Probiotic confusion

Last week, I answered a question from a reader who had seen a study showing that probiotic supplements reduced cold and flu symptoms in children. He reasoned that eating yogurt every day might be a good step and wondered how much he'd have to eat to get a similar "dose" of probiotics.   To answer his question, I compared the number of active cultures in a typical probiotic supplement to the number of active cultures in a typical yogurt.

But I missed an opportunity to clarify what I think is a widespread misunderstanding about probiotics. Many people think of all probiotic supplements and foods as being somewhat interchangeable. They're not.

Probiotics: an umbrella term for thousands of different bacteria

In terms of labeling foods and supplements, the FAO/WHO defines probiotics as "Live microorganisms which when administered in adequate amounts confer a health benefit on the host."  That's any health benefit.

There are hundreds of different strains of lactobacillus bacteria and they offer a variety of potential health benefits to humans. Some colonize the large intestine, others live in the lining of the stomach, still others have an affinity for the mucus membranes in the nose.  Of the many strains likely to colonize the large intestine, for example, some may improve gut immune function, others digest complex sugars, others may benefit the host by producing vitamin K.

There are also lactobacillus bacteria that don't do much of anything to improve or defend your health. These, while harmless, would technically not be classified as probiotics--although they might still be considered "live and active cultures.". 

Foods versus supplements

Most probiotic foods contain a variety of bacterial strains--your average supermarket yogurt might contain six different bacterial strains. And the lactobacillus bacteria found in yogurt are not necessarily the same as those found in other fermented foods like kefir or kim-chi.

Many of the studies you read about use "boutique" strains that are not likely to be found in any traditionally-fermented foods. In the case of the study I mentioned above, for example, they used two trademarked strains called Lactobacillus acidophilus NCFM and Bifidobacterium lactis Bi-07.

Is there any point to consuming probiotic foods?

I still think there are general health benefits to eating traditionally-fermented foods like yogurt, kefir, kim-chi, kombucha, sauerkraut, and miso. Eating a variety of fermented foods, which provides a wider variety of bacterial strains, might offer a wider range of benefits.

But we need to be careful about assuming that the findings on a particular strain apply to all probiotics and probiotic foods.  If you're going for a specific therapeutic benefit, such as protecting against side effects while taking antibiotics or improving flu resistance, there's no guarantee that yogurt or any other fermented food will contain the same bacteria as were used in a particular study.

Similarly, when shopping for probiotic supplements, pay attention to the individual strains in that supplement and how they compare with the strains used in various studies you might be responding to.

Is vitamin D your best protection from swine flu?

Dr. John Cannell is convinced that the swine flu epidemic could be vastly curtailed with vitamin supplementation.  (Cannell is the Executive Director of the Vitamin D Council, a non-profit organization dedicated to educating the public about the perils of vitamin D deficiency.)

Anecdotal reports support vitamin D as flu preventive

Cannell has been campaigning to get the NIH and CDC to investigate claims that vitamin D supplementation (2,000 to 5,000IU per day) confers virtual immunity against swine flu.   As evidence, he presents reports from two physicians, one from a long-term care facility in Wisconsin and one with a private practice in Georgia. Both doctors use aggressive vitamin D supplementation with their patients--and both report that their patient populations were virtually untouched by flu when it swept through their facilities and practice communities. You can read testimonials from the physicians on the Vitamin D Council website.

As supporting evidence, Cannell notes that vitamin D is involved in immune response and that low vitamin D status appears to increase one's susceptibility to respiratory infections.  Some researchers theorize that the reason that the flu season tends to peak in winter is that this is when most people's vitamin D levels are lowest. (This was not the case with H1N1, however, which had a robust summer season.)

Are public health officials dropping the ball?

So far, neither the CDC nor the NIH appear interested in investigating this further, although Canada's public health agency is adapting its current study on vitamin D and influenza to include the H1N1 virus.

But with H1N1 breathing down our necks, the results of this and other research will come far too late to protect us from this year's swine flu threat. Cannell argues that people have nothing to lose from vitamin D supplementation and much to gain.

Some researchers fear vitamin D could backfire

But is there really nothing to lose from vitamin D supplementation? An group of researchers from the U.S. and Australia isn't so sure. Their research suggests that vitamin D supplementation may actually suppress immune response. Interestingly, increasing vitamin D levels by exposing the skin to sunlight or UV-B rays does not appear to have this immuno-suppressive effect. (Here's a link to their entire paper, published in Autoimmunity Reviews.)

Since this paper was published earlier this year, I've been eager to hear some sort of response or analysis from Cannell and the crew at Vitamin D Council but haven't seen anything from them yet.I can see why the CDC is not ready to jump on the vitamin D supplement bandwagon quite yet.

What's your best move?

Where does this leave us in regard to this flu season? I think people (and their physicians) are going to have to weigh the evidence--all of which is preliminary--and decide for themselves whether the potential benefits outweigh the potential risks.  

Perhaps the best compromise is to get as much vitamin D as possible through natural sunlight. As we get into winter (here in the Northern hemisphere), your best bet at stimulating vitamin D production is to get outside at mid-day and bare as much skin as you can.  For those who missed it, here's a calculator that will help you calculate how many minutes a day you'd need to cover your vitamin D requirements.

Vote in our poll: Are you planning to get the swine flu vaccine?

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.)

Molasses and maple syrup: more nutritious sweeteners?

Q. I have read on your blog (and many other places) that all concentrated sweeteners are devoid of nutrients and count as "empty calories," but according to the nutrient info here on Nutrition Data, some less refined sweeteners, such as maple syrup and molasses, are high in many minerals. Considering that Americans eat almost a 1/2 cup of sweetener a day (mostly as refined sugar and high fructose corn syrup), wouldn't we better off nutritionally if we assuaged our sweet tooth with half a cup of maple syrup or molasses instead?

A. If you insist on driving 200 miles per hour, you'd make yourself a little safer by wearing your seat belt. But if you really want to improve your chances of surviving, you'd be better off slowing down--AND wearing your seat belt!

By the same token, replacing white sugar with maple or molasses might offer a slight nutritional upgrade. But if you're looking to improve your health, I think you'd accomplish more by  cutting back on sugar--as well as, perhaps, using less refined sources.

Let's take a closer look at the nutrients in molasses:

One-half cup of molasses supplies:

• 35% of DV for calcium
• 44% of DV for iron
• 56% of DV for vitamin B6
• 70% of DV for potassium
• 100% of DV for magnesium
• 129% of DV for manganese

Not so shabby!  On the downside, a half cup of molasses also contains 93 grams of sugar, about four times the amount suggested in the latest recommendations from the AHA and 489 calories (about 25% of the average daily calorie needs).

Obviously, you can get those nutrients (for a lot less calories and sugar) from other foods. Let's say you cut your consumption of added sugar to something closer to the level recommended by the AHA. Two tablespoons of molasses would only provide:

• 9% of DV for calcium
• 11% of DV for iron
• 14% of DV for vitamin B6
• 18% of DV for potassium
• 25% of DV for magnesium
• 32% of DV for manganese
  

Not quite as impressive. But, sure, why not choose the sweetener with the added nutrients over nutritionally devoid white table sugar? Just don't let it seduce you into thinking that more is better!

Maple syrup, by the way, is not as nutritious as molasses. Two tablespoons supplies:

• 2% of DV for magnesium
• 2% of DV for potassium
• 3% of DV for calcium and iron
• 11% of DV for zinc
• 66% of DV for manganese

How much (and what kind of fat) should you eat?

The Food and Agricultural Organization (FAO) and the World Health Organization (WHO), both agencies of the United Nations, just released a big fat report, all about fat.

These two agencies are charged with "providing science-based guidance on food and nutrition to national governments and the international community."  Periodically, they conduct sweeping reviews of the available evidence on various dietary questions and attempt to formulate some sort of guidelines based on the current state of the science.  Their most recent effort focuses on dietary fats--how much and which kinds make us healthy or sick.

In the introduction, the authors note:

"Knowledge of the role of particular fatty acids in determining health and nutritional well-being and how they exert these effects has expanded dramatically...The benefits and potential risks of these nutrients go well beyond their role as fuels: specific n–3 and n–6 fatty acids are essential nutrients, while others affect the prevalence and severity of cardiovascular disease, diabetes, cancer and age-related functional decline. This...demonstrates the need to focus on the role of individual fatty acids and how requirements vary with age and physiological status."

The entire report, which was published in the Annals of Nutrition and Metabolism, is available for free online.

Based on a quick skim,  it looks as if the recommendations for total fat intake (20 to 35% of calories) and saturated fat (no more than 10% of calories) aren't changing much but there are more nuanced recommendations regarding individual fatty acids, especially omega-3, omega-6, and monounsaturated fats.

If nothing else, it's helpful to have all the recent research on the subject--flawed as it may be--gathered and summarized in one place.  I'll be reading through it in the days ahead (or maybe weeks--there's 300 pages of material) and posting on anything that catches my eye, but I thought some of you might be interested in taking a look as well.

Can yogurt protect you from the flu?

Q. I recently read about a study showing that probiotics protected kids from getting the flu. It seemed like a pretty powerful study in favor of the health benefits of yogurt, at least in kids. Do you have any recommendations for a reasonable "dose" of yogurt would be for an adult?

A. Yes, I noted that study with interest as well. The kids (about 300 of them, aged 3 to 5) were taking probiotic supplements or placebo pills twice a day. The kids getting the probiotics had about half as many fevers, coughs, and runny noses, took fewer prescriptions and missed fewer days of school.

We should note that the study was funded by a company that makes probiotic products.  That said, the results were published in a peer-reviewed journal (Pediatrics) so the study design apparently passed muster.

There's no RDA for probiotics for kids or adults so it's hard to say what a good"dose" might be. Most probiotic supplements contain 10 to 20 billion active cultures per dose at the time of manufacture. Yogurt that carries  the "Live and Active Cultures" seal is certified to contain at least 100 million cultures per gram at the time of manufacture, which translates into about 22 billion live cultures in an eight ounce cup of yogurt.

So, I'm thinking that a single serving of yogurt every day would be a reasonable start for kids and adults. But the amount of sugar (often high fructose corn syrup) in sweetened yogurts is shocking. I'd advise you to steer clear of sweetened (and artificially-sweetened) yogurts and go for the plain yogurt. Sweeten (if you must) with fruit or a drizzle of honey.

Can yogurt protect you (or your kids) from getting the flu this season? Might help and can't hurt (unless you're lactose intolerant).

Genetics of obesity: Why we're never going to find one diet that's right for everyone

Any regular reader of this blog knows that we spend a lot of time debating the merits of various dietary theories. One of the reasons I sometimes find this debate frustrating (even tiresome) is that so many of the arguments boil down to this:

"Diet X has completely cured my diabetes (heart disease, weight problem, gout, wobbly upper arms, etc.).  Based on my experience, I'm convinced that Diet X is the one and only road to optimal health."

The problem is that "Diet X" may be a low-carb diet, a Paleo diet, a vegan diet, a raw diet, or any number of other mutually exclusive systems. At that point, the conversation starts to resemble discussions of religion or politics. Everyone spends a lot of energy proving their own point of view and trying to disprove alternate views. Some arguments are more articulate and compelling than others.  But in the end, few minds are changed.

In Defense of Wishy-Washiness

Perhaps you think I've been wishy-washy because I don't endorse one side or the other. After all, I've read the arguments and evidence. And I keep saying things like "Do What Works for You" and "One Size Doesn't Fit All." Shouldn't I have reached some sort of conclusion, even tentative, about which approach is "right," or at least "better"?

I really don't think there is one dietary prescription that is right for everyone. Part of this is simply pragmatic: It's a waste of time pitching a caveman diet to a committed vegan. But we're also beginning to see that genetics plays a big role in eating patterns.

Is it the carbs making my jeans so tight? Or my genes?

For example, some argue that eating carbohydrates disrupts the body's ability to regulate appetite and signal satiety (fullness)--leading to overeating and obesity.  As elegant as some of these diet/disease theories are, I don't think that the phenomenon of obesity (or its absence) can be fully explained by nutritional biochemistry alone. 

Recent research suggests that genetic variation also plays a significant role in how much we eat and whether or not we gain weight, or develop diabetes or heart disease. Here's a recent review article on the work in this field. (Subscription or library access required to view the entire article.)

The smart money now is on mapping out these genetic variations so that we can better predict who will fare well on what type of dietary prescription.  And here's a perfect example: This study suggests that a low-fat diet may be the best choice for people with a certain "obesity" gene.  Those with a double copy of the FTO gene are 2.5 times more likely to be obese. However, a low-fat diet neutralizes the effect of the gene.

In the meantime, people may need to try different eating patterns to find the one that is a good fit with their lifestyle and personal preferences.but allows them to maintain a healthy body weight over the long term.

Whither the Food Pyramid?

Many have questioned the validity of the U.S. Food Pyramid and Dietary Guidelines. But most simply want to replace them with pyramids and guidelines which better represent their own dietary dogma.  However, as nutritional genomics matures, one-size-fits-all efforts like the Food Pyramid and Dietary Guidelines may become less and less relevant.

Your thoughts?

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.

Do sugar substitutes hurt or help with weight loss?

The whole idea of zero-calorie sweeteners is that they save calories. But evidence against the usefulness of artificial sweeteners as a weight-control tool seemed to be stacking up.

It's been noted that consumption of diet sodas is linked obesity.  Studies have suggested that the hyper-sweet flavor may increase the desire for sweets.  Or that the stimulation of sugar taste sensors combined with lack of calories may induce an unintended hormonal or metabolic response.  Or, simply that the idea that one is "saving calories" by using sugar substitutes may lead one to over-consume other foods in compensation. 

(See also my previous post "Sugar-Free Doesn't Get You Off Scot--Free" and this recent episode of the Nutrition Diva Podcast)

There's also new brain-mapping research from the Utrecht University and University of Birmingham (Britain) showing that the brain can distinguish caloric beverages from calorie-free ones, even when the taste-buds can't. Researchers wonder whether this leads people to subconsciously replace those calories with other foods. (See this article from the Chicago Tribune for more details.)

So what are we to make of this latest study, from the International Journal of Obesity, which found that the use of artificial sweeteners was an effective strategy for weight maintenance.  The report also notes a 2002 finding that people who used artificial sweeteners lost more weight than those who didn't.

For now, I think the bottom line is that using artificial sweeteners doesn't automatically lead to a reduction in calorie intake.  For those who closely monitor their calorie intake, including artificially-sweetened beverages may make sticking to the budget just a bit easier.