Heavy metals in vegetable oils...:

Toxic truths

by Dr. Muhammed Waggr Ashraf

Pic: business.standard.com

With drastic changes in society and enhanced living standards, the common people are adopting healthier eating habits. Awareness about health-related issues, especially in the context of excessive weight gain have altered food habits for the better. The shift from animal fat-based cooking oils to vegetable oils is one such.

However, there is very little information on the heavy metal levels in edible vegetable oils used in many regions of the world, including Saudi Arabia, in the Middle East and North Africa (MENA) and islands such as Bahrain, Qatar and Sri Lanka among many others.

Vegetable oils have a wider use in cooking, cosmetic, pharmaceutical and chemical industries. The presence of essential fatty acids enhances nutritional value and are undoubtedly beneficial and popular due to the cholesterol-lowering aspect.

Animal-fat based oils in contrast, are predominantly saturated and tend to obstruct arteries. The quality of vegetable oils regarding freshness, storability and toxicity can also be evaluated through determining the metal content present in trace quantities in these oils.

Such trace metals are elements that play a pivotal metabolic role, although not to a great extent. Some of these however have no role to play in the body, and thus become toxic. The levels of trace metals such as Copper, Zinc, Iron and Manganese are known to increase the rate of oil oxidation and thus the quality deteriorates automatically. Other elements like Arsenic, Cadmium and Lead cause toxicity and have no metabolic role whatsoever in the body.

Contamination causes

Metal presence in vegetable oils depends on many factors. They might originate from the soil, where source plants are grown and the type of fertiliser used.

The presence of industries or highways near plantation sites, use of contaminated water for irrigation and natural fallout are a few notable contamination causes. Such metals might also get in the oils during production and packaging or from metal-processing equipment suspended in oil in such processes.

The harmful effects induced by toxic metals only cause problems when used in excess. A hazardous metal would induce adverse symptoms in the human body, if consumed even in trace amounts. There is currently considerable interest and demand to determine heavy metals in food. It is necessary to study the migration of trace elements and to monitor the highly toxic contents at all stages of processing or packaging food products.

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Toxic elements might prove harmful even at low concentration, when ingested over a long period. Essential metals can also produce toxic effects, while metal intake is excessively elevated. Trace metals enhance the rate of oxidation of edible oils through increasing the generation of free radicals from fatty acids. It is necessary to assess the levels of heavy metals in edible vegetable oils and report possible contamination which would cause health hazards.

It has been identified that food consumption is the main method of exposing humans to toxic metals, compared to inhalation and skin contact. Taking into account the metabolic role of some metals and the preference of vegetable oils, it is of significance to evaluate the presence of heavy metals in commercially available vegetable oils at present. A limited study revealed interesting results about the levels of heavy metals in such oils.

Copper is an essential element for the body but a high intake might cause adverse health problems. Its deficiency leads to anaemia and osteoporosis in children. The minimum and maximum values of copper have been seen in corn and olive oils. In a recent research it has been found that the lowest manganese content is usually found in rapeseed oil, while the highest is in peanut oil.

Manganese deficiency might produce skeletal and reproductive abnormalities. Cadmium, arsenic and lead levels found within legal limits set jointly by the FAO/WHO Expert Committee on Food Additives may not have a severe affect. Minimum and maximum lead levels have been found in rapeseed oil and sesame oil.

Intake of elements from food consumption depends on the element concentrations in food and its quantity consumed by individuals. World renowned agencies such as the US The Environmental Protection Agency (US EPA), Joint FAO/WHO Expert Committee on Food Additives (JECFA) and Institute of Medicine of the National Academies (IOM) provides guidelines on the intake of trace elements by humans.

An attempt was made to evaluate the possible health threats from the consumption of edible vegetable oils by the people. Results suggest that a 70 kg adult consuming 25g of edible vegetable oils daily have Copper, Zinc, Iron and Manganese levels far below the limits recommended by world health agencies.

The weekly consumption of 175g of edible vegetable oils in the Kingdom of Saudi Arabia did not pose any serious health risks due to environmental factors and food quality control steps that have already been put in place.

It is attributed to the fact that such edible oil processing industries had good raw materials, advanced processing technology and strict quality control standards.

A similar scenario does not prevail everywhere including other Asian countries specially Sri Lanka, which have still not developed food quality control mechanisms.

The Sri Lankan authorities must take a serious look regarding this issue, for healthy living stressing on vegetable oil quality control solutions.

(Dr. Muhammad Waqar Ashraf is Dean of the Core Curriculum Program at Prince Mohammad Bin Fahd University (PMU) in the Kingdom of Saudi Arabia. His research interests include environmental monitoring and assessment, food contaminationand& toxicology. He has published many articles in reputed scientific journals and daily newspapers.)