Grilled tuna steaks with cantaloupe salsa

Fresh off a few days in the midwest and a very satisfying diet of airport food, hot dogs, beer, and Dairy Queen, went back on the wagon last night with this recipe for grilled tuna and cantaloupe salsa. Super easy and delicious; could try this with honeydew melon and maybe a little pineapple. Tuna's a little pricey, but this would work well with swordfish or something similar...

Grilled tuna steaks with cantaloupe salsa

3/4 cup coarsely chopped cantaloupe
1/4 cup chopped onion
2 tablespoons chopped fresh cilantro
4 teaspoons olive oil
1 tablespoon fresh lime juice
1 teaspoon minced seeded jalapeño chili

2 5- to 6-ounce fresh tuna steaks (about 1/2 inch thick)

Prepare barbecue (medium-high heat). Mix cantaloupe, onion, cilantro, 2 teaspoons oil, lime juice and jalapeño chili in small bowl. Season salsa to taste with salt and pepper. Let stand 15 minutes.

Meanwhile, brush tuna steaks on both sides with remaining 2 teaspoons olive oil and sprinkle with salt and pepper. Grill tuna until just opaque in center, about 3 minutes per side.

Transfer tuna to plates. Spoon salsa alongside and serve.

Is the omega-6:omega-3 ratio of beef relevant?

Although it's still debatable what the optimal dietary ratio of omega-6 to omega-3 fatty acids is, there's good evidence that the contemporary dietary intake of polyunsaturated fatty acids has over time become heavily skewed towards a higher intake of omega-6 than omega-3 fatty acids (Cordain et al., 2005; Simopoulos, 2002). The current US diet is estimated to have a omega-6:omega-3 ratio between 10:1 to 12:1, while Cordain and colleagues estimate a ratio of between 2:1 and 3:1 for a traditional hunter-gatherer diet. There is growing consensus that reducing the omega-6:omega-3 dietary ratio may reduce the morbidity and mortality associated with a wide range of metabolic disorders.

This is all well and good, but ratios can be misleading and it's important to keep in mind the absolute mass of fatty acids consumed (Mozaffarian & Rimm, 2006; Wijendran & Hayes 2004). Case in point: one of the purported benefits of grass-fed beef is that grass-fed beef has a better omega-6:omega-3 ratio than grain-fed beef. This is also one of the reasons that wild-caught salmon is recommended over farm-raised salmon. What do the actual data look like? The table below shows the fatty acid profiles of the aforementioned meats.


A few things to note. First, the total PUFA content of grass and grain-fed beef is pretty low. Second, grass-fed beef only contains marginally more omega-3 fatty acids than grain-fed beef. This, together with a marginally lower omega-6 content results in a slightly lower omega-6:omega-3 ratio for grass-fed beef. In addition, the two samples of grain-fed beef are very similar in most respects, but one sample has an omega-6:omega-3 ratio of >17 while the other is <5. Does that mean one is healthier to eat than the other? Not in any meaningful way, looking at the ratio alone is misleading since it conceals the fact that this difference is due to a mere 30 mg of omega-3 fatty acids. To get a sense of how small that is, recall that current recommendations for daily omega-3 intake are over 2000 mg (ALA+EPA+DHA). The absolute amount of omega-3 fatty acids derived from beef is just too small, regardless of whether it is grass or grain-fed. A one pound steak only has between 70-225 mg of omega-3 fatty acids (most of which isn't the more beneficial marine omega-3s, EPA and DHA). Compare this to the amount of omega-3s you get from either wild-caught or farmed salmon. So while it's true that the omega-6:omega-3 ratios are lower for grass-fed beef, a look at the absolute masses of the separate fatty acid classes suggests that this isn't really practically relevant.

Now don't get me wrong, there are many other benefits of grass-fed beef. If money weren't a constraint, I would eat it all the time. However, I don't think that the omega-3 content of beef should be a factor when deciding whether to buy grass-fed over grain-fed. If you want to improve your omega-6:omega-3 dietary ratio, you would do better to eat more seafood and reduce your intake of vegetable oils.

Watch that tuna intake

You may be surprised by the mercury levels found in tuna in NYC. Seem to be a bit higher than I expected. Gotta start shopping at Fairway!

Get fat!

Good fats of course, those being ω-3 fatty acids (a type of polyunsaturated fatty acid [PUFA], another being the ω-6 fatty acids; these are also referred to as n-3 and n-6 fatty acids). Members of these families are derived from the essential fatty acids linoleate (LA) and α-linolenate (LNA). Strictly speaking, these two are the only essential fatty acids (required through diet), although that term is often extended to the entire family of PUFAs (Cunnane, 2003). The ω-3 and ω-6 fatty acids are critical for a host of bodily functions, which you can read about in reviews by Das (2006) and Wijendran and Hayes (2004). Very roughly speaking ω-6 fatty acids are pro-inflammatory whereas ω-3 fatty acids are anti-inflammatory. More specifically, the ω-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are antithrombotic and antiarryhthmic, and dietary intake of these fatty acids is associated with reduced risk of death from cardiovascular disease.

Source: Mozaffarian and Rimm 2006.

Although current evidence indicates that the relative dietary ratios of ω-3 and ω-6 fatty acids is a indicator for overall health (Wijendran and Hayes 2004; Simopoulos, 2002), the mechanisms by which EPA and DHA reduce the risk of cardiac mortality remain unclear. The assumption is that direct incorporation of these fatty acids into the myocardium of the heart underlies their health benefits. That dietary intake directly modulates myocardial phospholipid profile was recently documented by Metcalf et al. (2007). The authors examined the atrial tissue of people undergoing elective cardiac surgery following varying durations of dietary supplementation with fish oil (6 g EPA+DHA/day, for 7-60 days). They found that fish oil supplementation increased the amount of EPA and DHA in the cell membranes of both atrial tissue as well as red blood cells.


It has been proposed that the cardioprotective effects of EPA and DHA result from replacement of arachidonic acid (AA) in cardiac membranes. AA is a precursor of a wide array of eicosanoids (Funk, 2001). These compounds promote inflammatory responses, platelet aggregation, and vasoconstriction. Although these are essential metabolic functions, excess AA-derived eicosanoids can promote atherosclerotic disease and thrombosis.

Source: Calder 2006.

Metcalf et al. also showed that dietary fish oil supplementation reduced atrial AA concentrations, consistent with the idea that part of the benefit of EPA and DHA may be due to the reduction in AA-derived pro-inflammatory factors.


These phosphospholipid adaptations in atrial tissue may thus underlie the cardioprotective effects of dietary fish oil. In support of this, the timescale and magnitude of these changes is broadly consistent with the observation that the protective effects of ω-3 fatty acid supplementation begin early, but reach significance only after about three months.

Source: Marchioli et al. 2002.

Also of note is the fact that supplementing with flaxseed oil (high in ALA) did not result in any changes in ω-3 fatty acid concentrations. This is likely due to the fact that dietary ALA is converted to EPA and DHA at extremely low rates (Plourde & Cunnane 2007), which is consistent with suggestions that ALA supplementation is not cardioprotective (Matthan et al. 2005; Wang et al. 2006).

Saturday round-up

Nice post on freezing fish. Maggie's mention of flash-frozen fish prompted me to buy several pounds of fish to try out; it's a hell of a lot cheaper than fresh fish but I'm skeptical that it will taste as good. Check out the rest of the blog (Atom feed), it's pretty informative and amusing (e.g., great photo tutorial on cooking whole fish and all of these amazing recipes).

What the world eats (TIME photoessay). Click the link or the photo to go see the whole series. It's really neat. This is my favorite:
Here are links to some articles about diet/disease/health that have caught my attention:

Some novel hypotheses from Frank Booth here and here. The cycling hypothesis is interesting, particularly so in light of the recent work by Mattson on caloric restriction and intermittent fasting. Background reading on paleolithic and hunter-gatherer diets can be found here. A discussion specific to dietary levels of protein can be found here.

My current macro-breakdown according to

"Keep an open mind, but not so open that your brain falls out"
- Richard Feynman