Garlic and onion may boost mineral absorption

By Stephen Daniells, 06-Jul-2010

Related topics: Minerals, Phytochemicals, plant extracts, Cardiovascular health, Immune system, Maternal & infant health

Compounds in both garlic and onion may increase the bio-accessibility of iron and zinc from cereals seven-fold, according to new data from India.

Consuming garlic or onion with cereals increased the uptake of iron by about 70 percent, and zinc by to 160 percent, according to new results published in the Journal of Agricultural and Food Chemistry that could offer opportunities to tackle two of the globe’s major deficiency concerns.

“Both garlic and onion were evidenced here to have a promoting influence on the bio-accessibility of iron and zinc from food grains,” state the researchers, led by Krishnapura Srinivasan from the Central Food Technological Research Institute in Mysore, India.

“This novel information has the potential application in evolving a food-based strategy to improve the bioavailability of trace minerals and hence contributes to the human health benefit,” they added.

Global problems

Iron deficiency is reported to affect about a third of the global population, with two billion people anemic around the world. In addition, zinc deficiency affects 30 per cent of the world’s population.

The bioavailability of both micronutrients is said to be particularly low from plant foods.

In attempt to enhance the uptake of these minerals from plant sources, the Mysore-based researchers used a model of the gastrointestinal tract to simulate passage through a human gut. Two cereals – rice and sorghum – and two pulses – chickpea and green gram – were used in their raw and cooked forms, and in the presence of two levels of garlic (0.25 and 0.5 g per 10 g of grain) and onion (1.5 and 3 g per 10 g of grain).

Results showed that iron and zinc uptakes from both cooked and raw cereals were significantly increased in the presence of both garlic and onion, with increases up to 70 percent recorded. Improvements in the bioaccessibility of zinc were also observed for both spices, with increases in cereals ranging from 10.4 to 159.4 percent, and in pulses from 9.8 to 49.8 percent.

How?

Commenting on the potential mechanism behind the improvements, Srinivasan and co-workers point to the high sulfur content in garlic and onion: Sulfur-containing amino acids like cysteine have previously been shown to boost iron and zinc status in lab animals, they said.

“The information generated in this study on the promotive influence of natural sources of sulfur compounds on mineral bioaccessibility from food grains is novel and has a promising application in evolving a food-based strategy for alleviating deficiencies of these minerals in sections of the population,” concluded the researchers.

Into foods

Fortification of foods with iron poses several challenges, depending on the types of iron used. Using water-soluble iron sulfate or iron gluconate offer the advantages of providing high bioavailability, but the disadvantage of adversely affecting the color of the resultant product. On the other hand, water- insoluble elemental iron or ferric phosphate offer poor bioavailability.

Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, doi: 10.1021/jf100716t
“Higher Bioaccessibility of Iron and Zinc from Food Grains in the Presence of Garlic and Onion”
Authors: S. Gautam, K. Platel, K. Srinivasan