You don’t need a peer-reviewed scientific study to tell you that eating vegetables is good for your health. (1) Heck, it’s why the World Health Organization (WHO) recommends eating at least 400 grams of fruits and vegetables per day. However, most people don’t meet these recommendations, and many turn to supplementation in the form of greens powders instead. (2)
Greens or veggie powders are relentlessly promoted as a life hack for getting all your micronutrients, fibers, minerals, and so on at once, without the tediousness of cooking or having to keep an eye on the fresh produce in your fridge that seems to spoil before you know it. But the real question is this: Do greens powders actually work?
Can a single supplement really improve digestion, immunity, performance, recovery, and focus all at once? That’s the question — and this is your evidence-based answer.
Greens powders are supplements that often contain the powder of dehydrated fruits, grains, and grasses along with a blend of probiotics and digestive enzymes. They generally also include added vitamins, minerals, antioxidants, plant extracts, fibers, and, occasionally, caffeine. Plants contain polyphenols, which protect against a number of cardiometabolic diseases, cancers, and other health concerns. (1)
In some cases, these supplements contain proprietary blends, or collections of ingredients which are unique to the company. The amounts of each ingredient in a proprietary blend aren’t required to be listed on supplement fact labels, so they’re essentially a secret to the consumer. (3)
Supplements have the potential to improve upon a solid nutritional foundation, and it’s reasonable to conclude that a powdered blend of produce could function similarly to something like a smoothie — a hydrated, high-volume cousin to greens powder. Research on greens powders is lacking, but studies on similar products, like powdered fruit and veggie blends or fruit and veggie concentrates, may provide insight about the potential for greens powders to improve health.
Manufacturers commonly claim that greens powders provide nutrition or antioxidant activity equivalent to multiple servings of fruits and vegetables, resulting in a multitude of health benefits. The nutrients are absorbed, potentially impacting things like oxidative stress, immune function, or cardiovascular health.
Powdered fruit and vegetable concentrates contain absorbable nutrients, which can be measured in the bloodstream after supplementation. The participants in these studies reliably experience elevations in the concentrations of carotenoids, lutein, lycopene, folate, and vitamins C and E in their blood. (5)(6)(7)
Supplementation often results in higher concentrations of vitamins C and E, which act as antioxidants. Some studies have also observed reductions in protein carbonyl and oxidized low-density lipoprotein (LDL) concentrations, which may indicate reduced oxidative stress.(6)
Some studies have also reported reductions in the inflammatory marker tumor necrosis factor-alpha (TNF-ɑ), but reductions in C-reactive protein (CRP) are less consistent.(6)(8)(9)
A high concentration of homocysteine is considered to be a risk factor for cardiovascular disease, and supplementation with fruit and veggie concentrates can somewhat reduce homocysteine concentrations due to their high folate content. (6) One study observed elevations in plasma concentrations of dopamine, but this hasn’t been replicated. The authors concluded that this could translate to improved focus and cognitive function, but that hasn’t been confirmed. (9)
It’s a common assumption that ingredients like herbs and plant extracts are safe because they can be found in nature and purchased without a prescription, but that isn’t always the case. Greens powders are regulated like other supplements, which leaves them susceptible to contamination and liable to be totally ineffective.
Even when you’re using a product tested for purity and backed by solid evidence, you need to be aware of potential drug interactions which are common with some herbal ingredients.
In one randomized, placebo-controlled trial, several overweight women used a powdered fruit and vegetable concentrate for 16 weeks, followed by four weeks of replacing their habitual breakfast with a similar meal replacement shake.
At the end of the trial, women who traded their habitual breakfast for the shake had higher fasting glucose (which could indicate worsening insulin sensitivity), and none experienced improvements in markers of metabolic or immune function. (10) It’s worth nothing, however, that this study conflicted with the majority of other studies that observed improvements in these areas.
Lipid and DNA oxidation (markers of oxidative stress) are often measured with conflicting results. Sometimes these markers are unchanged after supplementation, but in other cases improvements are observed in both the treatment and placebo groups. Though vitamins C and E are elevated after supplementation, total antioxidant capacity rarely improves. (6)
A meta-analysis evaluated the effects of polyphenol-rich foods, juices, and concentrates on exercise recovery and muscle damage, and noted that the data was of medium or very low quality due to the risk of bias in the studies. The foods had no impact on common markers of inflammation or muscle damage, and provided only minor improvements in muscle soreness and recovery assessed by muscular contraction and lower body power. (11)
There is no evidence that greens powders would directly improve performance, nor that they should be universally recommended to athletes.(12)
If you’re lactose intolerant, you might get some benefit from using a lactase enzyme when you eat dairy. The applications of other enzymes are limited, both by a lack of quality research and a narrow window in which they maintain their specific functions. Some intriguing evidence suggests that certain enzymes might reduce osteoarthritis pain, but more research is needed, and claims related to digestive health aren’t well supported. (13)
The effects of probiotics are strain-specific, and they exert a fairly narrow set of well-researched benefits. In other words: if you’re taking a random blend of probiotics, you might not be using the one that would be effective for your specific gut health goals. Even if you are using the proper strain, you may not be receiving an adequate dose or formulation that’s enterically-coated (to survive passage through your stomach acid and inhospitable small intestine). (14)
The aforementioned breakfast meal replacement shake contained a blend of soluble and insoluble fiber intended to serve as a source of prebiotics and microbe-accessible carbohydrates. Though the meal replacement shake increased fecal butyrate, a beneficial fatty acid, this was likely due to the added prebiotic fiber, not the specific shake. There were no changes to the gut microbiome.(10)
Unlike prescription or over-the-counter drugs, supplements aren’t required to undergo safety, efficacy, or purity testing through the FDA before they reach the market. (4)
Hepatotoxicity, or liver damage, has been reported after the use (or overuse, in some cases) of several supplement blends sold for weight loss and nutritional support. In other cases, manufacturers have added ingredients banned by the World Anti-Doping Agency (WADA) without disclosing them in the ingredients. (15)
Though a very high dose of a vitamin or mineral might not be considered contamination, it’s also important to keep in mind that more isn’t always better when it comes to micronutrients. Taking too much vitamin C might lead to something unpleasant, like diarrhea, but habitually exceeding the safe upper limits of iron or Vitamin A could cause serious health issues. (2) On the other hand, since proprietary blend formulations aren’t disclosed on the label, supplements can include ingredients dosed too low to be effective. (4)
An estimated 20% to 25% of people in the United States take supplements along with prescription drugs. Some supplements influence the absorption, excretion, or activity of prescription drugs with potential serious consequences. (16)
Human studies and clinical reports indicate a high risk of interference from goldenseal and St. John’s Wort. Other herbs like black cohosh, cranberry, ginkgo biloba, ginseng, milk thistle, saw palmetto, and valerian could also interact with some prescriptions, though the risk is lower. It’s important to let your doctor and pharmacist know what supplements you’re using, and to check for potential interactions. (16)
If you’re thinking about buying a greens powder — or any supplement — here are some additional points to consider and things to know when choosing a brand.
Though supplement claims can’t include statements about preventing, treating, or curing diseases, they can imply that the ingredients support the function of the human body, like the digestive or immune systems. (4) For example, you’ll often see claims about greens powders supporting digestion because they contain probiotics, or supporting immunity because they contain sources of vitamin C.
Supplement manufacturers aren’t required to submit evidence substantiating their claims to the Food and Drug Administration (FDA), but the FDA recommends that claims be based on relevant human studies. This is intended to provide some protection for consumers against dishonest or inaccurate statements. (4)
In 2012, however, the Office of Inspector General of the United States Department of Health and Human Services analyzed 378 claims from 127 common nutritional supplements and found that less than half were based on data from human studies; of those, none of them met the FDA’s recommendations for relevancy or quality. (4)
Less than 15% of the human studies were randomized, double-blind, parallel group, placebo-controlled trials, and 49% were done in special populations that wouldn’t translate to the general public. Shockingly, of the 557 human studies used as evidence, only two used the actual supplement in question. (4)
This doesn’t mean that all manufacturers are intentionally misleading consumers with unscrupulous marketing tactics, but it’s something to keep in mind when the claims seem a little too good to be true.
Assuming that a single serving of a greens powder is required to exert its ostensible health benefits, it can be compared to the cost of an effective serving of fruits and veggies (though these supplements can’t actually replace whole foods.) (6)(7)(12)
The WHO recommends eating at least 400 grams of fruits and vegetables per day. According to a 2017 dose-response analysis of the protective effects of fruits and vegetables, the risk of chronic diseases was reduced significantly with every 200 gram serving, up to 800 grams per day. (1)
If you’re meeting these recommendations in your regular diet, you’re less likely to benefit from supplementing with additional plant matter. Several studies have noted very small improvements (or none at all) in biomarkers after supplementation in people who already ate fruits and vegetables — even at levels below WHO recommendations.
In fact, one limitation cited in studies is an inadequate ‘washout’ period prior to supplementation; in other words, they need their participants to stop eating fruits and veggies for a longer period of time before they start the study to actually observe benefits from supplementation. (6)(7)
On the other hand, if you’re not eating enough fruits or veggies, you might be in a position to benefit from adding a greens powder. However, make note of the fact that greens powders are more expensive on a gram-by-gram basis of the nutrients you’re after. Some fruit and veggie blends are priced at less than $1 USD per serving, while others cost over $3.00 USD per serving. A single 200 gram serving of an apple, on the other hand, costs about 22 cents. (17)
Some manufacturers volunteer for third party testing to establish the purity of their products, which can protect you from inadvertently ingesting a banned or potentially toxic substance. These include the U.S. Pharmacopeial Convention and NSF International, whose labels (USP and NSF, respectively) are added to tested products. (16)
These labels don’t ensure that the products will live up to their claims, but they can be especially important for people concerned about contaminants, like athletes competing in drug-tested events and individuals taking prescription drugs.
Powdered fruit and veggie blends can provide a nutrition boost for certain populations who aren’t eating enough fruits and veggies, but they can’t replace whole foods. Since most of the available research has focused on a specific brand of powdered fruits and veggies, it remains to be seen whether other blends would have similar effects.
If you’re not meeting the recommendations for fruits and vegetables, taking a greens powder could benefit you, but eating more fruits and veggies would have the same effect, potentially at a lower cost. Added proprietary blends might not provide any additional benefit while driving up the cost of the item, and if you’re using a product that hasn’t been third-party tested for purity, you might be taking something you don’t see on the label.
Greens powders work in some ways, and they could be helpful if you don’t have access to fresh produce. That said, if you want to choose the most evidence-based (and likely cost-effective) intervention with the best risk-to-benefit ratio, you might want to start with an apple a day.
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