Eye diseases and vision loss are becoming more common in the United States as diabetes rates rise and the population ages. Many eye conditions worsen very slowly and have no noticeable symptoms in their early stages. For this reason, getting an annual eye exam is extremely important. But is there anything we can do to prevent eye disease from a nutritional perspective? Experts believe that there is such a thing as an “eye-healthy diet.” I interviewed Dr. Jeffrey Anshel, President of the Ocular Nutrition Society, and Dr. Elizabeth Johnson, a leading nutrition researcher, to get their views on the subject. Please listen to the full HealthyVision podcast here.
Some of the my favorite learning points from the show:
1. Which foods are healthy for the eyes? The human retina contains about 1000 times more concentrated carotenoids (found primarily in plant pigments) than any other part of the body. Our eyes use these pigments to protect themselves from the photo-damage of sunlight. Carotenoids (including beta-carotene, lycopene, lutein, and zeoxanthin) are found in highest concentrations in dark green, leafy and brightly colored vegetables. Egg yolks are also a good source of carotenoids. Interestingly, our retinas have a predilection for omega-3 fatty acids (found in fatty fish) to protect the eyes from UV radiation. My bottom line – the most eye-healthy meal on earth is probably a salmon salad Niçoise (see photo image above)!
2. Are carrots good for our eyes? While carrots can be part of healthy diet, choosing carrots as our primary source of vegetable intake may not be a good idea. Carrots contain beta-carotene, which competes with other carotenoids for transport molecules. Beta-carotene is a pretty good competitor and can “bump off” lutein and zeaxanthin from getting transported to the retina. Adults don’t process beta-carotene as well as kids do, so too many carrots may not be a great thing after all (especially as we get older)!
3. Should I take nutritional supplements for the eye? It’s always best to get your carotenoids from real food. However, some people (who take blood thinners for example) cannot eat dark green leafy vegetables because they also contain Vitamin K which can interfere with the medicines. For those who cannot get sufficient carotenoids from food, supplements may be beneficial.
4. What is the connection between obesity and chronic eye disease? While obesity is a risk factor for diabetes, and diabetes can cause chronic eye disease, there may be another problem at play. Carotenoids are fat soluble, and so they are preferentially stored in fat cells rather than remaining suspended in our blood stream. When we have larger fat stores, that fat may “mop up” the healthy vegetable carotenoids that we eat, without allowing them to be transported to the eyes to support retinal structures. Some researchers suggest that obese individuals may need to increase their carotenoid intake with supplements in order to prevent eye pigment deficiencies and potential macular degeneration. Losing body fat is also an important strategy of course.
Other questions answered in the podcast:
* How does cooking impact the nutritional value of fruits and veggies?
* Is there such a thing as over-supplementation (especially with Zinc)?
* How many veggies do I need to meet my daily carotenoid requirements?
* How do I know which vitamin supplements to trust?
I hope you enjoy the podcast – and redouble your efforts to eat a diet rich in fruits, veggies, fish and eggs and maintain a healthy weight. Remember that even though your mom may have told you that Bugs Bunny’s diet was best for your eye health, Popeye’s veggie of choice is even better for you!
I am hesitant to review diet books because they are so often a tangled mess of fact and fiction. Teasing out their truth from falsehood is about as exhausting as delousing a long-haired elementary school student. However, after being approached by the authors’ PR agency with the promise of a book that contains science-based nutrition information I decided to agree to the review. This is how the book was described to me in an email:
In their provocative new book, Eat to Save Your Life, best-selling authors Dr. Jerre Paquette and Gloria Askew, RRN, sort through the piles of information and misinformation about nutrition to reveal the true connection between food and health. Fed up with the advertising hype and conflicting nutritional advice, the duo provides common sense explanations for consumers everywhere who are looking to make smart nutritional choices.
Unfortunately, I was sold (quite predictably) a bill of goods. And rather than ignore the book and simply not do a review, I figured that maybe a negative review would reduce the number of incoming PR requests for future tomes of pseudoscience. In the end, I’ll probably just become the focus of personal attacks by dedicated proponents of various snake oils.
And so, without further ado, here is a small sample of what authors Askew and Paquette have added to their half-true diet book recipe:
The “one true cause” fallacy: The book opens with an interesting review of vitamin C deficiency, noting that it (apparently) took the British Royal Navy 40 years before they accepted that the treatment for scurvy was citrus extract (rather than flogging). Citing this incident as an example of nutritional deficiency leading to life-threatening illness, it’s a short ride to the “one true cause” fallacy whereby the authors postulate that there are untold numbers of modern diseases caused by unrecognized nutritional deficiency syndromes. Nutritional deficiency may be the one true cause of most diseases, you see.
The appeal to research without references. Countless appeals are made to “mounting evidence” of this and that (arthritis being caused primarily by food-related inflammation for example), either without reference footnotes, or with mentions of sources of dubious credibility (such as the Canadian Association of Naturopathic Doctors).
The appeal to supplements in lieu of vaccines. No diet advice would be complete without a gratuitous attack on vaccines, right? The authors suggest that flu vaccines (for example) only provide immunity for 2 months “and only for certain individuals.” Meanwhile, they assert that a combination of Echinacea, garlic, and vitamin C support the immune system to successfully fight of viruses. These claims are simply unproven and multiple studies have already found no benefit (over placebo) of these supplements at preventing and treating the common cold.
Over-diagnosis. If you think that the world of medicine is predisposed to seeing disease where there is none, try the alternative medicine world. The authors assert that everything from zits, to rashes, to “brain fog” are potential signs of grave underlying immune compromise – caused by, you guessed it, dietary deficiencies.
Over-supplementation. The authors argue that “supplementation is a necessity in our nutrient-robbed world.” However, new evidence doesn’t support supplementation for the general population, though it had beentraditionally felt that multi-vitamins might be valuable. In addition, new studies are finding that food sources are preferable to supplements for daily nutritional requirements (such as calcium) and that anti-oxidants such as vitamin E may do more harm than good.
The “organic is more nutritious” argument. Although a recent systematic review of the scientific literature found no support for the notion that organic foods contain more nutrients than those grown with traditional methods, the authors attribute Americans’ supposed vitamin deficiencies to poor soil quality caused by non-organic farming methods.
Nutrigenomics and DNA hype. The authors do not take a sufficiently skeptical view of the emerging field of nutrigenomics (whereby certain foods and supplements are recommended to individuals based on their genetic profiles). They even suggest that nutrigenomic testing is so much fun, it’s “almost like being part of a CSI television show.” Who cares if it’s no more accurate than fortune telling?
So what’s the half true part? Well, obesity is certainly a driver of many modern illnesses, and obesity is caused by (in no small part) nutritional choices. The authors cite statistics on the ravages of heart disease, high blood pressure, and diabetes on the U.S. population which are all quite true. (How this supports the “deficiency” argument is somewhat lost on me – because it would seem more logical that a possible excess of nutrients could be the “one true cause” of a lot of these diseases, but I digress).
There are real nutritional deficiencies that cause medical problems, such as iron-deficiency anemia, neural tube defects related to folic acid deficiency, vitamin D deficiency and rickets, and osteoporosis contributed to by low calcium levels. These conditions underscore the importance of healthy eating habits, but do not support the idea that the entire population is deficient in these nutrients. In fact, a large population study analyzed by the CDC, suggests that most Americans are not deficient in any major nutrient even with their current sub-optimal and obesogenic eating habits.
In general, fair-minded individuals will find Eat To Save Your Life to be yet another example of a half-true, hysteria-peddling, micro-nutrient-obsessed diet advice book. Ironically, the book’s title itself states the opposite of what we really need to be doing to reduce obesity-related diseases: stop eating (so much) to save our lives.
I hate scientific studies that don’t investigate the assumptions on which they’re based. They do harm. The findings slither around and get into the heads of people who treat people for the issues the research purports to understand. And the misconceptions become protocol. Here’s one example:
Having a child cut the risk of early death, particularly among women.
The early death rate from circulatory disease, cancers, and accidents among childless women was four times as high as that among those who gave birth to their own child, and 50% lower among women who adopted.
Similarly, rates of death were around twice as high among men who did not become parents, either biologically or through adoption.
The prevalence of mental illness in couples who adopted kids was around half that of other parents.
What the study states but doesn’t investigate is that for their research they used: “population-based health and social registers, we conducted a follow-up study of 21 276 childless couples in in vitro fertility treatment.”
Do you hear the sound of “WHAT!??!” beginning to reverberate?
Might it be that couples who have been living in the infertility system for months, maybe years and have had their original life script expectations erased, have had doctors and drugs and timetables invade their intimate time, have spent gobs of money, and have had repeated cycles of devastating disappointment may be in a very different state than couples who have CHOSEN not to have children?
And let me state my assumption up front. Choosing not to have children is not dysfunctional. It’s not a psychological condition. It’s not an ethical/moral lapse. It’s not a sign of immaturity or selfishness. It’s a legitimate choice.
It may be that the researchers’ findings do apply to couples who undergo infertility treatment in order to have a child.
But there is harm in assuming that all couples who don’t have children are at higher risk for death and mental illness.
This year’s finalists for the Boys & Girls Clubs’ Fit Family Challenge are about to be announced. I’ve had the privilege of acting as nutrition coach for the semi-finalist families, and have had fantastic interactions with them about common nutrition questions. In my continuing Q&A series, I thought I’d share some of our email conversations:
Q: How many calories do I need per day, and how many should I eat to lose weight?
I like to use this Mayo Clinic calculator to get a rough estimate of daily caloric needs. If you enter your height, weight, age, and activity level it will tell you approximately how many calories/day you need to maintain your weight. To lose one pound a week, you need to subtract 500 calories/day from that number. So, for example if the calculator suggests that you need 2000 calories/day – you should follow a 1500 calorie/day diet to lose 1 pound a week. Studies have shown that people who drop more than 500 calories below their daily maintenance needs have a hard time sticking to their diet. You may feel weak, trembly, and irritable if you cut down too low too fast. You will have to play with the amount a little bit since the calculator is not exact – if you don’t see the scale moving when you cut out 500/day, then you have to wonder if you’re counting calories correctly or perhaps if you have to go a little bit lower still. Unfortunately, the “reward” for losing weight is that you have to permanently eat less when you are at your desired goal because there is less of you to feed!
Q: What do you think about sports drinks? Do my kids need them when running races?
As far as sports drinks are concerned, their benefits are often over-hyped and exaggerated. That being said, I believe they do have a role in hydration during endurance sports like long distance running. When you do strenuous exercise for long periods of time (over 1 hour of effort) you lose a lot of body salt and minerals (electrolytes) in your sweat. It’s important to replace certain key electrolytes so your body doesn’t become depleted and begin to cramp. This is more likely to happen to folks running very long distances, such as marathons and triathlons. However, if it’s hot during your race, you could be at risk for dehydration and electrolyte loss as well.
Regular Gatorade (made by Pepsi Co.) has water, sugar, sodium, and potassium in it. Powerade (made by Coca Cola) has water, sugar, sodium, potassium and B vitamins. Powerade has a little bit higher sugar concentration, which could be an advantage on a long run. Both are reasonable choices for hydration during a race.
The rough rule of thumb is to take in 6-12 oz of fluid for every 20 minutes of running. Water is sufficient for runs that last less than an hour. Sports drinks (or adding electrolyte gels/chomps to water) are helpful if your run will last longer than an hour. It’s better to sip the water slowly at regular intervals than to dry to gulp it all down at one time. You may feel nauseated or have a “sloshy stomach” feeling if you don’t spread out your hydration.
Sports drinks can be quite expensive – and you can easily create your own at home. The World Health Organization has a simple recipe for rehydration fluids, and I found this (probably slightly tastier) version on a blog site.
Outside of endurance sports, I don’t see a physiologic need for sports drinks (with the exception of extreme sweating in hot weather or during illness with vomiting and diarrhea) – they can add unnecessary calories to your diet.
Q: Should I cut down the amount of salt in my diet?
Not necessarily. Too little salt, as well as too much salt, have both been shown to be unhealthy. If you’re eating a lot of fast food, you’re probably getting too much salt. If you cook for yourself and focus on fruits and veggies, whole grains, and lean protein you may not need to cut back. Unless you have a kidney problem or very high blood pressure, salt is generally not dangerous for you. About 2.5g of salt/day (roughly a teaspoon full) is optimal, but for most people up to 4g/day probably won’t hurt (and at least one study suggests that heart disease risk doesn’t increase until the daily intake of salt exceeds 7g/day).
Miracles are pretty rare events. Except on television’s “Dr. Oz Show,” where they appear with astonishing frequency. Oz of course doesn’t claim to raise the dead or part the Red Sea, but he does raise people’s hopes of parting with their flab. And he’s certainly not shy about flinging the word “miracle” about. But it seems miracles fade as quickly as they appear. Raspberry ketones, acai berries and African mango, once hyped as amazing “fat busters,” have already given way to newer wonders.
Granted, Dr. Oz, or more likely his producers, do not pull miracles out of an empty hat. They generally manage to toss in a smattering of stunted facts that they then nurture into some pretty tall tales. Like the ones about chlorogenic acid or Garcinia cambogia causing effortless weight loss. The former piqued the public’s interest when the great Oz introduced green coffee bean extract as the next diet sensation. Actually “chlorogenic acid” is not a single compound, but rather a family of closely related compounds found in green plants, which perhaps surprisingly, contain no chlorine atoms. The name derives from the Greek “chloro” for pale green and “genic” means “give rise to.” (The element chlorine is a pale green gas, hence its name.)
An “unprecedented” breakthrough, Dr, Oz curiously announced, apparently having forgotten all about his previous weight-control miracles. This time the “staggering” results originate from a study of green coffee bean extract by Dr. Joe Vinson, a respected chemist at the University of Scranton who has a long-standing interest in antioxidants, such as chlorogenic acid. Aware of the fact that chlorogenic acid had been shown to influence glucose and fat metabolism in mice, Vinson speculated that it might have some effect on humans as well. Since chlorogenic acid content is reduced by roasting, a green bean extracts was chosen for the study.
In cooperation with colleagues in India who had access to volunteers, Dr. Vinson designed a trial whereby overweight subjects were given, in random order, for periods of six weeks each, either a daily dose of 1,050 mg of green coffee bean extract, a lower dosage of 700 mg, or a placebo. Between each six-week phase there was a two-week “washout” period during which the participants took no supplements. There was no dietary intervention; the average daily calorie intake was about 2,400. Participants burned roughly 400 calories a day with exercise. On average there was a loss of about a third of a kilogram per week. Interesting, but hardly “staggering.” And there are caveats galore.
The study involved only eight men and eight women, which amounts to a statistically weak sample. Diet was self-reported, a notoriously unreliable method. The subjects were not really blinded since the high dose regimen involved three pills, the lower dose only two. A perusal of the results also shows some curious features. For example, in the group that took placebo for the first six weeks, there was an 8 kilogram weight loss during the placebo and washout phase, but almost no further loss during the high dose and low dose phases. By the time, though, that critics reacted to Oz’s glowing account, overweight people were already panting their way to the health food store to pick up some green coffee bean extract that might or might not contain the amount of chlorogenic acid declared on the label. As for Dr. Oz, he had already moved on to his next “revolutionary” product, Garcinia cambogia, unabashedly describing it as the “Holy Grail” of weight loss.
We were actually treated to the Grail in action. Sort of. Dr. Oz, with guest Dr. Julie Chen, performed a demonstration using a plastic contraption with a balloon inside that was supposed to represent the liver. A white liquid, supposedly a sugar solution, was poured in, causing the balloon, representing a fat cell, to swell. Then a valve was closed, and as more liquid was introduced, it went into a different chamber, marked “energy.” The message was that the valve represents Garcinia extract, which prevents the buildup of fat in fat cells. While playing with balloons and a plastic liver may make for entertaining television, it makes for pretty skimpy science.
Contrary to Dr. Oz’s introduction that “you are hearing it here first,” there is nothing new about Garcinia. There’s no breakthrough, no fresh research, no “revolutionary” discovery. In the weight control field, Garcinia cambogia is old hat. Extracts of the rind of this small pumpkin-shaped Asian fruit have long been used in “natural weight loss supplements” Why? Because in theory, they could have an effect.
The rind of the fruit, sometimes called a tamarind, is rich in hydroxycitric acid (HCA), a substance with biological activity that can be related to weight loss. Laboratory experiments indicate that HCA can interfere with an enzyme that plays a role in converting excess sugar into fat, as well as with enzymes that break down complex carbohydrates to simple sugars that are readily absorbed. Furthermore, there are suggestions that Garcinia extract stimulates serotonin release which can lead to appetite suppression.
Laboratory results that point toward possible weight loss don’t mean much until they are confirmed by proper human trials. And there have been some. Fifteen years ago a randomized trial involving 135 subjects who took either a placebo or a Garcinia extract equivalent to 1500 mg of HCA a day for three months, showed no difference in weight loss between the groups. A more recent trial involving 86 overweight people taking either two grams of extract or placebo for ten weeks echoed those results. In-between these two major studies there were several others, some of which did show a weight loss of about one kilogram over a couple of months, but these either had few subjects or lacked a control group. Basically, it is clear that if there is any weight loss attributed to Garcinia cambogia, it is virtually insignificant. But there may be something else attributed to the supplement, namely kidney problems. Although incidence is rare, even one is an excess when the chance of a benefit is so small. So Garcinia cambogia, like green coffee bean extract, can hardly be called a miracle. But it seems Dr. Oz puts his facts on a diet when it comes to fattening up his television ratings.
Joe Schwarcz is director of McGill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.
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Eye diseases and vision loss are becoming more common in the United States as diabetes rates rise and the population ages. Many eye conditions worsen very slowly and have no noticeable symptoms in their early stages. For this reason, getting an annual eye exam is extremely important. But is there anything we can do to prevent eye disease from a nutritional perspective? Experts believe that there is such a thing as an “eye-healthy diet.” I interviewed Dr. Jeffrey Anshel, President of the Ocular Nutrition Society, and Dr. Elizabeth Johnson, a leading nutrition researcher, to get their views on the subject. Please listen to the full HealthyVision podcast here.
I hope you enjoy the podcast – and redouble your efforts to eat a diet rich in fruits, veggies, fish and eggs and maintain a healthy weight. Remember that even though your mom may have told you that Bugs Bunny’s diet was best for your eye health, Popeye’s veggie of choice is even better for you!
I am hesitant to review diet books because they are so often a tangled mess of fact and fiction. Teasing out their truth from falsehood is about as exhausting as delousing a long-haired elementary school student. However, after being approached by the authors’ PR agency with the promise of a book that contains science-based nutrition information I decided to agree to the review. This is how the book was described to me in an email:
I hate scientific studies that don’t investigate the assumptions on which they’re based. They do harm. The findings slither around and get into the heads of people who treat people for the issues the research purports to understand. And the misconceptions become protocol. Here’s one example:
This year’s finalists for the Boys & Girls Clubs’ 
Miracles are pretty rare events. Except on television’s “Dr. Oz Show,” where they appear with astonishing frequency. Oz of course doesn’t claim to raise the dead or part the Red Sea, but he does raise people’s hopes of parting with their flab. And he’s certainly not shy about flinging the word “miracle” about. But it seems miracles fade as quickly as they appear. Raspberry ketones, acai berries and African mango, once hyped as amazing “fat busters,” have already given way to newer wonders.
