Olive Oil Price Hike: The Affordable, Healthy Alternatives Deemed 'The Hateful Eight'

Olive oil is becoming liquid gold, not just in name but in price! This surge isn't isolated - Stats NZ reports olive oil, along with chocolate and potato chips, significantly contributed to April's overall food price increase.

Soaring olive oil prices in 2024 are due to a perfect storm of factors, mainly related to weather conditions in key producing regions. Southern Europe, particularly Spain, the world's biggest olive oil exporter, has been hit hard by prolonged drought and scorching temperatures. Experts point to climate change as a major culprit behind the harsh weather patterns. The increased vulnerability of olive trees to these conditions is causing long-term concerns for production with anticipated further price increases. 

'Olive-of-which' 😁 presents a great opportunity to refresh our knowledge on the world of affordable, healthy oils beyond the olive grove. This article is particularly timely given consumers are receiving conflicting messages on several affordable and healthy seed oil alternatives that have been categorised within, and referred to as the 'hateful eight': canola, corn, cottonseed, grapeseed, soybean, sunflower, rice bran and peanut oils.

Emerging as a top contender is canola oil. While it boasts a more neutral flavour profile compared to its olive oil counterpart, it offers impressive versatility. With a high smoke point, it’s ideal for cooking at higher temperatures. And nutritionally, it stands out due to its favourable fatty acid composition. It contains high amounts of unsaturated fats with low levels of saturated fat, especially compared to alternatives like coconut oil. This composition helps reduce LDL cholesterol levels, which is particularly beneficial for those managing cholesterol concerns.

While most dietary guidelines worldwide promote unsaturated fats, some commentators have 'seed oils' like canola on their no-go list  — even calling them ‘toxic’. Instead, these anti-seed oil fanatics champion saturated fats, such as those found in butter and coconut oil, as superior alternatives. This fear-mongering approach leads to confusion and potentially steers us towards less healthy food choices.

So, before we slide down the slippery slope of seed oil mania, let’s dive into the evidence.

The seed oil scare: separating fact from fiction

Firstly, what are seed oils? As the name suggests they are oils extracted from plant seeds, and are rich in omega-6 fatty acids, primarily linoleic acid. Common seed oil examples include canola oil, sunflower oil, sesame oil, safflower oil, soybean oil, corn oil, flaxseed oil, and grapeseed oil. In contrast, olive oil is extracted from the whole olive fruit, not just the seed.

It seems the concerns with seed oils stem from main two issues:

1. increased oxidation of lipids: FALSE. Some suggest seed oils can elevate the oxidation of lipids including LDL cholesterol, contributing to the atherogenic process (plaque buildup in arteries). This concern stems from the susceptibility of double bonds in seed oils to oxidation in in vitro (test tube) studies. These studies often measure lag time — this is where you take LDL particles and dump them in a solution such as copper sulphate and see how long it takes them to become oxidised (the longer the better). However, these studies often don't reflect the complexity of the human body. Seed oils naturally contain vitamin E, a potent antioxidant that mitigates oxidation in vivo (within a living organism), effectively negating this concern. And this is precisely why saturated fat food sources such as coconut oil and butter aren’t rich sources of vitamin E — because they don’t have any double bonds to protect. Furthermore, no human intervention trials have shown a link between higher linoleic acid intake (the predominant fatty acid in seed oils) and increased lipid peroxidation.
2. Conversion of linoleic acid to arachidonic acid: MISINFORMATION. Another concern centres around the conversion of linoleic acid to arachidonic acid, a precursor to eicosanoids, signalling molecules involved in various physiological processes like inflammation and blood clotting. Proponents against seed oils highlight the potential for increased levels of pro-inflammatory leukotrienes and pro-aggregatory thromboxanes derived from arachidonic acid. However, arachidonic acid also produces anti-inflammatory prostaglandins and prostacyclins, which have vasodilatory (blood vessel widening) effects, all factors associated with reduced cardiovascular disease (CVD) risk. It’s clear the actions of these eicosanoids are complex — cherry-picking their actions can result in misinformation. And for arguments sake, even if arachidonic acid increases CVD risk, studies have suggested the conversion of linoleic acid to arachidonic acid in humans is limited.

While there are plausible mechanisms suggesting that polyunsaturated fats might cause harm, these explanations don’t always translate to real-world effects in the body. Therefore, it’s crucial to evaluate this mechanistic evidence alongside human observational studies and intervention trials before making any firm dietary guidelines.

The Evidence on Seed Oils and Heart Disease

If seed oil consumption were linked to an increased risk of CVD, we would see a positive correlation in population studies. However, the opposite is true.

A meta-analysis by Marklund et al., examining adipose and blood biomarkers of linoleic acid intake revealed a significant decrease in total CVD, CVD mortality, and ischemic stroke for those with the highest linoleic acid intake (remember linoleic acid is an essential fatty acid, meaning our bodies cannot synthesise it, so its levels in tissues like adipose and blood reflect dietary intake). While it’s important to exercise caution when interpreting observational studies due to limitations such as confounding factors that cannot be fully controlled, these findings are corroborated by a Cochrane review and meta-analysis of RCTs on omega-6 fatty acids. This review found no harmful effects and even observed a reduction in myocardial infarction (heart attack).

Furthermore, substituting saturated fat with polyunsaturated fat (PUFA, which includes seed oils) has shown the most significant benefit in reducing CVD risk. Studies like the Nurses' Health Study support this, demonstrating a 25% reduction in coronary heart disease (CHD) risk when replacing saturated fat with PUFA. A further Cochrane meta-analysis showed that when saturated fat was swapped out for PUFA we see the most benefit in terms of CVD risk reduction — a 27% reduction in cardiovascular events.

Controversial Studies and the Importance of Context

The Sydney Diet Heart Study (SDHS) often features prominently in anti-seed oil rhetoric. This study, conducted in the 1960s among men who had recently experienced a cardiac event. The intervention group were advised to lower their SFA intake to less than 10% and increase PUFA to 15% of total energy. With a median follow-up of 3.3 years, the original publication only reported all-cause mortality, where there was a non-significant increase in risk in the high PUFA group (HR 1.62, 95% CI 1.00, 2.60). The wide confidence intervals suggest weak statistical power. A reanalysis of this study in 2013 reported that the PUFA arm of the trial significantly increased cardiovascular disease (HR: 1.70, CI: 1.03, 2.80) – again note the wide confidence intervals. These findings hit the headlines and caused quite the hoopla — as do most studies that contradict a substantial body of existing evidence. However, here’s the kicker — the study used margarine as the primary source of PUFA and at the time margarine production relied heavily on hydrogenation, a process that creates trans fats — well-established contributors to heart disease. This crucial detail is often overlooked, making the SDHS an unreliable source of evidence against seed oils.

A similar issue likely applies to the Minnesota Coronary Experiment (MCE), also conducted in the 1960s. This study involved patients in state psychiatric hospitals, many of whom were not exclusively in-patients and moved in and out of hospital, meaning the intervention was not continuous. Additionally, the mean follow-up was only 1.5 years — far too short to draw meaningful conclusions.

Anti-seed oil fanatics often cite certain meta-analyses to support their claims. One such study is a meta-analysis by Chowdhury et al. Interestingly, while this study showed a non-significant reduction in coronary outcomes with higher omega-6 intakes in RCTs (RR 0.86, 95% CI: 0.67, 1.07), when the SDHS was removed from the analysis, the reduction became significant (RR 0.81, 95% CI: 0.68, 0.98).

The Omega-6 and Omega-3 ratio

Another area of contention is the value of the omega-6 to omega-3 ratio. Some blame seed oils for a modern diet imbalance, favouring omega-6. However, many experts believe the absolute amount of omega-3 intake is more critical. Since Western diets tend to be low in omega-3s, the focus should be on increasing omega-3 rich foods like fatty fish, rather than obsessing over the ratio. While some concerns exist about competition between omega-6 and omega-3 conversion due to shared enzymes, the conversion rate is likely small. Ultimately, getting omega-3 directly from their source remains the best approach.

Quality Matters: Seed Oils and Processed Foods

A valid criticism of modern diets is the excessive use of seed oils in processed foods like deep-fried items and baked goods. Consuming seed oils in this context likely has different health consequences compared to using them to stir fry our vegetables. It serves to remind us about the importance of a balanced diet over fixating on individual nutrients. And the source of seed oils in research studies significantly impacts outcomes.

The Takeaway: Following the Science

All in all, this is a good example of how mechanistic hypotheses don’t always hold up under the scrutiny of human research. It serves as a valuable reminder to consider the totality of the evidence before jumping on a bandwagon that might be heading in the wrong direction.