Collards, Carrots and Lentils

There is much debate among nutrition scientists over whether meat eating is healthy. On one side there are the hardcore low-fat vegetarian advocates like Dr. Colin Campbell, author of The China Study, who believe all animal fat and protein is dangerous. On the other side are those who point to refined carbohydrates as the biggest threat to public health, citing studies that suggest meat alone is harmless or even helpful (for more information read Good Calories, Bad Calories, by Gary Taubes).

I tend to agree somewhat with both.

For heart disease, the evidence certainly seems to indicate that refined carbohydrates are the worst culprit. Though health advocates once pointed to saturated fat as the cause, this suggestion has not stood up to rigorous scientific testing. In fact, dietary fat (particularly from plants) seems to be protective against heart disease.

Refined carbohydrates are also the cause of type 2 diabetes and metabolic syndrome (a combination of insulin resistance, high blood pressure, heart disease and obesity), which is arguably the biggest health threat of our time.

For these reasons and many others, I avoid refined sugar and flour as much as possible in my daily life.

Heart disease and metabolic syndrome are not the only diseases that concern me, however. Cancer is another modern ailment that has been linked to diets high in both carbohydrates and meat. Though the studies are not perfectly consistent in showing harm or no harm regarding meat consumption and cancer, rarely does anything suggest meat eating is actually beneficial (though studies are almost always confounded because meat eaters also tend to eat the most sugar and refined grains).

Fish is another story entirely. Although fish is technically a meat, its properties are very different from land animals. For one thing, fish eating has consistently proven beneficial in scientific studies of heart disease and metabolic syndrome. It also seems to play a role in protecting the brain against degenerative diseases.

I am an avid fish eater and try to include seafood in my diet several times per week.

Until now, however, I have not read much about the role of fish in cancer. A new meta-analysis published in the British Journal of Cancer (part of the Nature publishing group) suggests that vegetarians have significantly less cancer than meat eaters, and that cancer rates are even lower in fish eaters.

The researchers analyzed data from two British studies of vegetarians from the early 80s and early 90s that includes over 60,000 individuals, mostly women but some men. The participants were followed until the end of 2006.

Incidence of malignant tumors was compiled for all the subjects and the relative risks were calculated. Vegetarians and fish eaters had significantly lower risk for stomach cancer, ovarian cancer, lymphatic and bone marrow cancers, and bladder cancer. Vegetarians had a higher risk of cervical cancer than meat eaters. Fish eaters had a lower risk of prostate cancer than meat eaters.

Overall vegetarians had 8% fewer cancers than meat eaters and fish eaters had 20% fewer.

Interestingly, no difference was found in breast cancer or colorectal cancer incidence, which have both been tied to meat consumption. The authors speculate that this study could be lacking in statistical power to observe a difference. However, the current data is inconsistent and no conclusions can be drawn.

While the results of this study are very compelling, there are several caveats that must be addressed. First, the number of cancers at individual sites were relatively few, meaning that findings may be exaggerated or due to chance. For me the most convincing numbers are of the overall cancer rates (the largest numbers and strongest statistics), but this leaves many questions about the causes of the different cancers.

Another issue is that vegetarians and fish eaters in the study tended to be younger and get more exercise than the meat eaters, so there may be important confounding factors that could influence the results. Likewise, studies that rely on self-reported dietary patterns have well-documented flaws (basically everyone believes they eat healthier than they really do).

It is not clear what is causing the differences in cancer incidence among vegetarians, fish eaters and meat eaters. Vegetables and fruits have been suspected of actively protecting against cancers, but so far the mechanisms are only speculative and not concrete. Recent studies have suggested vitamin D can be protective against certain cancers. Since some fish can be very high in vitamin D, this may explain some of the benefit seen in fish eaters.

The higher incidence of cervical cancer among vegetarians is also compelling and warrants further research.

Despite the flaws in this study it is mostly consistent with other research suggesting that an optimal diet is primarily fresh, unprocessed plants, some fish and little meat.

Moderation is usually the best policy.

What is your take on this study? How do you feel about health vs the ethics of fish consumption?

Tags: cancer, fish, vegetarian

1 lb Fat

Last week the New York Times and many other reputable news sources reported on a Canadian study that claims people with a normal body mass index (BMI) had a slightly increased risk of dying over a 12-year period than those with a BMI in the overweight range (25-29).

The use of the phrase “overweight was protective” landed this article just a hair’s width from being labeled Summer Tomato’s B.S. of the week on Friday. An observational study cannot determine cause and effect, as implied by the word “protective.” This study does not prove that extra body weight protects against all cause mortality, and saying so is irresponsible.

Studies (and reporting) like this have instigated wide-spread confusion about health and body weight. First people are told they are too heavy and should lose weight for health, then in the same breath they are told a little extra weight might not be so bad.

What is the average person supposed to believe? How should we act?

If you want to understand the facts it important to know exactly what the data does and does not say. Indeed, some studies (including one on Japanese men reported in the same issue of Obesity) have reported lower or equal risk of mortality for people with an overweight BMI compared to people of normal BMI (18.5-24). However, this is not the whole story.

First, the alleged benefit of being overweight has only been found in older individuals and does not apply to healthy, young people. Second, although it appears in some cases that overall mortality may be reduced, disease incidence is notably higher in overweight individuals compared to people of normal weight.

To point, a study in the most recent issue of Obesity (same journal, 2 weeks later) examines the relationship of BMI with many measures of cardiovascular disease in healthy, athletic men. In this study, those on the lowest end of BMI in the normal range (18.5-22.5) had a much lower risk of dying from or developing cardiovascular disease than normal weight men with a slightly higher BMI (22.5-25).

Men with the lowest healthy BMIs also had lower risk of hypertension, lower cholesterol and half the risk of diabetes. While the length of this study was only 7.7 years (compared to the 12 years reported in the Times story), there were more than double the number of participants (28,776 vs. 11,834).

(Why did this story not make the news? My guess is that it makes for a less compelling storyline and people would rather not hear it.)

Mortality is certainly an important measure in any study, but it is arguably not the most relevant endpoint. Disease and excess body weight can severely impact quality of life, particularly for older individuals (as illustrated by another study in the latest issue of Obesity). While I cannot speak for everyone, it seems probable that quality of life is equally if not more important than longevity alone. Thus it is questionable how much stock to put into studies that ignore these other factors.

It is also critical to remember that BMI is a measure that was designed to describe people at a population level, not as individuals. While large cohort studies can tell us useful things about relative risk, they are not directly applicable to individual people.

The inconsistency of the data related to BMI and mortality may in fact be an indication of its inadequacy as a general measurement. Remember that BMI represents a ratio between height and weight, making it possible to compare people of various body sizes. Normalizing for height may, however, be deceptive.

Decades of data on caloric restriction consistently show that smaller body size (irrespective of body fat levels and, possibly, BMI) is associated with longer life and decreased risk of nearly all diseases. This is true in all animals from yeast, to worms and flies, to mice and monkeys. While humans are certainly different from all these model organisms, there is tremendous evolutionary precedent indicating smaller body size as the best for health.

The principle of parsimony tells us the simplest hypothesis–that smaller body size is beneficial–is probably correct. Substantial evidence must be accumulated before this hypothesis can be rejected, and I have yet to see that data.

Furthermore, while the research on the risk of overweight may be slightly ambiguous, the data on obesity is not. It is painfully clear that the dangers of obesity are profound and on par with those of smoking cigarettes. Overweight is a necessary step to becoming obese, and according to the National Population Health Survey nearly a quarter of Canadians who were overweight in 1994/1995 were obese by 2002/2003. Since overweight is still a substantial risk factor for becoming obese, misleading public health messages about the benefits of body fat are especially dangerous.

As a consumer of information, the most important thing you can do is be skeptical of what you read. Just because something is printed in the New York Times does not make it true. In fact, many of our most trusted sources of health information do not base their recommendations on rigorous scientific thinking, which is probably the reason for the health disaster we are currently facing.

Thanks to Jan from Quest for Health for sparking this discussion.

What does your gut tell you about the relationship between health and body fat?

Tags: BMI, body fat, body mass index, caloric restriction, mortality

Collards, Carrots and Lentils

A new study published yesterday in the Archives of Internal Medicine suggests that both weight loss and risk factors for heart disease can be improved following a vegan version of the low-carb, high-protein Atkins diet.

The “Eco-Atkins” diet focuses primarily on soy, nuts and wheat proteins (gluten) to increase the amount of vegetarian protein in the diet. Carbohydrates were restricted to 130 g/day, which is on the higher end of most low-carb diets. All starchy foods such as bread, baked goods, potatoes and rice were eliminated. Carbohydrates were provided in the form of whole, intact grains (barley and oats) and low-starch vegetables.

In a small (47 participants), short-term randomized controlled trial, this diet lowered bad LDL cholesterol by 20%, without negatively impacting good HDL cholesterol (statin drugs improve cholesterol levels by 30%). The diet also substantially lowered blood pressure and other markers of cardiovascular disease, such as triglycerides and apolipoprotein B.

The original meat-based Atkins diet has been shown to be effective for temporary weight loss (after 1 year the effects of the Atkins diet are diminished), but cardiovascular risk factors such as LDL cholesterol and blood pressure are not substantially improved under the traditional Atkins regimen.

Interestingly, a traditional Atkins-style diet based on animal protein was not used as a control in this study, so a true comparison of the diets cannot be made using the present data. Instead the researchers chose a control diet representative of a typical high-carb, low-fat vegetarian diet that included eggs and dairy products. Both diets tested in this study represented a 60% decrease in total calories.

Because of the study design, we cannot conclude that this diet is more effective than the Atkins diet for health, though you would predict it would be if future studies made this comparison. On the other hand, it does seem that a plant-based high-protein diet is more effective at improving health than a high-carbohydrate lacto-ovo vegetarian diet, at least in the short-term in a highly controlled environment.

This study took place over the course of 4 weeks, and all the food was provided for the particpants by the researchers. Thus, compliance in the program was very high. It is not clear if the participants would have had the same level of success if they were instructed to provide their own food to comply with the dietary programs.

Despite this, satiety levels were notably improved in the high-protein group and it would be expected that the increase in satiety would encourage greater compliance in a free living situation.

A small four week study, however, tells us very little about the effectiveness of this diet. While it is possible to improve risk factors such as cholesterol and blood pressure in such a short period of time, disease outcome is the true measure of a successful diet. Also, this study did not test the feasibility of the Eco-Atkins diet in the long-term, and it is likely many dieters would object to a strictly vegan regimen.

Interesting points raised by this preliminary study include:

• Plant-based, high-protein diets may be more effective at improving cholesterol and other cardiovascular measures than traditional lacto-ovo vegetarian diets.
• Short-term weight loss is primarily determined by the number of calories consumed, not macronutrient content.
• Low-carb diets that include intact whole grains and plant-based protein can be effective at improving both weight and cardiovascular risk factors in the short-term.
• Plant-based high-protein diets can increase satiety compared to high-carb vegetarian diets.

However, many questions must be addressed before this diet can be recommended to individuals trying to improve cardiovascular measures and lose weight.

New questions:

• Can the Eco-Atkins diet be maintained in the long-term by normal individuals?
• Does the Eco-Atkins diet continue to improve cardiovascular risk factors including weight loss after 4 weeks?
• What would result from this study if beans and lentils were used instead of soy and gluten?
• Does the Eco-Atkins diet improve disease outcome?
• Does the Eco-Atkins diet extend life?
• Does the Eco-Atkins diet affect quality of life?
• Can these effects be attained through other diets that include some animal protein, more whole grains or more fat?
• Is the effectiveness of the Eco-Atkins diet affected by an individual’s level of insulin resistance?
• Can adding fish further improve the results of the Eco-Atkins diet?
• Can a further reduction in carbohydrates improve the results?
• Will you get these same results if the study is NOT funded by the soy industry?

In summary, the results of this study are interesting and encouraging, especially for those of us who think both carbohydrates and meat should be limited in a healthy diet. I very much look forward to future studies exploring this idea.

What concerns me most is the lack of marine omega-3 fatty acids (fish) in the Eco-Atkins diet, which could potentially improve cardiovascular measures even further. Fish is also important for cognitive health and may lower cancer risk.

I am also worried that a strictly vegan diet would not be feasible in the long-term for many Americans. Moreover, it is not necessarily the healthiest option available. Vitamin B12 deficiency is a particular concern, but could be addressed with supplements. Generally, however, I do not recommend relying on supplements for optimal nutrition.

Finally, this study was funded by a company that makes soy and gluten products. Personally I would have prefered to see these protein sources used in combination with other things such as beans and lentils. Many people question how much soy can be safely consumed and gluten intolerance is more common than ever, so wouldn’t it be interesting to know if there were safer alternatives? It really annoys me to see science being influenced by industry funding.

What do you think of the Eco-Atkins diet?

Tags: beans, eco-Atkins, gluten, high-protein, lentils, low-carb, soy, vegan, vegetarian

Vegetables

Most scientists agree that diet plays an important role in heart disease, but until now there has been no comprehensive analysis of which dietary factors most strongly affect disease outcome. A new meta-analysis published in the Archives of Internal Medicine reviews six decades of research (1950-2007) to assess how different dietary factors affect heart disease. Vegetables, nuts, “Mediterranean” and high-quality dietary patterns are strongly protective, while trans-fat, foods with high glycemic index or load and a “Western” dietary pattern were shown to be harmful.

The Study

This new study is unique for several reasons. First, the authors were only interested in factors that influenced heart disease directly, not simply heart disease risk factors such as cholesterol levels. Also, emphasis was placed on high-quality studies designed to identify strong dietary associations (cohort studies and randomized controlled trials) with long periods of follow up (at least one year). They asked whether the studies they reviewed were consistent with other data such as epidemiological reports, and sought to establish a causal link between diet and heart disease outcomes. Another important goal of the analysis was to identify factors that lack sufficient evidence to be conclusive and require further research.

Results

In addition to identifying vegetables, nuts, high-quality and Mediterranean dietary patterns as being strongly protective against heart disease, they also found monounsaturated fats (e.g. olive oil), dietary folate (e.g. whole grains, not supplements), dietary vitamins C and E (not supplements), alcohol consumption (in any form) and omega-3 fatty acids from fish (not plants, e.g. flax) to be moderately protective.

Factors that were not associated with heart disease in this study were dietary supplements (e.g. vitamins C and E), total fat, saturated fats, polyunsaturated fats (from plants), meat, eggs and milk. It is important to note, however, that negative findings in this analysis are not necessarily indicative of a lack of causality. Rather, it may indicate insufficient data to observe a significant positive association.

Dietary Patterns

The authors point out that “only overall healthy dietary patterns are significantly associated with coronary heart disease” in the controlled trials, while “evidence for most individual nutrients or foods is too modest to be conclusive.” They suggest that the reason an association exists for dietary patterns and not individual nutrients is that patterns “have the advantage of taking into account the complex interactions and cumulative effects of multiple nutrients within the entire diet.” The authors recommend future trials test various dietary patterns for disease outcome, including cardiovascular disease and cancer.

Taking this further, most dietary factors that were shown to be protective when consumed as part of a healthy diet were not protective when taken in supplement form. This finding bolsters the argument that overall diet rather than individual foods or nutrients are the best strategy for protecting against heart disease. The authors conclude that their findings suggest “investigating dietary patterns in cohort studies and randomized controlled trials for common and complex chronic diseases such as coronary heart disease.”

Based on their analysis, the dietary pattern that best protects against heart disease is rich in vegetables, nuts, fish, healthy fats, whole grains, and fruit. Likewise, the worst dietary pattern consists of refined carbohydrates and artificial trans-fats. The lesson: the best diet consists of plants, fish and whole foods, while processed foods contribute to heart disease.

What about red meat and saturated fats?

Interestingly, there was insufficient data to conclude that red meat or saturated fats are harmful for the heart. This is not terribly surprising, since the data has always been inconsistent. However, I would point out that many studies have looked at the role of red meat and saturated fat in coronary risk and the outcome always shows either harm or no result. And as explained above, no result can be indicative of a lack of statistical power rather than lack of causation. Importantly however, I cannot recall a single study suggesting that red meat and saturated fat is actually good for you.

From this the best we can conclude is that red meat or saturated fat may be involved in promoting heart disease, but if they are the effect is likely to be less harmful than a diet of processed foods. Practically this means small doses of saturated fat may not do much harm when eaten as a part of an overall healthy diet. This is a fairly compelling argument for exercising moderation.

Conclusions

Before you run out and order a ribeye, keep in mind that heart disease is not the only debilitating chronic disease that plagues our culture. Red meat is also associated with several kinds of cancer. Likewise, refined carbohydrates are highly correlated with type 2 diabetes. Vegetables and whole grains are protective against these other diseases as well, and fish may play a role in protecting against neurodegenerative diseases.

The take home lesson is that both diet and disease are complex systems that involve innumerable factors in several different regions of the body. When choosing what to eat it is important that you consider the context of your overall diet and do not get caught up is single foods or a single disease threat.

Tags: dietary pattern, fish, heart disease, Mediterranean diet, nuts, omega-3, red meat, refined carbs, saturated fat, trans fat, vegetables, whole grains

The Centers for Disease Control and Prevention (CDC) just released their 2005 report on cancer statistics. The web-based report contains official federal government statistics for cancer incidence in 96% of the United States population and mortality statistics for 100%. This is the seventh time the CDC’s National Program of Cancer Registries and the National Cancer Institute’s Surveillance, Epidemiology and End Results Program have combined registries to offer official federal statistics on cancer incidence and mortality for a single year.

Rates of cancer incidence are reported as the number of newly reported cases per 100,000 people. In 2005, the top four most common cancer diagnoses have not changed since 2000 and represent diseases strongly associated with lifestyle factors.

The number one diagnosed cancer in the US is prostate cancer (142.4), followed by breast (117.7), lung (67.7) and colorectal (48.3) cancers. The deadliest cancer is of the lung (52.8), while the mortality rates from prostate (24.7) and breast (24.0) cancer are nearly identical. Colorectal cancer is the fourth deadliest cancer (17.4).

Cancer is the second leading cause of death in the US, with heart disease being the first. Though most of us associate heart disease with lifestyle factors, cancer is usually regarded more fatalistically as being random or due primarily to genetics. While genetics does play a factor in some cancer cases, vast amounts of epidemiological data indicate that lifestyle factors, particularly diet and smoking, can largely account for high cancer rates in affluent countries such as the US.

There is abundant evidence that diets high in animal products and refined carbohydrates, and low in vegetables contribute to cancers of the prostate, breast and colon. A similar dietary pattern is responsible for cardiovascular disease, diabetes and neurodegenerative diseases. What is striking about cancer, however, is that there are no known drugs that stymie its development. Statins do not protect against cancer, nor do multivitamins.

The best diet to prevent all these diseases of affluence is a plant-based, whole foods diet.

Does fear of cancer impact your eating habits?

Tags: cancer, CDC, Centers for Disease Control, statistics