Homocysteine and heart disease

You don't hear a whole lot about homocysteine these days but ten or fifteen years ago it was quite the buzzword in nutrition and preventive medicine circles--and a cash cow for nutritional supplement sellers.

A little background on the homocysteine hypothesis

Population studies (aka epidemiological studies) showed that people with high levels of homocysteine in their blood had a higher risk of heart disease. Homocysteine is an amino acid which is an normal byproduct of protein metabolism. Ideally, it is further converted into another amino acid, methionine. However, if this "recycling"  breaks down, homocysteine can build up in the blood. 

When the link between high homocysteine and heart disease risk was noticed, researchers theorized that homocysteine might irritate the blood vessel lining, leading to injury, inflammation, and the formation of arterial plaques.

Certain B vitamins (B6, B12, and folic acid) act as co-factors in the conversion of homocysteine to methionine. Further research confirmed that those with high homocysteine tended to be low in one or more of these nutrients. Taking the next step, it was established that supplementing with these nutrients reliably reduced elevated homocysteine levels. It seemed all but certain that this would in turn lower heart disease risk.

Hold that thought

However, the homocysteine hypothesis recently took a big hit, in the form of a meta-analysis of eight studies involving some 24,000 subjects. The upshot? The authors found “no evidence that homocysteine-lowering interventions, in the form of supplements of vitamins B6, B9 or B12, given alone or in combination, at any dosage compared with placebo or standard care, prevents myocardial infarction, stroke, or reduces total mortality in participants at risk or with established cardiovascular disease.”

Ouch.

Those in the business of selling nutritional supplements are crying foul, claiming that the conclusions are "misleading."  Read responses from the Health Food Manufacturers’ Association (HFMA) and the International Alliance of Dietary/Food Supplement Associations (IADSA).

It's possible that those with very high homocysteine levels have more to gain than those with only mildly elevated levels--and that the meta-analysis obscures this reality. The meta-analysis also failed to evaluate whether B vitamins could prevent healthy people from developing heart disease. But, coming from organizations who profit from sale of dietary supplements, I find this argument less compelling.

I'm curious: How many of you have had your homocysteine levels tested? How many of you take B vitamins specifically to manage homocysteine levels? Share your comments below.

High cholesterol no cause for worry?

Q. I am a 24-year-old female. I'm a normal weight (5'7", 133 lbs). I work out at least 5 days per week. I  avoid all processed food and generally try to fill my days with whole grains, veggies, fruits and non-fat dairy sources. I usually have a small amount of caffeine in the mornings, I don't smoke, and I drink two or three times per month. All in all, I think I lead a pretty healthy lifestyle. However, I went to my doctor last week and was surprised to find that my cholesterol is slightly high (more than 200 mg/dL). I don't have a family history of high cholesterol or heart disease.  Is this a common problem in people who lead otherwise healthy lifestyles? I'm hoping to avoid taking prescription meds for the rest of my life.

A. I think it's a little soon to be thinking about prescription meds for life!!  Given all you've reported here, you may not have anything to worry about.  For one thing, high cholesterol does not mean you have (or will develop) heart disease.  Although elevated cholesterol is statistically linked to a higher incidence of heart disease, many people who die of heart disease have normal cholesterol...and many people with elevated cholesterol never get heart disease.  Cholesterol tests are screening tools, not diagnostic ones.

Cholesterol is only one piece in a larger picture. Given the rest of the details you've given (normal weight, not sedentary, no family history of heart disease or high cholesterol, normal blood pressure), your statistical risk of developing heart disease in the next ten years is extremely small. 

I'm also wondering about the details of your cholesterol--specifically about the break-down of HDL ("good") and LDL ("bad") cholesterol.  Your total cholesterol may be high because your HDL is high, thanks to all your healthy habits.   I would think before prescribing medication, your doctor would follow up with a more comprehensive lipid panel. I'd give even odds that a retest would show normal cholesterol, anyway. The slightly high reading may well have been an anomaly.

Finally, it sounds as if your diet is very low in fat and fairly high in carbohydrates.  If you wanted to see if dietary modifications might nudge your cholesterol numbers in the right direction (although, again, I'm not sure you really have that much to worry about), you might try adjusting the balance of your diet to be a little higher in fat and lower in carbs, particularly grains. Olives, olive oil, almonds, and avocados (all rich in monounsaturated fats) would be good choices.

Let us know what happens next.

 

Eating eggs might up your cholesterol. So what?

Q. One of my friends still insists that dietary cholesterol contributes to body cholesterol. Since I wasn't able to convince him that this isn't true, I tried to look for actual studies and research to prove my point.  Could you direct me to a few studies that show that that dietary cholesterol does not affect our cholesterol levels? Thanks?!

A. First, let me get this out of the way: Many experts strongly doubt that blood cholesterol levels have anything to do with heart disease and that worrying about cholesterol (in your food or your body) is a waste of time.

But you didn't ask me to help convince your friend that he doesn't need to worry about his cholesterol levels; you asked me to supply some evidence that dietary cholesterol does not effect blood cholesterol levels.

Maybe it's more accurate to say that, for most of us, dietary cholesterol doesn't affect blood cholesterol levels in any way that matters--even if you accept the cholesterol/heart disease hypothesis.

A review of 167 studies finds that increasing dietary cholesterol does increase blood cholesterol levels, but only minimally.  On average, every 100mg of cholesterol translates into a 2.2mg/dL increase in total cholesterol.

However, dietary cholesterol increases both "good" and "bad" cholesterol. In fact, even though total cholesterol levels may go up a bit, the HDL/LDL ratio (which many consider to be a better predictor of risk) does not appear to change in response to increased dietary cholesterol. You can read the entire article here: The Impact of Egg Limitations on Coronary Heart Disease

Could limiting dietary cholesterol lower your good cholesterol?

It's interesting to consider that people who limit dietary cholesterol may be reducing their "good" cholesterol as fast as they're reducing their "bad" cholesterol. Not to worry, because the impact of dietary cholesterol on blood cholesterol is fairly minimal. 

The one exception would be people who have a genetic abnormality that make them extremely sensitive to the effects of dietary cholesterol. These people usually know who they are because they have very high cholesterol levels very early in life.

Here's another review article that might be of interest: Cholesterol intake and plasma cholesterol: an update

From the abstract:

Reports from the Lipid Research Clinics Research Prevalence Study and the Framingham Heart Study have shown that dietary cholesterol is not related to either blood cholesterol or heart disease deaths. In a similar manner, 10 clinical trials (1994 to 1996) of the effects of dietary cholesterol on blood lipids and lipoproteins indicate that addition of an egg or two a day to a low-fat diet has little if any effect on blood cholesterol levels. This observation was noted in young men and women with normal cholesterol levels as well as older subjects with elevated plasma cholesterol concentrations. 

Unfortunately, this one isn't available on-line in full-text. But if you have access to a medical library the full article will include citations for all the individual studies that the author cites to support his conclusions.

Tropical Oils: A better saturated fat?

Shelly posted the following comment on a recent post on dietary fats:

"I've been reading some information that says coconut oil does not cause plaque build-up like other saturated fats because it is a medium-chain fatty acid, which apparently means it is digested more like a carb and doesn't have a chance to become plaque. I'd like to find more sources of this information, just to build some confidence. (When I relay this information about coconut, people look at me as though I'm from Mars.)"

Before I had a chance to respond, Dave posted a comment in response to Shelly's question:

"Short-chain fatty acids do take a different route than most fats. Most fats we eat are packaged up by the small intestine in large lipo-protein molecules called chylomicrons, which take a leisurely route through the lymphatic system before being dumped into circulation several hours after a meal. Short-chain fatty acids, by contrast, get a ride straight to the liver. The liver utilizes mostly fats for energy, so this probably frees up other energy sources for the body (the liver has high energy requirements), giving a quick-energy boost much like carbohydrates."

I love it when you guys do my work for me!  All I would add to Dave's little seminar on fatty acid metabolism is that the upshot of this is still largely hypothetical.  It might seem that medium and short chain fatty acids would be less likely to be stored as fat and/or form arterial plaques because they are metabolized differently. But there is very little research on what effect replacing other dietary fats with tropical fats has on weight or heart disease risk. (What research there is is contradictory.)

What's the take-home?

Shelly's question seems pretty straight-forward but there are actually a number of issues entwined in the tropical oil question. Here's my take on a few of them:

1. The role of dietary fat in obesity has been over-estimated in the past. But I think the pendulum may now have swung a bit too far in the other direction.The role of dietary fat in obesity is now being underestimated in some quarters.  In other words: Fat doesn't make you fat--but it probably doesn't make you thin either.

2. The role of dietary fat (and saturated fat in particular) in heart disease has probably been over-estimated. See also Steve Parker's post "Diet-Heart Disease Hypothesis: RIP".  My own pet theory is that the effect of dietary fats on health depends a lot on the quantity and quality of carbohydrates in the diet. Any study that fails to look at that interaction (which is most of them) is likely to reach unreliable conclusions.

3. Tropical oils are probably no more dangerous than animal saturated fats--which, as I noted above may not be as dangerous as we thought. 

4. Unrefined (extra virgin) tropical oils also contain some valuable antioxidants and phytonutrients.

5. Buyer beware: Many of the health claims being made for coconut oil these days are unsubstantiated and/or exaggerated. (See also my recent podcast on coconut oil.)

Is Paleo the new Mediterranean?

The Mediterranean Diet has been king of the hill for the last several years. While low-carb and low-fat camps continue to trade jabs, each amassing roughly the same number of studies in its favor, the Mediterranean diet (which is neither) has risen above the fray, trumping every diet it's compared with in study after study.

Just last week, for example, I noted a study finding that the Mediterranean diet helped diabetics lose more weight and use fewer medications than a low-fat diet.

But I sense a shift of power (or at least of focus) in the works.  The "Paleo Diet" has been garnering a larger and larger share of popular attention and support as the latest Solution To All Our Problems.  And now the research community is beginning to test the theory, designing studies that pit the Paleo diet against other dietary prescriptions.

The caveman versus the shepherd

While the Mediterranean Diet hearkens back a couple of thousand years ago to a pre-industrial, agrarian era, the Paleo diet turns the clock back by ten thousand years and attempts to replicate a pre-agricultural, hunter/gather diet.  Grains, dairy, legumes, and oils--mainstays of the Mediterranean Diet--are off the table in the Paleo diet, which is based on lean meat, fish, fruits, vegetables, eggs, and nuts.

The two went head to head in a small study of patients with heart disease. Paleo pinned Mediterranean to the mat, yielding greater improvement in glucose tolerance and greater decrease in waist size. Have the cavemen knocked the shepherds off the hill? Not yet. 

Studies are one thing; real life is another

For one thing, I wonder about the long-term practicality of the Paleo diet. Diets which depart dramatically from the cultural norm often lead to dramatic weight loss. This may be partly due to the metabolic "magic" put forth by proponents. But I think it's also at least in part behavioral and practical: when whole categories of food are off limits, you tend to eat less and weight loss ensues.

Paleo and other dietary theorists have compelling stories to tell, but what are the realities on the ground?  What are the subjects in the study going to eat when the study is over? History has shown that, while purists and zealots may succeed in renouncing grains, carbs, dairy, etc. for life, mere mortals eventually find these diets too difficult to maintain and lapse back into prior eating habits. 

And while cutting fat and calories and getting more exercise may seem hopelessly old-fashioned in an era of "good calories, bad calories," let's not ignore the fact that millions of people continue to lose weight and keep it off doing nothing more exotic than that.

Do what works

A change in diet only really improves health outcomes if it's sustainable. And sustainability involves practicality, logistics, economics, personal preferences and beliefs, as well as social conditioning and cultural norms. By all means, let's use what we're learning in the research lab to to nudge our social and cultural norms and public health and food policies in the right direction.

But changing cultural norms takes time. Right now, I think the Mediterranean diet may have a practical advantage over the more extreme Paleo approach.  Fortunately, we don't all need to agree on the same solution. If what you're doing isn't producing results, try a different approach. If you've found what works for you, keep doing it. But don't assume that what works for you is the (only) solution for everyone.

High fat diet increases insulin resistance?

I was just re-reading Tara Parker Pope's article in the NY Times on the now-famous rat study which found that high-fat meals impaired cognitive and athletic performance. Predictably, the study was dissed and dismissed by the low-carb and pro-fat bloggerati.

(By the way, for those who dismissed the study because it involved rodents, data from a parallel human study are still being analyzed but appear to line up with the original findings.)

Whatever the merits and implications of this particular study, I was struck by the following quote from Pope's article:

It’s not clear why fatty foods would cause a short-term decline in cognitive function. One theory is that a high-fat diet can trigger insulin resistance, which means the body becomes less efficient at using the glucose, or blood sugar, so important to brain function.

This, of course, is exactly the opposite of what low-carb/high-fat advocates are always telling us The story is that a high carbohydrate diet is the culprit (and a low-carb diet is the cure) for insulin resistance.

Specifically, ingestion of carbohydrates (especially high glycemic carbs) sends blood sugar soaring, which triggers insulin secretion. Over time, cells become less sensitive to the effects of all that insulin and blood sugar levels creep dangerously higher.  Next stop: obesity, Type 2 Diabetes, and heart disease. Cutting down on carbs reverses the whole cycle.

So what's all this about a high-fat diet triggering insulin resistance? 

In a long discussion, Mark Jenkins, MD, suggests that while carbohydrates may raise insulin levels, high insulin levels do not cause cells to become insulin resistant. Further, he suggests that obesity leads to insulin resistance and not the other way around.

Here are a few of his observations, which some may find surprising:

• High fat stores [in obese individuals] down-regulate insulin receptors and cause a resistance to circulating insulin.
• It has been repeatedly shown in the medical literature that...insulin sensitization is accomplished by aerobic exercise, low-fat / high-carbohydrate diet, and reduction of excessive body fat. Conversely, obesity and high fat diets have been shown to induce insulin resistance. 
• It is important that the high carbohydrate diet have predominantly complex carbohydrates and also have a high fiber content.  Overly refined, simple sugars do not appear to have the same effect as complex carbos. 

Please see Jenkins' entire discussion here and selected references here.

Maybe the problem is not the fat in our foods but the fat in our bodies

Jenkins' arguments don't separate the effects of diet composition from the effects of body weight or weight loss. In the studies he cites, those with insulin resistance aren't just eating a high fat diet; they're also obese. Those who see increased insulin sensitivity aren't just eating a low-fat diet, they're also exercising and losing weight. One wonders: Does a high fat diet lead to insulin resistance in normal weight people? Does a low-fat diet improve insulin resistance if the subjects don't lose weight? What if they lose weight on a high fat diet?

The epidemiological argument?

I find it interesting that both sides of this debate invoke epidemiological evidence. The pro-fat folks (the Weston Price gang, for example) claim that atherosclerosis and diabetes were "unheard of" in traditional cultures which had high fat, grain-free diets.  Jenkins, on the other hand, says:

If one looks at epidemiological data, the traditional diet of many third world countries consists of high complex carbohydrate content, very low fat, and high fiber. Atherosclerotic disease was virtually unheard of until the introduction of the high fat Western diet. 

Obviously the ratio of fats to carbohydrates does not tell the whole story.  Jenkin's observation about the difference between complex and simple carbohydrates is one key.

Maybe we can't blame the modern epidemic of obesity, heart disease, and diabetes on fat OR carbohydrates--but on a toxic combination of fat AND refined carbohydrates (with over-consumption and sedentary lifestyles playing significant supporting roles).

Your thoughts?

How much potassium do you need?

Q. How much potassium do I need?

A.  The Daily Value (DV) for potassium is 3500mg per day. When you look at the nutrition detail for any food or recipe here on ND, you'll see the amount of potassium listed, along with the percentage of DV. 

The Daily Value is a sort of one-size-fits all recommendation that is thought to represent the average needs of most healthy people. In 2004, the Food and Nutrition Board of the Institute of Medicine established an adequate intake (AI) recommendation for potassium based on the amounts that have been found to lower blood pressure, reduce salt sensitivity, and minimize the risk of kidney stones.  For adults, the AI is 4700mg per day. (Tip: You can personalize your nutrient targets using My Preferences.)

Another reason to eat your vegetables!

Recent surveys show that most Americans fall short of the recommended amount of potassium. I think this is mostly because most people don't eat enough fruits and vegetables, which are high in potassium. (People whose diets are high in fruits and vegetables usually get two to three times the recommended amount.)

Severe potassium deficiency is usually caused by things like severe vomiting or diarrhea, bulimia, laxative abuse, or use of certain diuretic medications.

The ratio of sodium to potassium is also something to think about. People who eat a high sodium diet may need more potassium than those who eat a low sodium diet. I discussed this at greater length in this post: http://blog.nutritiondata.com/ndblog/2009/03/sodium-and-pota.html.

For more information on potassium and health, see the Linus Pauling Micronutrient Information Center

More evidence that saturated fat has been falsely accused?

What if cancer, heart disease, and diabetes are really all the same disease?

An excellent commentary in this month's issue of the Journal of the American Dietetic Association lays out a compelling and detailed map showing how obesity and insulin resistance interact to promote the growth of cancerous tumors. The authors argue that weight loss (if appropriate) should be a central feature of cancer prevention and treatment. Going a step further, the journal's editors suggest that obesity (and insulin resistance) is the common culprit in all of the Dreaded Three: cancer, diabetes and heart disease. 

Now, if you ask the dietary establishment how to prevent obesity, cancer, and heart disease, they will most likely advise you to reduce your intake of total fat, saturated fat, and red meat. (See, for example, the American Cancer Society, the American Institute for Cancer Research, and the American Heart Association.)

Yet another study in the same issue of JADA tells a different story:

Saturated fat and red meat seem to prevent expanding waistlines

Danish researchers studied the links between consumption of various food groups and change in waist size.  Why are they worried about waist size? An increase in waist size signals an increase in visceral, or abdominal, fat. This is considered the most dangerous pattern of weight gain because abdominal fat is strongly linked to increased risk of heart disease, cancer, insulin resistance, and diabetes.  In fact, the association is so strong that a waist measurement of more than 35"  (for women) or 40" (for men) is an independent risk factor for heart disease.

Surprisingly (to some), they found that women who ate more butter and high fat dairy products gained less weight around the waist than those whose diets are lower in saturated fat. A similar association was observed with red meat--that is, those who ate more red meat had smaller waistlines. The researchers seem to be at a loss to explain these findings.

Some would argue that a diet higher in fat and protein may be lower in carbohydrates and that carbohydrates drive insulin resistance and obesity.

No consistent link found between animal fat and breast cancer

Then there was this study in the American Journal of Clinical Nutrition: Researchers from several European countries collected and analyzed dietary records for 319,000 women and found "no consistent association" between the consumption of eggs, meat, or dairy products with breast cancer. This, of course, contradicts previous observations.

I'm reminded of our extended debate over whether or not eating red meat increases your risk of cancer. And many of the same observations apply here: trying to draw definitive conclusions about the impact of diet on disease using diet records is a very tricky proposition. It's possible that red meat may be a red herring. For one thing, any category that lumps a char-grilled fast food hamburger (and the fries likely to accompany it) together with a grass-fed bison filet is completely meaningless.

Should you start eating more meat?

I'm not making any blanket recommendations one way or another.  Some thoughts:

The prevailing wisdom that meat and saturated fat are unhealthy is based on the same sort of inconclusive, circumstantial evidence as the studies I've noted here.  But if we really want to get to the truth, we're going to need to consider ALL the (flawed) evidence, not just that which supports our point of view.

As many of you know, I'm not a big meat eater myself--although this is more for environmental, ecological, and ethical reasons than nutritional concerns.  But I'm pretty sure that no one food or group of foods causes disease. In fact, to circle back to the beginning of this post (and a recurring theme around here), it seems that plain overconsumption of food in general is a bigger problem.  The fact that so much of that food is over-processed and nutrient-poor sure doesn't help.

If you're eating a calorically-appropriate diet made up mostly of whole foods, I'm prepared to be pretty darned flexible about the details.

Are grains necessary to a healthy diet?

Q. What is the purpose of eating grains?  If you are tracking your nutrition and getting all of the necessary nutrients, is there any reason that you couldn't eliminate grains from your diet?

A. What?! You want to eliminate one of the five basic food groups? Grains are the foundation of the Healthy Food Pyramid.  They must be essential to a healthy diet.

I'm kidding, of course. As far as I'm concerned, grains (such as wheat, corn, oats, rye, etc.) are not essential to a healthy diet.  I think the main reason that grains have long been counted as a basic food group is that dietary policy-makers have viewed them as an innocuous way to cover one's calorie needs (plus maybe some pressure from agricultural lobbies and interests).

You see, the powers-that-be don't want you filling your calorie needs with fat--especially saturated fat from animal products--because fat has long been seen as the villain in heart disease and obesity.  And it would be challenging to meet your calorie needs eating nothing but fruits and vegetables because, while they're packed with nutrients, vegetables are notoriously low-calorie.

Grains would seem to fill the void nicely. They're plentiful, filling, fat-free, shelf-stable, and relatively inexpensive--thanks in part to a government-subsidized agricultural industry.

They don't, however, provide any nutrients that can't be gotten from other foods. More to the point, many argue (ferociously) that the saturated-fat/heart-disease theory has been completely discredited and that carbohydrates--especially the refined, processed type) are the true culprits--in heart disease, obesity, and diabetes.  See for example Steve Parker's post "Are Saturated Fats All that Bad?" on the NutritionData Heart Health blog.

Although the carb-bashers can get a little strident, I'm on board with the basic concept.  I suspect that refined carbohydrates do a lot more damage than saturated fats, per se, do. I also think that being overweight, in and of itself, is more harmful than the foods you overeat to get that way. 

To get back to your question: Anyone who chooses to eliminate grains from their diets does so with my blessing, providing, of course, that they're covering their nutritional needs. But I'm not dogmatic about it.  Although grains are not essential to a complete diet, I think a healthy diet can include grains, ideally, whole and minimally processed. 

More importantly, the total number of calories you consume needs to be in line with what you need to maintain (or achieve) a healthy body weight. To repeat an opinion I expressed in a recent post, I think maintaining a healthy body weight is ultimately more important than what percentage of the diet is protein, fat, or carbohydrate.

I'm sure you've got some opinions: Let's hear 'em!

Four steps to a longer healthier life?

A giant study (involving over 20,000 subjects over 8 years) looked at how four "healthy lifestyle habits" affected the risk of common diseases like heart disease and cancer. The four habits they chose to track?

1. Never smoking

2. Maintaining a BMI of 30 or lower (Calculate your BMI here.)

3. Engaging in at least 3 1/2 hours of physical activity per week

4. Eating a healthy diet, which was defined as one high in fruits, vegetables, and whole grains and low in meat. (Don't shoot the messenger!)

Less than 4% of the subjects had zero healthy behaviors. About twice as many (9%) could take credit for all four.  Here's what's making headlines: The Four-Behavior Group had:

• 93% lower risk of diabetes
• 81% lower risk of heart attack
• 50% lower risk of stroke
• 36% lower risk of cancer

Of course, this study was purely observational, and there may be (and probably ARE) other unmeasured variables that came into play. 

But, for what it's worth, the correlation between these four behaviors (especially in combination) and the risk of the four most common diseases is notable.  Note that diabetes appears to be almost three times more "responsive" to lifestyle than cancer.

It's also interesting that of the four factors, diet had the weakest effect on risk.  Avoiding obesity was the strongest factor, followed by never smoking, exercise, and (in last place) diet. Of course, that could have something to do with the way they defined "healthy" diet.

But it does underline something I've been saying a lot lately in comments and discussion on the blog.  I suspect that obesity has a stronger impact on health than the details of dietary composition. In other words, it's an oversimplification to say that a certain diet (low-fat, low-carb, whatever) is healthier than another.  Whatever diet (within reason) helps you achieve and maintain a healthy body weight has my vote. And, obviously, we're not all the same.

Just for kicks, how do Nutrition Data readers stack up against the German subjects in this study?

Online Surveys & Market Research

Online Surveys & Market Research

Online Surveys & Market Research

Source: Archives of Internal Medicine