Phytochemical malabsorption: clinical significance

Abstract

Key Words: phytochemicals; vitamins; minerals; gastrointestinal malabsorption

CLINICAL SIGNIFICANCE OF PHYTOCHEMICALS

Until recent years, nutritionists have focused primarily on macronutrients and micronutrients in foods. Appreciation is now increasing that many food components, of plant origin (‘phytochemicals’) in particular, have the potential to affect human biology. Phytochemicals by definition are important components of food that may not be essential in the classical sense, and may not even be required to sustain life as vitamins or minerals do, but are likely to contribute to optimal health.

A problem in considering the place of phytochemicals in human health is that they are numerous, alongside a few known essential nutrients. Therefore, their net interactive effect ultimately requires a study of food itself and food patterns, so that food component intake may need to be subject to sophisticated mathematical modelling. However, the advant of advanced informatics may help resolve this dilemma.

Examples of phytochemicals, along with some of their food sources are listed according to their chemical structure in Table 1. The possible roles of these phytochemicals in the treatment of health conditions are rapidly unfolding[1], and the use of an index of preferred phytochemical intake has been suggested[2]. Yet limited information is available on the bioavailability of most of these compounds. With complex factors influencing the absorption and transport of phytochemicals, it is not easy to predict their bioavailability, let alone consider the implications of gastrointestinal malabsorption.

Table 1 Selected phytochemicals and their possible roles in health[3].

Phytochemicals	Some important food sources	Possible roles in health
Carctenoids	Orange pigmented and green	Antioxidants
	leafy vegetables, e.g.	Antimutagen
	carrots,	Anticarcinogen
	tomatoes, spinach	Immuno-enhancement
Flavonoids,	Green and yellow leafy	Antioxidants
isoflavonoids	vegetables, e.g. parsley,	Anticarcinogen
and saponins	celery, soy bean and soy	Oestrogenic
	products	Immuno-modulating
Polyphenols	Cranberry, raspberries,	Antioxidants
	blackberries	Antibacterial
	Rosemary, oregano, thyme	Reduce urinary tract infection
Calechins	Green tea	Antimutagen
		Anticarcinogen
		Anticariogen
Allyl thiosulfinates	Garlic, onions, leeks	Anticarcinogen
		Antibacterial
		Cholesterol lowering
Isolhiocyanates	Cruciferous vegetables, e.g.	Antimutagen
and indoles	broccoli, cabbage
Phytosterols,	Pumpkin seeds	Reduce symptoms of prostate
e.g. β-sitosterol		enlargement

This list is not exhaustive for phytochemicals.

BIOLOGICAL OCCURRENCE AND RELEVANCE OF PHYTOCHEMICALS

The presence and the physiological concentration of phytochemicals in biological tissues or fluids, especially blood and urine, create the opportunity for biomarkers of the consumption of phytochemical-containing foods[4-6] (Table 2). Equally, measurements of phytochemicals reflect bioavailability, including absorption.

Table 2 Occurrence of phytochemicals in human blood and tissues.

Phytochemicals	Where can we find them in the body
Carotenoids	Serum (five major carotenoids)
Lutein/zeaxanthin	Skin
β-cryptoxanthin	Adipose tissues
Lycopene	Lens and macula (lutein/zeaxanthin)
α-carotene	Various tissues like prostate (lycopene)
β-carotene
Flavonoids	Serum
Quercetin, kaempferol	Urine
Isoflavcnes	Serum
Geristein, daidzein	Urine
Catechins eplgallo-catechin gallate	Serum
Allyl thiosulfinates	Blood, serum, red blood cells
organosulfides	Adipose tissue
vinyl dithiins	Liver
	Kidney
	Breath
Tocotrienols	Sikin

For the moment, the presence of phytochemicals in tissues, is presumptive evidence of functional significance, especially where there is a plausible mechonism of action (e.g. carotenoids as antioxidants for serum lipoproteins). Observations like this generate a number of exciting hypotheses for further research.

CLINICAL SIGNIFICANCE OF PHYTOCHEMICAL MALABSORPTION

Given the putative health benefits of phytochemicals, gastrointestinal malabsorption may well contribute to a loss of their protective effects. This could result in a number of clinical disorders which could be referred to as ‘phytochemical deficiency disorders’[1]. Candidate disorders are:

a. The menopause as a ‘phytoestrogen deficiency disorder’[7]

b. Cardiovascular disease because of the role of certain phytochemicals as antioxidants, others as are regulators of endothelial function and others as modulators of myocardial function

c. Colorectal cancer in relation to a range of phytochemical intakes from various fruits and vegetables, and whole grain cereals[8]

d. Prostatic disease in relation to lycopene and isoflavones[9,10]

e. Maculopathy on account of the contribution to macular function of lutein and zeaxanthin[11]

Two cases of short bowel syndrome where carotenoids were undetectable in serum illustrate the potential for these orders (Case reports 1 and 2). In each case, it was possible to increase serum carotenoid concentrations by vegetable juice supplements.

Case report 1. Mrs BW (b. 1956)

Vaginal cancer (1990) treated with radiotherapy

Rectovaginal fistula → colostomy (1992)

Short bowel syndrome (1995) (Table 3)

Table 3 Not available.

Vegetable juice/soup		No	Yes
Serum concentration (nmol/L)	Reference range	Jan 96	May 97
Lutein/zeaxanthin	80-850	102	202
β-cryptoxanthin	175-1350	Not detectable	12
Lycopene	69-650	Not detectable	33
α-carotene	15-300	Not detectable	Not detectable
β-carotene	45-900	Not detectable	93

Case report 2. Mrs CM (b. 1956)

Severe road traffic accident (1976) → ruptured bowel, bowel resections

Short bowel syndrome (Table 4)

Table 4 Not available.

V-8ceTM (glass/day)		0	1 × 2	1 × 1
Serum concentration (nmol/L)	Reference range	Nov 95	May 96	Nov 96
Lutein/zeaxanthin	80-850	Not detectable	243	17
β-crytoxanthin	175-1350	Not detectable	18	Not detectable
Lycopene	69-650	Not detectable	32	11
α-carotene	15-300	Not detectable	Not detectable	Not detectable
β-carotene	45-900	Not detectable	10	8

CONCLUSIONS

Witn arnergent evidence for physiological roles of phytochemicals and for their potential for disease protection, the use of foods, which are good phytochemical sources, to prevent and manage disease will be encouraged. The malabsorption of phytochemicals is likely to be one of many pathways to so-called “phytochemical deficiency disorders”.