The nutrition fallacy of fruit

Fruits are glorious and compelling – colourful, aromatic, crunchy or juicy and, not only do they look ‘healthy’ they are promoted as such by all relevant authorities. So, you may be surprised to know that fruit is not particularly nutritious, and that there are no nutrients to be found in fruit that are not available in vegetables. There is no nutritional requirement to eat fruit, and little benefit (except pleasure) in doing so. Most fruits (except some berries and fruits we usually identify as vegetables) are high in sugar and thus contribute to our alarming increase in sugar consumption. Fruit juice in particular.

Plants and animals

Naturally enough, plants don’t see being eaten as a survival strategy, and they have developed a host of defences and deterrents to protect themselves. But, there is one significant exception – plants that fruit want animals to eat their fruit and disperse their seeds. Animals aren’t so much taking advantage of plants by eating their fruit, plants are making use of them.

Until a fruit is ‘ripe’ it is not pleasurable to eat. During this stage the plant is forming the seed for dispersal. Once the seeds form, the plant starts to make the fruit desirable. It changes colour (indicating freshness to the animal) and often adds aroma to attract the animal. It builds up sugars to make the fruit sweet and appealing so that the animal keeps eating. The plant’s cunning plan is that after the animal eats the fruit, some seeds will survive digestion. The animal wanders off and some time later deposits the seeds at another place in a pile of natural fertiliser.

From the perspective of a plant, there is no need to make the fruit nutritious – that would be a waste of the plant’s resources. The seeds have no use for nutrients in the fruit, they get the nutrients they need for germination from the animal poop instead. It’s not the plant’s job to feed the animal. All the plant needs to do is make the fruit enticing to the animal. Most fruiting plants have worked out that sugar is a great way to do that.

Plants have also devised various ways for the seeds to survive digestion. Some (like apple) contain cyanide and are bitter when chewed, so animals are more likely to swallow them whole and the digestive system is more likely to pass them through whole. Others (like stone fruits) encase the seeds in a hard protective exterior. Some (like apricots) take no chance, and do both. Even the fibre in fruit may serve the plant’s purposes by facilitating the passage of the seeds through the animal.

Perhaps the most remarkable strategy of them all is the chilli plant (chillies are a fruit). Its seeds are small and soft and would be destroyed by most animals who ate them. So, the chilli evolved capsaicin and put it in the seeds and the placenta that attaches them. Capsaicin binds to temperature receptors in the mouth of mammals and other animals, and signals heat to the brain. There is no heat, and there is no damage done to the mouth, but the brain thinks its mouth is on fire. This deters most animals from eating them in the wild. The genius of the strategy is that birds do not have temperature receptors in their beaks and do not register pain from capsaicin. Furthermore, birds are the ideal seed dispersers because they do not chew the seeds and damage them, and because they fly long distances before pooping out the seeds in a little pile of guano. Most chillies are brightly coloured to stand out and attract birds.

The ‘five-a-day’ campaign

The phrase ‘fruits and vegetables’ is a universal health slogan for authorities. The terms are rarely seen apart and it is assumed that, together, they are great for health and we should eat a certain number of serves of them every day. But, remember that fruit is not particularly nutritious, and vegetables are only somewhat better.

On measures of nutrition, animal-based products beat plant-based products hands down. If there was a scale of nutrition running from zero (not nutritious) to 100 (very nutritious), then what you would find up around the 100-mark are eggs, organ meats (e.g. chicken livers) and small oily fish (e.g. sardines). Eggs are a nutritional grenade. After that, in the upper-half (100-50) of the scale would come animal meats and their fats, and dairy products. At about the half-way (50) mark, vegetables would make an appearance. Under that (say the 25-mark) would be fruits. Right at the very bottom would be grain-based foods such as rice, pasta, cereals, bread and starchy carbohydrates such as root vegetables and potatoes.

Ponder that – it is pretty much the exact reversal of the food pyramid or ‘my plate’ campaigns, which urge greatest consumption of cereal and grain-based foods and starchy carbohydrates, followed by fruit and vegetables, while minimising animal products, dairy and natural fats. Until recently, eggs were a no-no because of cholesterol fears. I’ve never seen organ meats mentioned. This is how absurd official nutritional advice is, and it is remarkable that authorities can persist with this in the face of increasing scientific understanding and a massive downturn in public health.

How they get away with it is another (more frightening) story. For now, back to fruits and vegetables – how did the ‘five-a-day’ rule arise? It is science-based, right?

No. It is not evidence-based and it has no scientific support. It is nothing more than a marketing campaign by the fruit and vegetable industry.

It is a made-up rule that varies from country-to-country. In the UK and Australia it is 5 or 5+, in the USA it is 9, other western countries have made up other numbers and conditions. The definition of ‘serve’ varies widely. The exception might be France, that recommends 4 servings or fewer. Adding 5 servings or more of fruit and vegetables a day, especially fruits high in sugar, can increase obesity if it is not compensated for by a reduction in other sugary foods, and it seems it often isn’t. Fruit might be added to something perceived as an indulgence to make it ‘healthier’ – e.g. fruit and ice cream.

The rule originated in California in 1991, out of a partnership between the National Cancer Institute and something called the Produce for Better Health Foundation. The latter being an industry front for fruit and vegetable growers. Large-scale scientific studies since then have not shown that fruit and vegetable consumption reduces the risk of cancer (or other major health concerns such as heart disease). In the meantime, the Produce for Better Health Foundation has partnered with the US Centres for Disease Control & Prevention to widen its campaign for fruit and veggies across all health conditions.

Fruit sugars

There are two basic sugars in fruit – fructose and glucose (fructose means ‘fruit-sugar’). Fructose is naturally found in fruit and honey, and unnaturally found in table sugar and high-fructose corn syrup.

Fructose is one of the three fundamental dietary sugars, together with glucose (carbohydrates) and galactose (milk). All three of these sugars have the same chemical formula, but different structures and different effects on the body. Fructose stands out because we cannot metabolise it in the normal way. Instead, it is sent from the small intestine to the liver, which converts it into fat. The fat can remain in the liver, where it can accumulate and lead to non-alcoholic fatty-liver disease over time, or it can be transported (by very-low density lipoproteins, VLDLs) to adipose tissue and stored there. Fructose is, in essence, a fat generating sugar.

It gets worse, because fruits also contain glucose along with the fructose, usually in roughly the same proportions. So, while fructose is being converted into fat, the glucose is triggering insulin release. One of the main roles of insulin is to promote fat storage and to inhibit fat release from adipose tissue. Thus the fat made from fructose gets more readily stored in the presence of glucose. Any glucose not needed for energy or glycogen replenishment will also be stored as fat.

It gets still worse, because fructose suppresses satiety signalling to the brain and promotes appetite signalling. Thus fructose increases eating beyond need.

Consider a simple dessert of ice-cream, fruit and a drizzle of honey. Each of these three components contain fructose and glucose and work in harmony for fat storage. Deserts are not primarily fattening because of their calories, but rather because of the effects of their sugars on our fat-generation and storing mechanisms.

Finally, the main by-product generated when the liver converts fructose to fat is uric acid. This is bad stuff (usually associated with gout) and has a range of negative consequences for us, including reducing blood flow to the brain, inhibiting vasodilation in blood vessels of the body (leading to hypertension), and dis-regulation of the immune system.

Much of our understanding of fructose metabolism is startlingly recent, and as it is better understood the case against it is mounting.

Modern fruit

You might wonder why it is such a problem if we evolved eating fruit. Early fruits would have had nowhere near the amount of sugar as modern fruit.  Fruits would have been smaller and more fibrous. Eating fruit would have been seasonal. Animals may have derived some benefit precisely because fruit can be fattening (fat storage during plentiful times in preparation for a lean winter). Vitamin D may protect against some of the adverse effects of fructose. It may not be a coincidence that eating fruit seasonally often means during periods of plentiful sunshine, which stimulates vitamin D production in the skin.

The problem arises with modern fruit and its year-round availability. For decades, fruit strains have been selected or engineered for sweetness and shelf life (sugar is a preservative). Even fruits naturally low in sugar (such as strawberries) are being grown to be sweeter (and marketed as such). Fruit has been modified in many other ways to suit growers, supplier logistics and consumer expectations. Modern fruit is best thought of as a manufactured product (that is not the image of a ‘natural’ apple). Likewise vegetables. At the end of this post are a few images of fruit and vegetable antecedents. We do not know what our cave-dwelling ancestors ate, but their cave art is not known for depictions of fruit and veg.

Summary

There is no doubt that eating modern fruits can be a pleasure, and we should find time in our lives for pleasure (while understanding that it inevitably comes at a price). However, claims that we need fruit daily, and that it is nutritious and health-promoting, are not based on science. Such claims are nothing more than industry sloganeering.



A precursor to the banana –  Musa acuminata, a spindly plant with small, okra-like pods.

This renaissance painting of a watermelon shows how much has changed in just a few hundred years.

This is a wild carrot.

The plant on the left, teosinte, is the ancestor to our  modern-day corn


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Further reading:

Zoe Harcombe, The Obesity Epidemic