health dangers eating fruit
In the exploration of the Health Dangers of a Plant-based Diet fruit plays an interesting role. Most people think fruit is healthy because they are high in antioxidants, they are a good source of fiber, and they contain essential vitamins and minerals. And unlike other plant parts (roots, seeds, stems, and leaves) which the plant desperately wants to protect for survival, the plant actually wants predators to eat its fruit and spread their seeds. So here we'll explore if there are any health dangers of eating fruit.

Spreading Seed

Some plants don't want predators to spread their seeds (naked seeds). Others depend on animals to do so.

Naked Seeds

Naked seeds are exposed baby plants. They grow on grasses and vines and the parent plant drops these seeds right where they are growing. Then in the winter, when the parent plant dies, the offspring can sprout right there in the same area. Because they don't want pests and predators to eat these seeds, plants lace the seeds with phytochemicals to deter predators.

So while these naked seeds seem bare and exposed on the outside, on the inside they are potent fighters armed with chemical warfare agents.

Protected Seeds

Unlike plants with naked seeds, other plants protect their seeds. They need animals to spread these seeds so that the offspring don't have to compete for space and sunlight with the parent plant.

To accomplish this, plants enclose their offspring in a protective hull and house them in fruit. The fruit entices the predator and the hull protects the seed as it passes through the predator's GI tract. The animal then eliminates the seed in its dung, a natural fertilizer for the baby seed, in a distant location.

Spreading Protected Seeds

It's fascinating to think how clever these plants are.

We think we are using apple trees for their nutrition, when really they are using us.

An apple tree entices us (and other animals like a gorillas) visually with big red colorful fruit.

Further, they load it with sugar, appealing to our taste buds. And not just any sugar, but with fructose. This special sugar doesn't stimulate leptin which is a hormone that signals to us animals that we are full. Since fructose doesn't turn this hormone "on" we keep on eating more and more apples.

In addition, plants make these fruits easy to pick and even lace them with sugar alcohols that have a natural laxative effect. This speeds the seed through the digestive tract, further improving its survival chances. [r, r]

Green means "Stop" Red means "Go"

The tree uses us. It attracts us with color, and it makes sugar addicts of us. All so that we animals can spread its seeds.

The apple tree controls animal behavior every step of the way.

While the seeds and it's protective coating are still developing, the apple is green and bitter. Green doesn't attract us like red does. It blends in. And we want a sweet apple loaded with sugar, not a bitter, sour one.

So, during this unripe period, the apple has the highest toxic load of lectins. The gorilla loves apples but is deterred from picking it until the apple is ripe.

Incidentally, gorillas, like humans and all fruit eating animals, have color vision. [r]

While the apple ripens and the protective hull of the seeds develop, the apple gradually turns red, increases its sugar content and decreases its toxic load. The red, sweet, and less toxic apple is snatched up by us animals who will do the trees bidding, and spread it seed.

Fruit Phytochemicals

Based on the logic that plants intend for their fruits to be eaten one might think that these are a good choice for food.

However, fruits have a dark side.

Besides the dangers associated with the high lectin load in unripe fruit and the heavy dose of insatiable sugar that few people need today, there are other potentially toxic phytochemicals.

Phenolics Tannins

Many fruits have tannins which help protect a plant from harsh weather.

They also make proteins indigestible. If you were to eat a leather shoe, the reason you couldn't get protein from it is because the proteins are bound up with tannins.

So tannins bind up protein as well as digestive enzymes and can interfere with digestion (enzyme inhibitors). They also interfere with our ability to absorb plant iron and have an antinutrient impact. So they can cause nutrient deficiency and GI problems like bloating diarrhea, and constipation.

Tannins also play a role in deterring pests. They are potent against insects. But they are also troublesome for animals.

For example, if cattle get trapped in an area and have to resort to eating acorns, they can get poisoned from the tannins. In humans, large tannin consumption can cause kidney and liver damage. [r, r, r, r]


Isoflavone (a polyphenol, plant antioxidant) is found in many fruits and is also found heavily in soybeans.

This phytoestrogen can disrupt endocrine/hormone function and have estrogen-like effects. [r, r]


Other phenolics act as photosensitizers. This is a plant defense mechanism that makes animals sensitive to light.

The story goes like this: An animal eats the plant, then light hits the animal, and the animal is severely injured.

In humans we refer to this as photodermatitis.

For example, celery is a known occupational risk. Celery handlers that go out in the sun can get celery dermatitis. Lime juice is also a well-known cause of photodermatitis. An experiment I don't recommend trying, is squeezing limes then going out in the sun. The swelling can be horrifying.

Another example is grapefruit.

Grapefruit interacts with almost every prescription drug. It has these toxic furanocoumarins (photosensitizers) that the liver has to break down using p450 enzymes. But the same p450 enzymes in the liver trying to break down these grapefruit toxins are also needed to metabolize the drugs. So the liver gets overloaded and can't detoxify the drugs. This can result in high levels of the drug in the bloodstream which can have severe adverse effects. [r, r, r, r]

It's an interesting thought that grapefruit and prescription drugs require so much detoxifying...perhaps not the best things to be putting in the body in the first place.

Cyanogenic Glycosides

Entomologists (scientists that study insects) use cyanogenic glycosides to kill insects. These toxins are in a number of fruits (over 2,500 plant species) like cherries and in the pits of peaches.

They work in a similar way to how the glucosinolates ("Broccoli Bombs") activate. Cyanogenic glycosides are activated upon tissue damage. So when you bite into the fruit the glycosides mix with an activating enzyme creating hydrogen cyanide. Yes, that cyanide.

We can detox small amounts of cyanide but at slightly higher doses it can interfere with iodine and disrupt normal thyroid function leading to goiter and hypothyroidism. At slightly higher concentrations it can block cellular respiration, suffocate mitochondria and be fatal. [r, r, r, r]

This isn't a negligible issue either.

Cassava is one of the main sources of calories in the tropics. It also has significant concentrations of cyanogenic glycosides. Over a half a billion people eat cassava on a regular basis resulting in serious thyroid and neurological impacts. [r,r,r]


Salicylates are phytochemicals plants use to fight back against predators. There are many drugs developed from the salicylate family like aspirin (acetylsalicylic acid).

But many people are very intolerant to salicylates. They experience immediate allergy-like symptoms (asthma like symptoms from constriction of bronchial passages and mucus production, hives, swelling and GI upset). Salicylates are also associated with physical and mental symptoms like acne, restless leg syndrome, headaches, anxiety, disturbed vision, bad breath, and odor. [r, r, r, r, r]

While most people seem to be able to handle average amounts of salicylate in food and medications there is a danger that salicylates can bioaccumulate in the body over time. They can build up over time causing insidious harm (similar to the "Spinach Pricks" of oxalates).

Most fruits are high in salicylates. And like oxalates that bioaccumulate, they can be hard to pinpoint that they are the troublemakers.

Health Dangers of Eating Fruits

Even with all the phytochemicals fruit still very-well-may-be the best option to eat of all plant parts (and that is saying something about the other parts!).

It's the only part plants designed for predators to eat.

Unfortunately, the fruit today is quite different from the fruit of yesteryear. We've bred them for size and sugar, we've engineered them for survival of seasons and sprays. We pick them unripe (high toxic load), treat them with chemicals, then transport them across the world.

The combination of natural phytochemicals, synthetic treatments, genetic engineering, year-round access, and enhanced sugar load, transformed a food that was once a seasonal treat that provided some extra calories for famine, into an option most people would be far better without.

Just like agriculture moved us further and further away from what we are designed to eat fruit has fallen further and further away from the original tree.