Taste the Rainbow: Food Dyes, Natural Pigments, and Your Gut Health

The Seed Digest:

• Artificial dyes are now being examined for their potential links to neurobehavioral and other health concerns. 
• These dyes could disrupt the gut microbiome, but more research is needed to draw firm conclusions. 
• Naturally derived food colorings are alternatives that provide vibrant tints and benefits like improved gut diversity and barrier functioning.

Artificial food colorings are in the hot seat. 

Earlier this year, the U.S. Food and Drug Administration (FDA) revoked its authorization of Red No. 3, and the artificial dye that lends a cherry-red hue must be removed from food and ingested drugs come January 2027.¹ And at least a dozen states are pushing to pass laws that minimize or ban dyes and other chemical additives in foods; Oklahoma, for instance, is seeking to outlaw multiple blue, red, and yellow artificial dyes.² 

These bans and proposed restrictions are meant to protect public health from the colorings’ potential adverse effects, proponents say.³ But when it comes to gut health specifically, do artificial food dyes carry any legitimate risk? Here, an investigation into food dyes and your gut microbiome.

The Past, Present, and Future of Artificial Food Dyes

Naturally occurring pigments (from vegetables and minerals) have been used to color foods, drugs, and cosmetics for centuries. The first man-made artificial dyes were created in the late 1800s, often from the byproducts of coal processing. By the 1880s, the federal government started overseeing color additives and approving the use of artificial coloring in food for the first time—in butter and cheese, at that.⁴ 

By 1900, many foods, drugs, and cosmetics in the U.S. contained artificial colorings. Some of these colorants were made with “blatantly poisonous” chemicals like lead, arsenic, and mercury, per the FDA. In response, U.S. government agencies conducted reviews of certain colors and removed those that did not meet safety standards. They also established certification procedures to protect public health from toxic colorings throughout the 20th century.⁴ 

Flash forward to today, and there are nine certified color additives used in food that are regulated by the FDA.⁵ These dyes are mainly derived from petroleum (though their molecular structure is vastly different from gasoline or diesel).^4,6,7

The Agency lists new color additives, plus new uses for listed colors, that have been shown to be safe for their intended uses in the Code of Federal Regulations. It also certifies batches of synthetic color additives before sale and monitors their use, including product labelling.⁴

As shown in recent events, the FDA can also revoke authorization of color additives. In January, the Agency pulled its approval of the use of FD&C Red No. 3 in response to a 2022 petition, which highlighted two studies that showed a link between cancer and high levels of the additive in male rats. The mechanism through which the cancer developed doesn’t occur in humans, and exposure levels are typically much lower than what was used in the study, according to the FDA.

However, the Delaney Clause (enacted in 1960) prohibits the FDA from authorizing a food additive if it’s been found to cause cancer in humans or animals. Now, manufacturers will need to reformulate their food products without the cherry-red coloring by January 15, 2027. (It’s important to mention that one of the studies referenced was from 1987, and the researcher still stands by the conclusion that “this is not a problem for humans.”)^1,8

Food Dyes and Gut Health

Artificial food dyes are being questioned due to their potential links to behavioral concerns in children—but could they harm gut health?

To put it simply, there’s very limited scientific evidence showing a potential negative impact on the gut microbiome, particularly in humans. Some initial studies have found a link between certain dyes and possible gut microbiome disruption. Recent research, for instance, found that certain human gut bacteria are capable of breaking down common azo dyes (including Red No. 2, Red No. 40, and Yellow No. 5).^9,10

This process could turn the dyes into metabolites that are toxic to certain bacterial species, and in turn, alter the growth of some gut bacteria. In other words, the dyes may have the potential to disturb the gut microbiome’s delicate balance, but there isn’t concrete evidence just yet. 

Some animal research has shown that chronic exposure to artificial food colorings like Red No. 40 may increase susceptibility to bowel disorders, intestinal inflammation, and colitis.¹¹ Another investigation found that the colorant damages DNA (both in living organisms and in vitro) and, combined with a long-term, high-fat diet, contributes to dysbiosis and low-grade colonic inflammation in mice.¹² Still, the findings of animal studies can’t be broadly applied to humans, and there’s a lot that’s unknown. 

Since the gut microbiome is intricately tied to a host of other bodily systems—including the brain—it’s plausible that artificial dyes could influence cognitive and mental health. Several studies suggest these additives may influence neurobehavioral outcomes, particularly in children.^13,14,15 But again, there isn’t much research on the topic, especially as it pertains to the gut-brain axis, and more studies are needed to clarify these potential connections.

Of course, the effects can vary between individuals due to consumption levels. Plus, some people may have an allergic-like reaction to color additives. Yellow No. 5, for example—used in candy, breakfast cereals, and other foods—can trigger itching and hives in some cases.¹⁶ 

What Are Artificial Dyes Used In?

Of the nine certified color additives that are approved for use in food by the FDA, three are particularly pervasive.⁵ Red No. 40, Yellow No. 5, and Yellow No. 6 account for 90% of all the food dye used in the US, according to 2010 research.¹⁷ In fact, more than 38,000 food products sold in the U.S. contain Red No. 40, according to the U.S. Department of Agriculture’s branded foods database.¹⁸

Some foods that contain artificial dyes—like hot-pink frosting or electric blue ice cream—are easy to spot. Others are more covert. Pickles, wheat bread, canned vegetables, spices and condiments, cheese, and smoked meats and fish can, at times, contain artificial dyes to enhance or smooth out their colors. Dyes are particularly common in kids’ products.^18,19 One study found that of the 810 products marketed toward children in a single grocery store, more than 43% contained artificial food colors.²⁰ 

Most often, you’ll find artificial dyes in these product categories in the U.S.:^5,20 

• Baked goods
• Beverages
• Candy
• Cereals
• Condiments and sauces
• Confections
• Crackers
• Frostings and icings
• Frozen dairy desserts, ice cream, and popsicles
• Gelatin
• Hot dog and sausage casings
• Ice cream cones
• Snack foods
• Yogurt

It’s worth noting that avoiding artificial colorings altogether may not be possible for all people. Access to foods free of artificial colorings isn’t equitable, and many naturally colored foods come with a higher price tag.

Nature’s Colorful Alternatives

The health risks of artificial dyes are still up for debate, but one thing is clear: Consuming naturally colorful foods with plant-based pigments can help support your gut diversity.

Natural pigments can help enhance a plant’s odds of survival and reproduction. Green chlorophyll, for example, absorbs light energy to drive photosynthesis, while yellow, orange, and red carotenoids capture additional light energy and protect chlorophyll from potential excess sun damage. Meanwhile, bright pigments attract pollinators and signal ripeness to animals, encouraging them to eat the fruit and spread its seeds.^21,22,23 

These pigments also help protect plant cells from damaging UV radiation and other environmental stressors.^24,25 They can also deter herbivores from munching on the plant, often by resembling toxic plants or leaving a bitter aftertaste.^24,26 

In a beautiful reminder that all life on earth is connected, the pigments that protect plants can do the same for humans. Here are just a few shades that have proven health benefits: 

Carotenoids

Responsible for yellow, orange, and red hues, carotenoids can increase diversity of the gut microbiota, stabilize tight junctions to maintain gut barrier function, and regulate gut-immune function. They also have antioxidant properties that can protect gut cells from free radical-induced damage.^27,28 

Sources include:

• Carrots
• Sweet potatoes
• Pumpkins
• Tomatoes
• Watermelon
• Egg yolks

Anthocyanins

These red, purple, and blue pigments have been shown to promote the growth of beneficial gut bacteria, including Bifidobacterium and Lactobacillus. They also produce metabolites that support gut health and may ultimately reduce inflammation and oxidative stress.^29,30,31,32 

Sources include:

• Berries
• Cherries
• Red cabbage
• Grapes
• Eggplant skin

Chlorophylls

Found in all green plants, chlorophyll comes with a laundry list of potential benefits for the gut. Some animal studies suggest that anti-inflammatory, antioxidant-rich chlorophyll may support a balanced gut microbiome.^33,34,35 The compound has been shown to stimulate the release of specific proteins that help maintain the integrity of the gut lining’s tight junctions, and it may help reduce harmful bacteria without affecting beneficial microbes.³⁴

Animal studies, for instance, have found that derivatives of chlorophyll may have antimicrobial properties, which means they may help prevent gut infections without disrupting “good” bacteria.³⁶

Sources include:

• Leafy greens (spinach, kale, romaine, etc.)
• Matcha
• Algae

Pro tip: To get the most chlorophyll from your diet, consider eating raw or lightly cooked veggies, as the content tends to decrease when the plants are cooked, thawed after being frozen, or beginning to spoil.³⁷

Other beneficial pigments to look out for include betalains (red and yellow pigments found in beets), tannins (brown pigment found in tea and coffee), and curcumin (bright yellow pigment found in turmeric).

Frequently Asked Questions (FAQs):

• Why is artificial food dye bad for you? Some studies have shown a link between synthetic food dyes and neurobehavioral outcomes, allergic reactions, and potential gut health issues.^{11,13,14,15,38,39} While these findings should raise some level of concern, more research is needed on artificial food coloring’s risks. 
• Can food dyes cause stomach problems? Artificial food dyes may contribute to gut disruption and inflammation, initial studies in humans and animals suggest. However, there’s not enough evidence to say they cause stomach problems or harm the gut directly.

The Key Insight

The jury is still out on artificial food dyes’ influence on the gut. Some research suggests they could potentially become toxic to certain gut bacterial species as they are metabolized, and animal studies have shown that some colorings may contribute to inflammation.^11,12 However, more research is needed.

If artificial dyes are a concern for you, pay extra attention to the ingredient labels on pre-packaged snack foods, candies, cereals, drinks, bakery items, and frozen treats. Aim to swap these out with naturally colorful plant foods to taste the rainbow the gut-friendly way.