Humans, like many other animals, crave the taste of salt. Animals frequent salt licks, humans have traded salt for equal weights of gold, and the word “salary” comes from the Roman soldier’s allowance for purchasing salt. Salt appears in our language in idioms like “worth its salt” and “salt of the earth.” Shakespeare’s play King Lear is a variant of a folktale where a daughter tells her father she loves him as much as meat loves salt. In a murder mystery I read years ago, a character listed the four food groups as sweet, salty, sticky, and chocolate.
It’s no fair: everything that tastes good turns out to be bad for us. We love the taste of salt, but dietary guidelines tell us we should all limit our sodium intake to less than 2.3 grams (2300 mg) a day to avoid high blood pressure and death from cardiovascular disease. And those who are fifty-one, African American, or who have high blood pressure, chronic kidney disease or diabetes should limit their intake even further, to 1500 mg a day or less.
(Note: the salt molecule consists of an atom of sodium and an atom of chloride; 40% of the weight is sodium, so 1500 mg of sodium equals 3750 mg of salt, roughly ¾ of a teaspoon. Over 75% of our salt is already in the food, not added from the salt shaker.)
In 2010, the American Heart Association lowered its recommendations to 1500 mg a day for everyone. We thought that was good advice, but new evidence has muddied the waters.
You may have noticed that men and women are different. I hope you have noticed. As the French say, vive la différence! It’s not just that one has dangly bits and the other has bumpy chests. Or that one has to shave a beard and doesn’t like to ask for directions while the other has menstrual periods and likes to discuss feelings. There are differences in physiology and in the incidence of various diseases. For instance, normal lab values for hemoglobin are higher for men than for women, and autism is more prevalent in males while multiple sclerosis is more prevalent in females.
In the past, women have been underrepresented in clinical studies; when the first studies of aspirin for cardiovascular prevention came out, we knew it was effective for men, but we didn’t have enough evidence to recommend it for women. This is changing; researchers today are more aware of the need to include women in their studies. Now the American Heart Association/American Stroke Association (AHA/ASA) has issued the first evidence-based guidelines for reducing the risk of stroke in women. (more…)
ChiroNexus recently listed the top 10 chiropractic studies of 2013. In my experience, chiropractic studies tend to be of poor quality. A media report says “study shows chiropractic works for X,” and when I look for the study it turns out to be a single case report or an uncontrolled study. When Simon Singh was sued by the British Chiropractic Association for saying chiropractic treatment for certain childhood ailments was bogus, the BCA responded with a list of 29 studies they said provided evidence for their claims. Steven Novella showed that out of 29 studies on the list, only 17 actually constituted evidence for 4 clinical claims, and those 17 were poor quality, cherry-picked, and too weak to support the claims. I have a copy of a chiropractic textbook entitled Somatovisceral Aspects of Chiropractic: An Evidence-Based Approach and there is nothing in it that would qualify as credible evidence to a science-based thinker. Chiropractic commenters on SBM have told us that modern chiropractic rejects the “subluxation” paradigm and relies on evidence, and I am always willing to look at new evidence and give chiropractors another chance to convince me that a reform movement is really underway, so I looked up the top 10 studies and read them. I was not impressed.
Note: This is a long article with mind-numbing details that will not be of interest to most readers. Feel free to scroll down to the Summary section. You can just read the bold-faced headings describing the claims of each study on the way down.
Also note: For those who want more detail, the “Study #” headings are links to the full text when available online, or to the PubMed citation.