Having looked at a few key micro-nutrients (iron, zinc, B12, calcium) in What are Good Sources of Protein – Micronutrient Content, I want to move towards the wrap up of this series by looking at another issue of importance in choosing protein sources. That issue is the dietary fat content.
Now, without going into a lot of detail, but due to some more ‘fringe’ nutritional groups in the Internet, I suspect many will disagree with this article. The reason is that some groups have decided that 40 years of nutritional research is flawed and biased, that the current beliefs about fatty acid intake and health are exactly the opposite of the truth, etc, etc.
When and if I ever bother to address such points (it’s usually about as useful as responding to the anti-milk people), I’ll go into more detail about this. For now, I won’t except to say that I find both extremes of the argument to be flawed.
Saturated fat isn’t the killer nutrient that some make it to be, nor is it healthful and beneficial; the truth, as always lies in the middle and whether a high fat intake or a particular type of fat is good, bad or indifferent depends on the context. The rest of the diet, activity, body-fat stress, etc. all determine what is good, bad or otherwise. For more details, I’d refer readers to my two part article Carbohydrate and Fat Controversies where I go into detail as to my take on a lot of this argument.
And with that out of the way, let’s get started.
A Primer on Fats with a Bit on Cholesterol
There is often a lot of confusion regarding the issue of dietary fat not the least of which is a common misunderstanding between the issue of dietary cholesterol and dietary fat. Simply, cholesterol and dietary fat are completely distinct chemical compounds. The confusion, mind you, came out of the early research dealing with diet, dietary cholesterol, dietary fat intake, and blood cholesterol levels.
There’s a lot of confusion in this regards but this article isn’t the place to clear it up; at some point in the future, I’ll do a full feature article or series about dietary fats, for now you get the short version.
Dietary cholesterol is only found in products of animal origin and is completely chemically distinct from dietary fat in terms of the molecular structure. Without going into immense detail, the intake of dietary cholesterol really isn’t a big deal outside of a small subsection of folks who appear to be sensitive to it. So I won’t say more about it here.
Rather, I’ll focus on dietary fats. Dietary fats are more accurately called triglycerides which refers to the fact that each molecule is made up of a glycerol backbone attached to three fatty acid chains. It’s the fatty acid chains that are of interest as their chemical structure determines not only what the fatty acid is called but what effect it has on the body. There are four major categories of triglyceride which are
Saturated fat: these are found almost exclusively in animal products (with a couple of exceptions), are generally solid at room temperature and are generally blamed (somewhat unfairly) for a lot of health problems, especially increased blood cholesterol levels. And while some saturated fats certainly do raise cholesterol levels, others have no real effect.
Unsaturated fats: Unsaturated fats are typically liquid at room temperature and tend to be found to some degree in most foods that contain dietary fat; quite in fact, red meat (which is usually thought of as a major source of saturated fat) and eggs both contain a majority of their fat as unsaturated fat. In general, unsaturated fat is fairly neutral metabolically.
Polyunsaturated fats: Polyunsaturated fats are also liquid at room temperature and found in foods of vegetable origin. Polyunsaturated fats comes in two primary types: omega-6 and omega-3 fatty acids. Many readers are probably more familiar with the omega-3 (or w-3) fatty acids as fish oils.
As a generality, the w-3’s have extremely positive effects on health; an excess of w-6 has been thought to cause some health problems (especially in the context of insufficient w-3) although recent research is starting to question this. I realize that this last statement is a bit confusing but I don’t have space to explain it here. Since omega-6 fatty acids are found primarily in vegetable source foods, they really aren’t that critically relevant to an article on protein.
Trans-fatty acids: Along with high-fructose corn syrup, trans-fatty acids are a favorite whipping boy of people who want simple explanations for the complexities of modern health problems. Trans fatty acids do occur naturally in foods (a point missed by many of the anti-trans fat crusaders) but the majority realistically come from prepackaged man-made foods. Trans-fatty acids are made by bubbling hydrogen through vegetable oils, this produces a fat that is chemically modified but incredibly shelf-stable.
Good for food companies, maybe not so good for human health. A question is just how much trans-fatty acids the average diet will actually contain; of course this will depend on how much of those foods are eaten. Since trans-fatty acids don’t occur in massive amounts in most whole protein foods, I’m not going to mention it further.
There are also some odd fatty acids that are occasionally encountered. Medium chain triglycerides (MCT, so named because of their medium length) are found naturally occurring in some foods, as is conjugated linoleic acid (CLA).
I’m not aware of any protein source that contains significant MCT (coconut, of all things, is has about 50% of its fat as MCTs) so I won’t talk about it in any more detail. CLA is found in dairy products in small amounts. I’d note that most human research on CLA hasn’t been terribly positive; the fat loss effects seen in animals rarely show up and some data has found that CLA can cause insulin resistance. The amounts found in most foods are pretty tiny anyhow so it’s likely to be fairly moot; I bring it up only for completeness.
And with that introduction out of the way, I want to talk about the issue of dietary protein and dietary fat in terms of answering the question what are good sources of protein.
The Fat Content of Protein Foods
As with the issue of micro-nutrients, the presence or absence of dietary fat (either in terms of the quantity or quality) can impact on the choice of protein source. And this actually turns out to be a place where dietary fat content can vary massively, not only between protein sources but between different sources of the same protein.
As a singular example, while very lean red meat containing no more than 4 grams of dietary fat per 4 oz serving can be found at many stores (we get ours at Wal-Mart), it’s equally possible to find cuts of red meat that contain 20-30 grams of fat in that same 4 oz serving; a 6 to 8 fold difference. Other protein sources can show similar variance. I’d note that while isolated protein powders are typically extremely low in fat, this isn’t universal; there is actually a whole-egg protein that contains quite a bit of dietary fat, it’s quite creamy tasting.
With that said, I want to look at various whole food protein sources and how their fat intake might impact on whether or not they make a good protein source.
As mentioned, the fat content of red meat can vary massively. And while many have the idea that red meat is primarily a source of saturated fat, a quick look at the USDA database shows this to be false. Perhaps half of the fat content of beef is saturated with most of the rest being unsaturated, with a small amount of polyunsaturated fat usually present. I’d note that grass fed beef can actually have a better fatty acid profile than this.
Like beef, the fat content of fowl can vary dramatically. Cuts such as the thigh can contain quite a bit of fat while a skinless chicken breast may be essentially fat free. The fatty acid profile is similar to meat meaning that, while there is some saturated fat, the majority of the fat is actually monounsaturated with a small amount of polyunsaturates present.
Generally speaking, pork products are often high in fat; this can be especially true for prepackaged lunch meats (I’d note that low-fat ham is fairly readily available). A notable exception is pork tenderloin which is about as low-fat as the leanest chicken breast. Tasty, too.
Whole eggs contain a moderate amount of fat, typically 5 grams in a single whole egg. I’d note that the white of the egg is essentially fat free and many fat-obsessed athletes have gone the egg white route for this reason. It’s worth nothing in the context of protein quality that while whole eggs have an extremely high quality rating, egg whites are not so good. It’s also worth noting that, Rocky movies notwithstanding, egg whites appear to be digested terribly. That’s in addition to any potential issues with salmonella poisoning. Cook your eggs before you eat them.
Now, eggs have been in a weird place nutritionally since the early ideas about blood cholesterol, many felt that due to the high cholesterol content (note again that dietary cholesterol has, at most a minimal impact on blood levels anyhow); if anything the saturated fat content of eggs was the bigger issue. At the same time, whole eggs are an extremely high quality protein and other nutrients in the eggs can be quite beneficial.
As it turns out, a lot of the scare over whole eggs turns out to be false, while a small percentage of people are sensitive even the American Heart Association has removed it’s recommendations to limit egg intake. Clearly individuals trying to limit total fat intake may still wish to limit eggs (or make egg related dishes with a mixture of egg whites and fewer whole eggs).
Like red meat, while a portion of the total fat in eggs is saturated, nearly half is monounsaturated with the remainder being polyunsaturated. I’d note that, recently, high omega-3 eggs have become available, these are made by feeding chickens large amounts of omega-3 fatty acids which changes the fatty acid profile of the egg.
I’d also note that, in the big scheme of things, unless someone is eating a tremendous number of eggs, obtaining a significant amount of w-3 in this fashion tends to be a losing proposition; it would be cheaper to eat normal eggs and take supplemental fish oils.
Like the other foods listed, the fat content of fish can vary massively. Low fat fish such as tuna is essentially fat free (hence it’s popularity with athletes) while higher fat fish such as mackerel can contain perhaps 12 grams of fat per 3 oz serving.
However, of some interest, and as the names suggest, fatty fish tend to be an excellent source of the healthy omega-3 fish oils. Quite in fact, much of the interest in the omega-3’s came out of the observation that ethnic groups such as the Alaskan Inuit had low levels of heart attacks yet consumed a lot of oily fish. Fatty fish contain quite a bit of monounsaturated fats (about half of the total) with a small amount of saturated fat as well.
However, the reality is that, in my experience at least, most don’t care for the fattier fish and trying to obtain a sufficient daily dose of omega-3 fish oils is probably unrealistic (I realize this comment is biased by my living in the United States where we just don’t eat those kinds of foods). It can be done but I don’t know, practically, how realistic is.
Like the other foods discussed, the fat content of dairy foods can vary massively. Non-fat dairy foods are essentially fat-free (perhaps 0.5 grams fat per 8 oz serving) while whole-fat dairy can contain up to 8 grams of fat per 8 oz serving, 1% and 2% dairy products some in between those values. The fatty acid profile of milk is actually predominantly saturated with a small amount of monounsaturated fat and a very small amount of polyunsaturated fat.
As noted above, milk appears to contain a small amount of the fatty acid CLA; while this has shown impressive anti-cancer and fat loss effects in animals, these effects have not been seen in humans. Even if CLA were valuable to humans, it would generally take supplementation to reach significant intake levels.
Beans and Nuts
Although not often thought of as protein foods, beans and nuts can actually provide some protein to the human diet. And while most beans (tofu is a notable exception) are extremely low in fat, nuts can contain quite a bit of fat. However, a majority of the fat in nuts tends to come from the healthier monounsaturates and polyunsaturates. For example, a 2 oz serving of peanuts contains roughly 12 grams of fat of which nearly half is monounsaturated and most of the rest is polyunsaturated; the saturated fat content is very small.
And while the high-fat content of nuts might predict that they could cause problems with weight gain, as I discussed in the Q&A on Nut Consumption and Body Weight, the consumption of nuts doesn’t appear to have negative effects on body weight as a general rule.
Although they are technically a bean, soy tends to have enough issue surrounding it to deserve it’s own specific mention. Most of the issue having to do with soy have to do with the phytoestrogen content. Detailing this is far beyond the scope of the article although I spend quite a bit of time on the topic in The Protein Book.
Unlike most beans, soy can contain some fat, a half block of tofu for example contains just under 7 grams of fat with about half of that coming from polyunsaturated sources, the remainder comes from an even split of saturated and monounsaturated fat.
So, following up from Monday’s article What are Good Sources of protein – Micronutrient Content, I’ve now looked at the issue of fat content. Without going into detail, there are four primary types of fat in the human diet which can have quite varying effects on human health.
Saturated fats tend to be thought of as negative although the reality is far more complicated than this, monounsaturated fats are fairly neutral and the polyunsaturated fats are generally thought of as healthy (this is complicated by the fact that w-6 and w-3 fatty acids have distinct effects on the body and too much of one or the other can cause health problems). Trans-fatty acids are man-made fats (primarily) that tend to have only negative health impacts; since they are not found in protein foods to a significant degree, they aren’t that relevant.
The fat content of most protein foods tends to vary dramatically. While nearly fat-free versions of most foods are available, many cuts or types of protein can be exceedingly high in fat. In that high-fat diets can certainly be one contributing factor to overweight, the fat content per se of protein foods is worth considering when deciding on what are good sources of protein. Individuals trying to limit fat intake, need to choose proteins sources (or types of protein within a given category) that do not contain excessive fat.
In addition, there is the issue of the type of fat present, the fatty acid profile of the food affecting how a given food might impact on the body. In contrast to many long-held beliefs, most meat proteins are not as high in saturated fat as most people perceive. Rather, the predominant fat is typically neutral monounsaturated fat; most of those foods also contain some proportion of polyunsaturated fat as well.
Fatty fish is an exception to the above as it tends to contain a significant amount of polyunsaturated fat including the healthful omega-3 fish oils. Foods such as eggs, dairy, beans/nuts and soy all weigh in at different places on this spectrum as well, as discussed in the article.
Ok, we’re getting close to the end of this series. I’m going to use the next article as sort of a catch-all to cover any issues I haven’t discussed previously regarding different protein sources. I’ll finish up by providing an overview of this series to finally answer the question what are good sources of protein.