Q. Is there an optimal ratio of polyunsaturated, monounsaturated, and saturated fats that you’d recommend for optimal health?
A. Interesting question, and any answer I give will be controversial, but I certainly don’t mind getting the conversation started! (If you need a refresher, here’s a quick rundown of the different types of fat and which foods they are found in.)
Here’s how the typical American diet (which, one could argue, is clearly not optimal) breaks down, with fat taking up 34% of total calories.
Should We Eat More Monounsaturated Fats?
The traditional Mediterranean diet features a significantly higher percentage of MUFAs. Not only that, but it’s also relatively high in total fat, with about 40% of calories coming from fat. And yet, the Mediterranean diet is not only heart-healthy, it is also correlated to lower rates of obesity. In fact, some researchers argue that MUFAs might even be less “fattening” than other types of fat because of they are more likely to be burned and less likely to be stored. In her book, The Omega Diet, researcher Artemis Somopoulos, MD, proposes the following “ideal” mix of fats.
Should We Eat Less Saturated Fat?
Perhaps the biggest area of controversy is saturated fat. The 2010 Dietary Guidelines for Americans recommends limiting saturated fat to no more than 10% of calories and we’re almost there–averaging about 11% of calories from saturated fats.
However, many question whether limiting saturated fat is really necessary. After all, a 2010 meta-analysis published in the American Journal of Clinical Nutrition found that people who ate less saturated fat were just as likely to have heart disease as people who ate more.
However, as researchers from the Harvard School of Public Health pointed out, it really depends on what you replace those saturated fats with. Those who cut back on saturated fats and replaced those calories with refined carbohydrates (low-fat cookies, for example) or hydrogenated oils (margarine, for example) may have jumped from the frying pan into the fire in terms of heart-damaging ingredients. On the other hand, those who cut back on saturated fats and replaced them with PUFAs did enjoy a 20% reduction in their heart disease risk.
See also this post from my (discontinued) blog on NutritionData.com: Is Saturated Fat Back on the Hook?
How Essential Are Polyunsaturated Fats?
For the most part, the Dietary Recommendations lump MUFAs and PUFAs together as being “preferable” sources of fat. However, there are two “essential” fatty acids–meaning that the body cannot manufacture them and must get them from dietary sources. Both are PUFAs.
According to the National Academy of Sciences, adults need to consume at least 12 to 17 grams of linoleic acid (an omega-6 fat) and a minimum of 1 to 2 grams of alpha linolenic acid (an omega-3 fat) a day. For a diet that gets 30% of total calories from fat (the midpoint of the NAS’s recommended range of 25-35%), a diet that follows the Dietary Guidelines would look something like this:
I’m sure I don’t need to point out, however, that the Dietary Reference Intakes are merely intended to keep most people out of trouble. ”Adequate” is usually a far cry from ”optimal.”
The Omega Ratio
The only area where there is serious talk of optimal ratios, of course, is between the two major types of PUFAs: Omega-3s and Omega-6s. Although the Dietary Reference Intakes that I mentioned above imply a 10:1 ratio between Omega-6 and Omega-3, most believe that a lower ratio would be far preferable. The hard core aim for a 1:1 ratio; more moderate or pragmatic folk might settle for something like 4:1.
Given the modern food supply, maintaining a low ratio of omega-6 to omega-3 fats can be pretty challenging, especially if you don’t eat a lot of fish. Pounding fish oil is one way to do it. Limiting your intake of omega-6 (found in vegetable oils and foods made with them) is another.
See also this episode of my podcast: Fish oil and omega 3s
Is There an Answer in Here Somewhere?
As I’m sure you’ve probably realized by now, I can’t really give a one-size-fits-all answer to this question. For one thing, we don’t live on fat alone and the choices you make in the rest of your diet will have an impact here. For example, as I have observed in the past, people whose diets are very low in refined carbohydrates can often sustain a high intake of saturated fat without an increase in heart disease risk factors. Vegans, on the other hand, usually have higher carbohydrate intake but lower saturated fat intake–another equation that appears to be heart protective.
Personally, olive oil is my primary source of fat, with butter and dairy products in the #2 slot, followed closely by nuts, which I eat virtually every day. Other regular but not daily sources of fat include eggs, olives, avocados, fish, meat, flax and other seeds. I’d guess my omega ratio to be somewhere in the neighborhood of 2:1. My pie chart usually looks something like this, with fats at about 35-40% of total calories.
I’m not saying my diet would be optimal for everyone, of course, but it works well for me. And (full disclosure) when it comes to food, I’m balancing more than just nutrition. As I wrote in the introduction to my book, Secrets for a Healthy Diet:
“When it comes to diet, I am neither purist nor perfectionist. The fact is, very few of us make food choices based on nutrition alone. We are also influenced by taste, cost, availability, convenience, and habit. If you’re also trying to balance things like environmental impact, social and animal welfare, religious beliefes, and other factors, you’ll frequently have to pick your priorities….”
Fortunately, we humans appear to be fairly flexible, with the ability to thrive on a variety of dietary patterns. What’s more, we are extremely varied organisms and don’t all respond identically to the same inputs. Although it’s clearly possible to kill yourself with food (just look around you), I don’t believe there is just one “optimal” prescription for the human diet.