- Dietary recommendations change because science develops new understanding
- It is key to focus on an entire food’s role in health, not just one nutrient or chemical within that food
One of the most common criticisms of nutrition science is how confusing it can be. Recommendations will change from “eggs are unhealthy, avoid them” to “eggs are healthy, eat more of them” in a short time span.
The purpose of this article to explain why this happens. The reality is, nutrition is a relatively new and constantly evolving science. It’s a good thing that we see dietary recommendations change, because it means we learned something new and can apply those learnings to improve health.
The downside is it results in confusing messages for people. So, let’s walk through a couple of the most confusing food stories in recent decades and see what there is to learn.
Foods like eggs or coffee, staples for breakfasts far and wide, have both been a part of the human diet for centuries. For many years, though, we were encouraged not to consume them regularly lest we shorten our life span. For eggs, the concern was focused on the amount of cholesterol in an egg, thought to be associated with heart disease. For coffee, it was the caffeine. So, when did the egg- and coffee-shaming begin?
Are eggs healthy or not?
It all began in 1968 when the American Heart Association (AHA) recommended that people consume no more than 3 eggs yolks per week to lower risk of cardiovascular disease (CVD) [AHA 1968]. From the perspective of a health care provider, it was simple to explain to explain the link between dietary cholesterol and high blood cholesterol, and for patients it was an easy dietary modification. It appeared to be a win-win for everyone, unless you were an egg farmer.
Not until 1999, when Hu et al. published a large, long-term population study on egg intake and heart disease incidence did we start looking at the egg differently. The study, which included over 117,000 men and women, found there was no difference in CVD risk between people who ate one egg/week and those who ate one egg /day. Since then, multiple epidemiological and meta-analyses have reached the same conclusion [McNamara 2015].
Eggs are more than their cholesterol content
One theory is that dietary cholesterol does not impact our blood cholesterol as much as we once thought. Another theory, which is becoming more common in nutrition science, is that foods can be more than the sum of their parts, just as we’ve seen with dairy.
The ‘incredible edible egg’ is packed full with all kinds of nutritional goodies. Yes, one medium egg does have half of the daily value for cholesterol, but with it comes 6 grams of complete protein and many micronutrients that many people in the United States do not get enough of, like calcium, potassium, and choline, according to the 2015 Dietary Guidelines.
For egg-lovers and the egg farmers, nutrition science continues to show how important eggs are in our diet. Two recent studies have further supported the health benefits of eggs. The first, a 9 year cohort study, examined the effect of egg consumption in over 415,000 subjects who were free of any chronic disease (e.g. heart disease, diabetes) at the beginning of the study. Researchers found that 13% of the subjects had at least one or more servings of eggs a day, and 9% rarely consumed eggs. After nine years, the people that ate eggs every day had lower overall heart disease risk, with up to 26% less risk of hemorrhagic stroke, 28% less risk of dying from a hemorrhagic stroke, and 18% less risk of lethal complication from CVD.
The second study was designed to determine the effects of either high (>12 eggs/wk) or low (<2 eggs/wk) egg consumption in people with prediabetes or type 2 diabetes (T2D) on a 3-month energy-restricted diet [Fuller 2018]. Weight loss was similar between groups and there were no differences between groups in glycemia, traditional serum lipids, markers of inflammation, or oxidative stress. Interestingly, the presence of 12 eggs/week did not lead to weight gain [Fuller 2018].
Our understanding of egg’s role in a healthy diet has evolved quite a bit since 1968, which is why we have seen recommendations change over that period of time.
Is coffee healthy or not?
“Coffee: it will stunt your growth, give you a stomach ulcer and increase your risk for heart disease!” Does this quote sound familiar? For years doctors warned their patients not to drink coffee because of its purported negative health effects. There was also concern that when people drink coffee, they would become addicted to the “energy” they felt from the caffeine. As people increased their coffee consumption, they would develop a tolerance to caffeine and would need to drink more coffee in order to get that energized feeling. Thankfully for the more than 60% of Americans that drink at least one cup of coffee a day, research is now starting to highlight coffee’s positive health benefits and debunk the previous negative [Daily Coffee News].
So, why the change in heart? It is partly due to the recognition that the earlier studies on coffee did not account for common high-risk behaviors among heavy coffee drinkers (e.g. smoking, alcohol, physical inactivity) that each have their own role in heart disease risk [Mayo Clinic]. Scientists are also now identifying many components in coffee with potential healthful benefits (e.g. antioxidants, caffeic acid, cafestol, and so on) [Mellbye 2018, Kang 2009].
Other studies have suggested that drinking 3-4 cups of coffee per day is associated with ~25% lower risk of developing T2D compared to people consuming < 2 cups coffee per day [Huxley 2009, Santos 2016, Jiang 2014].
Where do things stand now? The 2015 Dietary Guidelines Advisory Committee reviewed the literature on coffee’s link to health, and found that moderate coffee consumption is associated with a reduced risk of heart disease and stroke. The science also showed that both decaffeinated and caffeinated coffee were associated with a reduced risk of developing type 2 diabetes. Finally, caffeine intake from coffee was associated with improved cognitive health and could play a role in preventing Parkinson’s disease [Scientific Report of the 2015 Dietary Guidelines Advisory Committee].
Coffee, cancer, and California: Missing the forest for the trees
Despite this evidence, debate around coffee continues. In 2018, California made an attempt to require warnings on coffee regarding a possible role in causing cancer, under Proposition 65, due to its acrylamide content. Scientists across the globe gathered to debate this legislation, due to the association between coffee consumption and the positive health outcomes listed above, and the legislation was eventually overturned.
This is a great example of the mistakes that can be made when we focus on one specific chemical or nutrient in a food, rather than the whole food’s role in health.
Moderation is key
While it the tide has definitely changed for coffee and health, it is important to keep in mind that the too much of anything is not necessarily a good thing, and coffee is no exception. For example, high consumption of unfiltered coffee (boiled or espresso) has been associated with mild elevations in serum cholesterol [Scientific Report of the 2015 Dietary Guidelines Advisory Committee].
It is also generally recommended that people consume no more than 200 mg of caffeine at once, and no more than 400 mg of caffeine over the course of a day [ILSI NA]. We are still learning how different individuals metabolize caffeine, so these are recommendations for populations rather than specific individuals.
The bottom line: use moderation and focus on the big picture
The verdict for eggs and coffee- they have their place in a healthy diet, but moderation is key. So go ahead and have coffee with your eggs in the morning, just keep an eye on the calories you may be adding to the eggs with different ingredients (e.g. butter) or the cream, sugar, or syrups in coffee.
Heather Nelson Cortes, PhD
Heather Nelson Cortes holds a PhD in Nutritional Biochemistry from the University of North Carolina-Chapel Hill. With over 20 years of industry experience spanning areas from product innovation to product launches, and everything in between, her passion is the intersection of science and business. She is currently a nutrition consultant specializing in the food, ingredient, and supplement markets.
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