Why don't humans eat blue food?

Yes, it's a generalization. But blue foodstuffs are conspicuously lacking in diets all around the world. Why?

Originally posted by FMF
Yes, it's a generalization. But blue foodstuffs are conspicuously lacking in diets all around the world. Why?

Because blue food is not common of course! (Thanks to iron in meat equalling RED and chlorophyl in plants equalling GREEN)

I eat blue cheese, blue broccoli, blue smarties and blue icing on birthday cakes ........ what else there?

Apparently the lack of blue foods has inhibited our appetite when we see blue and blue crockery and/or blue lighting can reduce your appetite!

In a prehistoric diet, blue food was pretty much absent. Therefore we now think blue food is bad.

Originally posted by FMF
Yes, it's a generalization. But blue foodstuffs are conspicuously lacking in diets all around the world. Why?

Our eyes see yellow-green best because that's the wavelength the sun puts out most of, not blue, so fruits and such have evolved those colors. Meat of course is red as are some fruits and vegetables.

There just aren't many blue foods. If something evolved as food, it would evolve away from blue because it's hard to see.

Actually, an interesting evolutionary explanation is that the way we perceive our spectrum depended on the environment and our ability to find food.. For example, primates needed greens and reds to be quite different, because fruits would stand out and be easier to find. Although we perceive them very differently, they are actually very close in terms of wavelength.

A possible corollary of this link between some colours and food, is that other colours have to be dissociated from food.

Blueberries, aubergines ...

Originally posted by Bosse de Nage
Blueberries, aubergines ...

You must have weird aubergines in the Southern hemisphere...

Some of the vegetables on the Debate Forum go blue in the face, regularly.

Originally posted by AThousandYoung
Our eyes see yellow-green best because that's the wavelength the sun puts out most of, not blue

But I thought most ambient light is predominantly blue because of the sky. Certainly I heard that film makers have to do color correction whenever they film out doors.
I thought that plants were green because they absorb the other colors and reflect the green. Does that mean that by not absorbing green plants are remarkably inefficient?

Originally posted by twhitehead
But I thought most ambient light is predominantly blue because of the sky. Certainly I heard that film makers have to do color correction whenever they film out doors.
I thought that plants were green because they absorb the other colors and reflect the green. Does that mean that by not absorbing green plants are remarkably inefficient?

These are excellent questions and I do not have definite answers for them. The question about why chlorophyll reflects the wavelengths with the greatest intensity of light is one that has bothered me for a long time.

According to the following, chlorophyll is inefficient about wavelengths but efficient in using the wavelengths it does use, that it evolved as a competitor to another purple photosynthetic pigment (retinal, aka Vitamin A which surprise surprise is what the eye is based on); but then this lineage mostly outcompeted the purple one for some reason:

http://www.livescience.com/environment/070410_purple_earth.html
http://www.newton.dep.anl.gov/askasci/mole00/mole00864.htm

The sky is blue because air molecules scatter blue light but let the red through. This means the blue is indirect lighting with the majority of the energy having been scattered into space. Direct sunlight is different; much stronger, and with the full range of wavelengths.

Originally posted by AThousandYoung
The sky is blue because air molecules scatter blue light but let the red through. This means the blue is indirect lighting with the majority of the energy having been scattered into space. Direct sunlight is different; much stronger, and with the full range of wavelengths.

So what wavelengths typically enter the human eye? We never stare directly at the sun.

Originally posted by twhitehead
So what wavelengths typically enter the human eye? We never stare directly at the sun.

Those which are reflected off of objects (fruits and such) from the sun. Yellows, oranges, reds, greens. This is why fire engines and McDonalds' are red and yellow in the latter case...it attracts the eye. In fact the best color for fire engines is lime green I think but they keep it red out of tradition.

Originally posted by AThousandYoung
Those which are reflected off of objects (fruits and such) from the sun. Yellows, oranges, reds, greens.

Wouldn't early humans see blue more often that reds and oranges because of the sky, the seas, rivers, etc? Fruits are rare (hence the advantage of perceiving red or orange as stand-out colours, or at least more than blue vs green).

Originally posted by AThousandYoung
Those which are reflected off of objects (fruits and such) from the sun. Yellows, oranges, reds, greens. This is why fire engines and McDonalds' are red and yellow in the latter case...it attracts the eye. In fact the best color for fire engines is lime green I think but they keep it red out of tradition.

My understanding was that we associate red with danger because dangerous fruits are typically red - and so it blood.
I believe yellow stands out more than other colors (hence yellow reflective strips, indicators etc) and this may have helped us find ripe fruit (yellow) against a sea of green.

Originally posted by twhitehead
My understanding was that we associate red with danger because dangerous fruits are typically red - and so it blood.
I believe yellow stands out more than other colors (hence yellow reflective strips, indicators etc) and this may have helped us find ripe fruit (yellow) against a sea of green.

http://dx.doi.org/10.1016/S0169-5347(03)00012-0

Diurnal primates eat mainly fruit and young leaves, and it has long been argued that trichromatic colour vision is an adaptation for frugivory. The specific spectral tuning of the M and L photopigments can be explained if they are selected for finding fruit [2]. However, a difficulty with this hypothesis is that Old World monkeys are uniformly trichromatic, but not all eat ripe fruit. The colobines (Colobinae), which are a major subgroup in Africa and Asia, eat mainly leaves and unripe fruit. At the same time, trichromatic howlers, Alouatta spp., are among the most folivorous New World monkeys. Lucas and colleagues propose that primate trichromacy evolved primarily for selecting young nutritious leaves on a background of tougher mature leaves [3]. They argue that young leaves are detectable only by a red–green signal, whereas many fruits present a blue–yellow signal visible to dichromats [4]. Although this work shows that trichromacy is valuable for finding young nutritious leaves in the tropics, Sumner and Mollon present a strong case that the data do not distinguish between the folivory and frugivory hypotheses [69]. In addition, the claim that trichromacy is not important for finding fruit because of its absence in the New World where most species are not folivorous, is not substantiated. Trichromacy is observed in nearly all New World primate species and the existence of allelic trichromacy cannot be explained in the absence of or under relaxed selection. Trichromacy in primates benefits both frugivory and folivory [26]. Furthermore, the maximum wavelength of photopigments might not be set by the targets themselves, but by the background within which such targets are set (i.e. mature leaves) [26]. This might help to explain the similarity in spectral tuning of primate photopigments in both the Old and New Worlds in spite of the differences in primate diets.