Is there too much radiation from X-ray exams?

If you search on the Internet for health risks as a result of radiation of X-rays, particularly dental X-rays since that's the most common source of X-rays we're exposed to, you'll find hundreds of articles. The most trustworthy ones are from well-respected web sites, such as Annual X-rays May Expose Patients to Unnecessary Risk on WebMD, New Dental X-ray Guidelines Spell Out Radiation Reduction on Medscape. Many articles including these two mention the 2012 study Dental x-rays and risk of meningioma that links brain tumor to frequent dental X-rays. On the other hand, dentists and some articles argue that dental radiation is insignificant compared to background radiation. According to Wikipedia, "A dental x-ray delivers a dose of 5 to 10 µSv" (or 0.005 to 0.01 mSv). "The average American receives about 3 mSv of diagnostic medical dose per year" (including chest, dental and other types of medical X-rays), while "Average annual human exposure to ionizing radiation" for an American is 3.10 mSv, mostly from inhalation of air, which naturally contains radon. If medical X-rays give us about the same amount of radiation as the background, how do we reconcile the apparent discrepancy between this fact and the 2012 study? Some say the study relies on people's memory of past medical check-ups, which is unreliable. But I'm thinking of another explanation.

In April 2011, I blogged Sun UV to trigger Vitamin D and skin cancer: intensity matters?, where I propose that given the same total exposure of sunlight for the purpose of producing Vitamin D, it's better to scatter the light around your body than to focus it on a small part. Now I believe the same theory can explain the risk of medical X-rays as opposed to the relative safety of continuous background radiation. An X-ray exam must have sufficient intensity to develop the film. Intensity is exposure per unit time per unit area. In contrast, background exposure has much lower intensity, especially on the time dimension. The reason why intensity rather than total accumulated exposure matters is that a biological body has self-correction mechanism. A cell can repair itself if it's not seriously damaged, as in the case of long time low intensity exposure to the background radiation. This is as simple as warming up your whole body in a warm water shower for a few minutes as compared to scalding your finger in boiling water for a few seconds, both receiving the same amount of heat energy.

I'm not aware of scientific study proving this theory. Total radiation exposure continues to be the standard by which health risks are assessed. I hope discrepancies in conflicting reports will be explained by radiation intensity as one of the contributing factors.

So, is there too much radiation from X-ray exams? The question can be rewritten as, Is there a limit of radiation below which radiation is safe? I see two ways to answer this question. (1) If the human body reaches the limit of repairing radiation-damaged cells, that's the limit of safe radiation. (2) If the intensity of X-ray radiation is comparable to that of background radiation, it's safe. It's difficult to provide Answer (1) and it's of course dependent on the person's health, age, etc. As to Answer (2), it is completely impractical to meet the requirement of such low radiation intensity and be able to develop the film. In short, treat all X-rays as risky for now, even if the equipment is the state-of-the-arts using the fastest film and is digital. As to frequency of dental X-rays, unfortunately, there's no better guideline than this.

[Update 2025-10] On the Wikipedia page for Linear no-threshold model, there is a graph for "Increased Risk of Solid Cancer with Dose for A-bomb survivors" in the "Origins" section. The text below the graph reads, "this exposure pathway occurred from essentially a massive spike or pulse of radiation, a result of the brief instant that the bomb exploded, which while somewhat similar to the environment of a CT scan, is wholly unlike the low dose rate of living in a contaminated area such as Chernobyl, where the dose rate is orders of magnitude smaller. LNT [i.e. Linear no-threshold] does not consider dose rate and is an unsubstantiated one size fits all approach based solely on total absorbed dose." The referenced article was published in 2009, which I missed when I wrote this blog. In short, we have talked too much about "dose" (what I call "total exposure") but we ought to talk about "dose rate" (what I call "intensity") in assessing the harm that X-ray or any non-ionizing radiation does to the human body.

Bilingualism and mental health

The January 9 issue of Journal of Neuroscience published an article Lifelong Bilingualism Maintains Neural Efficiency for Cognitive Control in Aging (full article). Although there's no difference in "simple working memory span" between mono- and bi-linguals, "older adult bilinguals switched between perceptual tasks significantly faster than their monolingual peers." And "older adult bilinguals showed a pattern of fMRI results similar to the younger adult groups: they outperformed monolingual older adults while requiring less activation in several frontal brain regions linked with effortful processing." "[T]he bilingual requirement to switch between languages on a daily basis serves to tune the efficiency of language-switching regions..., and that over time the increased efficiency of these regions comes to benefit even nonlinguistic, perceptual switching".

It's no more news that multi-language efficiency or simply studying a foreign language postpones Alzheimer's onset. (In a leisure-reading article I wrote, I almost gave up on finding a reasonable excuse for my study of foreign languages and reluctantly settled on possible prevention of Alzheimer.) But it's easy to lose sight of news that hints at the negative side of bilingualism. For example, in Cognitive and Linguistic Processing in the Bilingual Mind (full article), published in February 2010 of Current Directions in Psychological Science, we read "bilinguals typically have lower formal language proficiency than monolinguals do; for example, they have smaller vocabularies and weaker access to lexical items."

Lastly, if bilingualism has the same effect as more education on delay of the onset of Alzheimer, be aware that research shows that in spite of delayed onset, faster progression of the disease after onset is associated with more education.

Nevertheless, there're far more benefits reported in research than possible harm in bilingualism to mental health. There may even be more, although possibly diminishing, benefit in trilingualism than bilingualism, but no research has been conducted to my knowledge. In a nutshell, cerebral stimulus as in language study is highly recommended in our natural aging and should be followed throughout the life, not to be terminated when you no longer need to take exams or when you retire.

Benefit of a healthy person taking multivitamins

There're numerous reports on the ineffectiveness of multivitamins taken by healthy individuals even though millions of people still do. There's no point in repeating what those research papers say. But if I see one research that points at even modest benefit of taking multivitamins, I'd like to save that link on my blog, because it's so rare! According to an Oct 17, 2012 article by Consumer Reports, the magazine that habitually cools down healthy people's enthusiasm on taking supplements, a large cohort study conducted recently shows about 8% fewer people who took multivitamins were diagnosed with cancer than those who did not. The study is published in Journal of the American Medical Association.

Two minor points. One is that research that shows positive effect of multivitamins on healthy people is far less than otherwise. On the other hand, discouraging people from taking supplements should not exagerate the ineffectiveness to the extent that they are all harmful. For example, I've read articles that list all kinds of adverse effects of vitamin overdose, while the fact is that it's very hard or impossible to overdose on vitamin C, which is very different from vitamin A in this regard.

Is "Chi Nei Tsang" Chinese?

According to Wikipedia, Chi Nei Tsang (气内脏; 氣內臟) is "a hands-on holistic health practice of ancient Chinese Taoist tradition, rediscovered and further developed by Chi-Kung... involves the application of Chi-Kung in the manual treatment of the viscera (Nei-Tsang) and the deepest internal structures of the body... The contemporary form of Chi Nei Tsang, as being taught by Master Mantak Chia and his disciples worldwide, is deeply rooted in three different traditions: Classical Taoist Chinese Medicine, Traditional Internal Medical Thai Massage, and Western holistic medicine." Dr. Andrew Weil says "Chi Nei Tsang (CNT) is a centuries-old variety of healing touch therapy from China. It focuses on deep, gentle abdominal massage in order to 'train' the internal abdominal organs to work more efficiently, which in turn is said to improve physical and emotional health." In addition, the most prominant master of Chi Nei Tsang is Mantak Chia, a Thai born to a Chinese family. Earlier in his life, he followed a number of masters to study Thai boxing, Qi Gong, Kung Fu, Daoism. His most important teacher is said to have a name "Yi Eng (White Cloud)" of the Dragon's Gate sect of the Quanzhen Daoism (道家全真龙门派).

I'm no stranger to traditional Chinese medicine, not as a professional, but as a twenty plus year amateur in reading and occasional practice on myself. Honestly I've never heard of "气内脏" before. So I searched on the Internet, for both English and Chinese content. Almost all documents on this topic are in English. Three web pages in Chinese mention this term, none citing ancient Chinese sources. Since my knowlege of Daoism (Taoism) is limited to reading only a few books and browsing online once in a while, I posted a message to a Chinese forum asking for any Chinese source on this term. So far no ancient Chinese document is identified to have made the first use of this term. The three Chinese web pages that mention Chi Nei Tsang (see the first part of the message I posted to the forum) call it abdominal massage, detoxifying massage, and detoxifying and pressure reducing, respectively.

Then I searched for "Yi Eng" or with keywords "yi eng white cloud" or their Chinese equivalents, even though "yi" is unlikely to be a Chinese character meaning "white". None was found. But one Chinese page reports a conversation or an interview with Mr. Chia, and uses the Chinese words "一云" (pronounced yi1 yun2 in Mandarin pinyin), literally "one cloud", not "white cloud", to refer to Mr. Chia's Daoist master.

So, if no Chinese source claims to be the origin of this practice, why call it "practice of ancient Chinese Taoist tradition"? The only answer I can think of is a false attribution to ancient Chinese source to capture attention and admiration of prospective students or practioners, as if any health-promoting exercises must have originated from a haloed Oriental culture, obviously China being a reputable one. If this term was coined in recent decades, why not clearly say so, and happily become the originator of this exercise, the health benefit of which, by the way, I do not doubt?

Steve Jobs and apples

Medscape article Will an Apple a Day Keep Pancreatic Cancer Away? published on 09/07/2012 may be best read to Steve Jobs, the Apple co-founder and CEO, who died of pancreatic cancer this time last year. Note the title of my posting here has "apples", taken literally, not "Apple". (If you don't have an account, which is free, on Medscape, you can find the same article duplicated by other web sites.)