are eggs off the menu again?

With headlines this week suggesting eating as few as three eggs a week could increase our risk of cardiovascular disease, I feel like I have stepped back in time. For years everyone avoided eggs because of their high cholesterol content. Then suddenly it was OK to eat eggs again. Now a new study suggests maybe not. So what's going on? I've had a few people contacting me off the back of this one to ask if it's still OK to eat eggs - so here goes...

​In case you are wondering what I am talking about, a new study has been grabbing the headlines by linking egg consumption to increased risk of heart disease and premature death. You can find the actual study here. 

First up, if you are asking me whether it is safe for you personally to eat eggs then I am going to have to pass. I can’t offer you my professional opinion on your individual health needs via a blog post. What works for most of the population may not be appropriate for you personally. If you have health concerns and are wanting advice on your diet then that is where you should be seeking one to one support. You can find plenty of information about this on my website.
If you are interested in the truth behind the headline and you want to make up your own mind on whether you should be eating eggs or not then read on for my opinion.  I’m going to start off with a bit about cholesterol because that is going to help when we look at the article.

​When we talk about cholesterol there are a number of different ways we can look at it. We can talk about total cholesterol – the amount of cholesterol that is in an item of food (186mg in a large egg) or in your blood. We can split that down into HDL and LDL cholesterol – sometimes known as good (HDL) and bad cholesterol. Or we can dig even deeper into LDL and talk about whether your LDL particles are large and fluffy (good) or small and hard (not so good).

​What do we mean by HDL and LDL? If you think of cholesterol as a fat transporter, the LDL carries fat from your liver to cells in your body (our body needs cholesterol for all kinds of important things like cell membranes and hormones). The HDL carries cholesterol away from our arteries towards our liver where it can then be disposed of. So neither HDL or LDL cholesterol is inherently bad. The important thing is that we need the right balance of HDL and LDL to be healthy. If we have too much LDL this is when it can cause problems in our arteries, increasing our risk of heart disease (and that maybe it is small, hard particles of LDL that cause particular risk here).

So, that’s one important fact about cholesterol, but here’s another. Remember me saying we need cholesterol for normal functioning of our bodies (cell membranes). Well, in healthy human bodies the liver does a balancing act with our cholesterol. If we are getting lots of cholesterol from our diet then the liver will reduce the amount of cholesterol it produces. If we reduce the cholesterol in our diet then our liver will produce more cholesterol to compensate. Here’s where we get to the bit about personalised nutrition advice. Some people have a predisposition towards high levels of fat in their blood (a condition known as hyperlipidaemia). This means that even when they eat a healthy diet and exercise regularly they have a higher risk of heart disease due to high levels of circulating fats.  People with this condition need to be very careful in their consumption of dietary fat.
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The last thing I want to share about circulating fats is the role of sugars. We can worry a lot about diets high in fat raising our cholesterol but we tend to think less about sugar raising levels of fat in our blood. But here’s the thing. If we eat a diet that is high in sugar (or refined carbohydrates such as white bread, white rice and white pasta) our bodies need a way to store the excess sugars. The main mechanism for this is to convert sugar to fat and transport this fat in our bloodstream for storage in fat cells.
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Now, let’s return to the study behind the headlines. This study involved 29,615 people – so we are talking big numbers here. It pulled together data from six different cohort studies (cohort studies tend to follow large numbers of people for long periods of time. They collect data on a whole range of diet and lifestyle markers plus they tend to run blood tests and physical tests for things like blood pressure). Cohort studies are very helpful for unpicking potential risk factors for chronic disease like heart disease but they are not without their limitations. One of these limitations is use of diet diaries to collect nutrition information. Why? Because people are unreliable when it comes to diet diaries. We under-report things like snacks, we underestimate portion sizes and we just forget to log everything. Diet diaries are a good indicator of what people are eating but they are not an exact science.

That’s a general observation on cohort studies. Here’s a more specific point on this particular study. The headlines in the papers are attention grabbing. The one I linked you through to in the telegraph says “Eating as few as three eggs a week raises risk of heart disease, study suggests”. This is a little different to the (granted less catchy) title of the study “Associations of Dietary Cholesterol or Egg Consumption With Incident Cardiovascular Disease and Mortality”.  The study title suggests an association, the headline in the paper implies a causal link. ‘Associations’ is different to a cause. Association acknowledges that there may be something else going on here that is linked.

Then there is that word or  in the title of the paper, and that is really critical here. When you read the full paper eggs are looked at as part of the total amount of cholesterol that people were eating (eggs and other animal products). This is not the same as only measuring cholesterol from egg consumption. They looked at the average amount of cholesterol that an American eats daily in their diet (about 293mg per day) and then studied what happens to risk of heart disease when people in the cohort consumed more cholesterol than this. The risk increased for every 300mg per day of cholesterol that people in the cohort consumed ABOVE the American average (whether this was 300mg eggs or 300mg from other sources). To put it another way, people who ate double the average amount of cholesterol per day had an increased risk of heart disease.

But here is the take home message that wasn’t in the headlines. After looking at eggs as part of total cholesterol consumption (with products high in saturated fats such as processed meats) the researchers isolated egg consumption. This time they weren’t adding eggs to the average cholesterol, they were looking at egg consumption. When they did this they found no significant increased risk of heart disease in people who ate more eggs. Confusing? What the study is saying is that people who consumed around 600mg cholesterol per day had an increased risk of heart disease compared to those who ate closer to 300mg. Forget the eggs. And remember, when it came to cholesterol this was an association across a large population. There are individual variations within that.

What does this mean for you if you are an egg lover? Eggs are high in TOTAL cholesterol but that is a mix of HDL and LDL cholesterol. They are a cheap source of protein and contain a whole range of nutrients. This includes being an excellent source of choline - which is important in brain health in both mental focus and learning. Think about your diet overall. Eating a variety of whole foods is the simplest way you can improve your diet.
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If you think your diet is high in cholesterol and are worried about your blood cholesterol you can always get it tested. Some foods; including olive oil, oats, walnuts, oily fish and purple fruit and vegetables (high in something called anthocyanins); can raise levels of HDL (good) cholesterol. Exercise, stopping smoking and losing weight can all help to lower LDL cholesterol. Finally, when it comes to nutrition, never base your dietary choices on a single study. This wasn't a bad study, it acknowledged it's own limitatations. It was misrepresented in the newspaper headlines. It was just one study. Human nutrition is a tricky subject to study. There are so many variables to consider that it is hard to get it right. We need to take the evidence on balance not on each paper.
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