Choosing the Right Cooking Oils at Costco

The oils you cook with can support your health or introduce harmful toxins into your body. Cooking with low-quality oils—especially those made with industrial seed oils or packaged in plastic—can expose your cells to oxidative stress and inflammation. If you’re shopping at Costco, here’s a breakdown of what’s worth adding to your cart and what you’re better off leaving behind.

Marianne’s Avocado Oil: A Balanced Option

Avocado oil is widely regarded for its high smoke point and heart-healthy fats, making it an excellent option for cooking. Costco carries Marianne’s Avocado Oil, which is made with one ingredient: 100% avocados. This simplicity is a positive sign, but the oil is not certified organic, meaning pesticide exposure during cultivation is possible.

Another concern is the packaging. While the bottle is labeled BPA-free, it’s still plastic. Even BPA-free plastics can leach other toxins, particularly when exposed to heat or prolonged light, potentially leading to hormone disruption and chronic inflammation.

Despite these drawbacks, Marianne’s Avocado Oil is a far better choice than industrial seed oils such as canola or corn oil. These oils are highly processed, contain trans fats, and are often oxidized before reaching the store. If you’re seeking a high-smoke-point oil and don’t have access to better options, this avocado oil is a reasonable choice for maintaining cellular integrity.

Kirkland’s Signature Olive Oil: A Red Flag

Olive oil is often touted as a healthy cooking staple, but not all olive oils are created equal. Unfortunately, Kirkland’s Signature Olive Oil is a blend of refined olive oils with only 15% extra virgin olive oil. The lack of transparency about the sources and processing raises serious concerns about its purity and freshness.

For olive oil to offer cellular benefits, it must be 100% pure, extra virgin, cold-pressed, and preferably organic. Refined blends like this one may lack the antioxidant properties and monounsaturated fats that make olive oil so beneficial. Add the fact that it’s stored in a plastic bottle, and this product falls short in every category.

Kirkland’s Organic Olive Oil: A Step Toward Purity

Kirkland’s Organic Olive Oil is a step up for those looking for a better olive oil option. It’s certified organic, traceable to Mediterranean sources, and offers a level of quality missing in the Signature version. However, like Marianne’s Avocado Oil, it’s packaged in plastic, less ideal for maintaining the oil’s integrity.

While glass packaging is always preferable, this organic olive oil provides a healthier option for those who prioritize traceability and purity in their cooking oils. Its organic certification ensures fewer pesticide residues, a significant factor in protecting cellular health.

The Cellular Impact of Cooking Oils

The oils you use in your kitchen go beyond cooking—directly impacting your cellular health. Poor-quality oils, especially industrial seed oils, are prone to oxidation and can introduce free radicals that damage cellular membranes. Over time, this oxidative stress can lead to chronic inflammation and contribute to conditions such as heart disease and metabolic dysfunction.

To protect your cells, prioritize oils that are minimally processed, organic, and stored in safe packaging. While Costco’s options may not be perfect, making informed choices—like Marianne’s Avocado Oil or Kirkland’s Organic Olive Oil—can reduce exposure to harmful toxins and support your cellular function.