Garlic

People often say that garlic has medicinal properties. Some claim it lowers blood pressure, others swear it helps cholesterol and reduces clotting, and some even think it protects against cancer. I’ve also heard that garlic is “healthier” 10-15 minutes after it has been crushed or minced. Is any of this true?

The Science of Single Foods

As someone who regularly reads the scientific literature on the health benefits of food I can assure you that this is not an easy question to answer. The problem is that the effect of any single food on human health is likely to be small at best, and small effects are very difficult to detect with reliability. Studies must be incredibly well-designed to contribute anything of value to our understanding of how a food works in the human body. Also, many studies must be taken together in context for the data to be evaluated properly.

I have been researching this garlic question on and off for months and feel only slightly more confident today than I did when I started. To summarize, there are a good number of studies addressing the health value of garlic, but very very few of them are well-designed and published in reputable journals. The problem with having a large number of poor-quality studies is that results are often conflicting and difficult to interpret. Thus, when another scientist comes in to do a meta-analysis (pooling data from many studies and re-analyzing it for stronger statistics) the findings are usually inconclusive.

However, inconclusive findings do not enable me (or anyone) to say there is no benefit. What I can say is that more research is needed and if there is a benefit it is likely to be small. (How unsatisfying is that?!). But personally I would still recommend eating garlic for health. Why?

Small Benefits Are Important

Although we cannot say exactly why garlic is good for you, it is almost certainly not bad for you. Moreover, although it is difficult to attribute a particular health benefit to a single food, we do know that people who eat the most vegetables tend to be healthier than people who fewer.

Many nutrition scientists are beginning to suspect that the benefit of foods like garlic are primarily relevant in the context of a whole diet and cannot be evaluated independently. This means that it is less important that the individual studies I mentioned earlier are inconclusive, because they are likely not sensitive enough to evaluate the complex interactions of whole foods and food combinations on human physiology.

The Best Reason To Eat Garlic

The most important thing you can do for your health is eat a diverse diet of natural, unprocessed foods. Garlic is an amazing ingredient that imparts a unique and wonderful taste to the food it is cooked with. If you like garlic and it encourages you to eat your vegetables, then it’s good for you.

If it makes you feel slightly better knowing that it may help your heart or reduce inflammation, that’s awesome but less important.

What About The Crush?

If you do hope garlic can add to your health, is there any benefit in crushing it early? Probably.

Scientists have long suspected that the active ingredient in garlic is a substance called allicin. A recent study from Queen’s University showed that it is actually a decomposition product of allicin that has the most potent antioxidant activity.

Interestingly, allicin is created from an enzyme called alliinase that is not released from plant cells until they are damaged. Alliinase is what gives garlic (and onions) their strong odor and is thought to be a self-defense mechanism for these plants. When garlic is crushed, alliinase becomes active and begins creating allicin. As allicin is created and breaks down, the antioxidant potential of garlic is dramatically increased. Optimal antioxidant levels are created about 10 minutes after garlic is crushed.

It has not yet been shown that this increased antioxidant activity is a benefit to humans, but the principle is compelling enough to try to remember to crush your garlic a little early. If you are anything like me though, this feat is almost impossible. Apparently garlic hasn’t done that much for my memory.

What are your favorite reasons to eat garlic?

Originally published March 27, 2009.

Tags: allicin, alliinase, crushed garlic, garlic, minced garlic

Photo by Mr. T in DC

“I’ve always wondered what the scientific perspective of alcohol consumption is. I have been doing some research but the actual effects of it on the body range from beneficial to cancerous.”

The clinical science on alcohol consumption is vast and diverse. It’s easy to find studies that demonstrate the benefits of alcohol, but it is equally common to find research showing its dangers. Sorting through the data is not trivial, and getting the right answer from news reports is virtually impossible.

Let’s start with the facts:

1. Alcohol is addictive

Alcohol addiction is one of the most well-understood and dangerous risks of drinking. A propensity for addiction can run in families, but can affect anyone who drinks in excess. None of the health benefits of alcohol can negate the destruction caused by addiction, and anyone who drinks should be careful to avoid this terrible condition.

2. Alcohol damages the liver

Alcohol metabolism occurs in the liver and can cause severe damage when consumed in large quantities. Liver damage can usually be reversed if alcohol consumption stops.

3. Alcohol is associated with breast cancer (sort of)

Drinking is weakly associated with an increased risk of breast cancer. This is likely because alcohol increases aromatase activity in the human body, which increases estrogen production. Estrogen imbalance is a known cause of breast cancer. However, the association between drinking and breast cancer is negated by sufficient folate intake. Folate or folic acid is a B vitamin found in leafy green vegetables, fruits and legumes (and fortified foods). In other words, a healthy diet protects against alcohol induced breast cancer risk.

4. Alcohol protects against mortality from heart disease

Drinking alcohol reduces your risk of dying from a heart attack by preventing blood clotting. This effect is not limited to red wine, all spirits elicit substantial protection. The association appears to be dose-dependent, meaning that the more you drink the more protection you get. HOWEVER, you start raising your risk for the above mentioned problems with every additional drink per day. For men the ideal dosage is 2 drinks per day, for women it is 1 drink per day.

5. Alcohol raises good HDL cholesterol

Moderate drinking also reduces your risk of getting heart disease in the first place by raising beneficial HDL cholesterol without raising LDL cholesterol. Low HDL is a serious problem in America, and alcohol could be a significant benefit for some people. Here are other ways to raise your HDL cholesterol.

6. Red wine may slow aging

Aging research has been revolutionized by the discovery of a compound in red wine called resveratrol. Resveratrol has been shown to slow aging substantially in several model organisms. Though the effect in humans is still unknown, red wine is associated with many benefits that seem to go above and beyond the benefits of alcohol in general.

7. Red wine may protect against Alzheimer’s disease

Several studies have shown that red wine is associated with a decreased risk for Alzheimer’s Dementia, a devastating neurodegenerative disease that affects 1 in 4 people over the age of 90. The mechanism of action is unclear, but the benefits may be linked to the effect of red wine on fatty acids in the blood (raising the good stuff), or by slowing the aging process itself.

8. Alcohol causes accidents and behavioral problems

Even relatively safe levels of drinking can be deadly when combined with poor decision making. If you do choose to drink alcohol, always be sure that you’re in a safe environment and can get help if you need it. Being safe sometimes, or even usually, is simply not good enough.

There are plenty of good reasons to avoid alcohol if you choose, and many of the benefits can be garnered by simply increasing the amount or intensity of your daily physical activity.

However, the evidence is pretty clear that moderate alcohol consumption (1-2 drinks per day) can improve health and may be an important component of a healthy lifestyle. This is even true for those who pick up the habit later in life.

And last but certainly not least, some of the best times of my life have been over a drink with friends. And I guarantee you most of us aren’t thinking about our heart health while enjoying a great bottle of wine. As long as you consider safety first, never forget that smiling is one of the healthiest things you will ever do.

Here’s a fun question: what’s your favorite drink??

Tags: alcohol, breast cancer, cholesterol, HDL, heart disease, wine

Enough people have asked me if the kind of cholesterol in egg yolks is good or bad (hint: it’s neither) that I think it is time for a brief tutorial on this misunderstood molecule.

Rather than put you to sleep with a watered down version of a Wikipedia article I decided to explain the interaction of diet and cholesterol in a short video. Hopefully this will help clear up what cholesterol is and how you should eat to minimize your risk of heart disease.

As always, feel free to drop me questions in the comments.

If you like this story follow me on the new Digg!

Further reading:

• How To Raise Your HDL Cholesterol
• Intact Grains vs Whole Grains
• How To Make Eggs Taste As Good As Bacon
• Book Review: Good Calories, Bad Calories

Tags: cholesterol, eggs, HDL, heart disease, LDL

Many studies have been published associating lack of sleep with increased body weight, but I have never read through the literature myself to explore the connection.

This week fellow scientist Matthew Constantin of Best Weight Loss Triumph gives us a thorough review of the science of sleep and weight gain.

Matthew Constantin, PhD, is a biologist and postdoctoral research scientist at Saint Louis University. Twice awarded research grants from the American Heart Association for his studies on cardiovascular disease, Matthew also has a keen interest in the related field of obesity treatment and enjoys explaining the latest scientific research on weight loss in a way that is easy for everyone to understand.

His website contains reviews of some of the so-called best rated weight loss programs and offers a savings coupon for Medifast, a clinically studied weight loss intervention.

Obesity and Reduced Sleep: Will Sleeping Less Make Me Fat?

By Matthew Constantin, PhD

We have long known that too little sleep causes fatigue and a slowing of neurocognitive functions, resulting in a variety of symptoms like slowed reaction time and difficulty concentrating. Recent research, however, has discovered a new result of reduced sleep: metabolic effects that include an increased risk of obesity [1].

Western society has seen a rapid rise in overweight and obesity in recent decades. Accompanying this widespread weight gain has been a significant and rapid decrease in the amount of time the average person spends sleeping.

While young adults were sleeping close to 9 hours each night at the beginning of the 20th century [2], this had decreased to less than 8 hours by the late 1960s [3]. The trend is continuing into the 21st century. As of 2005, 16% of American adults were getting less than 6 hours of sleep at night, up from 12% in 1998.

Sleep and Obesity: A Subjective Study

Science has linked self-reported sleep habits and obesity for a number of years, but the precise relationship between the two has been difficult to establish. Because obesity is a risk factor for a number of diseases that can negatively impact sleep, such as sleep apnea, asthma, depression, and arthritis, it is hard to know whether reduced sleep leads to obesity or obesity leads to reduced sleep.

To shed some light on this question, data collected from 1986 to 2002 in the Nurses’ Health Study (NHS) was analyzed [4]. Women in this study were asked to report their sleep habits and body weight every two years.

The results of the study suggest that women who self-report receiving less sleep are more likely to gain weight and are at an increased risk for obesity in middle-age. In 1986, when the first round of data was collected, it was found that women who reported sleeping 7 hours in a 24 hour period weighed 2.6 kg less than those who slept 5 or fewer hours, and 1.3 kg less than those who slept 6 hours.

This pattern continued over the following 16 years, with women who reported getting 5 or fewer hours of sleep weighing the most every time weight data was collected and those getting 7-8 hours of sleep weighing the least. In 2002, those in the 6-hour group had gained 7.2kg (15.8lb) and those in the 5-hour or less group gained 9kg (19.8lb), while those in the 7-hour group had gained only 4.8 (10.6lb) kg.

Other prospective studies have found similar results among both adults and children, but there are a couple of caveats. Because the information in the studies is self-reported, it is subject to inaccurate estimates by the reports. Many people overestimate sleep time when self-reporting. It is also unknown whether shorter sleepers are heavier because of an increase in fat or an increase in lean muscle—a distinction which makes a significant difference for health repercussions.

Sleep and Obesity: An Objective Study

In response to the limitations of subjective studies on sleep and obesity, two groups of adults aged 65+ (one of men and one of women) took part in an objective study that also looked at sleep duration and weight. Rather than relying on self-reported data, participants’ sleep patterns were assessed through the use of wrist actigraphy, which determines if a person is asleep or awake by measuring wrist movement.

This objective measurement of sleep duration confirmed the results of the subjective study, finding that reduced sleep was associated with an increased Body Mass Index (BMI) among both men and women. When compared with those getting 7-8 hours of sleep per night, average BMI of those who slept less than 5 hours was higher by 2.5 units in men and by 1.8 units in women. Moreover, men getting 5 or fewer hours of sleep were 3.7 times more likely to be obese, while women were 2.3 time more likely.

Increased weight doesn’t necessarily mean an increase in fat and its related health problems—more muscle also means more weight, but is generally associated with improved health. The objective study looked at this question and found that the increase in weight associated with reduced sleep was a result of increased fat rather than muscle. Overall percent body fat in those sleeping less than 5 hours was 1.7% greater than those getting 7-8 hours, and percent body fat in the trunk 1.9% greater.

Why Could Reduced Sleep Make You Fat?

Research has clearly shown that reduced sleep is associated with greater weight, but why does reduced sleep make a person fat?

One strong hypothesis is that less sleep leads to increased or altered food intake. Animals studies have found that sleep deprivation leads to elevated levels of hunger [5], with particular increases for high-fat and high-carbohydrate foods. This increased hunger with sleep deprivation may be a result of the corresponding change in hormones that regulate hunger, with gherlin levels found to increase and leptin levels to decrease.

Alternatively, rather than a change in feelings of hunger, increased food intake could be the result of increased eating even in the absence of hunger. Reduced impulse control and trouble delaying gratification are known consequences of sleep deprivation.

It’s also possible that simply being awake more often will lead to increased eating when food is readily available, especially if time awake is spent in sedentary activities that encourage snacking.

As S.R. Patel mentions in his 2009 review paper titled “Reduced sleep as an obesity risk factor”, there are several other possibilities that have been proposed. One is that the feelings of fatigue that are associated with sleep deprivation may result in a disinclination to exercise. Another is that reduced sleep results in a reduction in involuntary activities such as fidgeting, which are known to have effects on weight regulation [6].

Finally, acute sleep deprivation has been found to result in a drop in core body temperature, meaning your body needs to spend less energy in order to maintain thermoregulation with the surrounding air. This change in thermogenesis (the process of heat production) may encourage the storing of fat, although a recent study found no effect of sleep deprivation on resting metabolic rate.

Conclusions

Current evidence clearly shows that short sleep is associated with obesity, but a causal relationship remains unclear. Does a reduction in sleep lead to weight gain, or is there some other reason for the association? We don’t yet know for sure. But as modern society sets aside less and less time for sleep and becomes increasingly prone to obesity, it is a possibility that must be considered.

With so few effective ways to prevent and treat obesity, wouldn’t it be wonderful if simply sleeping a bit more could keep us both thinner and healthier?

References

1. Patel, S.R. Short sleep and obesity. International Association for the Study of Obesity. Obesity Reviews 10 (Suppl. 2), 61–68.

2. Terman L, Hocking A. The sleep of school children, its distribution according to age, and its relationship to physical and mental efficiency. J Educ Psychol 1913; 4: 269–282.

3. Tune GS. Sleep and wakefulness in normal human adults. Br Med J 1968; 2: 269–271.

4. Patel SR, Malhotra A, White DP, Gottlieb DJ, Hu FB. Association between reduced sleep and weight gain in women. Am J Epidemiol 2006; 164: 947–954.

5. Spiegel K, Tasali E, Penev P, Van Cauter E. Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med 2004; 141: 846–850.

6. Levine JA, Eberhardt NL, Jensen MD. Role of nonexercise activity thermogenesis in resistance to fat gain in humans. Science 1999; 283: 212–214.
Matthew Constantin

Tags: BMI, sleep

Photo by Robyn's Nest

Artificial sweeteners and sugar substitutes can be very appealing to people looking to cut their calories or control blood sugar, and I get a lot of questions about them. Generally I don’t recommend processed or sweetened foods and encourage people to break free from regular sugar consumption, but I recently discovered coconut palm sugar and decided to look into it.

Coconut palm sugar has garnered attention as being a low-carb sugar substitute that is both more nutritious and sustainable than typical granulated sugar. Because of its complex flavor it is also gaining a reputation in foodie communities, with establishments like the popular Samovar Tea Lounge in San Francisco switching 100% of its sweeteners over to coconut palm sugar.

Pure coconut palm sugar is a natural product made from the nectar of the coconut palm tree. There are several different varieties of palm (Palmyra, date, etc.), and “coconut palm” specifically refers to the coco nucifera plant.

Most of the “palm sugar” commonly sold in Asian markets is not pure coconut palm sugar but is blended with other fillers such as white cane sugar. Pure certified organic coconut palm sugar is sold under the brand name Sweet Tree in the US, and can be found at some natural food stores. It is also available online.

The information in this article applies only to 100% pure coconut palm sugar. Check your labels carefully.

Pure coconut palm sugar reportedly has a naturally low glycemic index (GI)–a measure of how food impacts blood sugar–which has led some people to claim that it is a valuable sugar substitute for people with diabetes or those looking to control blood sugar (the low-carb camp). Indeed, a lower GI may be a good indication that a food is safer for diabetics, though it is not a guarantee.

When I first saw that coconut palm sugar has a low GI I figured it would be composed largely of fructose, similar to the popular sweetener agave nectar (and high-fructose corn syrup). Fructose does not impact blood sugar because it is transported directly to the liver and converted to fat. For an explanation of this mechanism, check out Dr. Lustig’s video on the dangers of fructose.

I was surprised to find, however, that coconut palm sugar is reportedly very low in fructose, and its main sugar component is sucrose (aka table sugar). What confuses me is that the GI of coconut palm sugar is supposed to be 35, while the GI of sucrose is 64.

I feel obligated to qualify the numbers on coconut palm sugar, however, since I could only find a summary of how GI was measured and not the published study itself. Also, this information was only available on the website of a company that sells coconut palm sugar. This doesn’t mean the number is inaccurate, it just means I’d like to see the study repeated by another credible source or two before taking it as fact.

The number of calories in coconut palm sugar is almost identical to the number in regular table sugar and its closer relative, brown sugar. But coconut palm sugar is notably higher in various micronutrients, probably because it is less processed than industrial sugars.

But does anyone really eat sugar for health benefits?

There are a number of good reasons to consider using coconut palm sugar as a substitute for white or brown sugar in your kitchen. For me the most obvious benefit is that it tastes amazing, similar to brown sugar but with a rich complexity I’ve never tasted in industrial sugars.

Coconut palm sugar is also supposed to be substantially better for the environment, having been called the most sustainable sweetener by the Food and Agriculture Organization (FAO) of the United Nations (couldn’t find the original FAO report though).

Overall coconut palm sugar is a tastier and possibly healthier and more sustainable substitute for granulated or brown sugar. I wouldn’t go so far as to call it a health food, or even low-carb just yet. However it is a nice pantry addition for foodies concerned with sustainable products.

Substitute coconut palm sugar for traditional sugar at a 1:1 ratio in normal cooking and baking.

Have you tried coconut palm sugar? What do you think?

Tags: coconut palm sugar, diabetes, fructose, glycemic index, sucrose, sugar, sustainable, sweeteners