Food-based antioxidants - bioavailability

Analysis of Food-based Antioxidants

As with broccoli, cabbage is B. oleracea, but is of the capitata group. Using SPME GC/MS white cabbage contains prop-2-enyl isothiocyanate derived from sinigrin, and the isothiocyanates and nitriles from glucoiberin, neoglucobrassicin, glucobrassicin and 4-methoxyglucobrassicin.

SPME GC/MS of swede (B. napobrassica L.) detects from the aliphatic glucosinolate, glucobrassicanapin, pent-4-enyl isothiocyanate in the headspace and from gluconasturtiin, 2-phenylethyl isothiocyanate found solely in the liquid phase. It is not known whether these isothiocyanates are therapeutic.

Bioavailability
(In search of Five Star antioxidants)

It is known from epidemiological studies that populations eating foods rich in antioxidants have lower incidences of cardiovascular disease, certain cancers and eye diseases.
From food analysis data, the nature and concentration of the major antioxidants in the staple foods of our diet are known. So, when a helping (say for convenience, 100 g) of food is eaten, a known amount of compound x (say y mg/100 g) is available for absorption from the gut.

For individual antioxidants a quick guide using the "Michelin" star system is proposed, based on the questions below. One star awarded for every successive affirmative to questions 1-5, based on the studies recorded in descending date order at the bottom of the page.
Information about the availability of antioxidants from fruit-based meals, together with the source reference has been added to the star ratings.

Question 1. Is the compound an in vitro antioxidant? ......................................................................
Question 2. Is it, or a derivative of it³, absorbed into the bloodstream after the meal? ......................
Question 3. Does this amount raise the plasma antioxidant capacity at the target site? ................
Question 4. Did this amount significantly reduce the oxidative stress? ......................................
Question 5. Finally, was there a therapeutic effect? ..............................................................

Evidence of therapeutic benefit, i.e. answering yes to all five questions, is not available. The problems are addressed elsewhere at this website:
1. Do primary antioxidants only work in combinations? The analytical enigma here is discussed on the chemical analysis page. In summary, how can single antioxidants be evaluated for antioxidant capacity?
2. Do primary antioxidants, or combinations, trigger the generation of secondary physiologically-active antioxidant compounds, such as uric acid?
3. Some antioxidants are rapidly metabolised during absorption, and it may be that only biochemical derivatives reach the systemic circulation.

Therefore, it may be some time before 4 and 5 star individual antioxidants are reported, if ever!

Individual antioxidant	Food sources and (study date)	Star rating
Lycopene	Watermelon juice, tomato juice (2004b)
Lycopene	Tomato puree (2000a)
Lycopene	Tomato paste - olive oil (2004a)
Lycopene	Tomato sauce pasta (2005b)
Beta carotene	Tomato puree (2000a)

Vitamin C	Cranberry juice (2000b)
Vitamin C	Blood orange juice (2005a)
Cyanidin-3-glucoside	Blood orange juice (2005a)
Beta cryptoxanthin	blood orange juice (2005a)
Zeaxanthin	blood orange juice (2005a)

Antioxidant class	Food sources Reference	Star rating
Anthocyanins ^*	Juice blend MonaVie Active G.S. Jensen et al., J. Agric. Food Chem., 56 (18), 8326-8333, 2008 (Study 10 below)
Anthocyanins ^*	Elderberries and juice M. Netzel et al., Food Res. Int., 38 (8-9), 905-910, 2005
Anthocyanins^*	Blueberries G. Mazza et al., J. Agric. Food Chem., 50 (26), 7731-7, 2002
Anthocyanins^*	Elderberries P.E. Milbury et al., Mech. Ageing Dev., 123 (8), 997-1006, 2002

^* Anthocyanins, which are anthocyanidin glycosides were thought to decompose before absorption. These studies have proved otherwise.

Total antioxidants	Food source Study Date	Star rating
Isocaloric soy milk shakes 1. with isoflavones 2. without isoflavones	Soy protein (2007)
total antioxidants freeze-dried powder	Wild blueberries (2002)

Study 10. Bioavailability of a juice blend
(2008)

Food per day

Type of study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

Restricted light meal, Overnight fast, no exercise,120 ml juice blend

Randomised
double blind
placebo-controlled
crossover study

2 study days
1 week apart

Serum antioxidant capacity (AOC) (CAP-e assay)
Serum lipid peroxidation (TBARS)
ORAC
Total phenolics (Folin-Ciocalteu)
Polymorphonuclear cells (ROS)

Yes
Rapid increase in serum AOC
Rapid decrease in serum lipid peroxidation

Conclusion: Ingestion of juice showed in vitro demonstration of AOC for protection of cells against oxidative damage. in vivo rapid (1-2 hr) increase in serum AOC via the CAP-e assay, and similarly rapid decrease in serum lipid peroxidation via TBARS test.
Source reference: G.S. Jensen, et al., J. Agric. food Chem., 56, (18), 8326-8333, 2008.

Study 9. Bioavailability of isoflavones
(2007)

Food per day

Type of study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

Diet + one of 3 isocaloric shakes [25 g soy protein with isoflavones (107 or <4 mg) or none, i.e. (total milk protein)]

Randomised
double blind
crossover study

on separate days

Antioxidant capacity (AOC) (5 different methods)
Serum isoflavone
Fat-soluble antioxidant
Plasma vitamin C

No
No significant increase in serum AOC among treatments

Conclusion: While significant differences occurred between the trace isoflavone and the total milk protein trials using one method (PCA-ORAC), overall, no significant differences, using analysis of variance methods, were detected.
Source reference: K.M. Heneman, et al., J. Nutr. Biochem., 18, (1), 46-53, 2007.

Study 8. The bioavailability of flavonoids (2006)
Statement: Large transient increases in plasma Total Antioxidant Capacity (TAC) have been experienced in humans consuming flavonoid-rich foods.
Hypothesis: Dietary flavanoids act as in vivo antioxidants.
Fact 1: Flavonoids are poorly absorbed from foods
Fact 2: Most flavonoids are extensively metabolised in vivo
Conclusion: Antioxidants other than flavonoids are responsible for the increase in plasma TAC (beneficial health effects?) of flavonoid-rich foods, which is likely to be caused by increased uric acid levels.
Source reference: S.B. Lotito and B. Frei, Free Radical Biol. Med., 41 (12), 1727-1746, 2006

Study 7. Role of lycopene and tomato products in prostate health.
(2005b)

Food per day

Type of study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

Diet + 30 mg lycopene in commercial spaghetti sauce

Human
intervention
study

32(M) with adenocarcinoma of the prostate

3 weeks

serum lycopene
lycopene in prostate tissue (biopsy)

Yes.
serum lycopene doubled from 638 nM to 1258 nM
prostate tissue lycopene tripled from 0.28 to 0.82 nmol/g

Conclusion: Lycopene is bioavailable (in serum) and appears to target prostate tissue.
Authors advocate caution since there may yet be a synergistic effect with other tomato phytochemicals : glycoalkaloids, phenolics, salicylates, carotenoids.
Source reference: M. Stacewicz-Sapuntzakis and P. E. Bowen, Biochim. Biophys. Acta, 1740, 202-205, 2005

Study 6. Effect of food intervention on the bioavailability of named antioxidants
(2005a)

Food per day

Type of study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

Diet + 600 ml
blood orange
(juice)

Human
intervention
study
- crossover

16(F)

21 days

plasma vitamin C
cyanidin-3-glucoside
beta cryptoxanthin
zeaxanthin

Question 2. (above)
Yes. All absorbed

Biomarkers: (evaluated as indicators of oxidative stress): malondialdehyde formation products (MDA), plasma glutathione peroxidase (GPX) and ferric reducing ability of plasma (FRAP)
Conclusion: All four of the antioxidants chosen from blood orange juice were shown to be bioavailable, but it remains to be demonstrated whether they are readily metabolised or are effective in raising the total antioxidant capacity.

Source reference: P. Riso, et al., J. Agric. Food Chem., 53 (4), 941-947, 2005

[Reprinted with permission from J. Agric. Food Chem., 53 (4), 941-947, 2005. Copyright 2005 American Chemical Society]

Study 5. Lycopene from two food sources does not affect antioxidant or cholesterol status of middle-aged adults.
(2004b)

Food per day

Type of study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

1. Diet alone.
2. Diet + 20.1 mg lycopene
from watermelon (juice)
3. Diet + 18.4 mg lycopene
from tomato (juice)

Human intervention
study
- crossover

5(F)
5(M)

21 days

total plasma cholesterol
high density lipoprotein cholesterol
triglyceride concentrations

No
plasma lipid concentrations - no change
antioxidant capacity - no change

Biomarkers: (evaluated as indicators of oxidative stress): malondialdehyde formation products (MDA), plasma glutathione peroxidase (GPX) and ferric reducing ability of plasma (FRAP)
Conclusion: The lycopene from watermelon or tomato juice does not affect plasma lipid concentration or antioxidant capacity of healthy subjects.

Source reference: J.K. Collins et al., Nutr J. 3 (15), 15 September, 2004

Copyright 2004 Collins et al. Open access journal

Study 4. Well-defined food-based delivery of lycopene (in tomato paste-olive oil mixture, (TP-OO))
(2004a)

Food per day

Type of Study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

Diet low in lycopene + TP-OO equivalent to lycopene in increasing doses 10 to 120 mg

Single-dose escalation
Phase I pharmacokinetic/toxicity study

5 groups of 5(M)

28 days

mean time, (t_max) to reach max. total lycopene concⁿ (C_max) + chylomicron lycopene

Yes, but
C_max not proportional to dose increments.

Conclusion: Suggests saturation of C_max at very low dosing levels and inter-individual variability may have been a contributing factor.

Source reference: D.M. Gustin et al., Cancer Epidem. Biomarkers Prevention, 13, 850-860, 2004

Study 3. Wild blueberry affects postprandial serum antioxidant status
(2002)

Food protocol

Type of Study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

week 1
high fat diet + control supplement
week 2
high fat diet + 100 g freeze-dried
blueberry powder

Single-blinded
crossover
Study

8(M)

14 days

H-ORAC
PCA-ORAC

Yes
increased ex vivo serum AOC

Conclusion: Antioxidants in wild blueberries are bioavailable, raising the antioxidant status of human serum.

Source reference: C.D. Kay and B.J. Holub, Br. J. Nutr., 88,(4) 389-398, 2002.

Study 2. Cranberry juice affects plasma total antioxidant capacity
(2000b)

Food per day

Type of Study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

Diet + 500 ml cranberry juice
(1.53 mM ascorbic acid)

Human
Intervention
Study

9(F)

21 days

Fremy's salt + ESR
FRAP

Yes
increased Plasma TAC

Conclusion: Compared to the blueberry juice (high phenolics/no vitamin C, only the cranberry juice (moderate phenolics/high vitamin C) raised the plasma TAC value, thus attributed to vitamin C content.

Source reference: C.B. Pedersen et al., Europ. J. Clin. Nutr., 54, 405-408, 2000.

Study 1. Effect of tomato consumption on plasma total antioxidant capacity
(2000a)

Food per day

Type of Study

Subjects/(sex)

Duration

Assays

Bioavailable?
yes/no

Diet + 25 g tomato puree
(7 mg lycopene + 0.25 mg beta-carotene)

Human intervention
study

11(F)

14 days

Carotenoid plasma concentration (CPC)
Plasma TAC
TRAP (see analytical)

No
CPC increased significantly
Plasma TAC - no change

Conclusion: Eating foods rich in lycopene and beta-carotene did not affect the total antioxidant capacity of the plasma

Source reference: N. Pellegrino, et al., Nutrition, 16 (4), 268-271, 2000

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