In 1747, one of the first controlled clinical trials in the history of medical science involved vitamin C, but the researcher had no idea what a vitamin was: vitamin C wasn’t discovered until 1912. Scurvy, a disease caused by vitamin C deficiency, was rampant in the British Royal Navy, disabling and killing more sailors than combat, storms, shipwreck, and all other causes combined. James Lind compared these six proposed remedies:
- a quart of cider a day
- 25 drops of elixir of vitriol, three times a day
- half a pint of sea-water a day
- a nutmeg-sized paste of garlic, mustard seed, horse-radish, balsam of Peru, and gum myrrh three times a day
- two spoonfuls of vinegar, three times a day
- two oranges and one lemon a day
The first five proved useless; the last one worked like a charm. Lind’s experiment established that scurvy could be cured (it can also be prevented) by adding fresh citrus fruits to the diet, eventually leading to the nickname “Limeys” for British sailors. It took a long time for the Royal Navy to adopt fresh citrus fruits; one glitch was that they assumed bottled lemon juice would do the trick; they didn’t know that the heat used in the bottling process would destroy the vitamin C.
Alas, poor Lind! He didn’t understand the significance of his experiment. He continued to believe scurvy was a digestive disease caused by blocked sweat glands.
Fast-forward to the present: vitamins are assumed to be some kind of miraculous panacea. People think they make us healthier, make us live longer, give us more energy, and prevent and reverse disease. Until 1935, food was the only source of vitamins; but today we can get them from pills, dietary supplements, and fortified foods.
How many people take vitamins? A 2019 Harris poll found that 86% of American adults take vitamins or supplements; other estimates are lower, but usually over 50%.
Vitamins are commonly added to other supplements and untested alternative health mixtures; they can add a veneer of health to unhealthy products. Yes, lots of people take vitamins; but most of them are taking them for the wrong reasons and because of misunderstandings.
The book Vitamania: Our Obsessive Quest for Nutritional Perfection by Catherine Price explains our obsession with vitamins, which she argues are actually making us less healthy. She says “…we are such believers in vitamins’ goodness that we don’t realize just how much scientists still don’t understand about how vitamins work in our bodies, or how much of each we require.”
What are vitamins?
Vitamins are essential nutrients that we must eat because our bodies can’t make them. There are other essential nutrients like minerals and some fatty acids, but they are not classified as vitamins.
Macronutrients (carbohydrates, fats, and protein) are burned as fuel. Vitamins are not; their role is to facilitate chemical reactions that keep us alive. Tiny amounts are enough: the recommended amount of B12 is equivalent to 1/67th the weight of one grain of salt.
There are 13 vitamins. Four are fat-soluble (A, D, E. and K). Fat is required for their absorption, and they are stored in body fat, where they can accumulate to high levels over time. The other 9 are water-soluble: Vitamin C and the 8 B-complex vitamins. Thiamine is B1, riboflavin is B2, niacin is B3, pantothenic acid is B5, pyridoxine is B6, biotin is B7, folate/folic acid is B9, and cobalamin is B12. (The missing B numbers were for substances that were once thought to be vitamins but turned out not to be.) Water-soluble vitamins are not stored and must be regularly replenished.
Sometimes vitamins are indicated for healthy people: vitamin K at birth, folic acid to prevent neural tube defects in fetuses, prenatal vitamins. Breast milk is said to be the perfect food for babies; but healthy breast-fed babies require vitamin K at birth and ongoing supplementation with iron, vitamin D, and fluoride. Otherwise, vitamins are not indicated unless you have a vitamin deficiency. If you don’t have a documented vitamin deficiency, taking vitamins will do nothing but give you expensive pee. We don’t know whether moderate deficiencies have any effect on health. In fact, trying to determine whether an individual has a significant vitamin deficiency is largely a guessing game.
Vitamins come in many different chemical forms. Vitamin B9 occurs as folic acid, dihydrofolate (DHF), tetrahydrofolate (THF), 5, 10-methylenetetrahydrofolate (5, 10-MTHF), and 5-methyltetrahydrofolate (5-MTHF). Try saying that fast ten times in a row! Folic acid is better absorbed than folate. Folate from natural sources is unlikely to cause side effects. Folic acid is synthetic; side effects are uncommon but can include bloating, appetite loss, and nausea.
Vitamins Are Not Risk-Free
Many people think vitamins are risk-free, and assume that if some is good, more will be better. This misconception led to megavitamin therapy and orthomolecular medicine, which is not supported by science.
Some people claim that our foods are no longer nutritious due to soil depletion; that’s not true. Some people assume that the more vitamins a food contains, the better it is for me. That isn’t necessarily true: if you add a lot of vitamins to a food that contains water or sugar but no other nutrients (in other words, “empty calories”), it doesn’t mean it would be a good choice for you.
Linus Pauling was smart enough to win two Nobel prizes, but he wasn’t smart enough to realize he was wrong about vitamin C. He thought it prevented and cured the common cold, but a Cochrane systematic review found otherwise. Pauling upped his intake to 18 grams a day, but that’s 9 times the tolerable upper limit of 2 grams a day. Commonly recommended doses of vitamin C are known to cause nausea and diarrhea.
Humans and a few other simians, fruit bats, and guinea pigs are the only mammals that can’t make their own vitamin C. Genetic analysis shows that we once had that ability; evolutionary biologists have speculated that losing it probably gave us some kind of evolutionary advantage. Various hypotheses have been suggested. I wonder if new technologies of genetic engineering might someday restore our ability to make our own vitamin C.
In the 1990s, cardiologists were recommending vitamin E and folic acid to all their patients because preliminary research suggested these vitamins would reduce the risk of heart disease. They stopped recommending them when better studies showed those vitamins not only failed to protect the heart, but high-dose Vitamin E was linked to a higher risk of heart failure, prostate cancer, and death. Oops!
Several Arctic explorers were thought to have died from vitamin A poisoning after eating polar bear liver, which has the highest level of vitamin A of any animal. That may be a myth: their cause of death has been questioned. But vitamin A is definitely known to be toxic in large doses.
One website claims that 92% of the U.S. population have vitamin deficiency. I can’t believe that, since vitamin deficiency diseases have become rare in the developed world. Other questionable sources say everyone should take a multivitamin. I don’t agree. I don’t think we even know how to diagnose significant deficiencies in individuals.
What constitutes a deficiency?
We read the numbers on food labels and trust them because they are precise numbers that look very scientific. But they don’t mean what we think they mean. Recommended Dietary Allowances (RDA’s) are not meant to be applied to individuals. They are the amounts estimated to meet the needs of 97-98% of the population; many individuals might get by with much less. RDAs have never been established for biotin, pantothenic acid, or vitamin K, and there are no RDAs for infants under the age of one year for any vitamin. I bet you didn’t know that; I didn’t. Dietary Reference Intake (DRI) is the general term for a set of reference values used to plan and assess nutrient intakes of healthy people. These values vary by age and sex, activity levels, and other factors.
Estimated Average Requirements (EARs) are lower than RDAs. They are meant to meet the needs of 50% of people in an age group. The EAR is the amount of a nutrient that is estimated to meet the requirement for a specific criterion of adequacy of half of the healthy individuals of a specific age, sex, and life-stage. As with RDAs, EARs were never meant to be used by individuals to measure the adequacy of their nutrition.
Vitamin levels are fiendishly difficult to measure accurately. They vary from day to day as well as by where they are measured in the body.
We must face reality: the diagnosis of a nutrient deficiency is a very uncertain business. We don’t really know how much of each nutrient we need to survive. We have no idea what the optimum amounts are for ideal health. And we certainly don’t know the health consequences of a mild deficiency; maybe most of us can tolerate a mild deficiency with no ill effects.
If you read a recommendation that “everyone should take this,” you will know to disregard it because the evidence is not clear and because we are not all the same.
Does everyone need a daily multivitamin?
The health of people who take a daily multivitamin is not appreciably different from the health of those who don’t. Some studies have shown a mild decrease in the risk of cancer; others have not. Some studies have shown that people who take multivitamins don’t live as long, but those studies may be flawed.
According to a Harvard website,
“After a review of 26 clinical and cohort studies, the U.S. Preventive Services Task Force concluded there was insufficient evidence to support any benefits of multivitamins or individual vitamins for the primary prevention of cardiovascular disease or cancer among healthy, nutrient-sufficient adults.” That website also says “A diet that includes plenty of fruits, vegetables, whole grains, good protein sources, and healthful fats should provide most of the nutrients needed for good health.
Taking a daily multivitamin is probably safe and has been recommended as “insurance.” I used to think of it as psychotherapy. I worried about whether I was eating right, and a multivitamin gave me an excuse to stop worrying. I soon realized that a faulty diet would be better addressed by improving the diet rather than taking a pill. Food has a vast array of nutrients and supplies fiber and enjoyment not to be found in a pill.
Beware of charlatans who offer to give you personalized nutrition advice based on your genome. They can’t do that.
So what should we do?
In the face of all this uncertainty, what are we to do? I think it’s a mistake to succumb to vitamania. Rather than obsessing over our nutrition, we can focus on remembering that food is one of the great pleasures of life and shared meals facilitate social interactions. I am reassured by two things: (1) vitamin deficiency diseases are very rare in America, occurring only in individuals whose diet is limited, faddish, bizarre, or atypical in some way, and (2) the tiny amounts of vitamins we need can be found in a variety of different foods.
As the author of Vitamania said, “The healthiest, most scientific, and most pleasurable way to eat is not that complicated at all.” Just eat a wide variety of foods that you enjoy, mostly plants, including plenty of fruits and vegetables, and don’t eat too much (avoid becoming overweight).
This article was originally published in Skeptical Inquirer.