Is Dairy Bad For Your Heart?

Is Dairy Right For You? 

Author: Dr. Stephen Chaney

dairy foodsWe have been told for years that dairy foods are good for us. They are part of the USDA five food groups. In fact, they are part of the dietary recommendations of every government and most health organizations across the world.

And dairy foods are nutritious. They are excellent sources of calcium, potassium, protein, and vitamins A and B12. And if they are fortified, they are also an excellent source of vitamin D. Many health experts consider them essential for healthy bones. So, you might be saying, “Case closed. We should all be eating more dairy foods”.

But, not so fast. Many dairy foods are high in saturated fats. In fact, 65% of the fat in dairy foods is saturated. We have known for years that when saturated fats replace polyunsaturated fats in the diet, LDL cholesterol levels increase. And, as I reported in a previous issue of “Health Tips From the Professor” there is excellent evidence that replacing polyunsaturated fats with saturated fats substantially increases the risk of dying from heart attack, stroke, and other forms of heart disease.

The widely accepted message from these studies is that saturated fats raise LDL cholesterol levels and increases our risk of dying from heart disease. If we accept this message, it poses a dilemma. Dairy foods are nutritious. But they are high in saturated fat. What should we do?

The answer from the American Heart Association and most other health organizations is simple. We should eat low-fat dairy foods.

But this is where it gets really confusing. Dairy foods are composed of much more than saturated fats. And you have probably seen the claims that full fat dairy foods don’t increase the risk of heart disease.

So, what is the truth about full-fat dairy foods and heart health? In this issue of “Health Tips From The Professor” I review three recent studies and the recommendations of the Heart Foundation because they shed light on this question.

Is Dairy Bad For Your Heart?

dairy products and heart disease cheeseBefore I answer this question, I should point out that there are two ways of looking at it.

  • As I said above, the studies proving that saturated fats increase the risk of heart disease, substituted saturated fats for polyunsaturated fats and controlled every other aspect of the diet. That has led the American Heart Association and other organizations to recommend that we eat low-fat dairy foods.
  • However, when most people hear that recommendation, they simply substitute low-fat dairy for full-fat dairy foods without changing any other aspect of their diet or lifestyle. The first two studies were designed to see if that approach was effective for reducing heart disease risk.

The first study (KA Schmidt et al, American Journal of Clinical Nutrition, 114: 882-892, 2021) was a randomized controlled trial that compared the effect of low-fat dairy foods and full-fat dairy foods on heart health parameters.

The participants in this study were:

  • Average age = 62
  • 56% male
  • 75% white
  • Average weight = 214 pounds
  • All of them were prediabetic

All participants were told to stick with their usual diets (probably typical American diets) except for the amount and type of dairy foods added to their diet. During the first four weeks they restricted dairy consumption to 3 servings of nonfat dairy/week so they would all be starting with the same amount of dairy consumption. Then they were divided into 3 groups for the 12-week study:

  • Group 1 continued with 3 servings of nonfat dairy/week.
  • Group 2 added 3 servings of low-fat dairy/day to their usual diet.
  • Group 3 added 3 servings of high-fat dairy/day to their usual diet.

At the beginning of the study and again at the end of the 12-week study LDL cholesterol, HDL cholesterol, triglycerides, free fatty acids, and blood pressure were measured. The results were:

  • There was no difference in LDL cholesterol, HDL cholesterol, triglycerides, free fatty acids, or blood pressure in the three groups at the end of 12 weeks.
  • There was no also significant change in LDL cholesterol, HDL cholesterol, triglycerides, free fatty acids, or blood pressure during the study in any of the three groups.

The authors concluded, “A diet rich in full-fat dairy had no effect on fasting lipid profile or blood pressure compared with diets limited in dairy or rich in low-fat dairy. Therefore, dairy fat, when consumed as part of complex whole foods does not adversely affect these classic cardiovascular disease risk factors.”

[Note: The last sentence is key. Remember the “proof” that saturated fats increase LDL levels and increase the risk of heart disease come from studies in which saturated fats were substituted for polyunsaturated fats and every other aspect of the diet was carefully controlled.

In this study, and others like it, the effects of saturated fats are studied in a complex food (dairy) in the presence of an even more complex diet containing many foods that influence the risk of heart disease.]

The second study (J Guo et al, European Journal of Epidemiology 32: 269-287, 2017) was a meta-analysis of Healthy Heart29 studies with 938,465 participants looking at the association of full-fat dairy consumption with the risk of dying from heart disease.

Seven of the 29 studies were conducted in the United States. Of the remaining studies 3 were from Japan and Taiwan, 2 were from Australia, and 17 were from Europe.

The results of the study were:

  • There was no association between full-fat dairy, low-fat dairy, and total dairy consumption and risk of dying from heart disease.

When the results were broken down into individual dairy foods.

  • There was no association between milk consumption and risk of dying from heart disease.
  • Consumption of one serving/day of fermented dairy foods was associated with a 2% decreased risk of dying from heart disease.

The authors concluded, “The current meta-analysis of 29 prospective cohort studies suggested no association of total, high and low-fat dairy and milk with risk of cardiovascular disease. In addition, a possible role of fermented dairy was found in cardiovascular disease prevention, but the result was driven by a single study.” [I would add that this effect, if confirmed by subsequent studies, is extremely small (2%).]

The first two studies do not say that full-fat dairy foods are heart healthy for everyone, as some headlines would have you believe. Instead, these studies show fairly convincingly that simply switching from full-fat to low-fat dairy foods, without changing any other aspect of your diet and lifestyle, is not as effective at decreasing your risk of heart disease as some experts would have you believe.

balance scaleThe third publication (WC Willett and DS Ludwig, New England Journal of Medicine 382: 644-654, 2020) was a review of the effect of dairy foods on our health. One of the authors, Walter C Willett, is one of the top experts in the field. The review covered many topics, but I will focus on the section dealing with the effect of dairy foods on heart health.

This review took a more nuanced look at full-fat dairy foods and examined the effect of substituting full-fat dairy for other protein foods.

The review concludes, “The association of milk with the risk of cardiovascular disease depends on the comparison foods. In most cohort studies [such as the studies described above], no specific comparison was made; by default, the comparison was everything else in the diet – typically large amounts of refined grains, potato products, sugar, and meat.”

The review went on to say that previous studies have shown:

  • “Both full-fat and low-fat dairy foods…were associated with a lower risk [of cardiovascular disease and stroke] than…the same number of servings of red meat but with a higher risk than seen with the same number of servings of fish or nuts.”
  • “Dairy fat…was associated with a higher risk of cardiovascular disease than was polyunsaturated or vegetable fat.”
  • “For persons living in low-income countries where diets are very high in starch, moderate intake of dairy foods may reduce cardiovascular disease by providing nutritional value and reducing glycemic load [the amount of easily digestible carbohydrate in the diet].”

Is Dairy Right For You?

dairy products and heart disease questionsNow I am ready to answer the question posed at the beginning of this article, “Is dairy bad for your heart?” The answer is, “It depends”.

  • As described above, the effect of dairy on heart health depends on our overall diet. It also depends on our lifestyle, our weight, and our health.
  • In addition, clinical studies report averages, and none of us are average. We all have unique diets, lifestyles, health status, and genetic makeup.

So, what does this mean for you? Perhaps it is best summed up by the recommendations of Australia’s Heart Foundation which take health status, lifestyle, and genetic differences into account:

  • A heart healthy diet can include dairy, but it is not essential [with careful planning and/or supplementation you can get your calcium and protein elsewhere].
  • Milk, yogurt, and cheese are considered neutral for heart health, meaning they neither increase nor decrease the risk of heart disease for the average person. However, the recommendations vary depending on health status, genetics, and lifestyle:
    • Low-fat milk, yogurt, and cheese are recommended for people with heart disease or high cholesterol because the fat in dairy foods can raise cholesterol more for these people. [Note: If cholesterol is elevated, it usually means that individual has a hard time regulating blood cholesterol levels because of obesity, genetics, or pre-existing disease. For these individuals, diets high in saturated fat are more likely to increase LDL cholesterol and risk of heart disease.]
    • Full-fat milk, yogurt, and cheese can be part of a heart healthy diet for healthy people provided most of the fat in the diet comes from fish, nuts, seeds, and healthy oils. [Note: Overall diet is important.]
  • Choosing unflavored milk, yogurt, and cheese helps limit the amount of sugar in your diet.
  • Ice cream, cream, and dairy desserts should be eaten only sometimes and in small amounts because they have more sugar and fat, and less protein, vitamins, and minerals than other dairy foods.
  • Butter raises LDL cholesterol levels, especially in people who already have elevated cholesterol.
    • There is no evidence that butter can be part of a heart healthy diet, so you should consider healthier options such as olive oil, avocado, nut butters, and spreads made with healthier oils, such as olive oil.

The Bottom Line

We have been told for years that dairy foods are good for us. They are part of the USDA five food groups. In fact, they are part of the dietary recommendations of every government and most health organizations across the world.

However, dairy foods have been controversial in recent years. Some experts claim that only low-fat dairy products can be heart healthy. Others claim that full-fat dairy foods are just as healthy as low-fat dairy foods.

I shared three recent publications and dietary recommendations from The Heart Foundation that shed light on these controversies.

The first study found that full-fat dairy foods did not increase LDL cholesterol, triglycerides, and other heart disease risk factors.

The second study was a meta-analysis of 29 clinical studies with almost one million people. It found that full-fat dairy foods did not increase the risk of dying from heart disease.

“Case closed”, you might say. However, these studies do not say that full-fat dairy foods are heart healthy for everyone, as some headlines would have you believe. Instead, these studies show fairly convincingly that simply switching from full-fat to low-fat dairy foods, without changing any other aspect of your diet and lifestyle, is not as effective at decreasing your risk of heart disease as some experts would have you believe.

Moreover, these studies do not account for the effect of overall diet, lifestyle, health status, and genetics on the risk of heart disease.

That is why I included the third study in my review. It took the overall diet into account and concluded the effect of full-fat dairy foods on heart disease risk depends on the overall diet.

  • For some diets full-fat dairy increases heart disease risk.
  • For other diets full-fat dairy has no effect on heart disease risk.
  • And for some diets full-fat dairy may even decrease heart disease risk.

Finally, I included recommendations of the Australian Heart Foundation because they included the effect of health status, lifestyle, and genetics in their recommendations.

For more details on the findings of the third study and the recommendations of the Heart Foundation, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease.

Which Foods Affect Stroke Risk?

Why Is Diet And Stroke Risk So Confusing?

strokeOne day we are told vegetarian diets reduce our stroke risk. The next day we are told they increase stroke risk. It’s the same with red meat, dairy, and eggs. We keep getting mixed messages. It’s enough to make your head spin. Why is diet and stroke risk so confusing?

Part of the problem is that there are two distinct types of stroke. The technical names for them are ischemic stroke and hemorrhagic stroke.

An ischemic stroke occurs when an artery in the brain becomes blocked, shutting off blood flow and damaging part of the brain. This is usually caused by the gradual buildup of fatty deposits and cholesterol plaques in the arteries. When a blood clot forms and lodges in one of the narrowed arteries leading to the brain, an ischemic stroke occurs.

  • Ischemic strokes account for 87% of all strokes.
  • Ischemic strokes are associated with obesity, elevated cholesterol, diabetes, high blood pressure, and smoking.

A hemorrhagic stroke occurs when a weakened blood vessel bursts and bleeds into the surrounding region of the brain. Because our brains are surrounded by a protective skull, that blood has nowhere to go. Pressure from the buildup of blood damages brain cells in the vicinity of the bleed.

  • Hemorrhagic strokes account for only for only 15% of strokes but are responsible for 40% of stroke deaths.
  • The most common cause of a hemorrhagic stroke is the localized enlargement of a blood vessel due to chronic high blood pressure. This weakens the wall of the blood vessel, making it prone to rupturing.

Part of the confusion about diet and stroke risk is because many earlier studies did not distinguish between the two types of stroke.

  • If the studies just measured the incidence of stroke, the data were dominated by ischemic strokes (87% of strokes are ischemic).
  • However, if the studies focused on stroke deaths, hemorrhagic stroke made a larger contribution to the data set (40% of stroke deaths are hemorrhagic).

Fortunately, recent studies have started to focus on the effect of diet on ischemic and hemorrhagic strokes separately. However, many of those studies have been too small to accurately assess the effects of diet on hemorrhagic stroke.

The latest study (TYN Tong et al, European Heart Journal, ehaa007, published February 24, 2020) is one of the largest studies to look at the effect of diet on both kinds of stroke. It has enough patients in the hemorrhagic group to get an accurate estimate of the effect of diet on hemorrhagic stroke.

How Was The Study Done?

Clinical StudyThis study analyzed data on diet and stroke from 418,329 participants in the EPIC (European Prospective Investigation into Cancer and Nutrition). Although the study has cancer in the title, it actually investigated the effect of nutrition on multiple diseases (Presumably, the study title was chosen because EPIC is a more appealing acronym than EPID (European Prospective Investigation into Diseases and Nutrition)).

The participants were recruited from 9 European countries (Denmark, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden, and the UK). The average age of participants was 50, and they were followed for an average of 12.7 years.

At the beginning of the study participants completed country-specific dietary and lifestyle questionnaires.

The dietary assessment was a food frequency questionnaire that asked participants about their dietary intake for the year prior to enrollment in the study. The food frequency data were used to estimate daily intake of red meat, processed meat, poultry, fish, dairy products, eggs, grains, fruits, vegetables, legumes, nuts, seeds, and dietary fiber (It measured total fiber and fiber from grains, fruits and vegetables individually).

The outcome measured was the incidence of ischemic and hemorrhagic strokes during the 12.7-year follow-up.

Which Foods Affect Stroke Risk?

Heart Healthy DietFor ischemic stroke:

  • Each 200 gram/day increase in consumption of fruits and vegetables decreased ischemic stroke risk by 13% (200 grams roughly corresponds to one large apple or one large orange without the skin).
  • Each 10 gram/day increase in consumption of fiber decreased ischemic stroke risk by 23%. Most of this decreased stroke risk was due to fiber from whole grains, fruits, and vegetables.
    • Each 4 gram/day increase in fiber from whole grains decreased ischemic stroke risk by 10%.
    • Each 4 gram/day increase in fiber from fruits and vegetables decreased ischemic stroke risk by 12%.
  • Dairy foods decreased ischemic stroke risk with the following breakdown:
    • Each cup of milk decreased ischemic stroke risk by 5%.
    • Each half cup of yogurt decreased ischemic stroke risk by 9%.
    • Each ounce of cheese decreased ischemic stroke risk by 12%.
  • Each 50 grams/day (2 ounces) of red meat increased ischemic stroke risk by 14%.
    • However, red meat was only half as likely to increase risk of ischemic stroke when the diet was also rich in fruits, vegetables, whole grains, and legumes.

For hemorrhagic stroke:

  • Each 20 gram/day increase in consumption of eggs increased hemorrhagic stroke risk by 25% (20 grams roughly corresponds to about 1/2 of a small egg or 1/3 of a jumbo egg).
  • This study did not measure the effect of salt intake on hemorrhagic stroke risk.

No other foods measured in this study had a significant effect on hemorrhagic stroke risk.

high blood pressureHowever, hemorrhagic stroke is highly associated with high blood pressure. When we look at the influence of foods on high blood pressure, here are the Harvard School of Medicine recommendations for keeping blood pressure low:

  • Eat more fish, nuts and beans in place of high-fat meats.
  • Choose fruits and vegetables instead of sugary, salty snacks and desserts.
  • Select whole grains rather than refined grains.Eat fruit instead of drinking fruit juice.
  • Use unsaturated fats like olive, canola, soybean, peanut, corn or safflower oils instead of butter, coconut oil, or palm-kernel oil.
  • Use herbs, spices, vinegar, and other low-sodium flavorings instead of salt; Choose low-sodium foods whenever possible.

Why Is Diet And Stroke Risk So Confusing?

egg confusionAs I mentioned at the start of this article, part of the reason that the headlines about diet and stroke risk are so confusing is:

  • Many studies did not distinguish between the two types of stroke.
  • Other studies were too small to reliably estimate the effect of food on hemorrhagic stroke risk.

However, there are still some unexplained inconsistencies among recently published studies. It is these inconsistencies I would like to address. For example:

1) In a recent issue of Health Tips From the Professor I reported on a major study (500,000 people followed for 8.9 years) in China. That study came to the opposite conclusion about eggs and risk of hemorrhagic than the EPIC study I discussed above. It found:

  • People consuming one egg per day had a 26% decrease in hemorrhagic stroke risk and a 28% decrease in hemorrhagic stroke deaths compared to people who never or rarely consumed eggs.

In other words, the two studies came to opposite conclusions. In the China study eggs decreased risk of hemorrhagic stroke. In the European study (EPIC) eggs increased risk of hemorrhagic stroke. The reason for this discrepancy is not clear, but one can speculate it might be explained by differences in the underlying diets of the two countries:

  • In China the diet is primarily plant-based. The addition of an egg/day may provide needed protein, fat, and cholesterol (Some cholesterol is essential. We just overdo it in this country).
  • In Europe the diet is already high in protein, saturated fat, and cholesterol. Getting more of them from eggs may not be such a good thing.

In short, if your diet is primarily plant-based, the addition of an egg/day may be a good thing. However, if your diet is already high in meat, saturated fat, and cholesterol, the addition of an egg/day may not be a good thing.

Vegan Foods2) In another recent issue of Health Tips From the Professor I reported on the EPIC-Oxford study that claimed vegetarians had 20% increased risk of hemorrhagic stroke compared to meat eaters.

Interestingly, the EPIC-Oxford study represented a very small portion (~10%) of the overall EPIC study and differed from the rest of the EPIC study in two important ways.

  • It looked at the effect of diets rather than foods on stroke risk.
  • Oxford was the only one of the 22 research centers involved in the EPIC study to invite people following a vegetarian diet to enroll in the study, so it had a much higher proportion of vegetarians than other centers that participated in the study.

The current study did not find any evidence that fruits, vegetables, nuts, seeds, beans, or whole grains influenced the risk of hemorrhagic stroke. In other words, in this much larger data set there was no evidence that the foods associated with a vegetarian diet increased hemorrhagic stroke risk.

However, most of the participants in larger EPIC study were also eating meats. They were not following a pure vegetarian diet.

As I said previously, “If the data on hemorrhagic stroke risk in the EPIC-Oxford study are true, it suggests it may not be a good idea to completely eliminate meat from our diet. However, you don’t need to add much meat to a vegetarian diet. The fish eaters in this study were consuming 1.4 ounces of fish per day. That was enough to eliminate the increased risk of hemorrhagic stroke.”

What Does This Mean For You?

Questioning WomanFor ischemic stroke (blockage of blood flow to the brain), which is the most common form of stroke, the data are clear cut:

  • Fruits, vegetables, whole grains and dairy foods are good for you. (Your mother was right.)
  • Red meat is not so good for you. However, the bad effect of red meat on ischemic stroke risk can be reduced by including plenty of fruits, vegetables, and whole grains in your diet.
  • These conclusions are consistent with multiple previous studies, and the mechanisms of these effects are well established.

For hemorrhagic stroke (bleeding from a weakened blood vessel in the brain) the data are not as clear cut.

  • If you are consuming a primarily plant-based diet, eggs appear to reduce your risk of hemorrhagic stroke.
  • If you are consuming a diet with lots of meat, saturated fat, and cholesterol, adding eggs may increase your risk of hemorrhagic stroke.
  • A vegetarian diet may increase your risk of hemorrhagic stroke. But you don’t need to add much meat to a vegetarian diet. Consuming 1.4 ounces of fish per day appears to be enough to eliminate the increased risk of hemorrhagic stroke.
  • The mechanisms of these effects of food on hemorrhagic stroke are unclear, so these conclusions may be modified by subsequent studies.

In terms of an overall take-home lesson on diet and stroke risk, my advice is: “A primarily plant-based diet is a good idea, but you don’t need to become a vegan purist. Nor do you want to follow fad diets that eliminate whole food groups. We have 5 food groups for a reason. Eliminating any of them may not be a good idea.”

The Bottom Line

A recent study examined the effect of various foods on the risk of the two major forms of stroke.

For ischemic stroke (blockage of blood flow to the brain), which is the most common form of stroke, the data are clear cut:

  • Fruits, vegetables, whole grains and dairy foods are good for you. (Your mother was right.)
  • Red meat is not so good for you. However, the bad effect of red meat on ischemic stroke risk can be reduced by including plenty of fruits, vegetables, and whole grains in your diet.
  • These conclusions are consistent with multiple previous studies, and the mechanisms of these effects are well established.

For hemorrhagic stroke (bleeding from a weakened blood vessel in the brain) the data are not as clear cut.

  • If you are consuming a primarily plant-based diet, eggs appear to reduce your risk of hemorrhagic stroke.
  • If you are consuming a diet with lots of meat, saturated fat, and cholesterol, adding eggs may increase your risk of hemorrhagic stroke.
  • A vegetarian diet may increase your risk of hemorrhagic stroke. But you don’t need to add much meat to a vegetarian diet. Consuming 1.4 ounces of fish per day appears to be enough to eliminate the increased risk of hemorrhagic stroke.
  • The mechanisms of these effects of food on hemorrhagic stroke are unclear, so these conclusions may be modified by subsequent studies.

In terms of an overall take-home lesson on diet and stroke risk, my advice is: “A primarily plant-based diet is a good idea, but you don’t need to become a vegan purist. Nor do you want to follow fad diets that eliminate whole food groups. We have 5 food groups for a reason. Eliminating any of them may not be a good idea.”

For more details, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

 

Health Tips From The Professor