinach loses 10% of its vitamin C when boiled for 5 minutes (a good duration for deactivating oxalates). Elsewhere it’s estimated that boiling spinach for ten minutes can deactivate up to three quarters of the heathy phytonutrients.
Rather than providing 47%, spinach gives you more like 35-40% of the RDA for vitamin C. In summary then, spinach contains a lot less valuable acne nutrition than the labels on bags from the supermarket would suggest.
Spinach is still highly nutritious
You only need 5 minutes of boiling to reduce spinach’s oxalates to an acne-friendly level. One study found that boiling spinach for just 5 minutes led to 30-87% decline in oxalate content. Steaming led to a 5-53% decline.
Make no mistake, spinach is still not as outstandingly nutritious as the internet suggests, but it seems that the study showing a 46.5% decline in vitamin C cooked the spinach for 30 minutes.
Another study found a 60% decline in vitamin C after 30 minutes. That’s completely unnecessary; 30 minutes would leave you with green slime.
Hence you’ll still have plenty of vitamin C left. Additionally, since magnesium isn’t warped or depleted by cooking, the deactivation of oxalates will most likely push the absorption rate to the equivalent of about 10% of the RDA.
According to this study, the oxalate content that remains in spinach after boiling or frizzling is not deleterious to magnesium bioavailability at all, and the magnesium was rich enough to make spinach “one of the most promising sources”.
Spinach could defend the skin against sunlight
Then there’s spinach’s numerous phytonutrients and antioxidants. Spinach is the second best known source of the carotenoid antioxidants lutein/zeaxanthin. As we discussed in this article on kale, which is the only vegetable that beats spinach for them, lutein/zeaxanthin has a potent power to reduce blood lipid peroxides.
This study concluded that feeding 10mg or 20mg of lutein to non-smokers dramatically lowered their levels of malondialdehyde, a blood marker of lipid peroxidation. That’s great because lipid peroxides are the worst free radicals for acne and blocked pores. Lutein/zeaxanthin works because it’s a fat-soluble, not water-soluble antioxidant.
This study also found that dietary lutein/zeaxanthin protected rats against sun-induced lipid peroxide damage to the skin. The two carotenoids (which are grouped together since they’re nearly identical) also build themselves into the cornea of your eye and protect against age-related macular degeneration.
Boiled spinach contains 15.691mg of lutein/zeaxanthin per 100 grams, whereas boiled kale contains 19.698mg and broccoli and brussel sprouts contain far less with 1.080mg and 1.541mg respectively. For some reason, the content of lutein in spinach increases through cooking whereas in kale it decreases.
After cooking is taken into account, spinach is slight inferior to kale for vitamin A (188% vs 200%), vitamin C, magnesium, and lutein/zeaxanthin.
However, the one area where spinach really shines is antioxidants. According to this 2003 analysis which tested the antioxidant capacity of common vegetables using three scientific assessments, spinach ranked at the top of all vegetables for two of the tests. Raw spinach has an official ORAC score of 1513, which stands well next to kale (1770) and broccoli (1510).
Studies on spinach and blood antioxidant levels are very promising:
- First there’s this 1998 study where scientists investigated the effect of several foods on serum antioxidant levels. Eight elderly women were fed either 240 grams of strawberries, 294 grams of spinach, 300ml of red wine, or 1250mg of vitamin C. Using the ORAC test, the blood antioxidant levels increased by 7-24% four hours after eating the foods. Urine levels of antioxidants increased by 27.5% for spinach, compared to 9.6% for strawberries and 44.9% for the vitamin C. Vitamin C levels also increased, but scientists commented that the vitamin C could not fully account for the increased antioxidant capacity from eating spinach. Clearly, spinach contains other acne-friendly antioxidants. The conclusion: “the consumption of strawberries, spinach or red wine, which are rich in antioxidant phenolic compounds, can increase the serum antioxidant capacity in humans”. A very promising result for acne.
- Next there’s a 2011 study where 8 participants were fed 225 grams of spinach for 16 days. Scientists were interested in the effect spinach had on oxidative damage to DNA, and they found that there was a big decrease. Antioxidant protection of DNA increased 6 hours after consumption and after 11 days of continuous spinach consumption. There was also a sizeable decrease in blood levels of homocysteine, an amino acid that not only causes heart disease but also increases oxidative stress levels. It seems that spinach hoovers up free radicals through many mechanisms. The conclusion: spinach has potent antioxidant power.
- A 2014 study wished to analyse the antioxidant effects of spinach, so scientists fed spinach extract to some rats for six weeks. The extract resulted in a big reduction in thiobarbituric acid reactive substances, a commonly used measure of free radicals.
The known number of different antioxidants yet identified in spinach is truly enormous. Lutein/zeaxanthin are carotenoid antioxidants that specifically reduce lipid peroxides. Other carotenoids in spinach include neoxanthin, fucoxanthin, violaxanthin, and beta carotene.
Spinach has many flavonoid antioxidants such as jaceidin and patuletin, and even two unique flavonoid antioxidants called spinacetin and spinatoside. In fact, scientists have only recently identified those two, so who knows what unique powers they may possess?
The acne-clearing appeal of spinach lies not in the overrated basic nutrition (except for vitamin A), but in its many smaller health compounds.
Killer acne benefit – improved gut health
The antioxidants and moderate acne nutrients in spinach are terrific but eating spinach is particularly smart if you’re looking to enrich your gut bacteria or heal leaky gut syndrome.
There’s two very interesting studies that recently caught my eye. Firstly, we have a study where scientists wanted to analyse the effect of thylakoids in spinach on gut health.
Hence the scientists extracted the thylakoids, a plant compound, and fed rats either a thylakoid-enriched diet or a control diet for 10 days. Analysis of the rats gut flora showed that they had increased levels of healthy lactobacilli strains, particularly lactobacillus reuteri.
Why is that such great news for acne? For digestive problems such as leaky gut syndrome, lactobacillus reuteri is one of the most protective bacterial strains scientists have yet identified. Lactobacillus reuteri is known to suppress the inflammatory bacterial strain helicobacter pylori, which assaults the intestinal wall, prevents nutrient absorption, and also causes peptic ulcers in third-world countries.
Lactobacillus reuteri was shown in this study to control intestinal permeability, which means less inflammatory molecules flooding into the bloodstream where they don’t belong and causing acne. This study found that l.reuteri had direct anti-inflammatory activity on human epithelial cells (the cells which regulate the passage of nutrients from food), upregulates an unusual anti-inflammatory molecule called NGF, and inhibits the pro-inflammatory messenger NF-kappaB.
Basically, increasing the l. reuteri levels in your gut is a great thing, and that study suggests that compounds in spinach can do that. The l. reuteri bacterial strain is definitely an ally of us acne-clearing fanatics.
Elsewhere, another set of compounds in spinach called glycoglycerolipids have been shown to protect the lining of the intestine from damage. That should directly protect the gut from becoming leaky.
If you’re unaware of what leaky gut syndrome is, then it’s when your intestine’s semi-permeable membrane gradually weakens and loses control of nutrients it absorbed. Instead of just absorbing healthy acne nutrients, other molecules enter the bloodstream and because they don’t belong there, they lead to systematic inflammation and hence acne. We discuss the condition extensively in my eBook Annihilate Your Acne.
More gut protection thanks to an overlooked compound
Since spinach thylakoids and glycoglycerolipids are so promising, I conducted further research and discovered that spinach is one of the best food sources of quercetin, a water-soluble flavonoid antioxidant which has unique and top-notch gut healing properties.
We discussed in this analysis of sweet potatoes, another good source, how quercetin directly lowers the activity of mast cells in the intestine which churn out pro-acne, pro-inflammatory molecules. In fact it’s better at doing so than the pharmaceutical drug cromolyn.
Well quercetin is even better than that, so for the first time, here are some studies on the subject of quercetin and gut health:
- One of the most important actors in curing leaky gut syndrome is the tight junctions. These proteins directly control the opening and closing of the semi-permeable membrane to allow nutrients through and keep inflammatory molecules out. Quercetin was found in this 2011 study to improve intestinal permeability through enhanced tight junction performance. Apparently, quercetin improves both the quantity and performance of tight junction proteins and thus improves the intestinal barrier function.
- This 2008 study found very similar results; quercetin enhances the function of the intestinal epithelial barrier by inducing a “strong increase” of tight junction proteins. The specific protein increased was one called claudin 4. I’ve haven’t got a clue what claudin 4 is, but it must be important because the scientists concluded that quercetin had “an important protective effect” against “barrier disturbance in intestinal inflammation”. If that sounds like gibberish then it means this: quercetin is superb for treating leaky gut syndrome.
- The results of this 2009 study on quercetin were virtually identical. The scientists concluded that “this study demonstrates that quercetin enhances the intestinal barrier function”. They actually compared quercetin and another flavonoid antioxidant called myricetin (found in blueberries) and found that quercetin was significantly better for treating a leaky gut. Once again, an increase in the protein claudin 4 was found to be responsible.
Quercetin is also known to combat food allergies, a common source of acne. Spinach contains 4.86mg of quercetin per 100 grams, whereas raw broccoli contains 3.21mg and kale is even better, with 7.71mg.
Combine the quercetin with the thylakoids and glycoglycerolipids and spinach may be a seriously great food for improving a leaky gut.
Major downside alert – organic spinach is necessary
The only real problem with spinach, outside of the goitrogens discussed in the kale article which only really cause issues in people with thyroid problems anyway, is the fact that it’s one of the very worst foods in the world for pesticide contamination.
For instance, an investigation of 43 different fruit and vegetable categories by the Environmental Working Group showed that sweet bell peppers, lettuce, celery, potatoes and spinach had the highest total residue of agrochemicals. Whatsonmyfood.com lists a grand total of 54 different pesticides detected on spinach by the USDA Pesticide Data Program, including 21 suspected hormone disruptors, 11 neurotoxins, 7 developmental or reproductive toxins, and 20 honeybee toxins. On the dirty dozen list published each year of the worst 12 foods for pesticide and herbicide contamination, spinach ranked seventh in 2015 (apples were highest).
The reason is simple. Spinach, kale and lettuce, all vegetables with high agrochemical contamination, are leafy vegetables, and that gives them a very high surface area. There’s far greater total area for insects to sink their teeth into and thus far more that has to be sprayed, and can be sprayed. Just consider the amount of square inches exposed to the outside world per 100 grams on spinach vs a whole potato.
Worse, producers cannot wash the pesticides off as easily before packaging. You can drench a potato with water and scrub it clean without damaging the inside, but wash and dry spinach thoroughly and the leaves will shred up and fall to bits.
Hence, more than 60% of the non-organic spinach tested by the FDA contains pesticide residue. The most ubiquitous example is the insecticide permethrin, a neurotoxin found on 51.9% of spinach samples. The US Environmental Protection Agency (EPA) claims that permethrin is carcinogenic and capable of causing lung and liver tumours in mice, as well as immune system problems. It’s also linked to tremors, loss of coordination, elevated body temperature, and behavioural problems.
As for acne, this study showed that glutathione is involved with the detoxification of permethrin; hence excessive permethrin may deplete your levels of glutathione and impair your all-important antioxidant functioning.
Another common pesticide is DDT; this chemical was banned by the USA in 1972 due to causing cancer, birth defects and reproductive damage, but it’s still being manufactured and shipped out en masse to developing countries in South America where insects are extra aggressive. Hence, imported spinach may well contain DDT. What more, DDT lingers in the soil for decades. Spinach grown in the US on non-organic fields has come up positive for DDT in some tests.
Compare this to broccoli and asparagus. Broccoli is sprayed, but pesticides don’t work as well on the plant so farmers often don’t bother. The plant has dramatically less surface area too. Asparagus, meanwhile, enjoys complete safety because insects have very little interest in it. Thus farmers don’t even need to spray it.
Spinach is more nutritious than either of those vegetables, but it comes last for chemical contamination. Given the fact that the authorities detect the presence of agrochemicals but don’t state the dosage, the contamination might be too insignificant to wreck your skin. The sheer nutrition in spinach could make even the conventional version a net bonus for acne.
Nevertheless, if you’re determined to avoid all chemical contaminants then spinach definitely has one major flaw next to other acne-friendly foods.
If your goal with spinach is, for instance, to flood your skin with tons of vitamin A, you’d be better off feasting on sweet potatoes, which have one of the lowest pesticide counts of any food. If you’re hunting for vitamin C you can eat tons of pineapple (protected by its thick shell).
If you want to heal a leaky gut then onions, with the highest natural count of quercetin on the face of the earth, will do the trick. Onions have their own natural pest control; the same strong sulphurous compounds that revolt many humans mean that insects refuse to go near them.
Alternatively, if you’re loaded with cash you can buy the organic version of spinach. Compared to organic kale it’s not a complete and utter rip-off, at least not here in the UK.
Conclusion – the verdict on spinach
The final judgement on spinach is that it’s great for acne if you 1) need lots of plant-based vitamin A, 2) if you’re looking for a food to heal leaky gut syndrome, and 3) if you want antioxidants.
Spinach is probably the second best green vegetable overall, behind kale. Kale wins for its effect on gut health, as it contains more quercetin. Kale also wins for vitamin A and definitely vitamin C, with 199% of the RDA vs 47%. However, spinach is the king of cruciferous vegetables for antioxidants.
Broccoli beats spinach for vitamin C, with 148% of the RDA. But spinach crushes it for vitamin A; broccoli contains just 12% per 100 grams. Spinach is moderately higher in antioxidants and quercetin, but 17 times higher in lutein/zeaxanthin. On the other hand, broccoli is better if you’re on a budget and cannot afford the organic version of spinach.
Remember that these comparisons are all relative. If you’re a newbie reading this website who currently eats no vegetables at all except for potatoes, any green vegetable will blast your skin with excellent acne nutrition.
Remember to cook your spinach properly. Boiling for approximately five minutes is optimal to deactivate the oxalates, and to avoid depleting the nutrients too much.
Finally, one piece of advice on selection – spinach leaves with an especially rich dark green colour have been shown to be optimal for acne. A study found that the darker the spinach leaves, the more vitamin C and phytonutrients they contain compared to paler leaves.
Thanks for reading!