A great discussion on vitamin D

10. April 2006 William Davis (0)
If you need better convincing that vitamin D is among the most underappreciated but crucial vitamins for health, see Russell Martin's review of vitamin D and its role in cancer prevention. You'll find it in March, 2006 Life Extension Magazine or their www.LEF.org website at:

http://search.lef.org/cgi-src-bin/MsmGo.exe?grab_id=0&page_id=1308&query=vitamin%20d&hiword=VITAM%20VITAMER%20VITAMERS%20VITAMI%20VITAMINA%20VITAMINAS%20VITAMINC%20VITAMIND%20VITAMINE%20VITAMINEN%20VITAMINES%20VITAMINIC%20VITAMINK%20VITAMINS%20d%20vitamin%20

Our preliminary experience over the past year suggests that vitamin D may be the crucial missing link in many people's plaque control program. We've had a handful of people who, despite an otherwise perfect program (LDL<60, HDL>60, etc.; vigorous exercise, healthy food selection, etc.--I mean perfect)continued to show plaque growth. The rate of growth was slower than the natural expected rate of 30% per year, but still frightening rates of 14-18% per year--until we added vitamin D. All of a sudden, we saw dramatic regression of 7-25% in 6 months to a year.

This does not mean that vitamin D all by itself regresses plaque. I believe it means that vitamin D exerts a "permissive" effect, allowing all the other treatments (fish oil, LDL reduction, HDL raising, correction of small LDL, etc.) to exert their full benefit. So please don't stop everything and just take D. This will not work. However, adding vitamin D to your program on top of the basic Track Your Plaque approach--that's the best way I know of.
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CT scans and radiation exposure

CT scans and radiation exposure

19. June 2007 William Davis (8)


The NY Times ran an article called

With Rise in Radiation Exposure, Experts Urge Caution on Tests at

http://www.nytimes.com/2007/06/19/health/19cons.html?_r=1&adxnnl=1&oref=slogin&adxnnlx=1182254102-vQpytpx6W/Z9gvAaNPDZvA



“This is an absolutely sentinel event, a wake-up call,” said Dr. Fred A. Mettler Jr., principal investigator for the study, by the National Council on Radiation Protection. “Medical exposure now dwarfs that of all other sources.”


Where do CT heart scans fall?

Let's first take a look at exposure measured for different sorts of tests:



Typical effective radiation dose values

Computed tomography Milliseverts (mSv)

Head CT 1 – 2 mSv
Pelvis CT 3 – 4 mSv
Chest CT 5 – 7 mSv
Abdomen CT 5 – 7 mSv
Abdomen/pelvis CT 8 – 11 mSv
Coronary CT angiography 5 – 12 mSv

Non-CT Milliseverts (mSv)

Hand radiograph Less than 0.1 mSv
Chest radiograph Less than 0.1 mSv
Mammogram 0.3 – 0.6 mSv
Barium enema exam 3 – 6 mSv
Coronary angiogram 5 – 10 mSv
Sestamibi myocardial perfusion (per injection) 6 – 9 mSv
Thallium myocardial perfusion (per injection) 26 – 35 mSv

Source: Cynthia H. McCullough, Ph.D., Mayo Clinic, Rochester, MN


If you have a heart scan on an EBT device, then your exposure is 0.5-0.6 mSv, roughly the same as a mammogram or several standard chest x-rays.

A heart scan on a 16- or 64-slice multidetector device, your exposure is around 1.0-2.0 mSv, about the same as 2-3 mammograms, though dose can vary with this technology depending on how it is performed (gated to the EKG, device settings, etc.)

CT coronary angiography presents a different story. This is where radiation really escalates and puts the radiation exposure issue in the spotlight. As Dr. Cynthia McCullough's chart shows above, the radiation exposure with CT coronary angiograms is 5-12 mSv, the equivalent of 100 chest x-rays or 20 mammograms. Now that's a problem.

The exposure is about the same for a pelvic or abdominal CT. The problem is that some centers are using CT coronary angiograms as screening procedures and even advocating their use annually. This is where the alarm needs to be sounded. These tests, as wonderful as the information and image quality can be, are not screening tests. Just like a pelvic CT, they are diagnostic tests done for legimate medical questions. They are not screening tests to be applied broadly and used year after year.

Always be mindful of your radiation exposure, as the NY Times article rightly advises. However, don't be so frightened that you are kept from obtaining truly useful information from, for instance, a CT heart scan (not angiography) at a modest radiation cost.



Detail on radiation exposure with CT coronary angiograms on multidetector devices can be found at Hausleiter J, Meyer T, Hadamitzyky M et al. Radiation Dose Estimates From Cardiac Multislice Computed Tomography in Daily Practice: Impact of Different Scanning Protocols on Effective Dose Estimates. Circulation 2006;113:1305-1310, one of several studies on this issue.
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Comments (8) -

  • Anonymous

    6/20/2007 1:13:00 AM |

    I had a calcium score scan on a 64-slice machine at the Morristown Hospital in New Jersey. No contrast was injected. The technician did three separate scans that included the lung, even thought I didn't for a lung scan. I wonder why three scans were taken. Does it mean that I had three times the radiation?

  • Dr. Davis

    6/20/2007 1:22:00 AM |

    Hi,
    Of course I can't comment specifically on what was done, but it is common practice to perform 1) a "scout" film for the technologist to identify the location of important "landmarks" like the sternum and the top and bottom of the heart to minimize the window of exposure, and 2) lung imaging as a routine part of  heart imaging, not necessarily an additional scan.

    If an additional and unrequested lung scan was performed, you may want to call and ask why this policy is in operation.

  • Anonymous

    6/21/2007 4:35:00 AM |

    What do you feel about yearly nuclear stress tests for people with CAD?  The radiation exposure seems high and the ability of a stress test to pick subtle changes in flow is low.  In the absence of symptoms it would appear that the common practice of nuclear stress tests for people with CAD is a questionable practice.

  • Dr. Davis

    6/21/2007 12:14:00 PM |

    I agree. The radiation is excessive. I tend to follow that route only when nothing else is possible. An alternative for stress testing is stress echocardiogram in its various forms, none of which involve radiation. They still suffer the other pitfalls of stress testing, of course, but do not involve radiation.

  • Mike

    12/20/2008 11:40:00 AM |

    I just launched a webiste that may answer some of your questions.  www.xrayrisk.com. It allows you to calculate your cancer risk based on studies you have had and answers some faq on radiation exposure and cancer.

  • Anonymous

    12/6/2009 12:52:26 AM |

    There are several ways to estimate your cancer risk - the best site for background information is probably the Image Gently campaign.

    The American College of Radiology has similar information pages for patients and the general public.

    To track your exposure, as Mike said there's the xrayrisk website.
    There's also a program for the iphone called Radiation Passport that tracks all of your radiation exposure and gives you the associated risk of developing cancer from your radiation exposure.

  • buy jeans

    11/3/2010 6:33:12 PM |

    CT coronary angiography presents a different story. This is where radiation really escalates and puts the radiation exposure issue in the spotlight. As Dr. Cynthia McCullough's chart shows above, the radiation exposure with CT coronary angiograms is 5-12 mSv, the equivalent of 100 chest x-rays or 20 mammograms. Now that's a problem.

  • Medical CT

    11/29/2010 4:34:03 AM |

    The CT scanner was originally designed to take pictures of the brain. Now it is much more advanced and is used for taking pictures of virtually any part of the body.

    The scanner is particularly good at testing for bleeding in the brain, for aneurysms (when the wall of an artery swells up), brain tumours and brain damage. It can also find tumours and abscesses throughout the body and is used to assess types of lung disease.

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When is a calorie not a calorie?

When is a calorie not a calorie?

10. April 2008 William Davis (8)
One ounce of raw almonds (about 23 nuts) contains:


6 grams protein

14 grams fat

6 grams carbohydrate

3.5 grams fiber

For a total of 163 calories per ounce.


(From the USDA Nutrient Database)


Calorie content of foods is determined by summing up the calories from each constituent: 1 gram of fat = 9 calories; 1 gram protein = 4 calories; 1 gram carbohydrate = 4 calories. Calorie content can also be directly measured using a device called a burn calorimeter, in which the amount of energy released from a specific food is measured by literally burning it and gauging precisely how much energy is released.


The problem with both of these methods is that it is assumed that all foods are digested with equal efficiency. That is, it assumes that a potato chip is as readily digested and absorbed as energy from table sugar, a pretzel, oatmeal, a piece of steak, or a handful of nuts. In real life, of course this is not true. Different foods are absorbed with varying efficiency.

For a long time I've suspected that some foods are very inefficiently absorbed. I've particularly suspected that raw nuts are relatively poorly absorbed and thus yield only a fraction of the calories ingested.

Among the studies recently reported at the Federation of the Association of Societies for Experimental Biology (FASEB) meetings I attended in San Diego this past week were several devoted to almonds.

One study, to my surprise, documented this phenomenon. In Manipulation of lipid bioaccessibility of almonds influences postprandial lipemia in healthy human subjects, it was determined that, of 100 calories ingested from the fat fraction of almonds, only about half was actually absorbed. The remaining half passed out in the stool. (They did this by collecting stool samples and comparing the fat composition after eating the different almonds prepartions. This is not discussed in the limited text of the abstract.) In addition, postprandial (after-eating) surges in triglycerides were much less with whole almonds compared to the oil separated from the nut (i.e., broken down into almond oil + defatted almond flour). The researchers attributed the difference to the inhibitory effects of the almond nut's "food matrix," or the structural properties of chewed foods.

Add to this the fact that, of 6 grams of carbohydrate per ounce of whole almonds, 3.5 grams are indigestible fibers. This means that 6 - 3.5 = 2.5 grams of digestible carbohydrates are present per ounce (assuming 100% release).

If we follow the reasoning that only about half the fat fraction of almonds are absorbed, and assume that the protein and carbohydrate (minus the indigestible fibers) are absorbed efficiently (100%), then we would re-calculate the calorie content of almonds to be 97 calories per ounce, or 40% less than calories calculated by composition or measured with a calorimeter.

If we were to assume that protein and carbohydrates were, like fats, inefficiently absorbed because of the effects of the food matrix, then one ounce of almonds yields 88 calories per ounce, or 46% less. This is, in fact, a likely scenario, since the food matrix is largely created by the cell wall and should impede digestive access to fat, protein, and carbohydrate equally.

My point? Almonds and other nuts at first appear to be calorically dense due to fat composition. However, this simplistic view of nuts is misleading because of the confounding effects of the food matrix. Stated differently: Whole foods yield less calories. And, judging by the postprandial triglyceride effects: Whole foods yield less undesirable effects, such as postprandial rises in triglycerides.

Some other observations with almonds included:

The effect of almonds on plasma lipids in persons with prediabetes This study confirmed the LDL-reducing and modest HDL-raising effects of almonds.

Almonds (Amygdalus communis L.) as a possible source of prebiotic functional food This curious observation suggests that almonds modify the bacterial flora of the intestinal tract in a positive way (like the cultures in yogurts).



Copyright 2008 William Davis, MD
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Comments (8) -

  • Anna

    4/11/2008 1:46:00 AM |

    I often soak raw almonds (and other nuts) about 24 hours in filtered water with sea salt, then dry them a day or two at about 150°F in the oven.  I doubt the studies take this kind of "processing" into account, but any idea how that might change the absorption scenario?

  • Anonymous

    4/11/2008 4:27:00 PM |

    I'm glad you posted this.  A few women I know have been wary of eating many nuts for fear that fatty nuts would cause them to gain weight.  

    Really like the little bit on healthy gut flora caused by almonds too.  A healthy gut is important to me.

  • Peter

    4/11/2008 8:19:00 PM |

    I would certainly agree that it is possible to eat enormous quantities of nuts without absorbing all of their calories. I noticed I could remain weight stable while sedentary and eating 3,500 calories back when I used to eat large quantities of nuts. Even when well chewed a proportion of them end up you-know-where! Just flush...

    Peter

  • brian

    4/12/2008 4:22:00 PM |

    Dr. Davis, this is a great example. Thanks for posting it. I have a question on the 88 calories. I tried to work through the calculations to demonstrate this to one of my clients. I couldn't come up with 88 calories per ounce.

    I kept coming up with 80 and here's how. 50% calories from fat is 63. I used 50% for protein and digestible carbs - based on the info provided. For protein, that leaves 3 gms or 12 calories. For carbs, half of 2.5 gms is 1.25 gms, which equals 5 cals. These add up to 80 (63 + 12 + 5).

    I’m probably making a silly mistake but I’d like to come up with the same numbers when demonstrating this to clients – makes me feel kind of silly.

    Thanks again for the blog, I greatly appreciate the information you post.

    Brian

  • Anne

    4/13/2008 9:57:00 PM |

    Does pasteurization affect the positive effect almonds have on gut bacteria? Last year it became manditory that all California almonds must be pastuerized by one of these methods: fumigation with propylene oxide, blanching and oil roasting. This is to prevent salmonella. http://www.almondboard.com/Programs/content.cfm?ItemNumber=890&snItemNumber=450

    I eat a handful of almonds just about every day. I have wondered if there benefits have been compromised.

  • Anonymous

    4/14/2008 12:25:00 PM |

    The study was sponsored by The Californian Almond Association

  • Katherine

    10/21/2008 6:30:00 AM |

    In the era of the 64-oz. soda, the 1,200-calorie burger, food companies now produce enough each day for every American to consume 3,800 calories per day as compared to the 2,350 needed for survival. Not only adults but kids are also consuming far more calories than they can possibly use. http://www.phentermine-effects.com

  • buy jeans

    11/3/2010 6:53:22 PM |

    For a long time I've suspected that some foods are very inefficiently absorbed. I've particularly suspected that raw nuts are relatively poorly absorbed and thus yield only a fraction of the calories ingested.

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