Rice and arsenic: the “Parboil-and-Absorb” method cuts levels by 73 percent

People who eat rice regularly consume more than carbohydrates and fibre: they may also be taking in arsenic. This substance occurs naturally in soil and water, but it can accumulate in the body and cause illness over the long term. Researchers have now tested a cooking technique that substantially lowers arsenic levels in rice without washing away all of its nutrients.

Why rice can absorb so much arsenic

Arsenic is naturally present in rocks and soils. Rainfall and erosion carry it into groundwater and surface water. This is precisely where the issue arises, as rice is grown in water.

In flooded paddy fields, rice plants remain in constant contact with arsenic-containing water. They absorb the substance through their roots and store some of it in the grain – the same grain that later reaches the plate as white or wholegrain rice.

Rice absorbs arsenic far more readily than other cereals, such as wheat or oats. For that reason, food safety authorities monitor it particularly closely. The European Food Safety Authority (EFSA) links exposure to inorganic arsenic with a higher risk of several cancers, especially skin and lung cancer. Damage to blood vessels and effects on the nervous system are also being considered.

Rice is a staple food worldwide – which is exactly why every reduction in its arsenic content matters for the health of many people.

To limit exposure, the EU has set clear maximum levels: 0.15 milligrams of arsenic per kilogram for white rice, and 0.25 milligrams per kilogram for wholegrain rice. These rules apply to cultivation and trade. However, Europe currently has no specific household guidance on how rice should ideally be cooked to remove arsenic.

What familiar TikTok & Co. advice actually achieves

Social media is full of suggestions: rinse rice several times, soak it overnight, cook it without draining it, or prepare it in a rice cooker. The claims vary widely, from “it removes everything” to “it makes no difference at all”.

The US Food and Drug Administration (FDA) has examined common methods more closely. It recommends cooking rice in a very large volume of water: six to ten parts water to one part rice. Once cooked, the excess water is drained away.

Cooking rice in plenty of water: effective against arsenic, poor for nutrients

This traditional pasta-style method does work: it can reduce arsenic content by 40 to 60 percent. Arsenic dissolves into the cooking water and goes down the drain when that water is discarded.

The drawback is that important nutrients are lost with the water too. According to the FDA, levels of the following fall by around 50 to 70 percent:

• folate (a form of folic acid);
• iron;
• niacin (vitamin B3); and
• thiamine (vitamin B1).

For people who rely on rice as a regular source of nutrients, this removes a considerable share of its nutritional value.

Simply rinsing rice before cooking is also frequently recommended but overestimated. According to the FDA, washing reduces arsenic only minimally, while it can also remove some vitamins and minerals from the surface of the grains. Its health benefit is therefore limited.

Washing rice alone is not enough – and cooking it in a huge pan of water washes away too many vitamins.

The “Parboil-and-Absorb” method: 73 percent less arsenic

Researchers at the University of Sheffield investigated a cooking technique that offers a much better compromise. The study was published in the scientific journal Science of the Total Environment and reported by various media outlets.

The approach combines two principles: draw arsenic into the water as early as possible, then cook the rice gently without continually leaching out nutrients. The researchers describe it as a method involving pre-blanching followed by absorption cooking.

How the Parboil-and-Absorb method works step by step

The technique is easy to use at home and does not require any specialist equipment:

• Measure out the rice and briefly rinse it with cold water to remove any coarse dust, if desired.
• Bring the rice to the boil in plenty of fresh water.
• Boil vigorously for five minutes.
• Drain all of the water and discard it – this is where much of the dissolved arsenic is removed.
• Add fresh water, using only enough for the rice to absorb while cooking, depending on the variety around 1.5 to 2 times the amount of rice.
• Cook over a medium heat with the lid on until the water has been absorbed and the rice has reached the desired texture.

The result: arsenic content falls by an average of 73 percent in white rice and 54 percent in wholegrain rice. At the same time, most nutrients are retained better than with the water-heavy method alone. Zinc in particular, which is important for the immune system and metabolism, largely remains in the grain.

With just five extra minutes at the hob, arsenic levels in rice can be cut substantially – without turning it into a nutritional desert.

Which rice varieties and groups are particularly affected

Arsenic exposure depends heavily on both the growing region and the variety. Wholegrain rice tends to contain more arsenic than white rice because more residues are found in the outer layers of the grain. Those same layers also provide fibre and minerals – a classic trade-off.

Anyone who eats rice occasionally does not need to panic. The issue becomes more relevant for people who consume rice products very regularly:

• children who often receive rice cakes or rice porridge;
• adults who eat rice as a side dish several times a week;
• people who depend heavily on rice as their main carbohydrate source for cultural or personal reasons; and
• fans of rice drinks and rice noodles.

For these groups, every way to reduce exposure is worthwhile, particularly when intake remains high for years.

Practical tips for everyday rice meals

The new cooking technique is an important part of the picture, but it does not replace common sense. Anyone wishing to be particularly cautious can combine several strategies:

• Alternate rice varieties, such as basmati, jasmine, parboiled and wholegrain rice.
• Vary carbohydrate sources by including potatoes, pasta, millet, bulgur or couscous.
• For babies and toddlers, choose products that are explicitly tested for arsenic.
• Avoid making rice the main component of every meal every day.
• Use the pre-blanching and absorption-cooking method for rice eaten frequently.

If you use a rice cooker, the technique can be adapted in part: first pre-cook the rice in a pan for five minutes, drain the water, then transfer the rice and fresh water to the rice cooker to finish cooking.

What arsenic does in the body – and why the dose matters

Arsenic affects a range of metabolic processes in the body. Inorganic arsenic, which may be present in rice, is associated with:

• an increased cancer risk, including skin, lung and bladder cancer;
• damage to blood vessels;
• impairment of the nervous system; and
• negative effects on child development where exposure is high and long-term.

Acute poisoning from normal rice consumption in Europe is extremely rare. The concern here is the cumulative effect of many small portions over years. This is why authorities seek to reduce exposure throughout the entire chain, from field to saucepan.

In practice, this means nobody needs to ban rice from their kitchen. Those who want to continue enjoying their favourite curry or sushi can do so. Adjusting the cooking method and introducing some variety in side dishes can significantly lower long-term intake.

Knowledge check: what terms such as “inorganic arsenic” mean

Reports often distinguish between organic and inorganic arsenic. Organic forms occur, for example, in some seaweeds and are considered less concerning. Inorganic arsenic is more closely linked to the harmful forms covered by maximum limits.

With rice, the concern is mainly inorganic arsenic from soil and water. Analyses specifically separate out this form when assessing contamination. Anyone reading studies or reports from authorities should pay attention to these terms in order to interpret the figures correctly.

It is striking that simple measures in the home kitchen can have major effects. The method presented does not alter the taste of rice, requires only a few extra minutes of effort and reduces a genuine risk that many people had not previously expected to find on their plate.