Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the practical application of health information. Nutrition. Exercise. Diet. Supplementation. I look at the science behind them, and let you know whether it’s something to consider or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
This episode began with reading yet another article about the “dangers of dietary supplements.” Rather than review the entire article, let me just recap what I said in response to the posted article on the dangers of dietary supplements.
‘This article is tired and old, restating what others have said dozens of times. Most of it are simple retreads that do not ask the correct questions. While it is true that some herbals interfere with the detoxification system to metabolize chemotherapy drugs, has it impacted the efficacy of chemotherapy? It doesn't seem to have happened with statins, medications used to lower cholesterol. As for the beta-carotene study, the amount of synthetic beta-carotene given to the smokers was 30 mg per day when the typical intake was less than 6 mg per day. Why would researchers select amounts 6 times the average intake in a human trial? If you're going to print something like this, which inspires quacks and people with a miracle story to respond, at least do a better job of actually investigating the claims. Writers: do better than this.’
Since the AMA and FDA have teamed up to train doctors about how to question patients and report any Adverse Events attributable to any DS they take, these types of articles have appeared over and over again from different expert sources but reposted on click-bait websites. And make no mistake about it: the Cancer Research Center is world renown with exceptional researchers. So I know they can do better than spout the party line so to speak when writing articles to inform the public. I’ll come back to this later when I talk about the CARET study, beta-carotene study referred to in my response.
When you’re a researcher and scientist, you almost always have that one question you always raise when reading research. I remember going on interviews for my first academic position. At one university, one of the faculty was someone I had seen for several years at sports medicine conferences. His question was the same after every presentation. It went something like “Could you explain the difference between the internal versus external validity of the study?” You would have thought that knowing that was his question, I would have been better prepared when I presented my dissertation research to the students and faculty during the interview process at his university. I wasn’t experienced enough to anticipate that was his question. I fumbled around and gave some sort of answer. Pathetic. But that was then.
Just so you have an idea of what that means, internal validity is to control variables so that it can remove any inherent bias. The simplest example would be to consider the age of assessing people for sarcopenia, the loss of muscle tissue. As sarcopenia happens as we age, if we did not consider age, it could bias the results. External validity is how well the results of a study applies to the population in general. This is often more difficult. An example, as has happened for decades, is using the same criteria for diagnosing heart disease in women the same as for men. It’s taken a long time to finally get research on women which shows that while there are similarities, there are major differences in how myocardial infarction is diagnosed in men and women. It has caused underdiagnosing MI in women until the last 10-15 years and even today, there is still more research that’s needed.
My question? A lot simpler. Can the methods used in assessing variables actually provide meaningful results? It’s not just whether a test or a tool can measure what it’s supposed to measure. Rather, is the standard error of the measurement small enough to provide meaningful differences. That’s why I’ve always criticized the use of Food Frequency Questionnaires in food intake studies. It’s just not precise enough to provide meaningful differences in things like mineral intake from foods. Another is cholesterol levels. The SEM is + or – 20 mg/dl as best as I can find. Yet physicians prescribe medications if someone has a cholesterol of 205 mg/dl. They could be as low as 185 and as high as 225 mg/dl. Yet no attempt has been made to make those measurement errors tighter.
That’s where I begin—even if it’s a methodology I’m not familiar with. If the SEM is wide, the predictive meaning of the test results is relatively meaningless in the real world. In case you were wondering, the internal validity of my study was not strong as I decided to control the fewest number of variables. I felt that important so that the external validity would be applicable to a majority of the obese population at that time.
Back to the CARET trial. This is the most often cited study for talking about the hazards of taking dietary supplements. The idea was that taking high levels of antioxidants would reduce the cases of lung cancer in cigarette smokers. Why? Because cigarette smokers who eat a lot of vegetables have lower rates of lung cancer. But why 30 mg in a supplement when the typical intake from food was between 4-5 mgs per day? It never made any sense except that after checking the background of every researcher, none were nutritionists nor dieticians. The study was flawed from the beginning. Years later, researchers found that high amounts of beta-carotene were actually pro-oxidants at those levels. One can’t blame the CARET Study researchers for things that hadn’t been done but there was no reason to use that high a level of beta-carotene in the study anyway.
Dietary supplements can be used effectively and safely. Hand picking case studies and flawed research papers to suggest they are all can be dangerous is just plain irresponsible. You just have to ask the right questions.
Another study on coffee was recently published. In this case, researchers examined the relationship between coffee and tea intake with diagnoses of dementia and tests of cognition, the ability to learn and remember. In this case, researchers used data collected from the Health Professionals Follow-Up Study and the Nurses’ Health Study, resulting in a total of just over 131,000 subjects that were followed up to 43 years depending on when they entered the study. The method used to assess coffee and tea intake were validated FFQ, as you know, not my favorite assessment device. In this case, because they were looking at cups of coffee or tea per day, the method was acceptable. It would not be effective if they were trying to assess phytonutrient content from the coffee or tea as those can vary by type of beans or leaves used. The FFQ was completed every 2-4 years during the study period.
The primary outcome was the diagnosis of dementia via medical or physician records. The secondary outcomes were the scores of recognized tests used to assess cognition and learning. What did they find?
During follow-up of 43 years, with an average time of just over 36 years, there were 11,033 diagnosed cases of dementia. 7975 cases or 9.2% in the NHS cohort and 3058 cases or 6,2% in the HPFS cohort. While the statistical analyses was complex to account for the high number of variables, here’s the bottom line. Drinking 2 to 3 cups caffeinated coffee, or 1 to 2 cups per day of tea, or 300 mg/d of caffeine was associated with the lowest risk of developing dementia compared with no consumption. Further, increased coffee or tea consumption was associated with higher cognition scores and lower cognitive decline scores on the various paper and pencil tests performed by subjects. If you love your coffee or tea, all I can say is bottoms up!
That’s all the time I have for this episode. If you like this podcast, please hit the share button and tell your friends and colleagues about it. Until next time, this is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
——-
N Engl J Med 1996;334:1150-1155
JAMA. doi:10.1001/jama.2025.27259
