From Abracadabra to Zombies
Diets, Supplements, and Health: It's Complicated
19 November 2010. A recently published meta-analysis of RCTs involving vitamin E and strokes advises caution in the use of vitamin E supplements. The researchers considered two kinds of strokes: ischemic and hemorrhagic. In an ischemic stroke, blood supply to part of the brain is decreased, leading to dysfunction of the brain tissue in that area. In a hemorrhagic stroke, blood accumulates due to hemorrhaging. The meta-analysis revealed that vitamin E increased the risk for hemorrhagic stroke by 22% and reduced the risk of ischemic stroke by 10%. "This differential risk pattern is obscured when looking at total stroke." (The study reviewed nine trials that had a total of 118,765 participants.)
Despite the fact that several large studies have shown the futility of taking vitamin and mineral supplements on a daily basis as a hedge against some unspecified adverse health effects, many people continue to do so. Some of these people may be overdoing it on some of the supplements, doing themselves harm instead of good. As Dr. Steven Novella writes:
There is widespread sentiment that vitamins are harmless, and that supplementing with vitamins is therefore a no risk-possible benefit scenario.
This sentiment goes against the scientific evidence, such as the study mentioned on vitamin E and stroke. The scientific evidence is too complicated for a simplistic "commonsense" view that supplements can't hurt you and they might help. Earlier studies have found dangers from excessive amounts of vitamin E (see Vitamin E supplements may increase heart risk, Vitamin E linked to lung cancer, and High doses of vitamin E may increase risk of death in the elderly).
Bill Bryson's latest book, At Home: A Short History of Private Life (2010), includes a short digression on the history of vitamins, herbs, and spices. Well into the 19th century, it was not generally thought that food played a major role in health and sickness. (Bryson muses, for example, on how early humans ever figured out that they needed some salt in their diet. Bottom line: we have no idea how they figured it out.) When long voyages were made possible by developments in the ship-making industry, scurvy became a problem for sailors who would go without fresh food for long periods of time. It's estimated that some 2 million sailors died of a lack of vitamin C between 1500 and 1850. Today, we know we need to ingest a small amount of vitamin C on a regular basis, but exactly how much, how often, and to what effect remains debatable. Many still think that large doses of vitamin C can either prevent colds or lessen their severity, despite the lack of scientific evidence for these beliefs. Worse, researchers from the University of California found that people who take 500 mgs of ascorbic acid a day have a 2.5 times faster progression of thickening of the carotid artery (hardening of the arteries) than people who take no supplement.
Other popular beliefs about vitamin C have not been supported by scientific studies. A five-year study involving more than 20,000 people aged 40 to 80 found that a daily dose of vitamin C, vitamin E, and beta carotene does not reduce the risk of heart disease, cancer, or mental decline. Prof Rory Collins, a co-author of the report at Oxford University's Clinical Trial Service, said: "Over five years we saw absolutely no effect." At the end of the trial, people taking vitamins had exactly the same risk of heart disease, cancer, cataracts, bone fractures, asthma, and mental decline as those who took a placebo. In contrast, cholesterol-lowering drugs reduced the risk of heart disease and stroke by around one third.
The fact is, as Bryson notes, vitamins are a curious lot. Among animals, only humans and guinea pigs, for example, can't make vitamin C in their own bodies. There's still much to learn about vitamins. We know we need them in small quantities, and we know what happens when we don't get what we need (in addition to scurvy there's beriberi, pellagra, and rickets, to name a few). According to Bryson, three ounces of vitamin A, evenly distributed, is enough to carry most people through their entire lifetime.
Casimir Funk, a Polish biochemist, is generally credited with the first formulation of the concept of vitamins in 1912. He was wrong about many things, but right about the idea that human bodies need certain things found in foods or ill health or death will result. As far as I know, vitamins are produced by plants and animals, but minerals are produced geologically and are absorbed from the soil by plants and ingested by animals when they eat soil, plants, or other animals. Whatever the case, our bodies also need small amounts of various minerals to function optimally. Some minerals are essential to good health, e.g., calcium, phosphorous, copper, fluorine, iodine, iron, and sodium. Others are not only not essential, they can be debilitating, e.g. lead and mercury. Just what is the optimum amount of vitamins and minerals that each of us should ingest is impossible to say, though many people and agencies have no shyness about saying what they recommend. What the scientific studies show us is that for most of us living in a modern, industrialized country like the USA where a reasonably varied diet is the rule, there is no health benefit to taking daily vitamin and mineral supplements and there are health hazards from ingesting too much of some vitamins and minerals.
Consider vitamin D. (I could complicate matters by noting that there are different forms of vitamin D, and A, and B, etc., but let's keep it sort of simple.) Sunlight stimulates the production of vitamin D, which is essential for a healthy immune system, but sunlight also exposes us to UV radiation, which has a detrimental effect on the immune system. How much sunshine is enough and how much is too much? It depends. In any case, the major function of vitamin D is to maintain normal blood levels of calcium and phosphorus, necessary for the maintenance of strong bones. Vitamin D may help regulate cell growth.* It's obviously important to have enough vitamin D, and some claim that the research shows that increasing vitamin D intake can significantly reduce the risk of certain kinds of cancer. However, before you run out and buy vitamin D supplements, consider:
Calcium deficits may lead to a lack of vitamin D adsorption and vice versa. Vitamin D increases bone calcium mobilization and calcium readsoption by the kidneys....People taking heart medication may not take vitamin D. (Lenntech.com)
Consider also that according to the Institute of Medicine, Food and Nutrition Board:
Vitamin D toxicity can cause nausea, vomiting, poor appetite, constipation, weakness, and weight loss. It can also raise blood levels of calcium, causing mental status changes such as confusion. High blood levels of calcium also can cause heart rhythm abnormalities. Calcinosis, the deposition of calcium and phosphate in the body's soft tissues such as the kidney, can also be caused by vitamin D toxicity.*
The panel warned that levels of vitamin D routinely sold in some dietary supplements could increase the risk of kidney and tissue damage and that extra calcium could boost the risk of developing kidney stones in people who take the pills regularly. It also cited "emerging evidence" that high levels of calcium may contribute to heart disease.
For most Americans, consuming 400 international units (IUs) of vitamin D daily is sufficient.... Spending as little as five to 15 minutes in the sun — without sunscreen — will produce much of one's daily recommended dose....The panel's conclusions drew protest from ... activists promoting vitamin D supplementation....[/update]
So, what's a good citizen to do? Clearly, using commonsense and a belief that supplements can't harm me and may even do me some good isn't a very smart position, given the potential for harm from excessive amounts of vitamins. We face a similar problem with minerals. Too much selenium has caused the deaths of wild birds and stabled horses. The human body, to be healthy, needs small amounts of such things as selenium, calcium, zinc, sodium, and iodine. Most of us can get what we need by eating a variety of foods. Take zinc out of the diet and we can't taste anything. Remove iodine and you get thyroid disease. Then there's magnesium. Food processing removes about 90% of the magnesium in grains and vegetables, but nobody really knows what the ideal amount of magnesium should be; arsenic, on the other hand, is known to kill in large doses, but all of us get arsenic in our diets, indicating a small amount is harmless or even necessary for good health.
Then there's salt. Our bodies need sodium and chloride, and the main source of both is salt, sodium chloride. Without the chloride in salt, cells shut down. "Too little chloride can cause muscle twitching, muscle spasms, or shallow breathing. Too much chloride can be associated with rapid deep breathing, weakness, confusion, and coma."* It's hard to deny that most of ingest way too much salt. Just about everything we eat these days has salt in it. Experts say we need about 200 milligrams a day. Most of us in the USA take in about 60 times that much on average. People in the rest of the world, at least in those places where salt is readily available, consume on average about 40 times the amount needed to sustain life (Bryson 2010). Is this harmful? Apparently. "An excess of sodium can cause edema, an accumulation of extracellular fluid, especially in conditions such as congestive heart failure. A low sodium intake leads to a lowering of the blood pressure and brings about diuresis, ridding the body of the excess extracellular fluid."* Lowering salt intake is usually advised if one's blood pressure is high.
I've seen a lot of crazy dietary recommendations over the years, but so far nobody has been touting salt supplements as necessary for boosting the immune system or enhancing vital energy.
Should everybody avoid supplements of any kind, then? Of course not. Some people have vitamin or mineral deficiencies and supplementation is necessary for them to maintain good health. I'm not a nutritionist, but even if I were I wouldn't be able to tell you what you probably want to know about vitamins and minerals. There really is a lot of guesswork in this field. On the other hand, I have come across a few items that may be of interest to some readers.
Some pregnant women should probably take vitamin D supplements. Also, taking folic acid supplements before conception has been linked to reduced risk of premature birth. Premature birth significantly increases the chances of complications such as cerebral palsy, mental retardation, chronic lung disease, blindness, and defects of the spinal cord and brain. Some experts recommend that every woman of childbearing age consume 400 micrograms of folic acid daily.* The FDA requires food manufacturers to fortify grain-based foods such as cereal, pasta, and bread with folic acid. A 2-oz. serving of dry pasta will supply about 100 micrograms a day of folic acid. A serving of some cereals provides 400 micrograms of folic acid. Click here for a list of some other good sources of this important B vitamin. Some good sources are oranges, lemons, and green vegetables. One study found that folic acid cuts dementia risk by 55%. Dangerous side effects from too much folic acid are rare.
In some parts of the world, many people do not have access to fresh fruits and vegetables. Some supplementation there could prevent some diseases. For example, in Linxian, China, people have one of the world's highest rates of esophageal and stomach cancer. It is thought that this may be due to a persistently low intake of several micronutrients. A study without controls of about 30,000 people over about 6 years found some evidence in support of vitamin and mineral supplementation. Four groups were given different supplements. A total of 2,127 deaths occurred among trial participants during the intervention period. Cancer was the leading cause of death, with 32% of all deaths due to esophageal or stomach cancer. The authors found some evidence that beta carotene, vitamin E, and selenium were associated with a reduction in cancer risk in this population. They found no support for intervening with retinol and zinc, riboflavin and niacin, or vitamin C and molybdenum. Even though the results of this study are not robust, and no strong conclusions can be justifiably drawn from the data, it is known in general without doing any studies at all that some people would benefit from an increased intake in vitamins and minerals. (I might add that smoking is widespread in China and there is no indication that the researchers controlled for smoking in their study or even thought of doing a study with non-smoking controls. Maybe they couldn't find any.)
Twenty-five years ago, The Lancet published the results of an observational study that looked at the possibility of vitamin D and calcium as being effective in preventing colon cancer. The initial study was optimistic, but later research has not been too supportive for calcium. The Cochrane Collaboration concludes:
Although the evidence from two RCTs suggests that calcium supplementation might contribute to a moderate degree to the prevention of colorectal adenomatous polyps, this does not constitute sufficient evidence to recommend the general use of calcium supplements to prevent colorectal cancer.
On the other hand, vitamin D has been given a boost as a potential protective agent from colon cancer by recent research. Those who did the study advise caution, however:
...before any public health recommendations can be made for vitamin D supplementation, new randomized trials are needed to test the hypothesis that increases in circulating 25-(OH)D concentration are effective in reducing colorectal cancer risk without inducing serious adverse events.
These researchers also found that higher consumption of dietary calcium, but not dietary vitamin D, was associated with a reduced risk of colorectal cancer. If what was said about vitamin D above didn't confuse you about the value of indiscriminate supplementing of vitamin D, this study should be enough to cause some delirium tremens.
It seems that many studies have found benefits in healthy diets rich in fruits and vegetable, but few studies have found much benefit from taking vitamin or mineral supplements. Here is a list of reports on various studies of supplements that have come out over the past few years; the headlines tell the story:
Yet, despite the lack of support from science and despite the poor economy, vitamin and mineral supplement sales are on the rise.* Some, no doubt, take massive doses of supplements in the mistaken belief that to do so is healthy. Some take supplements because they eat mostly junk food and are pretty sure they are not getting adequate nutrition from their diet. Some search the literature to find a study done somewhere by anyone with some letters after their names in support of their magical thinking. Some take supplements because their doctors practice scientific medicine and suspect a deficiency.
Anyone who thinks that taking supplements can adequately provide what good nutrition can't for most people isn't thinking. Some diseases require supplementation. Some defy it. Dr. Jerome Groopman describes a tough case that I recount in my review of his How Doctors Think:
The patient had been diagnosed by some thirty doctors over a period of fifteen years as having bulimia and anorexia nervosa, as well as irritable bowel syndrome. She actually suffered from celiac disease, an autoimmune disorder (an allergy to gluten) that causes an irritation and distortion in the lining of the bowel, making it nearly impossible for nutrients to be absorbed. May we all be so lucky as to have a doctor like Myron Falchuk, who came up with the correct diagnosis, as our physician.
Allergies complicate the issue of trying to determine what constitutes a healthy diet. I've written a few things on the subject of allergies. Rather than repeat myself, I'll just post links to the articles:
Finally, there is strong scientific evidence not only in support of eating a healthy diet but also in support of keeping one's weight at a healthy level. Weight loss has been shown to have many beneficial effects for overweight people, including lowering of blood pressure, lowering of cholesterol, lowering of triglycerides, and lowering of blood sugar readings. Unfortunately, the science shows that the only effective way to lose weight is to take in fewer calories or burn off more calories by exercise. You can lose weight eating nothing but Twinkies, candy bars, and donuts as long as you don't eat too many calories. Mark Haub did it, but he reduced his daily caloric intake from 2,600 to 1,800. (I'll leave it to the reader to determine how much harder it would have been to burn off 800 extra calories a day from more exercise. The real problem, though, is that most people who are obese are not fit enough to exercise vigorously enough to burn off 800 calories a day.) In ten weeks, he lost 27 pounds. Like everybody else on a diet, Haub cheated. He took a multivitamin tablet and drank a protein shake daily. He snuck in the occasional vegetable, typically a can of green beans or three to four celery stalks. He lost the weight despite his cheating. Losing the weight had several beneficial effects. His LDL dropped 20 percent and his HDL increased by 20 percent. His triglycerides level went down 39 percent. I had a similar experience a few years ago with the Atkin's diet. I dropped about 30 pounds in 20 weeks. I had scrambled eggs with cheese cooked in butter every morning and ate lots of meat and cheese. My LDL and triglycerides went down 25-30%. I wouldn't recommend either the Atkins or the Twinkie diet, however. If you want to lose weight, eat healthily but eat less and exercise more. What a concept!
Happy Thanksgiving, everybody!
* AmeriCares *