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Inhibitory effect of nuts on iron absorption
B J Macfarlane1, W R Bezwoda, T H Bothwell
1Department of Medicine, University of the Witwatersrand, Johannesburg, South Africa.
The American Journal of Clinical Nutrition
|February 1, 1988
Summary
Dietary nuts significantly inhibit iron absorption in women due to phytates and polyphenols. However, adding ascorbic acid can overcome this effect, improving iron bioavailability from these foods.
Area of Science:
- Nutritional Science
- Human Physiology
- Food Chemistry
Background:
- Nuts are a key protein source in developing nations.
- Dietary factors significantly influence iron absorption.
- Phytates and polyphenols are known inhibitors of iron absorption.
Purpose of the Study:
- To assess the impact of various nuts on iron absorption in Indian women.
- To identify the inhibitory compounds in nuts responsible for reduced iron absorption.
- To determine if ascorbic acid can counteract the inhibitory effects of nuts on iron absorption.
Main Methods:
- 137 Indian women participated in the study.
- Iron absorption was measured from meals containing bread with or without different nuts (walnuts, almonds, peanuts, hazelnuts, coconut).
- Inhibitor content (phytates, polyphenols) of nuts was analyzed. Ascorbic acid's effect was tested.
Main Results:
- Nut meals significantly reduced iron absorption (1.8%) compared to bread meals (6.6%).
- Coconut did not significantly inhibit iron absorption; it contained lower levels of inhibitors.
- Ascorbic acid (50 mg) effectively reversed the inhibitory effects of Brazil nuts and peanuts.
Conclusions:
- Common dietary nuts, except coconut, inhibit iron absorption in women due to phytate and polyphenol content.
- Ascorbic acid supplementation can mitigate the negative impact of nuts on iron bioavailability.
- Findings differ from previous studies on soy protein's inhibitory effects on iron absorption.