The topic of fat and cancer can be confusing and frustrating. While one source might tell you that fat is the bad guy to be avoided at all costs, another might sing the praises of a Ketogenic diet.  But it’s most important to know which fats create an environment where cancer can thrive, and which ones help reduce the risk of cancer—regardless of how much fat your diet contains.

To begin, it's important to understand that fat is not just one macronutrient. Several categories of fats exist with different functions in the body. Fats can basically be broken down by some simple structural differences that have to do with how the components, called fatty acids, are linked.

The fatty acid structure determines its stability when exposed to heat, light, and air. At room temperature, saturated fats tend to be solid while polyunsaturated fats tend to be liquid.  When exposed to heat, light, and air, saturated fats tend to be more stable, while polyunsaturated fats create dangerous free radicals. Monounsaturated fats fall in the middle of the spectrum: they are liquid at room temperature, and they have some resistance to damage by heat, light, and air.

Every commercial fat product or natural substance (like nuts and seeds) contains a mixture of each of these types of fatty acids but in varying proportions. For example, people refer to olive oil as a monounsaturated fat but actually it contains mostly monounsaturated fat plus some saturated fat and some polyunsaturated fat. Some oils, like olive oil or avocado oil, contain protective chemicals called polyphenols or vitamin E, an antioxidant, which help protect them against damage from heat. This article centers on two types of polyunsaturated fatty acids that play an important role in cancer prevention and treatment: omega-3 and omega-6.

The Omegas­—A Family of Polyunsaturated Fatty Acids

Polyunsaturated fatty acids  (PUFAs) are named by the differences in their fatty acid structure. The main types are called omega-3, omega-6, omega-7, and omega-9. Here I will focus on omega-3 and omega-6 fatty acids, two PUFAs that play important roles in cancer treatment and prevention. Our body can't make omega-3 or omega-6, so they are considered "essential.”

Omega-6s are needed to help our body mount an inflammatory response. If we get injured or ill, our body responds by creating inflammation to clean up the injury or heal the illness. Omega-3s do the opposite: they help reduce inflammation.

Two main types of omega-3s, which are commonly known as EPA and DHA, play important roles in regulating a healthy inflammatory response. We need some of each of these types of fatty acids, but our modern diet contains a far higher ratio of omega-6 to omega-3 than is ideal for our body. Modern refined seed oils (high in omega-6) weren’t part of our ancestors’ diets. And we eat far less amount of fish, game, and wild plants in our modern diets, which are rich sources of omegas-3s. Even the healthier nuts and seeds in the modern diet are high in omega-6s and low in omega-3s.

Although it may seem like a lot of time has passed since people subsisted on fishing, hunting wild animals, and foraging what we now consider weeds, this is a relatively short time (a few hundred years) compared to our evolution from early to modern humans (upwards of 100,00 years). If you want to dig deeper into genetic adaptations to dietary shifts in human evolution, here's a fascinating article. We need more omega-3s than we get in a typical modern diet, but how do we get them?

How to Add More Omega-3s to Your Diet

Fatty fish like wild salmon, sardines, ocean trout, mackerel, herring, and tuna are the .  Although farmed salmon is high in in omega-3s and is more economical, it isn’t the best choice it also contains omega-6s because of the artificial diet (which may also may contain contaminants). You can get small amounts of omega-3 from the eggs of chickens fed their natural diet of wild grasses and bugs or given feed supplemented with flaxseed, and you can get small amounts from eating the meat from cows, buffalo, or wild game that eat only their natural diet of wild grass (100 percent grass fed with no grain).  

Unfortunately, most commercially produced eggs and meat do not contain omega-3s. In fact, they typically contain an inflammatory combination of saturated fat and omega-6s.

One 3.5-ounce serving of wild Alaskan salmon delivers anywhere from 1100 to 2000 mg of omega-3s depending on the variety; 3 ounces of canned sardines in water provides 1800 mg of omega-3s, and 3 ounces of canned mackerel provides anywhere from 500-1000 mg of omega-3s depending on the source.  I typically serve wild salmon once a week in my household and then enjoy leftovers on a salad or with sautéed greens for one or two more days. I get additional servings from more economical sustainably caught canned fish.

In canned fish, look for either water or olive-oil packed and avoid soybean, canola, or sunflower oil (adds omega-6). Also watch for words like “sustainably caught,” fishing methods like “purse seine” that limit by-catch of other species, and ACS certification.

Eating just three servings of fatty fish a week is enough to support a healthy diet. Anyone who has had cancer or any chronic inflammatory disease may want to increase their consumption by adding supplements.  And as I’ll explain in an upcoming blog post, DHA appears to be most important for fighting cancer.

Maria’s Easy Sautéed Greens (or Salad Greens) with Fish

1. Heat a skillet at low-medium and add 1 tablespoon of extra virgin olive oil.

2. Sauté either a chopped clove of garlic or chopped onions for a few minutes until soft.

3. Add 2 cups of leafy greens such as kale, arugula, spinach, mustard, or chard and sauté for a few minutes then add a couple tablespoons of water and cover.

4. Steam for a few minutes then remove cover and cook until water is gone.

5. Turn off heat, season with salt and pepper, and mix in 3-4 ounces of omega-3 rich fish (first scraping dark matter from the bottom of the fillets).

6. Add a few splashes of balsamic vinegar, chopped Kalamata olives, chopped fresh or sun-dried tomatoes, and a couple teaspoons of pine nuts (optional, adds omega-6).

Notes: you can do the same thing with fresh greens and make a big salad. I often make extra portions of wild salmon during the week and use leftovers for salads or for sautés. If you eat dairy, soft goat cheese is a nice addition.

Omega-3s from Plants

Some nuts, seeds, and green leaves of wild plants contain an omega-3 called ALA that can be converted by specialized enzymes in our intestinal tract to EPA and DHA. Most humans have a limited ability to do this conversion, which is based on their individual genetics. I offer my clients Nutrition Genome, a test available to consumers to analyze this genetic marker along with many others that affect how we metabolize nutrients in our body. Interestingly, where our ancestors lived affects how our genetics have evolved to allow the conversion of plant omega-3 to EPA and DHA.  If your ancestors lived near water and ate fish, likely you can’t make the conversion, but if your ancestry goes back quite a ways to an area that was landlocked, you may be able to make the conversion because your genome has evolved to do it.

One thing all humans do well is creating an inflammatory state when we feed our bodies a lot of processed food, which is a common source of damaged omega-6s.

The Importance of the Omega-6 to Omega-3 Ratio

One term you may hear tossed around is the omega-6 to omega-3 ratio. This simply means the number of grams of omega-6 in your diet divided by the number grams of omega-3.  Typically this is computed on a daily basis.

Modern diets have been shown to be tipped in favor of omega-6 as much as 20:1, where the ideal diet is considered to be a 4:1 ratio or less. Cancer patients and anyone with a chronic inflammatory disease should strive for a ratio closer to 1:1.

You can simply look at the number grams of each of these types of fat in your diet by using an online tool like Self Nutrition Database or an app like Chronometer. Take care to look at the number of grams or ounces in a serving so that you compute the actual amount of the food you eat.  Even without doing these calculations, it's pretty easy to know if you are eating way too many omega-6s by taking a hard look at your diet.

A common misconception is that you can get all of your omega-3s from nuts and seeds. This simply is not true because most nuts and seeds also contain a lot of omega-6 even if they contain omega-3 ALA (for example, walnuts and hemp seeds).  Also, nuts that contain contain more monounsaturated fats and less omega-6 (for example, macadamia nuts) are actually a better choice to reduce omega-6 in your diet. Remember that seeds like chia and flax should be ground before eating or they may just travel on through your digestive tract without the fatty acids being absorbed.

Ironically, fish eaters can get away with more nuts and seeds in their diet than can non-fish eaters, vegetarians, or vegans. It’s important to look at the total amount of omega-6 and omega-3 you eat on a daily basis and strive for balance (somewhere between 4:1 and 1:1).  Sometimes supplementation makes sense.

How to Reduce Omega-6 in Your Diet

Where are omega-6s found? The main sources are nuts, seeds, and grains and the oils and butters made from them. The most concentrated sources are seed oils such as cottonseed, soybean, sunflower, or corn. Most restaurants cook with these oils and processed foods such as snack foods contain them—even the "healthier" versions.

It is easy to avoid eating too much omega-6 fat if you eat whole foods and avoid processed foods, using only extra-virgin olive oil, avocado oil, coconut oil, and butter or ghee in your cooking.  Increasing numbers of snack products are prepared with avocado oil or coconut oil.

With the shift toward low-carbohydrate and Ketogenic diets, many people have started substituting refined grains with more nut and seed butters and flours. While nuts and seeds offer an excellent combination of plant-based protein, fat, and fiber, they also have a high omega-6 content and are best enjoyed in moderation (a couple tablespoons or less per day) in the context of a diet that contains fatty fish and/or supplemental EPA/DHA.  

Nut and seed butters and flours concentrate a lot of omega-6 into a serving and are best used sparingly (for example, to coat fish or a couple teaspoons in a smoothie). Using a small amount of nut milk in a recipe or smoothie is ok as it only takes a couple tablespoons of nuts to make 2 cups of nut milk. Eating a palm-sized portion of nuts or sprinkling a couple teaspoons of chopped nuts on a dish are ways to enjoy nuts and seeds in moderation without overdoing the omega-6s. But bread or muffins made from nut flour or nut butter pack a huge punch of omega-6s.

Health Issues Associated with Eating Too Much Omega-6

In and of themselves, omega-6s are not all bad. In fact, we need a certain amount because they are essential fats and are essential to a normal inflammatory response to an injury or illness. But when omega-6s are eaten in excess, they are converted into excess inflammatory chemicals that can drive cancer and other chronic disease.

What's worse, both omega-3 (plant) ALA and omega-6 compete in our bodies.  When our diets contain an excess of omega-6, our bodies preferentially favor the inflammatory products from omega-6 and are even less able to convert ALA to either EPA or DHA.  So if you are relying on plant sources for omega-3, it's even more important to reduce omega-6 in your diet. If you have too much omega-6 in your diet, eating flaxseed won’t make much difference in your omega-6 to omega-3 ratio.

The “Good” Omega-6

One type of omega-6 called gamma-linoleic acid (GLA) is an exception: It is anti-inflammatory rather than inflammatory. GLA is also converted by our body to another anti-inflammatory fatty acid called DGLA, which boasts some impressive research for anticancer effects.

GLA is hard to find in our modern diet because it only comes from certain wild plants that we no longer eat, like borage. So supplementing is a good idea. Here's yet another example of how our ancestral genetics have not caught up to our change in eating habits.

The Role for Supplements

Taking an omega-3 supplement is another way to help improve your ratio. But not all supplements are high quality. With fish oil, look for the phospholipid or triglyceride form rather than the less bioavailable ethyl ester form used in cheaper brands. Reputable companies test their products for environmental toxins and contaminants like heavy metals and will provide a Certificate of Analysis for any lot of supplements they manufacture. This testing also should show peroxide, anisidine, and TOTOX values, which are a measure of oxidation.

Rancid fish oil is oxidized fish oil–and it is a health hazard rather than health promoting. Beyond looking at manufacturer testing, you can assess the quality of your fish oil simply by smelling it. “Fishy” fish oil is rancid and not fit for consumption. This can be harder to test with flavored capsules, so buying from a reputable company and paying attention to “use by” dates will help you choose a fresh product.

Fish oil supplements from Big Box stores, pharmacies, or grocery stores are likely to be poor quality. Often, cheaper fish oil supplements are “deodorized” with chemicals to cover up the fishy smell from rancid ingredients, or they use cheaper processing methods that yield a less bioavailable ethyl ester product.

Some manufacturers use only fish gelatin in their capsules, while others use beef gelatin.  You can find this information on the ingredient list.

Algae-based EPA/DHA supplements are an alternative for vegans or anyone who prefers to take a more ecological approach to their EPA/DHA supplementation, though these are typically more expensive. The same rules apply for freshness and contaminants with algae-based omega-3 oils as with fish oils. Rancid products are a hazard to your health!

Buy high-quality fish oil HERE (US only) or HERE Worldwide.

Personalizing Your Plan

We all have to find a balance between diet and supplements that works for us. While some may be perfectly happy to crack open a can of sardines every day, others may prefer to add an omega-3 supplement. One thing is clear: we all need to look at sources of omega-6 in our diet and reduce them. And we need to find ways to include more omega-3.

My writing on cancer nutrition is made possible thanks to clients who purchase professional grade supplements from my US Fullscript dispensary and worldwide at MCS Formulas:

Free access to my Fullscript discount supplement dispensary (button above) features a curated list of supplements for supporting integrative cancer protocols as well as for supporting overall wellness.

NEW: I now offer worldwide access to MCS Formulas. Use my Affiliate link (button above) and use the coupon code mariab5 to receive 5% off your order.