O3I: your index of health

Focus on omega-3 and 6 fats

Why are the right dietary fats so vital for health and performance? Well, fatty acids are essential components of cells, crucial for creating an optimal environment for membrane protein function. In particular, the quantity and type of unsaturated fats in cell membranes determine how fluid the membrane is, how efficiently cells can signal and the overall cellular function⁽³⁾. Therefore, consuming the right types of dietary fats in the right ratios is critical for health.

Beyond that however, intense physical activity and sport training is known to lead to metabolic changes in the utilization of fats as energy sources and the mobilization of fat reserves in adipose tissue, and the transport of lipids between organs and tissues⁽⁴⁾. Long-term and intense physical training can lead to changes in cell membrane composition, particularly in the ratio of long-chain omega-3 and omega-6 polyunsaturated fatty acids, which in turn impacts cellular processes and physiological functions^(5,6). And as we will see shortly, when the ratio of omega-3 to omega-6 fats in cell membranes tips too far in favour of omega-6 at the expense of omega-3, this can have a detrimental impact on health.

Box 2: Omega-3 and muscle function

Before we go on to look at the ratio of omega-3 to omega-6 in cell membranes, it’s worth mentioning that omega-3 fats have a special relevance to athletes. That’s because evidence has begun to accumulate that the long-chain omega-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) – see box 1 - play an important role in muscle protein synthesis and overall skeletal muscle health.

As we explained in a recent SPB article, it turns out that when EPA and DHA are taken up into muscle tissue, they are able to help activate anabolic signalling proteins that are known to regulate muscle protein synthesis(7). In other words, they appear to help ‘switch on’ signals that instruct muscle cells to take up amino acids and incorporate them into muscle proteins. Good evidence for this comes from a study on fish oil supplementation (a superb source of EPA and DHA) in healthy young and middle-aged men and women⁽⁸⁾. This supplementation led to enhanced activation of a key signalling pathway known as ‘mTOR-p70s6k’, which in turn led to a 50% increase in muscle protein synthesis. Another study on resistance-trained young men demonstrated that EPA/DHA supplementation boosted the anabolic response produced compared to just feeding protein alone⁽⁹⁾.

More generally, consuming EPA/DHA may positively influence several other mechanisms involved in resistance-training adaptations. These enhanced mechanisms include factors such as muscle fiber type transition, enhanced neurological recruitment of muscle fibers, reduced muscle protein breakdown, improved insulin signalling (helping amino acids to be taken up into muscle cells), enhanced muscle cell membrane function and the correct regulation of inflammation following training^(10-12).

Omega-3 to omega-6 ratios and inflammation

As we suggested above, when the ratio of omega-3 to omega-6 fats in cell membranes tips too far in favour of omega-6 at the expense of omega-3, there are negative impacts on health and performance. To understand this, it’s important to appreciate how the metabolism of omega-3 and omega-6 oils in the body differs. Without delving too deeply into complex biochemistry, we can summarize this difference in terms of inflammation and inflammatory processes; the metabolism of omega-6 fats leads to intermediate compounds that can stimulate inflammatory processes in the body, whereas the metabolism of omega-3 fat leads to intermediate compounds that tend to dampen down inflammatory processes in the body (see figure 1). While the body requires both omega-3 and omega-6 fats to function, an excessive intake of omega-6 and insufficient omega-3 intake can promote chronic inflammation, which is associated with a number of diseases, particularly cardiovascular disease⁽¹³⁾.

Figure 1: Omega-3 and -6 intake and inflammation

Omega-3 and omega-6 fats are both required for human health. However, the metabolism of omega-6 (red pathway) produces intermediates that promote inflammation, while the omega-3 intermediates tend to dampen down inflammatory processes. The anti-inflammatory properties of omega-3 fats are thought to be due to EPA’s inhibition of eicosanoid synthesis from the omega-6 intermediate known as ‘arachidonic acid’(14). A relative excess of omega-6 intake compared to omega-3 therefore is associated with chronic inflammation, which can lead to degenerative diseases such as heart disease.

The omega-3 index

The importance of the right ratio of omega-3 to omega-6 in cell membranes has led to the development of the ‘omega-3 index’ (sometimes abbreviated (O3I). This index is defined by the amount of the two important omega-3 fatty acids EPA and DHA in red blood cell membranes expressed as a percentage of the total lipids (fats) in the red blood cell membrane. The recommended protective level score in O3I is approximately 8%, while omega-3 levels below 4% are linked to a higher risk of diseases such as cardiovascular disease (see figure 2).

Figure 2: The omega-3 index

In practical terms, the omega-3 index is calculated by taking a blood sample from the fingertip, using a simple pin-prick method and letting it dry to a spot. The dried blood is then chemically analyzed to measure the ratio of omega-3 fats to all other lipids. The O3I is considered reliable and suitable as a test of omega-3 status because it is not affected by day-to-day fluctuations in omega-3 or other fat intake⁽¹⁵⁾. That’s because it takes time for new red blood cells to form and take up fats into their cell membranes, which means your O3I score is a reflection of your long-term dietary intake (weeks and months) of omega-3 and other fats, and will also reflect overall omega-3 concentrations in the body.

The omega-3 index matter and athletes

Although the omega-3 index was developed principally in the context of research into nutrition, health and disease, it is also relevant for athletes. It’s not just that athletes are (or should be!) mindful of short and long-term health, but also that an athlete’s omega-3 status is likely to impact his or her performance. 

In a new study on this topic published recently in the Journal of Functional Morphology and Kinesiology, a team of Italian scientists have reviewed the data on omega-3 nutrition and the use of the omega-3 index in relation to athlete health and performance⁽¹⁶⁾. In this study, they point out that various factors, including training intensity and volume or bodyweight, can impact the omega-3 index scores for athletes, and that the consensus of existing data is that the recommended O3I target range for athletes is in the region of 8–11%⁽¹⁷⁾.

Based on the data they reviewed, the researchers went on to discuss a number of aspects in relation to athletes, their omega-3 nutrition and their O3I scores. The key recommendations that emerged as a result were as follows:

·        Cardiovascular health in athletes – Numerous studies have suggested O3I as a valuable clinical biomarker for assessing cardiovascular risk, even in athletes, due to its strong correlation to EPA and DHA levels in cardiac tissue. Unfortunately, studies examining the dietary habits of athletes have shown that most do NOT meet the recommended intakes levels for EPA and DHA. Examples include a study of 404 Division I football players, which found that none had an O3I above 8%⁽¹⁸⁾, and another study which found that almost all of the 106 German elite winter endurance athletes studied had a low O3I⁽¹⁹⁾!

·        Omega-3 and injury – Because DHA/EPA exert anti-inflammatory effects and inflammation is a major factor following injury, there’s good evidence that optimizing EPA/DHA intakes can help prevent or at least ameliorate the effects of injury. Since studies have demonstrated that positive changes in omega-3 status can reduce traumatic brain injury effects caused by impacts, and that a reduction in DHA levels in the brain occurs as a result of traumatic brain injury (leading to slower recovery of motor function), it is perfectly logical and recommended that athletes whose sports involve impacts and collisions should ensure they maintain an ideal O3I score (8+)^(20,21). The same is true for athletes suffering chronic injuries involving inflammation. Studies show that in rotator cuff tears of the shoulder, a lower O3I index is associated with a greater risk of injury⁽²²⁾. In recreational runners, higher O3I values are associated with a decreased risk of running-related injuries in recreational runners, while runners with an O3I score of under 4% are at increased risk of injury⁽²³⁾.

·        Omega-3 and sport performance – As we hinted at earlier, a growing body of evidence suggests that an optimum omega-3 status can directly and positively impact sports performance. In particular, studies show that omega-3 supplementation and the consequent O3I score increase can enhance athletes’ adaptation to training, thereby improving sports performance and supporting post-exercise recovery^(24-26). In the review study conducted by the Italian researchers mentioned above, there is robust evidence that a better O3I score via supplementation or diet or both can improve strength and power, endurance performance and mitigate exercise induced fatigue. For a summary of this evidence, readers are directed to table 1 on page 5 of the study PDF. Athletes should also be aware that this evidence also suggests increased training volume and intensity reduces O3I scores. In plain English, the longer and harder you train, the more omega-3 you need!

·        Supplementation of omega-3 – Given the benefits of omega-3 and ensuring an optimum omega-3 index score, the consensus is that athletes can benefit from supplementation, especially when the diet does not contain plenty of oily fish (salmon, sardines, mackerel, herrings, trout etc). The current recommendations from recent studies are that athletes should supplement 2-6 grams per day of fish oils rich in EPA/DHA, with higher doses helping to improve omega-3 index scores more rapidly^(27,28). At higher supplementation levels, desirable O3I scores (over 8%) can be achieved in athletes in only eight weeks⁽²⁹⁾. Even better, studies on a range of athletes, from recreational athletes to professional soccer players, has found that as little as five weeks of supplementation with EPA/DHA is sufficient to improve key markers of cardiovascular health and provide cardio-protective effects^(30-32).

In summary

Of all the nutrients essential for good health and performance, the omega-3 oils EPA and DHA are probably the least appreciated - not just among the general population, but among health professionals too. Athletes are also likely to be unaware of the importance of these nutrients and maintaining a good O3I score. That’s partly because omega-3 oils are not considered ‘sexy’ within the athletic community and also because athletes in training have higher omega-3 needs.

Unless your diet is especially rich in omega-3 oils (eg you eat fatty fish 2-3 times per week), the chances are that your O3I score will be below the optimum 8-12%. Of course, you can remove any uncertainty by taking an O3I test. Home test kits are available online for under $100, and all that is required is a simple finger pin prick to collect a drop of blood, which is allowed to dry on a swatch, and then mailed back to the lab.

If after taking a test, you find your score is below optimum, the best strategy to bring it up to optimum is to supplement with omega-3, while increasing your intake of dietary fatty fish and other good sources of omega-3 such as walnuts, and pumpkin seed. If you like salmon and can get hold of unfarmed salmon, so much the better. Remember too that there’s something of an omega-3/omega-6 seesaw; given that omega-6 metabolism increases inflammatory intermediates, you should aim to increase omega-3 intake while ensuring your omega-6 intake is curtailed. In reality this means not using polyunsaturated oils and spreads (such as sunflower, rapeseed etc) and instead switching to cold-pressed olive oil and butter.

Regarding supplements, most athletes can benefit from taking 2 grams per day of omega-3 oil that is rich in EPA/DHA. For those who eat no fatty fish, this can be increased to 3 or 4 grams per day. If an O3I test shows your status is low, higher doses of 4-6 grams per day of omega-3 will bring it up more rapidly. Remember though that it takes many weeks or even months to raise omega-3 levels within cells, so regarding this as a long-term strategy rather than a quick fix!

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