Phytoestrogens: Helpful or harmful?

Q. I consume about 1-2.5 tbsp of ground flaxseeds per day. I know from my symptoms (breast tenderness etc) that I have a bit of estrogen dominance. Could the phytoestrogens be negatively impacting my estrogen balance?

A. Does flax contain phytoestrogens? Yes.  In fact, flax seeds are a more potent source of phytoestrogens than soybeans. Is the ground flax causing your symptoms? Hard to say.

The whole issue of phytoestrogens (estrogen-like compounds found in plant sources including soy and flax) continues to bedevil researchers. Do they block the effects of estrogen, thereby protecting against things like breast cancer? Or, do they exert weak estrogenic effects, thereby protecting against things like heart disease and osteoporosis? Both? Sometimes one and sometimes the other?

Despite copious research, we still don't have a definitive answer on how phytoestrogens behave in the human body and why.  

Searching for clues in a sea of conflicting and confounding information, it appears that phytoestrogens probably don't do much for hot flashes but may help preserve bone density and reduce risk of heart disease.  The findings on cancer are even less conclusive. Phytoestrogens may protect some people against cancer,  but those with hormone-sensitive cancers are usually advised to avoid them. 

I have fewer concerns about whole foods like flaxseed and soybeans than I do about supplements which extract, isolate, and concentrate the bioactive compounds.

Returning to your question: I don't know if your symptoms are due to "estrogen dominance" or not. But the easiest way to find out whether flaxseed is contributing to them might be to stop eating flax for several weeks (try to keep everything else about your diet the same) and see if you notice any improvement.

Health benefits of sourdough?

Q. I use homemade whole-grain sourdough daily. I am totally convinced it has exceptional health benefits. But I can't find nutritional info on it. It seems to me that it has to have probiotics, for instance.

A.   Sourdough starter does contain lactobacillus bacteria, often referred to as probiotics. It's the lactobacillus that give sourdough its characteristic sour flavor. But it's hard to say for sure which strains are present in a sourdough without laboratory analysis. The sourdough in my kitchen probably has different strains than the one in yours, for example. And different strains of lactobacillus offer varying health benefits, as discussed in this recent post on probiotics.

But whatever beneficial bacteria may be present in your sourdough starter, they will probably be destroyed by cooking. Most lactobacillus bacteria are only viable to about 112 degrees F.  So while sourdough starter could be considered a probiotic food, sourdough bread would not.

Another potential health benefit of sourdough is that the bacteria partially "digest" some of the starches and sugars in the grains.  As a result, sourdough bread appears to cause less of an increase in blood sugar than yeast breads. (Here's a link to the study.)

In terms of the relative nutritional value of sourdough, the biggest factor is probably whether it's made with refined or whole-grain flour. And, although whole-grain sourdough may be healthier than regular white bread, it is still basically bread. I wouldn't eat it in unlimited quantities!

For more on the science of sourdough, see this article.

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Can you absorb fat-soluble vitamin D from skim milk?

Q. I recently read that Vitamins A, D, E, and K are fat soluble, meaning that they dissolve in fat instead of water. Does this mean that these vitamins need to be eaten with some type of fat source for the body to absorb them? For instance, if somebody ingested just a cup of skim milk would any of the Vitamin D not be absorbed because of the lack of fat?

A. It's not so much that fat-soluble vitamins dissolve in fat, but that they are carried across the intestinal cell barrier by lipid (fat) molecules.  So, while it is true that fats are necessary for transport and absorption of fat-soluble vitamins, it doesn't take much!

A couple of years ago, there was a study that found that eating avocado with vegetables increased the absorption of fat-soluble beta-carotene from the vegetables. However, a study that looked specifically at vitamin D found that vitamin D was absorbed just as well from both skim milk and orange juice as it was from whole milk. (Maybe the fiber in the vegetables plays a role somehow?)

The most likely causes of fat-soluble vitamin deficiency includea missing or malfunctioning gall bladder, bariatric (weight loss surgery), intestinal resection, or other serious digestive diseases that interfere with absorption of fats.

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.

 

How much omega-3 is too much?

Q. Is there any upper limit as far as how many grams of omega 3 you can take? I'm aiming for an omega-6 to omega-3 ratio of 4:1.  As an example, if I ate 10g of omega 3 and 40g of omega 6, that's still in the 4:1 ratio but is 10g of omega-3 too much? What would be the upper limit?

A. There is no UL (tolerable upper limit) for omega-3 or omega-6 fatty acids (PUFAs).  The USDA feels it has "insufficient evidence" to set one. Instead, you might want to consider how much total fat you're going to eat and how you want to divide that up. For example, consuming large amounts of PUFAs might either cause you to miss out on the benefits of other fats, such as monounsaturated fats, or lead you to eat too much total fat.

Many experts recommend that PUFAs should make up 5-10% of your dietary calories and that seems reasonable to me.  The rest of your fat calories would come from monounsaturated fats like those found in olives and avocados and/or saturated fats from meat, dairy, and tropical oils.  Trans fats from hydrogenated oils and fried foods should ideally be kept to an absolute minimum.

In your example, you'd be eating 50g of PUFAs, for a total of 450 calories. Unless you're eating 4500 calories a day, that might be a little out of balance.  Without knowing the particulars of your situation, sounds as if you might want to think about ratcheting your intake of BOTH kinds of PUFAs back a bit.

Building your dietary fat "profile"

Here's how a healthy distribution of fats might look for a typical person eating 2500 calories a day:

30% of calories as fat = 83 g 

Of that:

    15% of calories from monounsaturated fat = 40g

    7% of calories from saturated fat = 20g

    7% of calories from polyunsaturated fats = 20g

To maintain a 4:1 ratio of omega-6 to omega-3, that would be 16g omega of omega 6 and 4g of omega 3.

Fish or flax?

As far as the dangers of taking too much omega-3, it depends whether you're talking about 10g of flax oil, which provides alpha-linolenic acid (ALA), or 10g of fish oil, which contains the much more biologically active forms of omega 3 (EPA and DHA). 

Ten grams of fish oil could potentially create some issues, such as interfering with blood-coagulation and immune function (not to mention digestive distress). Whether or not these might be concerns for you is a question for a licensed nutrition professional who knows the details of your situation.

       

   

Did the Dairy Council set the RDA for calcium?

Q. The RDA for calcium seems impossible to achieve unless someone eats dairy (or takes supplements), but considering that dairy has been part of the human diet for only a short period of time (and most people are lactose intolerant), how can our requirements really be that high? Is there scientific evidence that we need that much calcium or has the Dairy Council had a hand in the government's guidelines?

A. You mean, was there a conspiracy to get Americans to consume more dairy products by setting the recommendations for calcium intake higher than necessary? I wouldn't go that far (although I'm sure some would!).

The RDA for calcium reflects the realities of the typical Western diet

The RDA for calcium represents the amount that will meet the needs of most (97%) healthy individuals. They're taking into account not only the amount needed to prevent acute calcium deficiency but also to prevent long-term consequences like osteoporosis.

This is based on scientific research, of course. But most of that research is done on people who eat a typical Western diet--which is relatively high in both protein and sodium. Coffee and soft drinks (containing caffeine and phosphates) are frequently consumed.  All of these things can increase the body's calcium requirements.

The RDA for calcium reflects how much calcium it takes for someone with a typical Western diet to maintain adequate calcium stores.  Those on a lower protein or lower sodium diet might require less.

Non-dairy sources of calcium

Not only are dairy products some of the richest sources of dietary calcium, but the calcium in dairy is well absorbed by the body. But if you're not into dairy, canned salmon and sardines are great non-dairy sources. Tiny bones in the fish--so soft that they're simply consumed with the flesh--are what makes these fish good calcium sources.  Kale and collard greens are also good sources. A cup of collards has as much calcium as a cup of milk.

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.

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