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Fatty Foods Enhance Memory By Same Mechanism As Emotional Learning

by | May 4, 2009
Go Nuts!

Go Nuts!

Have you ever noticed that some of your strongest food memories are of rich, fat laden meals shared with family and friends? According to new research, this may not be a coincidence. A study published last week in the Proceedings of the National Academy of Sciences demonstrates that digesting fatty foods enhances memory consolidation using the same neural pathway as emotional learning.

This finding has far reaching implications for cognitive therapies to fight over-eating, but may also suggest new, easy to implement strategies for memory enhancement. Pistachios anyone?

In the study, rats being trained on memory tasks were administered a substance called oleoylethanolamide (OEA) that normally increases in the gut after the ingestion of dietary fat (not carbohydrate or protein). Several days later, the rats given OEA performed better on the tasks than rats that were not, demonstrating enhanced learning.

To determine the neural pathway involved in this effect, the researchers chemically blocked signaling in the region of the brain that receives neural inputs from the gut (solitary nucleus), which abolished the effect of OEA. Next they selectively blocked neural transmission between this region and another region of the brain that has been shown to be critical for emotional learning (amygdala). This also eliminated the memory enhancement effect of OEA, indicating that emotional memory and memory enhancement from fatty food ingestion share the same neural network.

These findings may partially explain the emotional component that is often associated with chronic over-eating, something that frequently involves learned habits triggered by emotional situations.

However, OEA does more than enhance memory. It is also critical in feelings of satiety after a meal (decreasing hunger) and has been implicated in controlling body weight. Is it possible this new information could be harnessed for the power of good?

Low-fat diets have proved to be a colossal failure for both health and weight loss, partially because they encourage over-consumption of starchy (usually refined) carbohydrates. Moreover, vegetable and fish oils are protective against many chronic diseases that plague Western culture. Regularly seeking healthy fats in your diet can help control hunger, promote weight loss and lower risk of disease. But it now seems that healthy fats could also be a useful tool in overcoming emotional eating, a problem more complex than the standard weight gain that comes from 21st century living.

Another interesting corollary of this study is that fat (specifically oleic acid, a healthy fat found predominantly in olive oil and nuts) may enhance learning and memory. Since the benefits of OEA were only evident when it was administered at the time of or immediately after training, the next time you study or prepare for a presentation you might want to have some nuts around to snack on. Almonds, cashews, hazelnuts, macadamia nuts, peanuts, pecans and pistachios are highest in oleic acid.

Are you interested in foods that could provide cognitive enhancement?

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Vegetables, Nuts and Overall Healthy Diet Protect Against Heart Disease

by | Apr 20, 2009
Vegetables

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.

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The Curious Case of HDL Cholesterol

by | Mar 9, 2009

cholesterol chemical structureDrug treatments that raise the “good” high density lipoprotein (HDL) cholesterol do not improve health outcomes, according to a new analysis. But some researchers suspect raising HDL through lifestyle changes may still be effective in treating heart disease.

HDL is the form of cholesterol that actively removes dangerous lipids from the blood, and has long been thought to be protective against heart disease. This form of cholesterol is believed to work in opposition to low density lipoprotein (LDL) cholesterol, which is strongly correlated with heart disease and cardiovascular mortality. Thus the ratio of HDL to LDL cholesterols is often considered the most important indicator of heart disease risk.

Strong clinical evidence shows that LDL lowering drugs like statins can protect against heart disease and cardiovascular mortality. However there is still no effective way of improving cardiovascular outcomes by directly targeting HDL cholesterol.

Pharmacological treatments that raise HDL cholesterol levels include fibrates, niacin and a Pfizer drug called Torcetrapib. However, trials that tested these drugs for improved cardiovascular outcome have yielded mixed results. Rather than lowering mortality risk, evidence suggests that fibrates and Torcetrapib actually increase mortality in patients. Some trials have shown niacin to be effective at reducing cardiovascular events, but the data are inconsistent.

A new meta-analysis published in the British Medical Journal asked whether pharmacological treatments that are known to raise HDL can improve cardiovascular outcomes. After adjusting for several known confounders (including the effect of LDL cholesterol) pharmacological treatments that raise HDL were not effective at protecting against heart disease.

Does this mean that HDL is not important for heart disease? Not necessarily.

The original studies that implicated HDL in heart protection were observational. For example, it was shown in the Framington Heart Study that people with HDL levels greater than 60 mg/dL have a reduced risk of heart disease compared to individuals with lower HDL. Likewise, individuals with less than 40 mg/dL of blood HDL are considered at risk for coronary heart disease, even when LDL cholesterol is relatively low.

Additionally, lifestyle choices that contribute to raising HDL are associated with a lower risk of heart disease. Examples of these are physical activity, weight loss, not smoking, increased omega-3 fatty acid consumption, decreased trans fat consumption, alcohol consumption and dietary soluble fiber. Also, diets low in saturated fat but relatively high in unsaturated fats have been shown to raise HDL and decrease heart disease risk.

All these HDL raising activities can improve cardiovascular outcome. However, this does not mean that HDL itself prevents heart disease. Rather, it seems to be a good biomarker (observational correlate) of heart disease.

Why are pharmacological methods of raising HDL not helpful (and possibly even harmful) at treating heart disease?

One possible explanation for this discrepancy is the observation that HDL has different forms, some that are protective and others that are harmful. For instance, some interventions may raise HDL cholesterol by limiting its breakdown (harmful), while others raise it by increasing HDL production (more beneficial). Also, some methods that increase HDL do so in a way that creates new problems, such as increased blood pressure.

The complex interaction between pharmacological interventions, HDL metabolism and cardiovascular outcome may have made it difficult to detect any benefit of raising HDL cholesterol in this meta-analysis. Since pharmacological intervention for raising HDL does not consistently help (and sometimes harms) cardiovascular outcome, lifestyle changes remain the most promising target for raising HDL to protect against heart disease.

Anyone want to guess how high my HDL cholesterol is??

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Cancer and Diet

by | Feb 16, 2009

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?

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New Evidence Ties Vitamin D Deficiency to Multiple Sclerosis

by | Feb 9, 2009
Vitamin D

Vitamin D

Both environmental and genetic factors seem to play a role in the development of multiple sclerosis (MS), but determining an exact cause of the disease has been elusive. Now new evidence suggests that vitamin D may play a direct role in regulating a gene known to be associated with MS. This finding helps bridge the gap between environmental and genetic risk factors, and strengthens the hypothesis that vitamin D could be instrumental in MS prevention.

MS is an autoimmune disease that attacks myelin, a component of the nervous system essential for the conduction of neural impulses. Onset of MS usually occurs between the ages 18 and 35, and is more prevalent in females than males.

One of the most interesting epidemiological findings associated with MS is that it is more common in regions farthest from the equator, with a few notable exceptions. Climate, sunlight and vitamin D are all suspected candidates in the occurrence of MS, as are genetics and diet. Importantly, the relationship between geographical location and MS risk seems to be most significant in early childhood years. After age 15, risk of MS for immigrants is closer to that of their home country than to that of their new country.

Sunshine is the most common source of vitamin D for humans. Vitamin D is created when ultraviolet B (UVB) light contacts skin. Dietary vitamin D is rare, though it can be obtained at significant levels with certain foods, particularly oily fish (e.g. sardines and salmon). Notably, Norway and many Asian countries have relatively low prevalence of MS. It has been suggested that fish consumption is the reason for these regional discrepancies that cannot be explained by sun exposure. This makes vitamin D a particularly strong candidate for MS prevention.

In addition to environmental factors, certain genetic risks are linked to MS. In particular, proteins associated with the body’s immune cells are mutated in many MS cases. Mutations in these proteins disrupt the ability of immune cells to determine which particles in the body are foreign and which are “self.” When this happens, the cells get confused and begin to attack their own body’s tissues.

A new article published last week in PLoS Genetics investigated the relationship between vitamin D and the genetic variants associated with MS. They found that vitamin D directly interacts with these genes at a molecular level, providing insight into the mechanism by which vitamin D may affect the disease. Though it is still not clear what specific role vitamin D plays in its interaction with MS genes, a new avenue of exploration has opened up into MS etiology.

The tie between vitamin D and MS is still vague, but it is a good idea to ensure your vitamin D levels are adequate. People living at latitudes greater than 40 degrees from the equator (San Francisco is on the border) should be taking vitamin D supplements. This is true for many reasons; MS is not the only disease that is linked to low vitamin D levels.

Vitamin D pills are now easy to find, and can be obtained at both Trader Joe’s and Whole Foods. Take one or two oil-based 1000IU vitamin D supplements daily. Men should avoid vitamin D supplements that contain calcium, because excess calcium increases risk of prostate cancer.

Do you take vitamin D supplements?

UPDATE: This article can also be found in Synapse.

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High-Fructose Corn Syrup Contaminated With Mercury

by | Jan 27, 2009

I swear, it is too early for April Fool’s Day and this headline is not a joke. I wish it were.

The Institute for Agriculture and Trade Policy reports that two new U.S. studies have found detectable levels of mercury in 55 brand name foods made with high-fructose corn syrup (HFCS, from three different manufacturers).

Mercury is a potent toxin that effects the brain and nervous system. It is particularly dangerous for developing children and is associated with learning disabilities and other neurological problems. Because mercury has a particularly long half-life in the human body, women of childbearing age should also avoid mercury.

What upsets me the most about this finding is that these are the kinds of products that are directly marketed toward children.

Maybe you have heard of some of these:

  • Quaker Oatmeal to Go
  • Coca-Cola Classic
  • Yoplait Strawberry Yogurt
  • Minute Maid Berry Punch
  • Hunt’s Tomato Ketchup
  • Smucker’s Strawberry Jelly
  • Nutri‐Grain Strawberry Cereal Bars
  • Hershey’s Chocolate Syrup
  • Pop‐Tarts Frosted Blueberry

For the complete list of contaminated products, click here.

The author of one report is careful to point out that this is “just a snap shot in time,” because they only tested one sample from each product. I hardly find this reassuring, however, since their analysis was also limited to the handful of products they selected and does not tell us about everything else on the grocery store shelves.

At this point we have no way of knowing which products contain mercury and which do not. What we do know is that all of them contain high-fructose corn syrup and are products of our industrialized food system.

I’m starting to wonder, how many outbreaks and contamination scares does it take to screw in a light bulb? That is, the idea light bulb within our federal government that asks,

“Maybe we should take steps to improve the safety and nutritional value of our nation’s food supply?”

Crazy thought, I know.

Keep in mind we are not even talking about the colossal damage these products do to our health and economy without mercury.

Are fresh, natural foods that grow from the ground such a ludicrous alternative?

Please share your thoughts, this topic always baffles me.

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Should Doctors Recommend Wine To Patients?

by | Jan 15, 2009

Today I have an article out in Synapse called “Wine May Increase Heart Healthy Fats in the Blood.” I am making an executive decision that it is too science-y for this blog, so instead I would like to open a discussion about how doctors should treat information like this.

For you uber-nerds (like me), here is the PubMed link to the original paper.

Let’s start with some excerpts from my article:

  • Moderate alcohol consumption has long been known to be protective against mortality from coronary heart disease, but the biological mechanism of this effect is unknown. A new analysis suggests that drinking wine may alter the composition of healthy fats in the blood, mimicking the beneficial effects of seafood consumption and conferring protection against heart disease.”
  • “The beauty of this finding is that the improvement in fatty acid profile from wine consumption seems to be clinically relevant. Based on the current consensus, small dietary changes in fatty acid consumption have a large clinical effect, so a 38% to 50% increase in EPA levels among moderate wine drinkers is noteworthy. Similar levels of improvement in lipid profiles from studies of fish consumption have shown considerable benefit for cardiovascular outcome.”
  • “Thus, the present finding may offer dietary intervention as a possible method of cardiovascular protection, particularly when combined with increased omega-3 consumption.”
  • “In the present study, the difference between participants in the low fatty acid group who did not drink and those in the high fatty acid group who drank the most was an 83% increase in blood EPA, a change associated with a 50% to 75% reduced risk of heart attack. Such a dramatic difference represents a useful alternative to fish consumption for those who may not have access to seafood for whatever reason.”
  • “Thus, increasing both dietary omega-3 fatty acids and wine consumption may be helpful to protect against cardiovascular events. Plant-derived omega-3 fatty acids are abundant in walnuts, soy, flax and canola oils, and one gram per day is the current recommendation for heart protection. “Moderate” alcohol intake is one glass per day for women and two for men.”

From a clinical perspective, the evidence that alcohol provides a tremendous protection against mortality from heart disease is undeniable. It is thought to work by both raising good HDL cholesterol and reducing blood clotting.

This effect is not limited to red wine, all spirits elicit substantial protection.

Despite these benefits, there are also a number of obvious reasons to avoid alcohol, particularly excessive consumption. Excessive alcohol consumption is associated with addiction, liver disease, stroke and can cause accidents and other behavioral problems.

Notably, benefits similar to those seen with alcohol can be conferred by increasing exercise amount or intensity.

If you want to experience the benefits of alcohol you need to use it in moderation, which is 1 drink per day for women and 2 for men, or possibly slightly more. More than one drink per day for women is associated with an increased risk of breast cancer, however this effect is attenuated by sufficient folate intake.

Doctors have been recommending increasing exercise for decades, but only a small percentage of the population makes an effort to get enough to make it as valuable against heart disease as alcohol. Also, there is a large population of individuals that have physical ailments that prevent them from performing vigorous cardiovascular exercise.

But to this day the American Heart Association–the same agency that recommended the low-fat, high-carb diet that many argue actually promotes heart disease–refuses to recommend moderate alcohol consumption. The basic tenet of their argument is that alcohol is not necessary because heart protection can be achieved in other ways, and the risks outweigh the benefits.

Is this right? I’m not so convinced.

Do you think doctors should discuss the potential benefits of alcohol with their patients? Should the AHA change their recommendation?

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Controlling Blood Sugar May Help Preserve Your Memory

by | Jan 5, 2009

High blood sugar levels are known to accelerate aging and decrease longevity in many different species. Now it seems blood sugar may also be tied to how well you keep your memory as you age.

Aren’t you glad you have cut back on refined carbohydrates and sugars since you started reading this blog? I thought so!

A new study published in the December issue of the Annals of Neurology examined the effect of high blood sugar on the region of the brain responsible for memory formation, the hippocampus. Researchers examined patients with either diabetes or stroke (in other, non-hippocampus, parts of the brain) and determined that both groups had defects in the hippocampus compared to normal patients, but the problems were in different hippocampal subregions.

Patients with diabetes had defects in a part of the hippocampus called the dentate gyrus, which has been shown to be especially sensitive to aging and memory loss. Stroke patients had problems with a region of the hippocampus called CA1.

Diabetes is a disease that involves misregulation of blood sugar, so the scientists examined if blood sugar levels alone correlated with problems in the dentate. This is important because some patients that have not been diagnosed with diabetes may still have high blood sugar levels. The scientists did indeed find a correlation between high blood sugar and hippocampal deficits in the dentate gyrus. Interestingly, blood sugar levels were also linked to memory performance.

Correlational findings are very interesting, but it is easy to imagine situations that would give this result without there being a causative role for blood sugar in memory function. One reason this study is particularly compelling is because they repeated the analysis on rhesus monkeys and found the same relationship between blood sugar and hippocampal defects.
Even better, they were able to show a causative relationship between blood sugar regulation and dentate gyrus deficits in mice. In this experiment the scientists induced type 2 diabetes in the animals, then measured hippocampal function. Mice that could not regulate blood sugar had hippocampal deficits in the dentate compared to control mice.
Taken together, this study provides strong evidence that high blood sugar levels are related to hippocampal and memory dysfunction.

What does this mean for you?

This is actually great news for the rest of us because blood sugar is something we can self-regulate fairly easily.
The study’s principal investigator and professor of neurology at Columbia University, Dr. Scott Small says,”This would suggest that anything to improve regulation of blood glucose would potentially be a way to ameliorate age-related memory decline.”

That means both diet and exercise may work together to preserve memory function into old-age by controlling blood sugar.

“We had previously shown that physical exercise strengthens a part of the brain involved with aging but, at the time, we didn’t know why physical exercise would have this selective benefit,” Small affirmed. “Now we have a proposed mechanism. We think it’s because subjects who exercised had better glucose handling.”

Though the role of diet in hippocampal function has not been directly tested in humans, evidence is mounting that it is important for maintaining cognitive function and protecting against Alzheimer’s disease.

——————–

The best way to control your own blood sugar levels is to eat and live in a manner that improves insulin sensitivity. An added bonus is that you will probably lose weight, live longer and reduce your risk of a bunch of other diseases too, including cancer.

Sensitivity to insulin is affected by two dietary factors: 1) How much glucose is in your blood at any one time and 2), the composition of fat in your diet. It is also improved by exercise.

Keep these things in mind when you eat if you want to control and improve your insulin sensitivity:

  • Limit sugars and refined carbohydrates, including all white bread, white rice and pasta.
  • Choose whole, intact grain carbohydrates such as brown rice and oats.
  • Make vegetables the bulk of your diet.
  • Consider substituting legumes for carbs.
  • Reduce saturated fats from red meat and dairy
  • Eat more healthy fats from fish, olive oil and nuts.
  • Avoid processed foods with hidden sugars, yogurts and salad dressings come to mind.

Basically just eat real food and you’re on your way. And don’t forget to keep reading this blog to learn how to make healthy eating both easy and delicious.

Let me know which of the above suggestions you find the most difficult to follow and I may be able to give you a few pointers….

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FDA Revises Fish Recommendations: Is Something Fishy?

by | Dec 17, 2008

The US Food and Drug Administration (FDA) is asking the White House to amend its own previous warnings that children and pregnant women avoid seafood for fear of mercury poisoning, the Washington Post reports. The agency argues that the neurological benefits of omega-3 fatty acids, selenium and other minerals are worth the risk of mercury poisoning.

But not everyone is happy about this.

The US Environmental Protection Agency (EPA) and other consumer advocate organizations are outraged by the proposed change, accusing the FDA of catering to fishing industries and ignoring public health. The EPA has called the FDA document “scientifically flawed and inadequate” and an “oversimplification” of the health concerns involved.

There is a large body of scientific evidence that mercury can cause problems in the developing nervous system, so the new recommendations would have to be careful to educate consumers about both the positive and negative aspects of consuming more fish.

I have not seen the report myself, so I cannot pass judgement immediately. However, as I have explained in Synapse the dynamics of fish consumption and mercury contamination are very complicated, particularly for children and pregnant women.

My advice is to be careful with fish regardless of what the FDA report says. While it is extremely important to consume adequate omega-3 fatty acids as well as vitamin D from fish sources, mercury contamination is a serious concern that should not be overlooked.

To get the maximum benefit from fish and minimize mercury consumption

  • Eat fish at least twice per week
  • Avoid large fish such as tuna, shark and swordfish
  • Seek fatty fish such as salmon, sardines and mackerel
  • Take vitamin D and omega-3 supplements (fish oil based) when fish is not available
  • Enjoy vegetarian sources of omega-3s like soy, flax and walnuts

Recently I have been experimenting with canned sardines and anchovies and they are much better than I expected them to be. I also enjoy canned salmon as well as smoked salmon or lox (but watch your nitrate intake!). If you can afford it, fresh fish is always wonderful.

Do any of you have strong opinions about the FDA report or know if it is available to the public yet?

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You Should Be Taking Vitamin D Supplements

by | Dec 10, 2008
Vitamin D

Vitamin D

For the past several years the data in support of increasing vitamin D intake for every living human has been mounting. This week the American Journal of Clinical Nutrition features a collection of new research articles addressing the trends in vitamin D status and optimal dose recommendations.

This week’s take home lesson: While current research indicates we should be getting more vitamin D than is presently recommended, as a whole our vitamin D levels appear to have decreased in the past 15 years. The best way to combat this deficiency is with vitamin D supplements.

Vitamin D is a fat-soluble prohormone and essential nutrient produced when ultraviolet radiation (UVB) contacts our skin. It is probably best known for its role in bone metabolism (it has been shown to be more important than calcium for maintaining bone health), however recent studies indicate that vitamin D is essential for other physiological process as well.

Low blood levels of vitamin D have now been associated with many different chronic diseases including cancer, coronary heart disease, multiple sclerosis, Alzheimer’s disease, tuberculosis, depression, hypertension, periodontal disease, schizophrenia, seasonal affective disorder and type 1 diabetes.

In light of these findings, many nutrition researchers have argued for increasing recommended levels of vitamin D intake, but making population-wide recommendations have proved difficult for world health agencies because of large variability and uncertainty in vitamin D requirements.

There are several things to consider when evaluating vitamin D status in an individual. Latitude (sun exposure) is probably the single best predictor of vitamin D status. Anyone living in San Francisco or further north cannot get enough sun exposure to achieve sufficient vitamin D status, particularly during the winter months.

Because vitamin D is fat-soluble, it is retained in body tissues for several months after sun exposure. For this reason, people living at far north latitudes are particularly vulnerable to vitamin D deficiency because they frequently do not store up sufficient vitamin D during the summer to sustain their needs during the winter.

To further complicate matters, it is incredibly difficult to obtain vitamin D through dietary sources. Fatty fish and eggs are the only natural sources of vitamin D, though they are probably insufficient to achieve optimal status. Milk and soy products are typically fortified with vitamin D, as are some juices.

Skin pigmentation, sun avoidance and body composition (high body fat) are all associated with vitamin D deficiency. Darker skin tones do not convert sunlight to vitamin D as easily as lighter skin tones. Sunscreen blocks virtually all vitamin D synthesis. Body fat reduces bioavailability of vitamin D tissue stores.

This week’s study by Anne Looker et al, suggests that increased body mass as well as awareness of skin cancer risk and use of sunscreen have contributed to a significant decline in vitamin D levels in north America in the past decade.

The good news is that supplementation does appear to be effective at improving vitamin D status. Though there is still some disagreement on what the optimum blood levels of vitamin D are, it is generally agreed that they are much higher than currently recommended by any world health organization. One of the principle motivations of the present studies is to inform new vitamin D recommendations.

Kevin Cashman et al offers estimations of dietary requirements of vitamin D for healthy adults. They performed a randomized, placebo-controlled study testing the effects of different vitamin D doses and how they effect blood vitamin D levels.

The absolute minimum amount of vitamin D supplementation recommended by the study is 8.7 ug/day, or approximately 400 IU. This was to maintain blood serum levels greater than 25 nmol/L, and is double the current FDA recommendation for people under age 50. However, this suggestion is only sufficient to avoid deficiencies associated with bone loss and not other chronic diseases.

“The data from the present study clearly show that vitamin D tissue stores, developed during summer via exposure of skin to sunshine, were not sufficient to maintain serum 25(OH)D concentrations of greater than 25 nmol/L in most of the population [during winter], and that dietary vitamin D is an absolute requirement to maintain status above this minimum threshold.”

But the recommendations do not stop here. To maintain blood serum levels of greater than 50 nmol/L–a range more consistent with lowering risk of chronic disease–the study recommends 28 ug/day or 1100 IU of vitamin D. To keep blood serum above 80 nmol/L (from all I have read this is what I would recommend), 41 ug/day or 1650 IU is needed.

Remember this is most important if you are overweight, live north of San Francisco, get little sun exposure or have darker skin. Very rarely do I recommend vitamin supplements (they are not usually effective and are sometimes dangerous), but in this case the evidence is unequivocal.

Vitamin D supplements are easier to find than in the past, but they are usually packaged with calcium and are insufficient in dosage. Men should be wary of excess calcium supplementation since it is associated with an increased risk of prostate cancer.

I will continue looking for a good vitamin D supplement and will post when I find one I am happy with. If you have any recommendations, please share them with us.

Look for supplements where vitamin D is in the form of cholecalciferol, or vitamin D3.

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