Veröffentlichungen • Serum beta-carotene concentrations in women consuming a healthy diet

M. J. Groeneveld, I. Hoffmann, C. Leitzmann
Poster auf dem Second Karlsruhe Nutrition Symposium, Okt. 1997

Introduction

In recent years several epidemiological studies have shown that a high consumption of vegetables and fruits is associated with reduced risk of heart disease and some forms of cancer (Ziegler 1991). Although the exact mechanism of the apparently protective effect is unclear, possible explanations include the high intake of beta-carotene and corresponding high concentrations in plasma. On the base of epidemiological data it has been estimated that a beta-carotene plasma concentration of > 0.4 µmol/l may be optimal (Gey 1993). The recommendations for the intake extended from 2-20 mg/d. For professionals working in the prevention of Western life-style diseases it is an important question whether the recommended plasma concentration of beta-carotene can be achieved solely with the diet.

Objective

In a cross-sectional study 372 healthy women aged 25-65 years were examined to assess whether a recommended plasma concentration of > 0.4 µmol/l may be reached solely with a non-supplemented, non-fortified healthy diet. One group of 238 women consumed a healthy diet meeting the recommendations for the prevention of nutrition related diseases for at least 5 years. This diet consisted mainly of vegetables, fruits, whole grain products, potatoes, legumes and dairy products but little or no meat. This study group is compared to a corresponding control group of 134 women eating a mixed western diet. Both groups neither took supplements nor fortified food.

Methods

Study design: cross-sectional study with healthy women aged 25-65 years

Study group: healthy diet - 238 women

Control group: mixed western diet - 134 women

Recruitment:

• nationwide by advertisements in journals and magazines
• selection for further participation on the basis of a semiquantitative food frequency
  list

Instruments: 7-day estimated food record (validated)

Blood-samples: venous blood, 12 h fasting period

Beta-carotene:

• chromatographic separation of hexane extractable beta-carotene by silicagel (Si-60, Merck) and subsequent detection at a wavelength of 450 nm

Results

The plasma concentrations of beta-carotene were found to be 1.7 µmol/l in the healthy diet group and 0.9 µmol/l in the control group. In both groups the plasma concentrations are far above the recommended minimum concentration. For both study groups together increasing plasma concentrations were observed with increasing consumption of vegetables (Fig. 1). The carotenoid-intake was 9.0 mg per day in the healthy diet group and 5.1 mg in the control group. Most of the carotenoid-intake derived from vegetables. The women on the healthy diet consumed 374 g vegetables and legumes per day, those on the mixed diet 224 g (Fig. 2).

Conclusions

This study clearly shows that a high beta-carotene plasma concentration can be achieved with a healthy diet containing 2-3 servings of vegetables per day, without supplementation or fortification. It should be noticed that the healthy diet group also showed a high intake of further protective nutrients (e.g. complex carbohydrates, other antioxidants, dietary fiber) and a high nutrient density. Simultaneously they had a low intake of substances known to be unfavourable (e.g. total fat, saturated fatty acids, cholesterol, alcohol).

Literature:

Ziegler RG

Vegetables, fruits and carotenoids and the risk of cancer
Am J Clin Nutr 53, 251S-259S, 1991

Gey KF

Prospects for the prevention of free radical disease, regarding cancer and cardiovascular disease
Br Med Bull 49, 679-699, 1993

Groeneveld M

Beurteilung einer vorwiegend lakto-vegetabilen Ernährungsform anhand der Zufuhr und der Versorgung mit Vitaminen
Wissenschaftl. Fachverlag Dr. Fleck, Niederkleen, 1994