Juicing vegetables like kale and spinach has become a popular health trend in recent years. Proponents claim that drinking these dark, leafy greens provides a concentrated dose of nutrients that can boost energy, improve health, and help with weight loss. But is juicing kale and spinach really as healthy as it seems? Let’s take a closer look at the potential benefits and downsides.
Potential Benefits of Kale and Spinach Juice
There are some compelling reasons why juicing kale and spinach may be beneficial:
- Increased nutrient absorption – Juicing breaks down plant cell walls, releasing the nutrients so they can be better absorbed by the body.
- Weight loss – Vegetable juices are low in calories and high in nutrients, which can help promote satiety and reduce calorie intake.
- Detoxification – The nutrients in kale and spinach may help support the body’s natural detoxification processes.
- Disease prevention – The antioxidants in these greens can help fight inflammation and oxidative damage linked to chronic diseases.
- Energy boost – Juices provide an immediate shot of vitamins, minerals, and phytonutrients to help fight fatigue.
Let’s explore the evidence behind these potential benefits in more detail:
Increased Nutrient Absorption
Juicing extracts the fluid from fruits and vegetables, leaving behind the indigestible fiber. This allows the nutrients to be absorbed into the bloodstream more quickly.
For example, one study found that drinking vegetable juice led to a significantly higher plasma carotenoid level compared to eating whole vegetables. Carotenoids are antioxidant compounds found in dark leafy greens that play important roles in health.
By removing the fiber, nutrients can be absorbed in as little as 15 minutes. This can be especially beneficial for people who have trouble digesting raw vegetables.
Kale, spinach, and other dark leafy greens are very low in calories and high in nutrients. This makes them an ideal food for weight loss. Juicing concentrates these low-calorie nutrients into a liquid form.
Drinking kale and spinach juice can increase satiety and reduce appetite due to its high water and fiber content. One study found that overweight adults who drank about 2 cups of low-calorie vegetable juice per day lost 4 pounds over 12 weeks, while the control group gained 1 pound.
Replacing higher calorie beverages like juice or soda with kale and spinach juice can also contribute to lower overall calorie intake.
The nutrients in green leafy vegetables may support the body’s natural detoxification processes.
Kale and spinach are high in antioxidants, including vitamin C, beta-carotene, quercetin, and glutathione. These compounds bind to toxins and help neutralize oxidative damage.
A study in 192 women found that drinking just under 1 cup of green leafy vegetable juice daily increased antioxidant capacity and reduced oxidative stress levels after 2 weeks.
However, research has not conclusively proven that juiced greens can “detox” the body or support liver function. More research is needed on the impact of vegetable juices on detoxification.
The nutrients and antioxidants in kale and spinach juice may help lower risk factors for chronic diseases like cancer and heart disease.
Spinach is high in carotenoids, vitamin C, E, and magnesium, which have anti-inflammatory and anti-cancer properties. Studies suggest spinach consumption is linked to decreased risk of breast, prostate, and colon cancers.
Kale contains compounds that may protect against heart disease by lowering cholesterol and blood pressure levels. One study found that drinking kale juice lowered LDL “bad” cholesterol and increased HDL “good” cholesterol.
However, most research looks at eating whole vegetables. More studies are needed on specifically juicing kale and spinach for disease prevention.
Some people drink green juices like kale and spinach to raise their energy levels. Juices provide micronutrients that play essential roles in energy production, including iron, magnesium, B vitamins, and manganese.
In particular, iron helps carry oxygen throughout the body, which can relieve fatigue. Magnesium is needed for converting food into energy.
Juices also provide an immediate boost of nutrients, unlike whole vegetables that need to be broken down and absorbed. The rapid absorption can result in a quick influx of carbohydrates, amino acids, vitamins, and minerals for an energy boost.
However, due to the high sugar content of most fruit and vegetable juices, an energy crash can follow shortly after the initial rush. The fiber in whole vegetables also helps stabilize energy levels over a longer period.
Potential Downsides of Kale and Spinach Juice
Despite the benefits, there are some potential downsides to consider with juicing kale and spinach regularly:
- Lower fiber content – Juicing removes most of the plant fiber, which helps promote fullness and gut health.
- High oxalate content – Spinach and kale contain oxalates that can contribute to kidney stone development in some people.
- Higher cost – A juice habit can get expensive compared to eating whole veggies.
- Temporary nutrient boost – The flood of nutrients may not be fully absorbed and utilized by the body.
- Blood sugar spikes – The natural sugars in juice can spike blood glucose levels.
- Tooth decay – Drinking juice frequently exposes teeth to sugars and acidity.
Let’s explore these downsides and precautions around juicing spinach and kale:
Lower Fiber Content
Juicing strips away the insoluble fiber contained in whole vegetables. Fiber provides bulk that helps you feel full and satisfied after eating. It also feeds the healthy bacteria in the gut microbiome.
Without fiber, juices are less filling. This can lead to increased hunger and calorie consumption. For example, one study found that drinking a vegetable juice 30 minutes before a meal did not decrease food intake compared to drinking water.
Fiber also slows the absorption of sugars from whole fruits and vegetables. The juicing process eliminates this beneficial effect.
High Oxalate Content
Spinach and kale contain high amounts of oxalates, compounds that bind to calcium to form crystals. For those prone to kidney stones, oxalates can contribute to stone development.
However, both spinach and kale also contain compounds that inhibit kidney stone formation. For most people, eating these greens likely has an overall beneficial effect on kidney health.
Those who are prone to oxalate-containing kidney stones should consult their healthcare provider before regularly juicing spinach and kale.
Drinking fresh vegetable juice every day can get very expensive, especially if you rely on a juicing service or buy prepared bottles rather than making it yourself.
It takes around 2 pounds of leafy greens like kale or spinach to produce one 16 oz juice. Compared to buying whole greens that can be stretched into multiple meals, juicing is far less cost-effective.
If you drink store-bought kale and spinach juices, expect to pay $3-12 for a 16 oz bottle, depending on the brand. Making juice at home using an appliance like a blender or juicer can help lower the cost somewhat.
Temporary Nutrient Boost
While juicing may provide a quick burst of vitamins and minerals, the body may have trouble fully utilizing large amounts at once. Excessive amounts of some antioxidants like beta carotene can be harmful.
Juicing also provides vitamins and minerals without the natural food matrix. For example, vitamin K1 from kale is better absorbed when consumed along with fat.
The temporary flood of nutrients into the bloodstream can give the illusion of increased health and energy. But the effect may be fleeting.
Blood Sugar Spikes
Vegetable juices contain simple sugars naturally found in the plants that can spike blood sugar when consumed in excess. While spinach and kale are relatively low in sugar, combining them with sweeter veggies or fruits significantly increases the total carbohydrate content.
For people with diabetes or metabolic syndrome, juicing can cause concerning blood sugar elevations if consumed in large amounts.
Some dentists raise concerns with frequent juice consumption due to the potential for tooth decay. Juices have a high concentration of simple sugars that feed decay-causing bacteria.
The acidic nature of most juices also contributes to enamel erosion. Swishing with water after drinking juice can help neutralize acidity.
Those who drink juice regularly may want to take extra precautions for dental health, such as increased brushing and using products to remineralize tooth enamel.
Balancing Benefits and Precautions
Based on the evidence, juicing kale, spinach and other greens can provide some impressive health benefits but also requires caution for certain individuals.
Here are some tips for balancing the pros and cons of incorporating kale and spinach juice into your diet:
- Consume juice alongside whole foods and fiber – Pair juice with whole fruits, veggies, grains and lean proteins.
- Limit to 1 small glass per day – Stick to 4-8 oz juice per day to get key nutrients without excess.
- Drink slowly – Sip juice over 30 minutes to minimize blood sugar spikes.
- Rinse mouth after drinking – Swish water in your mouth to wash away sugars.
- Use a straw – Minimize contact between juice and teeth.
- Get screened for kidney stones – If you have a history of oxalate stones, check with your doctor before regularly consuming high-oxalate greens.
- Buy whole produce when possible – It’s healthier and more affordable than bottled juice.
The Bottom Line
Juicing kale, spinach, and other leafy greens provides a megadose of vitamins, minerals, and antioxidants that can optimize health when consumed moderately as part of an overall healthy diet. But striping away the fiber found in whole vegetables may impact satiety, blood sugar management, and dental health.
Aim to get an array of nutrients from a varied whole foods diet focused on fruits, vegetables, lean proteins, whole grains, and healthy fats. Work in a small daily green juice if you enjoy it, but don’t rely on it as a magic bullet for health.