English corner: Bioavailability of polyphenols

*) How much β-caroten do we convert in retinol (vitamin A)?
=> 1/12^th when eating β-caroten from food. (1) At best, depending on age and the conditions of the intestines.
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We only need 5-10 mcg carotenes per day, preferably from natural sources (cis-form). I won’t eat more than once a raw carrot per day because of oxalates, and because of possible chelation of useful nutrients. Soluble fiber binds to some minerals, such as calcium, magnesium and iron; it reduces their absorption. This can affect your mineral status, especially if you have a low intake of some nutrients. Which ones?
Binding of fibers to minerals - Does fiber bind to nutrients?
Dietary fiber can bind some minerals and decrease their absorption. However, if mineral intake is adequate, a recommended dietary fiber intake will not compromise mineral balance (25-30 g fibers). So no problem if you eat a carrot salad once a day. Preferably with some fat to optimize the absorption of b-carotenes (2 => 6 / 12 UI). By the way no need for a high level of carotenes since we can hold them several days in serum. (2)
To be reminded: Smokers needs some more vitamin E and vitamin C to counteract nitric oxide from the smoke. For most people 20-25 mg Vit E is optimal but it’s not enough for smokers.
Note that caroten supplement are trans, while natural carotens are mostly cis. No problem if you don’t overload: the body can absorb both forms. But too much of a good thing is bad, especially for carotens (pro-oxidant) if the excess is not well counter-balanced with kiwi, strawberries or fresh lemon juice (for vitamin C). But this vitamin C could be used elsewhere in the body, for other purposes.
Binding of iron
The amount of iron bound depends upon iron concentration, pH, quantity of fiber, and the presence or absence and quantities of inhibitors of binding. Binding is minimal, although appreciable, below pH 4.0, but rises rapidly above pH 5.0 to a maximum near pH 7.0, the limit of stability of iron in the system used. (3)
So pH is going to rise if you eat cereals but not if you eat a fruit salad with greens and a steak. 
However, with a mix meal, it appears that the effect of dietary fiber on iron availability is greatly dependent on the ligands present in the meal (from fiber, ascorbate, citrate, and oxalate). For polyphenols, capture concerns only one type of iron: non-heme iron (vegetable source). Moreover, the body has the ability to modulate the absorption level of iron, provided all the parameters are functional.
Tea and coffee polyphenols
Tea and coffee polyphenols have no impact on heme sources (meat), but well on non-heme sources (vegetable and fruits). If you add some lemon juice on your greens, you’ll saturate the polyphenol molecules and make it easier to absorb iron, provided you have enough cofactors. Biosynthesis of heme requires Vitamin B6, riboflavin (B2), biotin, pantothenic acid (B5), and lipoic acid and the minerals zinc, iron, and copper.
Note that polyphenols have a preference/strong affinity for trivalent cations (Fe and Al) over bivalent cations (Cu and Zn). For these last two cations there is a weak affinity, under normal physiological conditions. (4) By this I mean that there should be no consequences for Zn and Cu if you do not suffer from a negative result during a blood test.
There is no chelation with alkali ions (Na, K and Ca). There is little interaction with Mg, especially in the presence of phosphates (competition).
Note: I target between 8 mg Fe a day. 15 mg if you’re deficient. Higher is not a good idea if you can manage differently (pro-oxidant).
Biotin availability
Mind supplement with white egg protein because of avidin. No problem if pasteurized. If egg white powder has been pasteurized – usually it is –, it inactivates the avidin glycoprotein. Otherwise avidin binds to biotin in raw eggs. Avidin present in egg white tightly binds biotin thus making biotin unavailable for intestinal absorption. However heating eggs could destroys avidin harmfulness. (5) So, those who eat cook eggs are not likely to suffer from biotin deficiency, if you eat them hard boiled. Indeed, it is difficult to offset avidin when egg is normally cooked like frying and boiling. The majority of avidin is found to be inactivated by thermal processing at 121° C for 25 min (Zhu et al., 2018). The results vary: A 1991 assay for the Journal of Food Science detected substantial avidin activity in cooked egg white: "mean residual avidin activity in fried, poached and boiled (2 min) egg white was 33, 71 and 40% of the activity in raw egg white."
*) Lutein and zeaxanthin for eyes
In a post on bioenergeticcom forum “Is lutein a Magic Bullet for cognition?”, I said:
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If we want to summarize the best molecule to target some particular body elements:
- Lutein and zeaxanthin in the eye (6 mcg).
- Vitamin E and b-carotene for vessel membranes (2 x 4mcg)
- Mainly lutein and carotenoid for the brain (+ lycopene).
- Lycopene for prostate. (4x/wk tomato, preferable in sauce).
Note: Not all together, of course. Once a time, in cure; with pause. I won’t take any supplement for B-carotene: No need and could be problematic if you smoke.
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*) To protect against harmful blue light: lutein. Lutein and zeaxanthin both highly absorb light having a wavelength of roughly 400 to 500 nm, which corresponds with the blue light portion of the visible spectrum. (6)[Vous devez être inscrit et connecté pour voir ce lien]
*) How much lutein?
10 mg lutein intake over 12 months had a positive impact on healthy older adults’ brain activities during learning, resting-state connectivity, and gray matter volumes. (7)
=> In cure, in order to correct a deficiency, by people who’ve never cared for diabetes type III.
*) Carotenoids in the brain:

Lutein, b-caroten, zeaxanthin and lycopen are the most prevalent for brain targeting. Lutein is widely more present in the brain of centenarian people.
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*) To protect membrane vessels: Vitamin E and b-caroten for vessel membranes (2 x 4mcg) Vit E (20-25 mg), B-carotene (5-10 mcg). (8-10) β-carotene, zeaxanthin, lutein, and tocopherols dissolve in the phospholipid bilayer of the membranes. 
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*) Foods with the highest level of beta-caroten and zeaxanthin in total carotenoids. Not the relative highest level, but the proportions.
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Pay attention: If you eat spinach on a regular base, It's very rich in oxalate. So you better have a rich source of calcium at the menu (to amalgam oxalate). When I eat spinach or rhubarb, I always take 2 doses of potassium citrate (1.35 g x 2). Prevention of lithiasis.
*) From food, yes; from supplement, only in cure.
            Phenols are molecules that are part of the plant defense system. Polyphenols are involved in defense against ultraviolet radiation or aggression by pathogens. (13)
Flavonoids are cytotoxic and interact with different enzymes through complexation (binding). Both flavonoids and isoflavonoids protect the plant against insect pests by influencing the behavior, and growth and development of insects.^{[Vous devez être inscrit et connecté pour voir ce lien]} 
*) Typical loss of Lutein+Zeaxanthin when processing food (as compared to raw food) (17)
5% Freeze, 50% Dry, 25% Cook, 35% Cook+Drain, 10% Reheat.
Note that the results would be often different in other experiments. It varies much.
Sources and References on next page.

Sources and references
1)  Bioconversion of B-carotens in retinol equivalent (RE)
a) [Vous devez être inscrit et connecté pour voir ce lien]
The use of μg RAE rather than μg RE or international units (IU) is preferred when calculating and reporting the amount of the total vitamin A in mixed foods or assessing the amount of dietary and supplemental vitamin A consumed.
RAE = retinol activity equivalent.
μg RE = mcg retinol equivalent
Example: A diet contains 1,666 IU of retinol and 3,000 IU of β-carotene.
(1,666 ÷ 3.33) + (3,000 ÷ 20) = 650 μg RAE.
b) Newcastle University.
 [url=http://www.nugo.org/downloadattachment/40988/11000/georg Lietz.pdf][Vous devez être inscrit et connecté pour voir ce lien]
West et al. 2002
2) Half-life of retinol and carotenoids
DOI: [Vous devez être inscrit et connecté pour voir ce lien]  Serum carotenoid depletion follows first-order kinetics in healthy adult women fed naturally low carotenoid diets. 2001 B J Burri et al.
=> Serum carotenoid concentration decreases during depletion, following first-order kinetics. The half-lives determined in decreasing order were as follows: lutein (76 d) > alpha-carotene (45 d) > beta-cryptoxanthin (39 d) > zeaxanthin (38 d) > beta-carotene (37 d) > lycopene (26 d).
3) Iron availability.
a) [Vous devez être inscrit et connecté pour voir ce lien]
b) Heme, iron, and the mitochondrial decay of ageing [Vous devez être inscrit et connecté pour voir ce lien] 2004.  
c) Iron metabolism. [Vous devez être inscrit et connecté pour voir ce lien] 
4) Chelation of minerals
Flavooids and other polyphenols. Lester Packer. Elsevier. (Ph. Dr)
5) Avidin in eggs: Raw egg whites only cause biotin deficiency if consumed in excessive amounts (6 whites).
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The pasteurization process heats the egg white to 134 degrees for 3 1/2 minutes. This proper temperature kills the salmonella and neutralizes the Avidin without damaging the protein, to allow the egg white to be digested safely by the human body. "
A mini of 4 min boiling is required for complete inactivation of avidin.
[Vous devez être inscrit et connecté pour voir ce lien]  [Vous devez être inscrit et connecté pour voir ce lien] Visualizing structural changes of egg avidin to thermal and electric field stresses by molecular dynamics simulation 2021
6) To protect against harmful blue light
Nutrients 2021/09/17. Diego Gazzolo et al. Early Pediatric Benefit of Lutein for Maturing Eyes and Brain— An Overview
DOI: 10.3390/nu13093239
7) How much lutein
[Vous devez être inscrit et connecté pour voir ce lien] (2021)
8.) Vitamin E homologs are mainly transported by very low−density lipoprotein (VLDL) with the α-tocopherol being preferably recognized by the α-tocopherol transfer protein in liver.
doi: 10.1016/j.freeradbiomed.2021.10.016.
It’s not a general truth !!
Although LDL and HDL were the main carriers of alpha-tocopherol in both males and females, more tocopherol was found in LDL than in HDL in males but the opposite was true in females. The distribution of alpha-tocopherol in males was: VLDL, 8%; LDL, 59%; and HDL, 33% whereas that in females was VLDL, 2%; LDL, 42%; HDL, 56%. The distribution of protein in lipoprotein from males was: VLDL, 4%, LDL, 37%; and HDL, 59% and in females: VLDL, 2%; LDL, 25%; and HDL, 73%. The data suggest that the different distribution of alpha-tocopherol in plasma lipoproteins in males and females is due to the different levels of proteins in those lipoprotein fractions. Overall, tocopherol and protein levels were highly correlated in HDL, a lower correlation was found in LDL.
9) Astaxanthin & vitamin C outside the membrane,  b-caroten inside the membrane
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10)  β-carotene, zeaxanthin, lutein, and tocopherols dissolve in the phospholipid bilayer of the membranes. 
Source: [Vous devez être inscrit et connecté pour voir ce lien]  Shristi Ram et al. – J Funct. Food 2020
*) RDA in Europe 4.5 mg b-carotens
In most European countries, the recommended intake is based on the assumption that 4.8 mg beta-carotene is needed to meet the requirement of 800 micrograms vitamin A (conversion factor 6). The IOM, the Institute of Medicine in USA, applies a conversion factor of 12 for beta-carotene and 24 for other carotenoids such as beta-cryptoxanthin [Vous devez être inscrit et connecté pour voir ce lien]. For very complex matrices (i.e. spinach, kale), human studies have revealed even higher conversion factor for beta-carotene such as 1:21 for a fruit/vegetable mix or 1:26 for vegetables [Vous devez être inscrit et connecté pour voir ce lien].
11) Role of lutein and zeaxanthin in visual and cognitive function throughout the lifespan. Nutrition Review. Elizabeth J Johnson. PDF 
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Given that the major dietary sources of lutein are fruits and vegetables,72 low intakes of these foods reflect low dietary intakes of lutein. Low dietary intake of lutein is related to low macular pigment density.77 Macular pigment density and brain concentrations of lutein are highly variable in the infant and adult.5,6,51,78
12) Lutein and zeaxanthin are the most common xanthophylls in green leafy vegetables (e.g., kale, spinach, broccoli, peas and lettuce) and egg yolks [25] (Table 1). + Pistachio and corn.
doi: [Vous devez être inscrit et connecté pour voir ce lien] Nutrients 2013
13) Phenols are molecules that are part of the plant defense system
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A normal dose of polyphenols is useful and regulates the intestinal flora. In excess (500 mg) it starts to pose a problem. But only the dose makes the poison. No problem if it is via whole foods and if we vary and make staples (hormesis principle). But taking / combining anti-phyto-chemicals for anti-inflammatory purpose– such as white willow bark / salicin / aspirin, curcumin, quercetin, etc. – could interfere with the pathway CYP450.  Polyphenols inhibit Cyp450 detox enzyme partially. So you have to take breaks.
All studies seem to agree that resveratrol, curcumin, quercetin and bioperine are potent inhibitors of CyP450.
Table Drugs & CyP450 interference
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14) A minimum fat intake needs to be consumed to optimize lycopene absorption. Optimal lycopene absorption requires a minimum of 10 g of fat in a meal containing processed tomato products, while 15 g (just over 1 tablespoon) may be necessary for uncooked foods like salads or raw tomatoes.
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15) Interactions with other carotenoids, nutrients, and dietary compounds
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16) Absorption, Metabolism, and Bioavailability (of Carotenoids)
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17) Loss of Lutein + Zeaxanthin (as compared to raw food):
5% Freeze, 50% Dry, 25% Cook, 35% Cook+Drain, 10% Reheat.
Source: Nutritional Effects of Food Processing
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Freezing, Drying, Cooking, and Reheating.
Note: the results are often variable.