Quote from Dr. Garrett Smith on November 15, 2018, 1:43 pm

Some background before we begin.

The main colors of carotenoids aka Poison/"Vitamin A" in fruits and vegetable are yellow, orange, and red.

The white or cream-colored parts of fruits and vegetables contain almost NO carotenoids aka Poison/"Vitamin A".  If you have the same type of fruit or vegetable, and one is white and the other is a carotenoid-related color, you can bank on the fact that the white one has TONS less Poison/"Vitamin A".  An example:

Carotenoids in white- and red-fleshed loquat fruits.

Fruits of 23 loquat ( Eriobotrya japonica Lindl.) cultivars, of which 11 were white-fleshed and 12 red-fleshed, were analyzed for color, carotenoid content, and vitamin A values. Color differences between two loquat groups were observed in the peel as well as in the flesh. beta-Carotene and lutein were the major carotenoids in the peel, which accounted for about 60% of the total colored carotenoids in both red- and white-fleshed cultivars. beta-Cryptoxanthin and, in some red-fleshed cultivars, beta-carotene were the most abundant carotenoids in the flesh, and in total, they accounted for over half of the colored carotenoids. Neoxanthin, violaxanthin, luteoxanthin, 9- cis-violaxanthin, phytoene, phytofluene, and zeta-carotene were also identified, while zeaxanthin, alpha-carotene, and lycopene were undetectable. Xanthophylls were highly esterified. On average, 1.3- and 10.8-fold higher levels of colored carotenoids were observed in the peel and flesh tissue of red-fleshed cultivars, respectively. The percentage of beta-carotene among colored carotenoids was higher in both the peel and the flesh of red-fleshed cultivars. Correlations between the levels of total colored carotenoids and the color indices were analyzed. The a* and the ratio of a*/ b* were positively correlated with the total content of colored carotenoids, while L*, b*, and H degrees correlated negatively. Vitamin A values, as retinol equivalents (RE), of loquat flesh were 0.49 and 8.77 microg/g DW (8.46 and 136.41 microg/100 g FW) on average for white- and red-fleshed cultivars, respectively. The RE values for the red-fleshed fruits were higher than fruits such as mango, red watermelon, papaya, and orange as reported in the literature, suggesting that loquat is an excellent source of provitamin A.

That last bolded sentence basically states that there is ~18 TIMES less (8.77 / 0.49 = ~18) Poison/"Vitamin A" in the white loquat than in the red loquat.  White = MUCH less Poison/"Vitamin A".  Moving on to the colors.

There is an aposematism article I wrote here that discusses how it is known that animals and plants mark themselves as TOXIC/POISONOUS with color(s). BRIGHTER colors = MORE toxic, and YELLOW, ORANGE, and RED are the most OBVIOUS colors used for this.  Now, there are energetic costs to manufacturing color compounds, so plants tend to have to "pick" one type of compound preferentially (carotenoids versus polyphenols, but not both, see below).  To confuse the matter a bit more, some plants are brightly colored as a visual defense so predators avoid eating them due to the appearance of toxicity, when they aren't actually toxic. Nature is all about "not dying", so being a little dishonest about displaying a "false" toxicity is OK in the rules of that game.  This is all in that other thread and shown in research papers.

The first part is pretty simple.  From my research so far, the yellow and orange color in the parts of plant foods that are commonly consumed by humans are mostly due to carotenoids.  That said, polyphenols can also bring yellow color to fruits and vegetables, but this seems less prevalent.  There are TWO major exceptions to the "yellow and orange are typically plant carotenoid signals and one should generally minimize/avoid them" guideline that I know of at this time, and these are important...pineapple and turmeric/curcumin.  I will go over those foods in other threads, and I believe both of those things are generally good for people and are protective against Poison/"Vitamin A" problems.  See the bromelain thread on this as well.

Red spectrum--so this includes pink (basically light red) and orange (red + yellow = orange) and purple (red + blue = purple)--fruits and vegetables. These are more complicated, because there are two major groups of compounds in the fruits and vegetables humans eat that mainly provide the red spectrum.

• Fruits and vegetables that are in the red spectrum from CAROTENOIDS are the WORST of all (think tomatoes, peppers/capsicum, and how nightshades have a long association with causing disease, there are multiple threads here about them).  See the Aposematism thread where red is discussed as apparently the scariest warning color given by plants telling animals to avoid eating them.
• Foods that are in the red spectrum (and purple and blue) from POLYPHENOLS (cyanidins, oligomeric proanthocyanidins, OPCs, resveratrol, pycnogenol, etc.) are generally observed in the research to be very GOOD for people. This may be a case of the "false aposematism", where the plants are using this compound to "look toxic" when they actually aren't.

The green color in fruits and vegetables is typically from mainly chlorophyll, and some carotenoids.    That said, many vegetables that are green ALSO have significant white portions to them. Think green cabbage (lots of white internally) and green onions.  This will be a generally good combination.

So...you will see in the research that surprisingly good results will come from eating WHITE fruits and vegetables, as well as GREEN, while the other colors can present quite mixed results. Also, you must realize that the researchers were likely going into the studies with the same BIAS that many of us were raised with, that the more colorful a fruit or vegetable is, the healthier it is...so, their results will often show that bias.

Colors of fruit and vegetables and 10-year incidence of stroke.

RESULTS: During 10 years of follow-up, 233 incident cases of stroke were documented. Fruits and vegetables were classified into 4 color groups. Medians of green, orange/yellow, red/purple, and white fruit and vegetable consumption were 62, 87, 57, and 118 g/d, respectively. Green, orange/yellow, and red/purple fruits and vegetables were not related to incident stroke. Higher intake of white fruits and vegetables was inversely associated with incident stroke (Q4, >171 g/d, versus Q1, ≤78 g/d; HR, 0.48; 95% CI, 0.29-0.77). Each 25-g/d increase in white fruit and vegetable consumption was associated with a 9% lower risk of stroke (HR, 0.91; 95% CI, 0.85-0.97). Apples and pears were the most commonly consumed white fruit and vegetables (55%).

CONCLUSIONS:  High intake of white fruits and vegetables may protect against stroke.

Colors of fruits and vegetables and 3-year changes of cardiometabolic risk factors in adults: Tehran lipid and glucose study.

RESULTS: The mean age of men and women at baseline was 39.8±12.7 and 37.3±12.1 years, respectively. Mean total intake of FV, red/purple, yellow, green, orange and white FV was 706±337, 185±95, 141±91, 152±77, 141±87 and 22±18 g/day, respectively. In men, 3-year changes of weight (β=-0.13, P=0.01) and waist circumference (β=-0.14, P=0.01) were related to intake of red/purple FV; the yellow group was inversely associated with 3-year changes of total cholesterol (β=-0.09, P=0.03) and High-density lipoprotein cholesterol (β=-0.11, P=0.03). Consumption of green and white FV was inversely related to abdominal fat gain, and atherogenic lipid parameters in men (P<0.05). In women, higher intake of red/purple FV was associated to lower weight and abdominal fat gain, fasting serum glucose and total cholesterol (P<0.05); yellow FV was also related to 3-year weight gain (β=-0.11, P=0.01).

CONCLUSIONS: Various colors of FV subgroups had different effects on cardiometabolic risk factors; higher intake of red/purple FV may be related to lower weight and abdominal fat gain, and yellow, green and white FV may be related to lipid parameters.

More white and green fruits and veg = less belly fat gain, and better cholesterol-related test results.

Colors of vegetables and fruits and the risks of colorectal cancer

RESULTS
High total intake of vegetables and fruits was strongly associated with a reduced risk of colorectal cancer in women (OR = 0.32, 95%CI: 0.21-0.48 for highest vs lowest tertile) and a similar inverse association was observed for men (OR = 0.60, 95%CI: 0.45-0.79). In the analysis of color groups, adjusted ORs (95%CI) comparing the highest to the lowest of the vegetables and fruits intake were 0.49 (0.36-0.65) for green, and 0.47 (0.35-0.63) for white vegetables and fruits in men. An inverse association was also found in women for green, red/purple and white vegetables and fruits. However, in men, orange/yellow vegetables and fruits (citrus fruits, carrot, pumpkin, peach, persimmon, ginger) intake was linked to an increased risk of colorectal cancer (OR = 1.61, 95%CI: 1.22-2.12).

White and green fruits and vegetables come up as reducing risk for colorectal cancer in both men and women.

That last sentence is important.  INCREASED risk of colorectal cancer with greater intake of YELLOW and ORANGE fruits and vegetables.  Those two colors are very associated with mainly carotenoids (not as much with polyphenols).

Then there's this whole roundtable paper cheering for white fruits and vegetables:

White Vegetables: A Forgotten Source of Nutrients: Purdue Roundtable Executive Summary

Whether it was planned or accidental (likely some of both in my opinion), our world's health has only gone downhill since the misguided "eat the rainbow" and "white foods are all bad" tropes have been trotted out to everyone.  The evidence is there that white fruits and vegetables have a special benefit that others don't, with green ones following close behind (because the green color is mostly from chlorophyll, green fruits and vegetables often have a significant white portion as well, think green onions and zucchini, and not as much color coming from carotenoids).  The other colors should be assessed, in my opinion and based on the chemistry behind it, on whether or not they are high carotenoid or high polyphenol.  I bet the research would show vast differences in health outcomes if they were looked at in that manner.

 

CONCLUSIONS:  High intake of white fruits and vegetables may protect against stroke.