“All oil crops can be associated with wasteful use of water; harmful use of fertilisers, herbicides, and pesticides; and the conversion and loss of natural ecosystems,” they write. “Most are also associated with reported human rights abuses and exploitation.

“Rather than labelling oils as good or bad, we need approaches that reveal performance on biodiversity, human rights, and land use.”

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Walter Willett, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health, agrees that the issue of vegetable oils is nuanced.

Globally, vegetable oil crops account for more than one-third of all agricultural lands, and the production value of vegetable oils is estimated at more than $US265 billion, annually.

“When we are trying to feed over 8 billion people, almost everything we do has environmental impacts, and almost all major crops have a range of environmental impacts depending on where and how they are produced,” Willett says. “It is more complex than just good or bad.”

As for the health profile of the different oils, all unsaturated fats are good for us, says Dr Elena George of the Institute for Physical Activity and Nutrition at Deakin University.

A higher ratio of monounsaturated fats (MUFAs) to polyunsaturated fats (PUFAs) is more favourable for cholesterol and blood sugar regulation.

Let’s take a closer look at vegetable oils for our health and the planet’s:

PALM OIL

Palm is historically grown in Indonesia and Malaysia. It is also now produced in Thailand, India, Africa and parts of Latin America.

A large monocultural of palm that displaces natural tropical forests has a very different environmental impact to these same crops managed in subsistence or smallholder settings in areas that were converted to agriculture many centuries ago. Plus, the authors add, it uses vastly less land: palm oil plantations produce four to 10 times more oil per hectare than most temperate oil crops, such as soybean, canola, olive or sesame.

This is often overlooked in mainstream discussion, says Laurance: “It’s a fair point, but still, I think that palm oil does have a problem.”

The tropics, where oil palm is grown, has outsized impacts on biodiversity and carbon emissions, which is why oil palm and soybean expansion are especially concerning, says Kimberly Carlson, an associate professor in the Department of Environmental Studies at New York University.

“When shopping for products containing palm oil, I will preferentially choose those that contain RSPO-certified palm oil,” she says.

Health: Palm oil is higher in saturated fats, although it has a high MUFA composition, says George. She says people with higher cardiovascular risk should avoid it.

SOYBEAN

While palm often cops the brunt of the backlash against vegetable oils, soybean oil is in the same category because it also causes tropical deforestation, says Laurance.

“Tropical deforestation is flat out going to have more biodiversity and other environmental impacts that lead to destruction than something of a temperate forest,” he says. For the environment, tropical forests “simply are the most important”.

The biggest emitter of greenhouse gases, in the tropics, large-scale industrial soybean and maize production has also driven Amazonian deforestation (Brazil is the third-biggest producer behind China and the United States) and been associated with harmful exposure to pesticides.

Willett agrees that, from a planet perspective, soybean and palm are on par:

“Expanding soybean oil production is leading to destruction of tropical rainforests, which is not so different than in South-East Asia with palm oil.”

Health: Soy is better in many ways, says Willett. “It contains large amounts of both N-6 and N-3 fatty acids, which are both beneficial,” he says. “Palm oil has very little, but it could be possible to develop strains that have a better fatty acid profile.”

CANOLA

Canada is the world’s largest producer of canola oil, which helps to explain its name (a mash-up of Canada and “ola” for oil).

Rapeseed (the crop variety canola comes from) plantations use twice the amount of land as palm plantations and have caused significant harm to wild bee populations, which have declined more than 30 per cent in some areas.

Health: Rich in cholesterol-lowering PUFAs, canola is also highly refined, often requiring a lot of heat and chemicals to process. Buying organic, expeller-pressed canola oil is one way to avoid chemical processing, as well as synthetic pesticide use.

OLIVE OIL

Industrial-scale olive production has killed millions of roosting birds and replaced traditional agroforestry systems. It has the highest water footprint among oil crops.

However, perennial crops such as olives, with their enduring root systems, also help to preserve soil biodiversity and mitigate erosion.

“I like to choose Australian, local, extra virgin olive oil that I know has been cold pressed from fresh olives,” says George. “These aspects also contribute to biodiversity and sustainability, as well as making it a better choice for heath.”

Health: High in polyphenols and a rich source of monounsaturated fatty acids, olive oil also has a favourable ratio of MUFA to PUFAs (7:1). Buy oil in a dark glass bottle and store in a cool, dark place to maintain the anti-inflammatory and antioxidant benefits.

SESAME

In some source regions, such as Sudan, sesame production has been linked to severe human rights abuse. While the crop is native to Africa, the world’s biggest producers are China, India, Africa and Myanmar. Opting for cold-pressed generates less waste, requires minimal water, and has a relatively low impact on the environment.

Health: High in unsaturated fats, with even amounts of MUFAs and PUFAs, it is also high in antioxidants and may protect heart health.

COCONUT

The Asia-Pacific region produces about 90 per cent of the world’s coconut supply, threatening species that are not found anywhere else on Earth.

Opting for Rainforest Alliance Certified coconut oil and Fair Trade Sustainability Alliance standards helps to ensure ethical, sustainable practices.

Health: The highest in saturated fats. George wouldn’t suggest people at higher risk of cardiovascular disease consume coconut oil regularly. A small amount, however, is likely to be fine.

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