Skin Damage From Sun

Written by Dr. Steve Chaney on . Posted in Health Current Events, Skin Damage From Sun, Vitamin D

Author: Dr. Stephen Chaney

skin damage from sunSkin damage from sun is a real danger.  The dog days of summer are here. For some of us that means staying inside as much as possible. Others want to enjoy the fleeting days of summer as much as possible before summer turns to fall, and fall turns to winter. That means lots of outdoor activities in the sun – such as outdoor sports, working in the yard, and vacations in fun locations with lots of sun. So it’s time to ask the perennial question “How much sun exposure should I be getting?”

Some people like to aim for as much sun exposure as possible. When I was a teenager everybody was searching for “the perfect tan”. Back then it was popular to slather your skin with tanning oils that allowed you to just baste yourself in the sun without your skin drying up. (Did I just date myself again?)

Other people like to follow their dermatologist’s advice and use SPF maximum (the sun shall never touch my skin) sunscreens. And, just to be on the safe side they also follow their dermatologist’s advice to limit sun exposure between 10 AM and 4 PM and wear a hat, sunglasses, and protective clothing whenever possible. I can see the hat and sunglasses, but the protective clothing isn’t particularly compatible with the summer heat in my native North Carolina. Believe me, you want to wear as little as possible here in the summer.

Skin Damage From Sun

sun exposureNow that we’ve explored the extremes, let’s return to the central theme of this health tip which is “How much sun exposure should I really be getting?” Let’s start by focusing on the vanity factor – skin aging. Let’s face it. Excessive sun exposure increases the risk of skin cancer. However, skin aging is the consequence most people really care about. This is the concern that has most people reaching for the sunscreen before they head out the door.

A recent clinical study clearly showed that sunscreen usage helps prevent skin aging (Hughes et al, Annals of Internal Medicine, 158: 781-790, 2013). Now you might be saying to yourself “This is nothing new. I’ve heard that for years.” Yes, that advice has been around for a long time. But the problem is that the old advice was never based on actual clinical studies, only studies done on hairless mice. So first, let me analyze this clinical study for you and then put the findings into perspective.

The good news is that this was a very well done clinical study. The authors enrolled 903 adults under the age of 55 from sunny Australia into the study for a 4.5-year period from 1992 to 1996. The study was restricted to adults younger than 55 years because, in that age range, skin aging is primarily caused by sun exposure rather than the normal aging process. The study also excluded people who were already using sunscreen on a daily basis. Variables such as skin color, skin reaction to sun exposure, amount of time spent outdoors, sunburn history, and smoking status were determined at baseline and used to normalize the results.

Half of the participants were given a sunscreen with an SPF 15 factor and were instructed to use this sunscreen on a daily basis. The other half were given nothing and were just instructed to keep doing what they had been doing (It was deemed unethical to give them a placebo sunscreen as it could cause skin damage from sun). Compliance was assessed by measuring the weight of the returned sunscreen bottles every three months and by using a biennial application frequency questionnaire. Compliance wasn’t perfect, but of those enrolled in the sunscreen portion of the study 77% used sunscreen 3 to 4 times per week, compared to 33% of the control group.

Skin damage from sun was assessed by taking an impression of the back of the left-hand and analyzing it for the number and depth of lines and the flattening of the skin. And the results were fairly clear-cut. Those study participants who used sunscreen on a daily basis had 24% less sun damage over the 4.5-year period than the control group. I am not an expert, but dermatologists who have evaluated this study say that a 24% decrease in sun damage is visibly significant.

What Does This Study Mean For You?

It turns out that the old advice that too much sun exposure can cause significant skin damage as we get older is actually true. Who would have guessed? If the threat of skin cancer isn’t enough to dissuade you from pursuing the perfect tan, perhaps the thought of ugly, wrinkled skin as you get older will do it.

On the flip side, however, we need to remember that sun exposure is also required for vitamin D formation. And recent studies show that up to 80% of Americans have low levels of 25-hydroxy vitamin D, the biologically relevant form of vitamin D, in their blood – perhaps because many of us actually follow our dermatologist’s advice and never go out of the house without sunscreen, sunglasses, hat, and protective clothing to help prevent skin damage from sun.

Recent clinical studies have linked low levels of 25-hydroxy vitamin D with a number of health concerns. That has led one prominent dermatologist who studies vitamin D, Dr. Michael Holick, to recommend that we should be getting 10 to 15 minutes of unprotected sun exposure during midday – a recommendation that many of his colleagues consider to be heretical.

How Can You Have Your Cake And Eat It Too?

vitamin DSo what is a person to do? How can we reconcile the need to improve our vitamin D status with our desire to have a healthy, good looking skin well into our golden years? The simple answer is to make sure that we are getting plenty of vitamin D in our diet. The most recent RDAs are 600 IU per day of vitamin D in children and adults up to the age of 70 and 800 IU per day for adults over 70.

Many experts are even recommending that we get 1000 to 2000 IU of vitamin D per day. The Institute of Medicine (the group that actually sets the RDAs) considers that to be in the safe range for vitamin D intake. If you are thinking of exceeding that dosage, my advice would be to first get your 25-hydroxy vitamin D levels determined (20-50 ng/ml or 50-125 nmol/L is considered optimal) and then consult with your doctor as to what the best dosage of vitamin D is for you.

And, if you are relying on supplements for your vitamin D intake, you should be sure to choose a company that manufactures their supplements according to pharmaceutical standards. A recent study(E. S. LeBlanc et al, JAMA Internal Medicine, 173:585-586, 2013)  analyzed commercially available vitamin D supplements and found some brands in which the potency from bottle to bottle ranged from 9% to 140% of what was on the label. That is unacceptable.

 

The Bottom Line

  • A recent study has confirmed what we have been told for years, namely that regular use of an SPF 15 sunscreen reduces skin aging. Specifically, the study showed that regular sunscreen use reduced skin aging by 24% over a 4.5-year period in people 55 years old or younger.
  • On the other hand, sun exposure is required for our bodies to synthesize the active form of vitamin D. Vitamin D experts like Dr. Michael Holick recommend that we get at least 10-15 minutes of unprotected sun exposure a day during the summer months to assure that our bodies make the vitamin D we need for optimal health.
  • If you want both young looking skin and optimal vitamin D status, you will probably want to consider a vitamin D supplement. Recommendations for how much and what kind of vitamin D supplement are found in the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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A Low Carb Diet and Weight Loss

Posted January 15, 2019 by Dr. Steve Chaney

Do Low-Carb Diets Help Maintain Weight Loss?

Author: Dr. Stephen Chaney

 

low carb dietTraditional diets have been based on counting calories, but are all calories equal? Low-carb enthusiasts have long claimed that diets high in sugar and refined carbs cause obesity. Their hypothesis is based on the fact that high blood sugar levels cause a spike in insulin levels, and insulin promotes fat storage.

The problem is that there has been scant evidence to support that hypothesis. In fact, a recent meta-analysis of 32 published clinical studies (KD Hall and J Guo, Gastroenterology, 152: 1718-1727, 2017 ) concluded that low-fat diets resulted in a higher metabolic rate and greater fat loss than isocaloric low-carbohydrate diets.

However, low-carb enthusiasts persisted. They argued that the studies included in the meta-analysis were too short to adequately measure the metabolic effects of a low-carb diet. Recently, a study has been published in the British Medical Journal (CB Ebbeling et al, BMJ 2018, 363:k4583 ) that appears to vindicate their position.

Are low carb diets best for long term weight loss?

Low-carb enthusiasts claim the study conclusively shows that low-carb diets are best for losing weight and for keeping it off once you have lost it. They are saying that it is time to shift away from counting calories and from promoting low-fat diets and focus on low-carb diets instead if we wish to solve the obesity epidemic. In this article I will focus on three issues:

  • How good was the study?
  • What were its limitations?
  • Are the claims justified?

 

How Was The Study Designed?

low carb diet studyThe investigators started with 234 overweight adults (30% male, 78% white, average age 40, BMI 32) recruited from the campus of Framingham State University in Massachusetts. All participants were put on a diet that restricted calories to 60% of estimated needs for 10 weeks. The diet consisted of 45% of calories from carbohydrate, 30% from fat, and 25% from protein. [So much for the claim that the study showed low-carb diets were more effective for weight loss. The diet used for the weight loss portion of the diet was not low-carb.]

During the initial phase of the study 161 of the participants achieved 10% weight loss. These participants were randomly divided into 3 groups for the weight maintenance phase of the study.

  • The diet composition of the high-carb group was 60% carbohydrate, 20% fat, and 20% protein.
  • The diet composition of the moderate-carb group was 40% carbohydrate, 40% fat, and 20% protein.
  • The diet composition of the low-carb group was 20% carbohydrate, 60% fat, and 20% protein.

Other important characteristics of the study were:

  • The weight maintenance portion of the study lasted 5 months – much longer than any previous study.
  • All meals were designed by dietitians and prepared by a commercial food service. The meals were either served in a cafeteria or packaged to be taken home by the participants.
  • The caloric content of the meals was individually adjusted on a weekly basis so that weight was kept within a ± 4-pound range during the 5-month maintenance phase.
  • Sugar, saturated fat, and sodium were limited and kept relatively constant among the 3 diets.

120 participants made it through the 5-month maintenance phase.

 

Do Low-Carb Diets Help Maintain Weight Loss?

low carb diet maintain weight lossThe results were striking:

  • The low-carb group burned an additional 278 calories/day compared to the high-carb group and 131 calories/day more than the moderate-carbohydrate group.
  • These differences were even higher for those individuals with higher insulin secretion at the beginning of the maintenance phase of the study.
  • These differences lead the authors to hypothesize that low-carb diets might be more effective for weight maintenance than other diets.

 

What Are The Pros And Cons Of This Study?

low carb diet pros and consThis was a very well-done study. In fact, it is the most ambitious and well-controlled study of its kind. However, like any other clinical study, it has its limitations. It also needs to be repeated.

The pros of the study are obvious. It was a long study and the dietary intake of the participants was tightly controlled.

As for cons, here are the three limitations of the study listed by the authors:

#1: Potential Measurement Error: This section of the paper was a highly technical consideration of the method used to measure energy expenditure. Suffice it to say that the method they used to measure calories burned per day may overestimate calories burned in the low-carb group. That, of course, would invalidate the major findings of the study. It is unlikely, but it is why the study needs to be repeated using a different measure of energy expenditure.

#2: Compliance: Although the participants were provided with all their meals, there was no way of being sure they ate them. There was also no way of knowing whether they may have eaten other foods in addition to the food they were provided. Again, this is unlikely, but cannot be eliminated from consideration.

#3: Generalizability: This is simply an acknowledgement that the greatest strength of this study is also its greatest weakness. The authors acknowledged that their study was conducted in such a tightly controlled manner it is difficult to translate their findings to the real world. For example:

  • Sugar and saturated fat were restricted and were at very similar levels in all 3 diets. In the real world, people consuming a high-carb diet are likely to consume more sugar than people in the other diet groups. Similarly, people consuming the low-carb diet are likely to consume more saturated fat than people in the other diet groups.
  • Weight was kept constant in the weight maintenance phase by constantly adjusting caloric intake. Unfortunately, this seldom happens in the real world. Most people gain weight once they go off their diet – and this is just as true with low-carb diets as with other diets.
  • The participants had access to dietitian-designed prepared meals 3 times a day for 5 months. This almost never happens in the real world. The authors said “…these results [their data] must be reconciled with the long-term weight loss trials relying on nutrition education and behavioral counseling that find only a small advantage for low carbohydrate compared with low fat diets according to several recent meta-analyses.” [I would add that in the real world, people do not even have access to nutritional education and behavioral modification.]

 

low carb diet and youWhat Does This Study Mean For You?

  • This study shows that under very tightly controlled conditions (dietitian-prepared meals, sugar and saturated fat limited to healthy levels, calories continually adjusted so that weight remains constant) a low-carb diet burns more calories per day than a moderate-carb or high-carb diet. These findings show that it is theoretically possible to increase your metabolic weight and successfully maintain a healthy weight on a low-carb diet. These are the headlines you probably saw. However, a careful reading of the study provides a much more nuanced viewpoint. For example, the fact that the study conditions were so tightly controlled makes it difficult to translate these findings to the real world.
  • In fact, the authors of the study acknowledged that multiple clinical studies show this almost never happens in the real world. These studies show that most people regain the weight they have lost on low-carb diets. More importantly, the rate of weight regain is virtually identical on low-carb and low-fat diets. Consequently, the authors of the current study concluded “…translation [of their results to the real world] requires exploration in future mechanistic oriented research.” Simply put, the authors are saying that more research is needed to provide a mechanistic explanation for this discrepancy before one can make recommendations that are relevant to weight loss and weight maintenance in the real world.
  • The authors also discussed the results of their study in light of a recent, well-designed 12-month study (CD Gardener et al, JAMA, 319: 667-669, 2018 ) that showed no difference in weight change between a healthy low-fat versus a healthy low-carbohydrate diet. That study also reported that the results were unaffected by insulin secretion at baseline. The authors of the current study noted that “…[in the previous study] participants were instructed to minimize or eliminate refined grains and added sugars and maximize intake of vegetables. Probably for this reason, the reported glycemic load [effect of the diet on blood sugar levels] of the low-fat diet was very low…and similar to [the low-carb diet].” In short, the authors of the current study were acknowledging that diets which focus on healthy, plant-based carbohydrates and eliminate sugar, refined grains, and processed foods may be as effective as low-carb diets for helping maintain a healthy weight.
  • This would also be consistent with previous studies showing that primarily plant-based, low-carb diets are more effective at maintaining a healthy weight and better health outcomes long-term than the typical American version of the low-fat diet, which is high in sugar and refined grains. In contrast, meat-based, low-carb diets are no more effective than the American version of the low-fat diet at preventing weight gain and poor health outcomes. I have covered these studies in detail in my book “Slaying The Food Myths.”

Consequently, the lead author of the most recent study has said: “The findings [of this study] do not impugn whole fruits, beans and other unprocessed carbohydrates. Rather, the study suggests that reducing foods with added sugar, flour, and other refined carbohydrates could help people maintain weight loss….” This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.

The Bottom Line

 

  • A recent study compared the calories burned per day on a low-carb, moderate-carb, and high-carb diet. The study concluded that the low-carb diet burned significantly more calories per day than the other two diets and might be suitable for long-term weight control. If confirmed by subsequent studies, this would be the first real evidence that low-carb diets are superior for maintaining a healthy weight.
  • However, the study has some major limitations. For example, it used a methodology that may overestimate the benefits of a low-carb diet, and it was performed under tightly controlled conditions that can never be duplicated in the real world. As acknowledged by the authors, this study is also contradicted by multiple previous studies. Further studies will be required to confirm the results of this study and show how it can be applied in the real world.
  • In addition, the kind of carbohydrate in the diet is every bit as important as the amount of carbohydrate. The authors acknowledge that the differences seen in their study apply mainly to carbohydrates from sugar, refined grains, and processed foods. They advocate diets with low glycemic load (small effects on blood sugar and insulin levels) and acknowledge this can also be achieved by incorporating low-glycemic load, plant-based carbohydrates into your diet. This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.
  • Finally, clinical studies report averages, but none of us are average. When you examine the data from the current study, it is evident that some participants burned more calories per hour on the high-carb diet than other participants did on the low carb diet. That reinforces the observation that some people lose weight more effectively on low-carb diets while others lose weight more effectively on low-fat diets. If you are someone who does better on a low-carb diet, the best available evidence suggests you will have better long-term health outcomes on a primarily plant-based, low-carb diet such as the low-carb version of the Mediterranean diet.

For more details read the article above.

 

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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