In this article, we delve into the truth behind online superfood claims, contrasting digital misinformation with scientific facts.
Superfoods like kale, spinach, and blueberries are renowned for their nutritional prowess, but how accurate are the health benefits touted online?
We explore their nutritional properties, scientific content analysis, and the role these foods play in disease prevention.
This evaluation offers evidence-based dietary recommendations, providing a clearer picture for consumers navigating the complex world of online health information.
Main Findings
- Web pages generally present accurate but oversimplified information about superfoods.
- The most commonly mentioned superfoods are kale, spinach, salmon, blueberries, avocado, chia, walnuts, beans, fermented milk, and garlic.
- There’s a mismatch between the health claims made on websites and the scientific evidence available.
- The positive health effects of superfoods are often overstated without detailed explanations or scientific backing.
What Are Superfoods?
The concept of ‘superfoods’ emerged in the 1990s, describing a category of foods with superior nutritional qualities, known for their macro- and micronutrient richness and benefits to human health 1.
These foods are often linked with natural production and traditional agricultural practices of indigenous populations.
However, the increased demand for superfoods has led to significant changes in their production, including the shift from traditional to intensive farming methods 1 2.
The term ‘superfood’ lacks a formal legal definition, leading to its widespread use in marketing and social media by influencers.
This popularity, while highlighting the health benefits, often overlooks the variability in chemical composition and the potential risks associated with some superfoods 3 4.
The internet has transformed how people access nutritional information, with search engines becoming a primary source.
This change, however, has also led to the spread of misinformation, as not all digital sources provide evidence-based information 5 6.
The categorization of certain foods as ‘superfoods’ influences consumer demand and perceptions.
Despite numerous studies on this subject, there is a noticeable lack of research on the accuracy of superfood information available on the web.
This study aims to bridge this gap by examining the most frequently mentioned superfoods on websites, analyzing the claims about their nutrients and health benefits, and evaluating the reliability of this information against recent scientific findings 7 2 4 8 9 10.
How We Analyzed Superfood Information
The study aimed to evaluate online claims about superfoods’ validity.
Google and Bing were the primary search engines used for this study 11.
Measures were taken to ensure unbiased results, such as clearing cookies and using a VPN.
The search focused on the term ‘superfoods’ with language settings adjusted for English results.
Search dates were on 20 May 2022, and ‘any time’ and ‘past year’ settings were compared.
Only the first two pages of search results were considered due to user behavior 11.
45 web pages were selected for analysis after excluding commercial, repetitive, inaccessible, non-English, or irrelevant pages.
Various types of web pages were included, such as health information sites, media, blogs, shopping sites, medical centers, and academic institutions.
To validate claims, a scientific review was conducted using the Clarivate Web of Science database.
The focus of the review was on superfoods, narrowing down searches to review articles from the last five years in ‘Food Science and Technology’ and ‘Nutrition Dietetics.’
The study aimed to provide a comparison between online claims and the current scientific understanding of superfoods as of 4 November 2022.
Online Superfood Claims: Top 10 Superfoods
Kale
Kale, a member of the Brassicaceae family, has been frequently mentioned as a ‘superfood’ on various websites 12 13.
Recognized for its rich content in fiber, vitamins A, E, K, C, folates, calcium, and iron, kale stands out for its high concentration of fiber and vitamin K compared to other plant foods.
It’s also noted for having a good amount of vitamin A and more vitamin C than many salad and cruciferous vegetables.
Additionally, kale is a source of various B vitamins 14.
Despite its nutritional value, the anti-nutritional factors in kale, such as oxalates, tannins, and phytate, which can hinder nutrient absorption, are often overlooked on websites.
Kale, however, has a lower oxalic acid content than other vegetables, offering high bioavailability of calcium and iron, making it an excellent choice for vegan diets 14 15.
Online sources frequently cite kale’s health benefits, including antioxidant activity, cardiovascular disease prevention, cancer risk reduction, and aiding digestive disorders.
However, these sites rarely detail the specific compounds or mechanisms involved.
Scientific literature supports these claims, though much of this information is derived from in vitro studies, with limited in vivo research 16 17 18.
The phytochemical and nutrient levels in kale are influenced by various factors such as the plant’s variety, growth conditions, and post-harvest handling.
This variability means that the health benefits of kale can differ greatly.
Cultural factors also play a role in the general population’s consumption patterns, complicating the interpretation of epidemiological studies 13 16 17.
Kale’s antioxidant properties are attributed to vitamins C and E, polyphenols, carotenoids, and glucosinolates’ hydrolysis products.
These include flavonoids, phenolic acids, and the carotenoids β-carotene, lutein, violaxanthin, and neoxanthin.
Glucosinolates, transformed into bioactive compounds upon hydrolysis, contribute to kale’s anti-inflammatory and antimicrobial properties 19.
Consuming kale has been linked to reduced risk of coronary artery disease and various cancers, as well as improvements in digestive health.
These benefits are partly due to compounds like sulforaphane and indole-3-carbinol, found in kale, which exhibit activity against several types of cancer 20 21 22.
Finally, the impact of processing and cooking on kale’s nutrient content is significant.
Methods like blanching and boiling can lead to nutrient loss, while steaming or microwaving helps preserve or enhance the conversion of glucosinolates to bioactive compounds.
The bioavailability of these nutrients and compounds is also affected by the cooking and handling processes 23.
Spinach
Spinach, identified as the second most mentioned ‘superfood’ on various websites and the top leafy green vegetable, is celebrated for its rich content of fiber, vitamins A, K, C, folate, calcium, and iron.
It also contains significant levels of magnesium, manganese, potassium, phosphorus, zinc, and copper, although these nutrients are less frequently mentioned online 24 25 26.
Spinach does have anti-nutritional compounds like oxalates and phytic acid, which can reduce the bioavailability of minerals such as calcium and iron.
Websites often highlight spinach’s health benefits, including cardiovascular disease prevention, cancer risk reduction, antioxidant activity, and bone health preservation.
These benefits are attributed to spinach’s polyphenols, carotenoids, ascorbic acid, and phytochemicals, which have strong antioxidant properties.
In particular, flavonoids, β-carotene, and lutein are crucial in spinach’s antioxidant profile, higher than in cruciferous vegetables.
Epidemiological studies suggest that spinach consumption may lower the risk of breast, esophageal, and colon cancers, with anti-cancer properties linked to specific spinach compounds like glycoglycerolipids, glycolipids, p-coumaric acid, carotenoids, and chlorophylls 24 27 28.
Cardiovascular health benefits are the most frequently mentioned positive effect of spinach.
While many studies show an inverse relationship between leafy greens and cardiovascular disease, some report no correlation.
Factors like serving sizes, lifestyle, and dietary choices are often not considered in these studies.
Spinach’s cardiovascular benefits are thought to come from antioxidants and nitrates, which are converted in the body to nitric oxide (NO), lowering blood pressure and improving vascular health 29 30.
The nitrate content in spinach can pose health risks, as nitrates can transform into potentially harmful nitrosamines and cause hypoxemia in infants.
However, risks are minimized with controlled fertilizer use and proper storage conditions, making spinach consumption generally safe.
Other health benefits of spinach, such as antimicrobial activity, anti-inflammatory effects, digestive and eye health, weight control, and diabetes risk reduction, are less commonly mentioned online but are supported by scientific literature.
These effects are mostly observed in studies using spinach leaf extracts 24 28.
The phytochemical concentrations in spinach are influenced by environmental conditions, agronomic practices, harvesting stage, and storage.
Cooking methods also affect spinach’s nutritional content; for instance, drying reduces the availability of ascorbic acid, carotenoids, and flavonoids.
Blanching and boiling decrease phytochemicals, while steaming is more effective in retaining water-soluble bioactive compounds.
Microwave cooking yields variable results depending on the compound 24 27 31.
Salmon
Salmon, widely recognized as a ‘superfood’ on various websites, is noted for its significant health benefits, particularly in cardiovascular disease protection, anti-inflammatory effects, and enhancing memory and learning skills 10.
These benefits are primarily attributed to its rich content of polyunsaturated fatty acids [PUFA], especially eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA], as highlighted on numerous websites 32.
These fatty acids are known for their role in preventing endothelial dysfunctions, reducing blood viscosity and pressure, and offering anti-inflammatory properties.
However, the cardiovascular benefits of salmon may also be due to a combination of various lipid compounds present in fish, including carotenoids, vitamins A, E, and D, and n-3 PUFA-rich phospholipids and glycolipids, not just n-3 PUFAs alone 33.
Salmon’s carotenoid astaxanthin, a red pigment, is effective against oxidative stress and inflammation, thereby reducing cardiovascular risks.
The fish also contains lutein and β-carotene 34.
The benefits of n-3 PUFAs are facilitated by multiple metabolic mechanisms and their influence on intestinal microbiota 35.
Additionally, the presence of Vitamin D and selenium in salmon enhances the neuroprotective properties of EPA and DHA 32, though these nutrients are less frequently mentioned online.
Lesser-known benefits of salmon consumption, such as cancer risk reduction, immunity enhancement, prevention of neurodegenerative diseases, and antidepressant effects, are also associated with n-3 PUFA intake 36.
Salmon’s protein content, noted as the second most mentioned nutrient, includes essential, nonessential, and functional amino acids with potential in preventing various disorders.
Interestingly, while salmon has a higher Vitamin E content than terrestrial meats, known for its cardiovascular and neurological benefits, it is not commonly cited as an important nutrient in salmon by websites 32 36
The levels of n-3 PUFAs and other lipid bioactives in salmon vary based on several factors, including season, fish life cycle, gender, habitat [farmed or wild], temperature, diet, and cooking methods.
In recent years, the EPA and DHA content in farmed salmon has decreased due to changes in feed composition, although farmed salmon remains a good source of these fatty acids in the diet 37.
Algal biomasses are now used in commercial salmon feeds to improve long-chain n-3 PUFA content 38, but factors like fish size, species, environmental conditions, and production system also influence fatty acid incorporation into fish tissue 39.
The nutritional quality of salmon can be diminished by severe thermal processing and cooking methods, such as boiling, frying, and steaming, which increase the oxidation of carotenoids, PUFAs, and other lipid bioactives 33 34.
Blueberries
Blueberries, scientifically known as Vaccinium Section Cyanococcus, are frequently touted as a superfood online for their rich nutrient content, including fiber, vitamin C, and various minerals.
Although less mentioned, they also contain vitamins E and K, manganese, and potassium.
Scientific studies corroborate these findings and add vitamins from the B complex, E, A, selenium, zinc, and iron to the list, although these are less cited online 40 41.
Websites highlight blueberries’ antioxidant activity and their role in preventing cardiovascular diseases, reducing cancer risk, and aiding in weight loss.
The health benefits of blueberries are primarily attributed to their high concentration of phenolic compounds, especially flavonoids like anthocyanins.
Other flavonoids, phenolic and cinnamic acids, and proanthocyanins are also significant contributors to their health-promoting potential 40 42.
Their antioxidant properties are linked to anticancer and anti-mutagenic effects, protecting against DNA oxidation and inhibiting tumor cell proliferation.
However, most studies have been conducted with blueberry extracts in cell lines and animals, necessitating human studies for confirmation 43 44.
Blueberries’ flavonoids are associated with cardiovascular protection by improving blood flow, endothelial function, and inhibiting platelet aggregation.
Anthocyanins, in particular, show a positive effect on vascular function and hyperlipidemia and may reduce myocardial infarction risk.
However, the impact on blood pressure remains uncertain 45 46.
Neuroprotective properties, like memory enhancement and prevention of neurodegenerative diseases, have been reported in scientific literature, attributed to blueberries’ antioxidants and anti-inflammatory compounds 47.
Regarding weight loss, blueberries do not significantly impact weight gain or fat accumulation, but anthocyanin extracts may have a reducing effect 40.
Other less mentioned benefits, such as anti-inflammatory and antimicrobial activities, digestive health improvement, diabetes risk reduction, and anti-aging effects, are also supported by scientific research 42 43 48.
The efficacy of blueberries’ health benefits varies based on trial duration, participant characteristics, and the anthocyanin dosage and form.
While frequent consumption is generally considered beneficial, further research is needed to fully understand these effects 41 47.
Avocados
Avocados [Persea americana Mill.]
are widely praised online for their high content of monounsaturated fatty acids [MUFA] or ‘healthy fats’, mentioned notably more than other nutrients.
Fiber, magnesium, and potassium also receive significant mentions, while vitamins E, K, C, and B, along with copper and manganese, are cited less.
Scientific literature confirms avocado as a good source of these nutrients 49 50.
However, some websites incorrectly label avocado as a rich source of polyunsaturated fatty acids [PUFA], which isn’t supported by scientific evidence 51.
The nutrient composition of avocados can vary based on factors like plant variety, environmental conditions, and soil composition 52.
The high MUFA content in avocados enhances the absorption of other fat-soluble compounds like phytosterols and vitamin E, potentially amplifying the fruit’s health benefits.
Websites commonly cite avocados for their role in preventing cardiovascular diseases and reducing diabetes risk, alongside antioxidant properties, cancer risk reduction, and eye health promotion.
Avocado’s cardiovascular benefits are attributed to its carotenoids, tocopherol, phenolic compounds, and phytosterols.
These components help reduce blood vessel damage, cholesterol absorption, and platelet aggregation.
Clinical studies have shown avocados can lower triglycerides and cholesterol levels, contributing to heart health and weight management.
However, these studies show varied results due to factors like avocado consumption amounts and study duration 51.
The fruit’s impact on type 2 diabetes is linked to its high indigestible carbohydrate content, shown to lower blood sugar levels in both animals and humans 49.
Avocado’s anticancer potential, particularly evident in laboratory studies using extracts from various parts of the fruit, suggests possible applications in cancer treatment.
Clinical research is needed to validate these effects in cancer prevention.
Additionally, carotenoids like lutein and zeaxanthin in avocados may slow the progression of age-related eye diseases such as cataracts and macular degeneration 51.
Chia Seeds
Chia seeds [Salvia hispanica L.] are often highlighted online for their content of protein, healthy fats [notably linolenic acid], fiber, and minerals like magnesium.
Scientific studies confirm these findings, emphasizing chia’s high dietary fiber and lipid content rich in polyunsaturated fatty acids, especially α-linolenic acid.
Compared to other seeds, chia seeds also have a high protein content with good digestibility.
Additionally, they are sources of calcium, macro- and microelements, and vitamins [A, E, C, and B complex], though these are less frequently mentioned online 53.
The nutrient content in chia seeds varies based on factors like origin, environmental conditions, and storage methods.
Roasting chia seeds can negatively impact the bioactive properties of their lipids, reducing their polyunsaturated fatty acids and phenolic compounds 54.
Websites commonly cite chia seeds for their antioxidant activity and cardiovascular disease protection.
Other benefits mentioned include weight control, anti-inflammatory properties, diabetes risk reduction, and bone health maintenance.
These health benefits align with scientific literature, which reports antiobesity, antioxidant, anticarcinogenic, hypotensive effects, and cardiovascular protection in both animal models and clinical studies.
The mucilage from chia seeds, which is released upon soaking in water, is thought to increase satiety due to delayed gastric emptying, contributing to weight control 55 56.
The antioxidant activity is attributed to their phenolic compounds, flavonoids, and carotenoids, potentially offering protection against heart disease and cancer 57.
Chia seeds’ benefits include decreasing atherogenic lipids, blood pressure, and inflammation markers, partly due to the conversion of α-linolenic acid to long-chain n-3 PUFAs [EPA and DHA] 58.
However, there is some controversy in in vivo studies regarding these health benefits.
In animal studies with unbalanced diets, chia seeds have been shown to cause fat redistribution and reduce abdominal fat, improving cardiovascular health, glucose tolerance, and insulin sensitivity 59 60.
Clinical studies suggest that the effects of chia seeds on lipid and glucose levels may vary based on factors like dosage, form of consumption, and participant characteristics.
Ground chia seeds appear more beneficial for blood pressure and glucose levels than whole seeds, with effects more pronounced at higher doses 61.
Further research is needed to fully understand the health effects of chia consumption, considering methodological aspects of trials.
Walnuts
Online sources frequently highlight walnuts [Juglans regia L.] for their protein, healthy fats [especially linolenic acid], and fiber content.
Scientific literature supports these claims, identifying walnuts as a rich source of these nutrients 62.
Additionally, walnuts provide iron, zinc, potassium, vitamins E, B3, B5, B1, B6, biotin, folate, magnesium, manganese, copper, and phosphorus, though these are less frequently mentioned online 63.
Websites often credit walnuts with antioxidant activity and cardiovascular disease prevention, both mentioned significantly.
Other noted benefits include anti-inflammatory effects and enhanced memory and learning skills.
These health properties are linked to walnuts’ bioactive compounds like phenolic compounds, phytosterols, γ-tocopherol, dietary fiber, protein [high in L-arginine], phytomelatonin, and α-linolenic fatty acid 64.
Consumption of walnuts has been shown to improve lipid profiles in adults, reducing triglycerides, total cholesterol, and LDL cholesterol, which are key factors in decreasing cardiovascular disease risk 65 66.
Walnuts’ PUFA content is believed to enhance brain function, with cognitive improvement observed mainly in long-term consumption 67.
The ellagitannins in walnuts release ellagic acid, offering antioxidant and anti-inflammatory benefits.
However, despite these properties, clinical studies have not consistently linked walnut consumption with reduced inflammation markers or improved glucose homeostasis.
Nevertheless, including walnuts in diets has been observed to positively alter gastrointestinal microbiota and reduce proinflammatory factors.
While walnuts are likely beneficial for health, more research is needed to conclusively establish their effects, considering varying dosages and participant diets in clinical trials 66.
Beans
Websites frequently highlight beans [Phaseolus vulgaris L.] for their protein, fiber, vitamins, and minerals like iron and magnesium.
Scientifically, beans are rich in protein, comparable to meat, but lower in certain essential amino acids.
Their protein digestibility is improved with proper cooking, overcoming the effects of protease inhibitors and tannins 68.
Beans are also a good source of folate, a fact less mentioned online.
Additionally, they contain significant amounts of calcium, phosphorus, copper, manganese, selenium, and zinc, which are often overlooked on websites.
The health benefits of beans, according to online sources, include cardiovascular disease protection and type 2 diabetes risk reduction.
Beans are rich in bioactive components like polysaccharides, oligosaccharides, proteins, phenolic compounds, minerals, and vitamins, contributing to their health potential 68 69.
They have been shown to reduce LDL cholesterol, aiding in cardiovascular health, and decrease postprandial glucose levels, albeit with varying results.
The high fiber content and minerals like iron and zinc in beans are linked to type 2 diabetes benefits.
Beans’ resistant starch supports glycemic and blood pressure control and maintains healthy gut microbiota.
Additionally, beans peptides may have antithrombotic and antihypertensive effects 70 71.
However, some phytochemical compounds in beans can affect nutrient bioavailability and pose health risks under specific conditions.
These include trypsin inhibitors, α-amylase inhibitor, phytic acid, and oxalate.
Lectins in beans can cause health issues, but most antinutritional factors are significantly reduced by thermal processing, soaking, and fermentation 68 72 73.
Although beans are thought to have cancer-preventing properties, current evidence does not strongly support this claim 70.
Variations in clinical studies, such as bean variety, growing conditions, participant characteristics, and administration form, challenge the determination of beans’ precise health effects 70.
Fermented Milks
Websites often highlight the protein, calcium, and various vitamins and minerals in fermented milks, like yogurt and kefir.
Scientifically, these products are indeed rich in protein, calcium, and vitamins D, A, E, B2, B3, B12, and folates.
Fermented milks also contain essential minerals such as phosphorus, zinc, magnesium, and potassium, although these are less mentioned online 74.
The primary health benefits of fermented milks, as per online sources, are digestive health and immunity improvement.
Traditional yogurt, produced with symbiotic bacteria, and kefir, with its natural microbiota, are recognized for their probiotic qualities, contributing to gut health.
These products have shown positive effects in managing digestive disorders and boosting gut microbiota, especially in individuals with gut health alterations 75 76.
Fermented milks are also linked to enhanced immunity against viruses and pathogenic bacteria.
They potentially reduce allergic disorders through gut microbiome modulation, a claim requiring further investigation.
Kefir, in particular, may influence gastrointestinal immune functions and promote secretory immunoglobulin A production, although its colonization capability in the gut remains unconfirmed 77 78.
Additional health benefits, such as cardioprotective properties, anti-obesity and anti-diabetes effects, and bone health and cognitive improvement, are supported by literature but rarely mentioned online.
These benefits are thought to arise from bioactive compounds like peptides, bacteriocins, and exopolysaccharides, which exhibit antimicrobial, antioxidative, and immune-modulatory properties 79 80.
Regular yogurt intake has been linked to lower cardiovascular disease risk, and kefir shows a range of probiotic health effects 81.
However, discrepancies between animal and human trial results highlight the need for further research, considering human diets, lifestyles, and gut microbiomes 79.
Garlic
Websites often understate the nutritional composition of garlic [Allium sativum L.], rarely mentioning its fiber, minerals [like zinc, phosphorus, potassium], vitamins [A, C, and B complex] more than three times.
However, scientific literature confirms garlic’s richness in these nutrients 82.
Garlic is acclaimed online for cardiovascular disease protection, antimicrobial properties, anti-cancer activity, and immunity improvement.
Its health benefits stem from a variety of bioactive chemicals, including organosulfur compounds, phenolic compounds, saponins, and polysaccharides.
These compounds’ bioactivity varies with preparation, extraction conditions, and storage 82 83.
Organosulfur compounds, particularly alliin and allicin, are pivotal in garlic’s health properties.
For instance, black garlic, produced by heating raw garlic under controlled conditions, sees an increase in bioactive compounds due to the Maillard reaction.
This process increases levels of S-allyl cysteine, polyphenols, and flavonoids compared to raw garlic 84 85.
Garlic exhibits antibacterial, antifungal, and antiviral activities, with allicin playing a crucial role.
It also promotes cardiovascular health by improving lipid profiles and blood pressure.
Allicin’s antiplatelet and antihypertensive effects contribute significantly to these benefits 86.
In cancer risk reduction, garlic’s efficacy against various cancers is linked to organosulfur compounds.
They act by inhibiting angiogenesis, regulating carcinogen metabolism, and inducing apoptosis 87.
Polysaccharides are the main immunomodulatory compounds in garlic, with allicin also contributing to immune function enhancement 84 88.
However, most studies use garlic extracts or purified compounds, making it challenging to apply findings to regular garlic consumption.
More clinical research is needed for concrete conclusions on garlic’s impact on health.
The Truth About Superfoods
Websites provide generally accurate information about the health benefits of popular ‘superfoods’ based on scientific literature, but there are nuances.
Most of these benefits come from bioactive compounds, often tested in vitro and in animal studies.
Clinical studies on superfoods are limited, especially when it comes to direct intake.
Human trials vary in design, methodology, participant characteristics, serving sizes, duration, and measured health markers, making it challenging to draw definitive conclusions.
The concentration of bioactive components in superfoods is influenced by factors like growing conditions, storage, varieties, diet, and living conditions.
Processing, cooking methods, and interactions with other food compounds also impact the availability of bioactive chemicals.
Website information on superfoods tends to oversimplify complex scientific findings.
This oversimplification can create unrealistic expectations among consumers.
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