Omega-3 and omega-6 fats

The health effects of omega-3 (n-3) and -6 (n-6) fats is an active and controversial area of research. The mainstream idea is this battle between n-6 and n-3 fats, where n-6 fats are the villain and n-3s play the role of the hero. N-6 fats supposedly cause inflammation, and n-3 fats are anti-inflammatory.

After reading dozens of papers on this, it’s clear that there’s more to the story, and that the mainstream view is grossly oversimplified.

TL;DR

You don’t need to worry about n-3 and n-6 foods. There’s good evidence to show n-6 fats are not the boogeyman they are made out to be. Eating whole foods that have a lot of n-6 fats does not cause inflammation or lead to health problems – contrary to many popular articles claiming so.

There’s no point to try to balance the n-3 and n-6 fats in your diet. Focusing on the ratio distracts you from what’s important; getting enough of the long-chain omega-3 fats found in fatty fish and seafood.

Simple dietary recommendations to live by:

Do your best to minimize vegetable and processed oils in your diet. There’s some data to show that eating less LA can make EPA and DHA more effective. And that’s why I believe there’s no point in having concentrated LA sources in your diet.
Make sure you get long-chain omega-3 fats from your diet. Good sources include fatty fish, seafood, and omega-3 enriched foods, like omega-3 enriched eggs.
I would not worry about omega-6 rich whole foods, like nuts, seeds, and meat.

Inflammation, heart disease, and mortality

Countless studies have been done on the relationship between dietary n-6 intake and inflammation. The results are a huge mess. Many studies show that eating more n-6 fats reduces signs of inflammation. Some studies show an increase in inflammation. Yet others show no effect. The same is true for dietary n-3 fats.

I think these two quotes drive home the point. Note that linoleic acid (LA) is the most common form of n-6 fat. First, a 2012 review shows there’s no good evidence to show that eating more LA would increase inflammation.

The results of this systematic review show that virtually no data exist to suggest that dietary LA increases inflammatory markers among healthy, free-living human beings older than age 1 year.

Johnson, G. H. & Fritsche, K. Effect of dietary linoleic acid on markers of inflammation in healthy persons: a systematic review of randomized controlled trials. J Acad Nutr Diet 112,1029–41, 1041.e1–15 (2012). https://www.ncbi.nlm.nih.gov/pubmed/22889633

On the other hand, when researchers reanalyzed the data from The Sydney Diet Heart Study, conducted between 1966 and 1973, where the participants were asked to replace saturated fats (SFA) with safflower oil (high in LA), they concluded the following.

In this cohort, substituting dietary n-6 LA in place of SFA increased the risks of death from all causes, coronary heart disease, and cardiovascular disease.

Ramsden, C. et al. Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. BMJ346, e8707 (2013). https://www.ncbi.nlm.nih.gov/pubmed/23386268

While the results of this study are alarming, it’s important to keep it in perspective. The study shows an increase in heart disease and death in the group that consumed more processed vegetable oil. Plenty of studies show no increase in heart disease, or mortality, from an increase in overall n-6 fat intake.

In 2016, the Journal of American Heart Association published a comprehensive paper evaluating the health burden, as far as cardiovascular diseases are concerned, of ‘non-optimal’ intakes of n-6, saturated fats, and trans-fats. According to the researchers the optimal intakes of these fats are:

Omega-6: 12% of total energy
Saturated fats: 10% of total energy
Trans-fats: 0.5% of total energy

They determined these levels by:

The levels that were associated with the lowest levels of cardiovascular disease in previous long-term studies.
Diet and cardiovascular data from 186 countries around the world.
General consistency with national and international dietary guidelines.

In total, the researchers looked at data from 14 different studies compassing nearly 1/2 a million participants and 11,000 coronary events.

The results of this paper show that eating too little n-6 fats caused 711,800 deaths from heart disease, as compared to 250,900 due to eating too much saturated fat. Finally, 537,200 were due to eating too much trans-fats.

I know this isn’t directly related to acne, but the point I want to make is that the idea that n-6 fats are completely unhealthy is likely wrong and that there’s no real reason to go out of your way avoid n-6 fats.

What about other sites that say n-6 fats are dangerous?

If you’ve been reading health blogs, books, and articles, I’m sure you’ve read many times that n-6 fats are dangerous. As an example, Authority Nutrition published an impressive looking post that claims n-6 fats are dangerous. In one part of the post, they wrote this:

There have been several controlled trials where people replaced saturated fats with Omega-6 fats and had a significantly increased risk of heart disease (6, 7, 8).

I clicked to see the studies used to support this claim:

One is from 1965 and showed that people who were asked to restrict fried foods, pastries, milk, eggs, and butter and replace it with 80g of corn oil a day did worse than people who just continued with their normal diet. It’s possible that the corn oil was high in trans-fats, and this explains the difference. The paper makes no mention of trans-fats.
The second reference is to a study from 1966. The participants were asked to follow a ‘prudent’ diet that limits animal foods and emphasizes fish, fruit, vegetable, and grain consumption. Butter was replaced with a high PUFA margarine, and a minimum of 1oz of vegetable oil was taken a day. The control group was asked to continue their normal diet. The control group had three times as many new coronary events (diagnosed heart problems) than the group following the prudent diet. More people died of heart problems in the prudent diet group, but the death rated in neither group were unusual. And due to the small overall number of deaths, it’s not possible to conclude anything from that. You can find a more descriptive writeup of the study here.
The third citation is to a study from 1978. One group was asked to restrict saturated fats and eat more PUFAs, and another group was asked to do the opposite. From the study conclusion: “Multivariate analysis showed that none of the dietary factors were significantly related to survival.” In other words, the diets had nothing to do with the difference in survival levels.

These studies don’t prove that n-6 fats are dangerous. 2 of the 3 studies cited doesn’t even support the conclusion. One sort of does, but it has several problems. The larger point is that these studies are ancient and go against more recent and better studies.

I think this is just an example of confirmation bias. People ‘know’ n-6 fats are dangerous and seek to find studies and evidence to prove it.

Effect on hormones

Insulin levels

A 2011 meta-analysis pooled the results from 11 high-quality studies on the effect of n-3 supplementation on insulin sensitivity. They concluded that supplementing with n-3 fats has no effect on insulin sensitivity or insulin levels.

In conclusion, we found that n-3 PUFA consumption did not affect IS [Insulin sensitivity]

Akinkuolie, A. O., Ngwa, J. S., Meigs, J. B. & Djoussé, L. Omega-3 polyunsaturated fatty acid and insulin sensitivity: a meta-analysis of randomized controlled trials.Clin Nutr 30, 702–7 (2011). https://www.ncbi.nlm.nih.gov/pubmed/21959352

Studies on PCOS patients

A study from 2004 examined what happens in women with PCOS when saturated fats in the diet are partially replaced with walnuts. The purpose was to reduce saturated fats and increase PUFAs without affecting overall fat intake. The answer is not much. Androgen levels dropped a bit, but due to the small number of participants it’s hard to say what to make of it.

In another study, 51 women with PCOS were given six capsules of either soy oil, flax seed oil, or fish oil. The goal was to supplement with approx. 3.5g of n-3 fats per day, except for the soy oil group, which acted as a control. Blood sugar levels worsened slightly in all groups during an oral blood glucose test. Fish oil had a mildly negative effect on insulin (levels went up). Androgen levels dropped slightly in the soy oil group but didn’t change in the other groups. In other words, the supplementation had very little effect on acne-relevant measures.

An Iranian study from 2012 showed supplementing with 1600mg of long-chain n-3 fatty acids (EPA and DHA) reduced insulin and blood sugar levels in women with PCOS. The supplementation had no effect on any of the measured markers of inflammation.

N-6/N-3 Ratio

Many people suggest that the ratio of n-3 and n-6 fats is what really matters. To understand this, we have to look at the different types of n-3 and n-6 fats. The most common type of n-6 fat is linoleic acid (LA), and the most common n-3 is alpha-linolenic acid (ALA). But the fats that really matter are the longer-chain versions of these:

The most important long-chain n-6 is arachidonic acid (AA), which is known to be inflammatory.
On the n-3 side, the most important ones are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These are the fatty acids that make fish oil and seafood so heart healthy.

Several studies have shown that tissue ratios of these longer-chain variations do affect different diseases. Generally speaking, the more AA and the less EPA/DHA in the tissues, the worse you’ll be. Similarly, there’s enough evidence to show EPA and DHA are good for the heart.

In the Western diet, there’s an imbalance of n-6 and n-3 fats (especially EPA and DHA, but also ALA to a smaller degree). LA makes for something like 90% of all PUFAs people in the West eat.

This is said to be a problem because the same enzymes are required for converting LA and ALA into their longer-chain versions. The theory goes that eating too much LA would both increase AA levels and reduce EPA/DHA by hogging all the enzymes required for conversion.

In 2007, the UK Food Standards Agency held a workshop where scientists discussed and reviewed the importance of n-6/n-3 ratio on cardiovascular health. They concluded the following.

On the basis of this review of the experimental evidence and on theoretical grounds, it was concluded that the n-6:n-3 fatty acid ratio is not a useful concept and that it distracts attention away from increasing absolute intakes of long-chain n-3 fatty acids which have been shown to have beneficial effects on cardiovascular health.

Stanley, J. et al. UK Food Standards Agency Workshop Report: the effects of the dietary n-6: n-3 fatty acid ratio on cardiovascular health. Brit J Nutr 98,1305–10 (2007). https://www.ncbi.nlm.nih.gov/pubmed/18039412

They concluded that focusing on n-3/n-6 ratio is not useful based on the following observations:

The conversion of ALA into EPA and DHA depends on the absolute amounts of LA and ALA in diet, not their ratio.
Several studies have shown dietary LA can reduce heart disease; whereas the n-6/n-3 ratio theory predicts dietary LA to be bad for the heart.
No evidence to show that high n-6/n-3 ratio causes inflammation.
Reducing dietary LA does not decrease AA levels in tissues, but increasing dietary EPA and DHA does.

In summary, the ratio of LA to ALA in the diet doesn’t seem to matter. What is important is how much EPA and DHA you get from diet. Though there is some evidence to suggest reducing LA can somewhat increase the levels of EPA and DHA in tissues.

Conclusion and recommendations

Based on, what I believe to be, a very honest and transparent reading of the evidence, the commonly accepted view that omega-6 fats are harmful and should be avoided is wrong. There’s no good data to show that eating moderate amounts of omega-6 fats would cause inflammation and lead to health problems. In fact, data exists to show the opposite is true.

Based on the evidence, doing bean counting with omega-3 and omega-6 fats and trying to create the optimal balance in your diet is a fool’s errand. What matters is getting enough long-chain omega-3 fats (EPA and DHA).

With this in mind, here’s what I recommend:

Do your best to minimize vegetable and processed oils in your diet. There’s some data to show that eating less LA can make EPA and DHA more effective. And that’s why I believe there’s no point in having concentrated LA sources in your diet.
Make sure you get long-chain omega-3 fats from your diet. Good sources include fatty fish, seafood, and omega-3 enriched foods, like omega-3 enriched eggs.
I would not worry about omega-6 rich whole foods, like nuts, seeds, and meat.