vitamin-d-sourcesFew people are aware of the relationship between vitamin d and cholesterol, but it’s an important one and it shouldn’t be ignored. Although it’s called a vitamin, it’s actually a hormone and a deficiency of it can be life threatening!

It’s Actually a Hormone

Vitamin d refers to a number of is a fat soluble steroid molecules that are involved in the absorption of important minerals in your intestinal tract.

The two most important factors are:
vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol)

It’s also called the “sunshine vitamin” because it can be bio synthesized in your body when your skin is exposed to natural sunlight. This is especially important to people of African ancestry that live in temperate climates that have long winters.

Since their darker skin pigmentation filters out some of the suns rays, they are at increased risk of deficiency because of their skin filtering out natural sunlight (especially during long winters.)

For black people, supplements are a MUST! It appears that pretty much every disease that people of African descent suffer from disproportionately is linked with vitamin d deficiency. This is not widely known, but can still cause lots of health problems that could be avoided with wise use of supplementation.

The Cholesterol Connection

The human body is amazingly resourceful at bio synthesizing what it needs from what we put into our bodies. Thus when we have a deficiency of vitamin d the body will make it from cholesterol. This can cause your cholesterol levels to rise, because your body needs the extra cholesterol in order to synthesize this vitamin/hormone.

You have read in this blog that lowering cholesterol is not necessarily needed to prevent heart disease because it has been found not to be a direct causative factor. However if your cholesterol levels are elevated because of a lack of vitamin d then you need to take steps to supply your body with this nutrient by getting more sun exposure and taking supplements when you can’t get enough sun, such as in the winter.

Elevated cholesterol levels can indicate other problems in your body that you need to address. This is another reason why statin use can be problematic. It can mask the symptom (elevated cholesterol) that is being caused by another problem (like vitamin d deficiency).

Effects of Vitamin D Deficiency

  • increased risk of heart attack and stroke
  • depression
  • Parkinson’s Disease
  • increased risk of cancer
  • increased risk of infection
  • increased risk of multiple sclerosis

Some Food Sources of Vitamin D

  • Cod liver oil
  • Butter from grass fed cows
  • Beef or Calves liver
  • Egg yolks
  • Cheese
  • Water packed tuna
  • Oil packed sardines

Supplementing Vitamin D

Supplementary forms of this vitamin can be found in any health food store. My favorite is Jarrow Formulas D3. I opt for 5,000 units per day in the winter and half that dosage in the summer. It is difficult to overdose on this vitamin, as long as you are not using a synthetic version of it.

The ideal situation is that you get your levels tested by a doctor and do follow ups until the levels are where they are supposed to be. This is a fat soluble vitamin and so should be taken with a meal that contains healthy fats.

Vitamin k2 should be taken with vitamin d as those two nutrients work togegher to ewnsure that your body handles calcium properly. One of the top experts on vitamin K2 Dr. Rheaume Bleue suggests a ratio of 100-200 micrograms of K2 for every 1,000 IUs of vitamin d.   Again I would go with Jarrow Formulas MK-7, combined with their D3 product.

Sun Expose is Healthy

It’s been said before, but bears repeating…sun exposure is HEALTHY! Human beings evolved on the surface of the Earth. We NEED sun exposure in order for out bodies to function properly. Don’t avoid getting sunlight, because if you do, you are undermining your health in a critical way.

sunshine vitamin

sunshine helps your body synthesize vitamin D

Use common sense of course. Don’t overdo it, as too much of anything can be a problem, but remember that getting out in the sun and fresh air has benefits that go far beyond making you feel good and improving your mood.

How Much Sun Exposure?

This depends on how dark your skin is. Light skinned people should avoid prolonged exposure such as beyond 10-15 minutes in the sun. Darker skinned people of course can tolerate longer exposure, but you should be conservative with your time in the sun and gradually build a tolerance to sun exposure over time as you get more tanned.

Wearing a wide brim hat, proper sunglasses, and long sleeve clothing can help protect you as well. Remember also that you can get burned even on a hazy day because enough of the suns rays still get through and you may not be aware of how long you have been exposed.

Remember also that sunblock will prevent your body from making the vitamin d it needs from sun exposure, so If you are using sun screens on your skin you are defeating the purpose of getting sunlight.

artichoke-leaf-extract

Artichoke leaf extract capsules

Did you know that better heart health and lower cardiovascular risk can be had with two natural products that you can buy right over the counter? Well it’s true! Artichoke extract and pantethine are what we are talking about, and it can help you cut your risk of heart disease without dangerous side effects.

Interested? Well then read on…

Millions of people use the popular statin drugs to lower cholesterol but heart disease still continues to be the number one killer of Americans. Statins lower LDL cholesterol and inflammation while raising hdl but they have serious side effects that can dramatically lower the quality of life and put you at risk for serious health complications. One area where statins fall short is raising HDL levels. They don’t elevate HDL enough to significantly improve your HDL LDL ratio.

Statins can also raise your risk for rhabdomyolysis: (muscle breakdown), kidney damage, and even diabetes. This is due to it’s interference in the biochemical pathways which bio-synthesize both cholesterol and coenzyme Q10, which your body needs to help create energy from the foods you eat in order to power the cells of the heart.

Thus statins not only commonly cause muscle pain and weakness, but can also ironically increase the risk for cardiomyopathy which is muscle damage to the heart!

While there are certain people for whom the risk of statins is justified by their effectiveness, the vast majority of people would likely be better off with natural alternatives, and there are two good ones we have access to, pantethine and artichoke extract. These two supplements or “nutraceuticals” as they are sometimes called, can lower LDL AND raise HDL safely and naturally without the risks of serious side effects.

Enter Artichoke Extract…

An extract from artichoke leaves can raise your levels of HDL, while pantethine which is an analog of vitamin b-5 can lower LDL without causing deficiency of coenzyme q10 (as statins do). The use of these two compounds together has been shown to reduce by up to 11% the risk of heart disease. Pretty powerful stuff for two natural substances!

Artichokes which are actually considered to be in the “thistle’ family contain powerful substances called flavonoids that can lower LDL levels and increase HDL. The flavonoids act as antioxidants, preventing the oxidation of LDL particles in your arteries. In addition artichoke extract can increase your levels of bile acids, which help remove cholesterol from the body.

The clinical results with artichoke extract were based upon an intake of 1,800 mg/day of dry artichoke leaf extract for 6 weeks. This resulted in an 18.5% reduction in total cholesterol, with an improvement in the HDL/LDL ratio. It was also shown to cause an average of over 36% increase in endothelial function (the layer of cells that line the arteries) which also helps to prevent heart disease.

Next Up – Pantethine…

Pantethine lowers LDL levels without reducing coenzyme q10. It does this by inceasing the breakdown rate of serum cholesterol and reducing the rate of cholesterol synthesis. Pantethineis an energy molecule that helps increase fat burning in the body.

It also improves the ratio of HDL to total cholesterol which has a protective effect on your artery walls, reducing plaque formation and lesions in the aorta and coronary arteries.

A four month study was undertaken where the dosage of pantethine was 600mg/day for the first eight weeks and then a higher dose of 900 mg/day for the second eight weeks. This resulted in a modest decrease of LDL with a slight increase in coenzyme q10, unlike statin drugs.

When you consider that every reduction of 1% in LDL levels equals a 1% reduction in heart disease risk, pantethine significantly reduces the risk of heart attack by 11%. This is a very significant result and more reason to include pantethine in your supplement regimen.

In Summary…

All of us are at risk for heart disease as we age, and the primary issue in that risk is elevations in inflammatory LDL particles and low HDL levels. Many of the
patients put on statin drugs stop taking them because of the severity of the side effects, leaving them vulnerable to risk of heart disease once more. However the
combination of pantethine and artichoke extract can help lower LDL and raise protective HDL without the side effects that characterize statin use.

People who are at low risk may be able to achieve effective protection just by using these natural compounds rather than statins drugs. For people who have
extremely high LDL and/or very low HDL, a combination of low dose statins AND natural compounds like pantethine and artichoke extract may be the ideal
combination to avoid side effects AND effectively decrease the risk of heart disease.

As always, any therapy whether drug based OR natural that is intended to protect against heart disease should be managed by your doctor, possibly with the help of
a nutritionist or other wellness professional who is well versed in natural healing therapies, nutrients, and nutraceuticals.

Medical References:

Atherosclerosis. 1984 Jan;50(1):73-83.
Controlled evaluation of pantethine, a natural hypolipidemic compound, in patients with different forms of hyperlipoproteinemia.
Gaddi A, Descovich GC, Noseda G, Fragiacomo C, Colombo L, Craveri A, Montanari G, Sirtori CR.

Plant Foods Hum Nutr. 2015 Aug 27. [Epub ahead of print]
Pharmacological Studies of Artichoke Leaf Extract and Their Health Benefits.
Salem MB1, Affes H, Ksouda K, Dhouibi R, Sahnoun Z, Hammami S, Zeghal KM.
Int J Food Sci Nutr. 2013 Feb;64(1):7-15. doi: 10.3109/09637486.2012.700920. Epub 2012 Jun 29.
Beneficial effects of artichoke leaf extract supplementation on increasing HDL-cholesterol in subjects with primary mild hypercholesterolaemia: a double-blind, randomized, placebo-controlled trial.
Rondanelli M1, Giacosa A, Opizzi A, Faliva MA, Sala P, Perna S, Riva A, Morazzoni P, Bombardelli E.

niacin taken to lower cholesterolNiacin for cholesterol has for years been the choice of natural supplements that lower cholesterol.  Niacin (vitamin b-3) can improve cholesterol profiles when used in high doses such as 1,000 to 3,000 milligrams per day.

The use of niacin to lower cholesterol has a lot of sound scientific research behind it. It is considered to be the most effective way to lower cholesterol naturally that is currently available.

This is far above the MRD (minimum daily requirement for vitamin b-3, so when it’s being used to lower cholesterol levels, we call that a “therapeutic dose.” These dosages will cause a reaction call a “niacin flush,” which if you are not used to it may be a little disturbing.

This flushing can be controlled by gradual increases in the dosage so that the body has time to adjust and does not react as strongly.

When using niacin for cholesterol, your skin will turn red and you will feel itchy. This is due to what’s called vasodilation. Niacin (also referred to as nicotinic acid) will lower cholesterol levels, reduce triglycerides, and improve the cholesterol hdl ratio, by boosting hdl levels.

Recent studies have shown that a lower dose (1.5 grams/day) of niacin is effective in lowering ldl levels and also boosting hdl levels. This dosage is better tolerated by the majority of people and is thought to be relatively safe for the liver.

Non-flush – niacin for cholesterol

There is a form of niacin that will not trigger as much flushing as regular niacin. The information on this form is contradictory, but some research indicates that it can be effective at both lowering ldl and raising hdl. It’s called extended release niacin.

People DO still get some flushing from this form, but much less. The issue of people not taking the regular form of niacin to lower cholesterol is because of the unpleasant flush, is not a problem with extended release niacin. Because it is so much milder, it may be more effective simply because people will not avoid taking it. This is called “patient compliance” in medical terms.

Together with using extended release niacin, other strategies to lessen the flush reaction are taking it with meals or snacks, and avoiding alcohol when taking it.

Niacin to lower cholesterol – dosage and side effects

Taking niacin for cholesterol, inhibits the breakdown of hdl in the body, which obviously results in higher hdl levels and a better cholesterol hdl ratio. Higher hdl levels alone lower the risk of heart disease, but niacin helps in another way, by lowering ldl levels as well.

Niacin taken at (1-3 grams/day) prevent the breakdown of fats which the liver uses to make lipoproteins. This lowers levels of both ldl and triglycerides, a very beneficial result. Lower triglyceride levels result in lower levels of ldl cholesterol which also lowers risk of heart attacks.

Side effects beyond the flushing reaction are rare but can include alterations in blood pressure, gastrointestinal distress, and liver damage. Although vitamins that lower cholesterol are safer than drugs, you really should seek expert medical advice when using niacin for cholesterol, both from the standpoint of safety and effectiveness.

You also need medical advice to avoid potential bad reactions from taking niacin for cholesterol with any drugs that you are on. Again the advice of a doctor is needed, because they are familiar with side effects and adverse reactions from combining drugs and nutrients.

Natural supplement or prescription

Odd as it might seem there ARE prescription forms of niacin. I have no information which suggests they work any better than what you can get over the counter, and in fact, they may have more side effects depending on how they were formulated.

If you are advised to take a prescription form of niacin for cholesterol, research the side effects very carefully as they are likely to be greater than what you would get with a natural supplement. You want to lower cholesterol naturally and safely!

Remember also that as effective as niacin is, you have to do all of the other things which protect you from heart disease, like eating a healthy diet, getting the right exercise, and reducing your stress. These strategies work together to keep your heart healthy.

The MTHFR gene is a hidden culprit in heart disease and explains much in the reasons why cholesterol numbers don’t tell you what your real risk for heart disease is. Understanding how this gene defect affects your good cholesterol levels and how to treat it is essential to protecting yourself from heart attacks.

MTHFR geneWhat is the MTHFR Gene?

This gene is responsible for operating what are called “methylation pathways” that involve your body’s ability to convert certain substances into their reduced or active form. If this gene is defective in your body, these vitally important methylation processes cannot be completed properly, and certain substances (vitamins and amino acids) can’t be absorbed by your body and you develop deficiencies.

Some of these substances are:

  • vitamin b-12
  • folic acid
  • cystiene

In the case of b-12 and folic acid, these substances are converted to their active forms of methylfolate and methylcobalamin. These active forms are what your body can actually use, and so if you can’t convert them properly, you end up with a deficiency.

Cystiene is converted to the toxic amino acid homocysteine and then to methionine. If your methylation pathways are not working properly due to the MTHFR gene defect, then you end up with an accumulation of homocystiene which is highly inflammatory and causes damage to your arteries.

How is Your Good Cholesterol Level Affected?

HDL-C also called the “good cholesterol,” can be effectively lowered by a certain type of MTHFR gene defect called: C677T polymorphism.  Since HDL is protective and lowers your risk of heart disease, this gene defect can raise your risk by lowering your good cholesterol level.

There are several variants of this gene defect, and they affect cardiovascular risk in different ways, but it’s important to be aware of their impact so that you can protect yourself. Remember that 50% of heart attacks occur in people who have what’s considered normal cholesterol levels.

The affect of the MTHFR gene is seen by many researchers as the missing piece of the puzzle in trying to determine why this is so. With this information you can go about protecting yourself by applying this new knowledge and lowering your risk not only for heart disease, but also for other chronic diseases that are caused by inflammation.

What Other Problems Can This Lead To?

A defect in the MTHFR gene can also result in increase risk for the following diseases:

  • Cancer
  • Stroke
  • Fibromyalgia
  • Polyneuropathy

How Do You Know if You Have it?

This is a very important question, because once you detect this, then you can guard against it’s effects. The most simple test you can do is to eat asparagus and note if your urine has a strong odor in the hours following your meal.

If this odor is present when you urinate, (you can’t miss it), then you can be sure that you do in fact have a defect (called a polymorphism) in the way your MTHFR gene operates. There are also lab tests that your doctor can do to detect this problem.
It may be necessary to have formal lab tests done so that this problem can be medically verified. It’s also important because your doctor has to order it for your insurance to cover it. The best and most responsible advice I can give you is to go through your doctor and get tested for this.

Fortunately there are ways to treat this problem, that will work and help to protect your health, but of course the first step is to determine whether you have it or not, and your doctor can order the tests to confirm it.

What Can I Do?

A defect in the MTHFR gene results in failure to operate certain methylation pathways and convert amino acids properly. However, forms of critical b-vitamins, vitamin B-12, and Folic acid, in their “active” forms, which means they do not have to be converted or methylated, CAN be absorbed by your body and help ensure these critical chemical reactions happen as they are supposed to.

Thus instead of taking folic acid, you would take “methyl-folate.” Instead of taking vitamin B-12 (cyanocobalamin) you would take “methylcobalamin.”

There are other substances that can help. They are called “methyl donors” because they donate or provide what’s called a “methyl group” to help the chemical reaction complete properly. There are foods that contain “methyl donors,” such as garlic, onions, avocadoes, ect.

There are also nutritional supplements such as trimethylglycine, and SAMe, as well as special formulations that contain combinations of these methyl donors to help provide what your body needs to do these conversions properly.

None of these substances are drugs, nor are they prohibitively expensive. However, most mainstream doctors do not know about them, nor about defects in the MTHFR gene, and so you may have to search for a physician that is up on the latest genetic research, that can help you safely manage this problem.

The website I recommend is:

http://mthfr.net/

which is a website run by Dr. Benjamin Lynch. There is a wealth of information on this website regarding methylation issues and the MTHFR gene. If you have this gene defect, I would highly recommend that you visit this website and educate yourself.

You can also click on this video:

to learn more about this topic, and start arming yourself with powerful information that will allow you to protect yourself against heart disease, cancer, strokes, Alzheimers, and other effects of methylation problems.

My reasons for delving into this topic is that it fills in the missing information that cholesterol numbers leave out. The effects of this gene defect on your good cholesterol level is probably one of the main reasons for the increased risk of heart disease.

Defects in the MTHFR gene are one of the most significant drivers of chronic disease, and by knowing if you carry this defect, you can takes very strong steps to protect your health and to live better and longer.

references:

Cardiovasc Diabetol. 2012 Oct 8;11:123. doi: 10.1186/1475-2840-11-123.
Several genetic polymorphisms interact with overweight/obesity to influence serum lipid levels.

J Atheroscler Thromb. 2009;16(6):815-20. Epub 2010 Jan 9.
Association of C677T polymorphism in MTHFR gene, high homocysteine and low HDL cholesterol plasma values in heterozygous familial hypercholesterolemia.

J Hum Genet. 2001;46(9):506-10.
An association of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphism and common carotid atherosclerosis.

 

Cholesterol lowering exercise has three basic functions, to lower triglycerides and LDL, lower blood sugar, and to raise HDL cholesterol. Any form of exercise that does those three things will help.

kettlebell exerciseExercise and cholesterol are inversely related. This simply means that the more exercise you do, the more you can reduce your cholesterol levels, provided you are exercising correctly.

Most of the studies on exercise and cholesterol were done on aerobic exercise like  running or jogging. These activities are reported to lower LDL between 5-10%, and raise HDL cholesterol from 3-6%. These are estimates in a range of results, so your individual results may be more or less than this.

The important thing is that any activity is beneficial, and you have to modify the type of cholesterol lowering exercise to suit your individual circumstances. For instance, if you have injuries or orthopedic problems, you might want to do some kind of exercise in a pool that is non impact like swimming, or other water exercise. Even walking is preferable to being idle.

With that said, lets look at what types of cholesterol lowering exercise is best  and what makes these forms of exercise so effective.

Aerobic Exercise

This form of exercise utilizes oxygen as you go and will raise HDL cholesterol. It is the most studied form of exercise to help prevent heart disease. However I would caution that aerobics can be overdone, and have negative effects on your hormonal system if you do them too long at a slow steady pace because it raises cortisol which is a stress hormone that is bad for the heart.

Interval Training

Interval training is a great compromise as it can increase heart and lung function, but will not negatively effect your hormonal system. Interval training utilizes short intense bursts of exercise followed by a slowdown or rest period.

Heavyhands and kettlebell training are two examples of exercise that use interval training rather than steady state cardiovascular exercise. Intervals are not specific to the exercise device or equipment, rather it is exercise pace and timing that makes interval training so effective.

A good example of this is the PACE program of Dr. Al Sears M.D. This program utilizes a form of interval training to raise peak fitness and prepare the heart and lungs for occasional bursts of intense activity.

It is the stress of sudden intense activity in an unconditioned person that is most likely to trigger a heart attack, so getting the body used to handling this stress can protect against it.

Kettlebells

Kettlebell training is my favorite form of cholesterol lowering exercise,  because it combines strength training with cardiovascular exercise at the same time. It will help maintain muscle mass, which will lower triglycerides by keeping blood sugar low.

As I mentioned previously, you can do interval training  very effectively with kettlebells but you have to be cautious and make sure you use proper technique as these exercise implements can be tricky to handle.  I strongly suggest you either get professional instruction, or purchase a good book or DVD that teaches how to do these exercises properly.

Kettlebell training can help raise HDL cholesterol because of the cardiovascular aspects of this exercise. Since you cannot adjust the weight of a kettlebell, you will need to come up with creative ways to make the exercises more intense and physically demanding. This form of training seems to be very effective for burning stored bodyfat , which is important when exercising for heart health.

The Bottom Line

Cholesterol lowering exercise can range from light simple exercise like walking to intense exercise like intervals or kettlebell training. The most important thing is that it fits your physical limitations, lifestyle, and individual needs.

Start easy and keep it simple, but get moving and make regular exercise a part of your life. You will look and feel better, and will lower cholesterol naturally.

What is Cholesterol

What is cholesterol? Among other things it is a very much misunderstood substance that people have been unnecessarily frightened of. They have been told repeatedly by “experts and authorities” that it’s a dangerous substance, that must be lowered in your body before it kills you!

what is cholesterolIn this information website, we will try and demystify this perfectly natural substance and disprove once and for all that it causes heart disease! We will also provide good solid information and easy to implement strategies that will help you prevent heart disease instead of just “lowering cholesterol.”

Let’s start with a discussion of  what is cholesterol…

Cholesterol is a fat (also called a lipid) that is made in the liver. It’s part of a class of compounds called steroids which are made in the bodies of all animals. This substance is vital to your body, is transported through the blood, and is contained in the external layers of all cells.

The origin of the word cholesterol originally comes from the word chole which means bile in Greek. The other part of the word derives from the Greek word stereos meaning stiff or solid. This waxy fatty substance is necessary for your cells to maintain their structural integrity.

This is why it is absolutely vital for life, and in fact your body actually manufactures this substance for use in all of your cells. Statin drugs interfere with the production of cholesterol which is why they cause so many side effects.

What is cholesterol used for?

There are many functions for this amazing substance:

  • It is used in creating the myelin that coats and protects your nerves somewhat like the insulation on a wire.
  • It is used for synthesizing bile acids which your body needs for digestion.
  • Your body uses it to make sex hormones (androgens and estrogens) and also in the synthesis of the adrenal hormones such as cortisol and aldosterone.
  • It’s used in to metabolize vitamins A, D, E, and K (the fat soluble vitamins)
  • It is used in the reactions that synthesize vitamin D from sunlight.
  • It’s essential for maintaining the outer structural layer of your cells and also for keeping the cell membranes permeable so that certain molecules can pass through the membrane and enter the cell.

In order to travel through your bloodstream, it needs to have a protein coating and thus becomes something called a “lipoprotein.” They are called lipoprotiens because they contain both protein and fat.

The four main types of these lipoproteins are:

  1. LDL or low density lipoproteins often called bad and are associated with an increased risk of heart disease when they are high
  2. Chylomicrons (triglycerides) consisting of approximately 90%  fat
  3. HDL or high density lipoproteins (often referred to as the “good cholesterol”) HDL is thought to “protect” the arteries from damage by carrying away LDL particles so they can’t build up on your artery walls.
  4. VLDL or very low-density lipoproteins (often referred to as a very bad form of lipoproteins) These particles are considered to have the highest risk of contributing to heart disease because they are small dense highly inflammatory particles that can damage artery walls.

The role of triglycerides…

Triglycerides are fat molecules that come from the fat in the foods we eat, or can be synthesized from carbohydrates that are not burned for energy. These triglycerides are stored in your body and released to be burned for energy when your body does not get enough food to meet it’s energy needs. The truth is that it is triglycerides that really increase the risk of heart disease!
Hypertriglyceridemia is a term used to refer to high levels of triglyceries in the blood and researchers now know that this is a risk factor for cardiovascular disease. High glycemic carbohydrates can raise levels of triglycerides and greatly increase risk of heart disease.

While this area is still somewhat controversial, it’s clear that triglycerides have a major role in heart disease and they are increased by sugar consumption. It makes sense for this reason to keep your intake of sugar and high glycemic carbohydrates low to avoid setting yourself up for cardiovascular disease.

A Complex Question…

Doctors have been taught to calculate your risk of heart disease using ratios of these lipoprotein particles. They have also been given guidelines for what the “safe” and “dangerous” levels are.  Now these guidelines have been called into question, as new information has changed what the medical community “thought” they knew!

Even though the question of  what is cholesterol is a complex one, you will see that terms like good  and bad cholesterol are misleading and inaccurate. All of these forms of this vital substance have their necessary roles. Instead we should be looking at the effects of chronic inflammation and how we can neutralize it, because it is really inflammation that causes heart disease!

References:

Curr Cardiol Rep. 2011 Dec;13(6):544-52. doi: 10.1007/s11886-011-0220-3.
The role of triglycerides in atherosclerosis. Talayero BG, Sacks FM.
Source: Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA. btalayer@hsph.harvard.edu