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Prevention & Early Detection (34 posts)  RSS

Can Vitamin D prevent cancer?

June 16, 2015

By Marji McCullough, ScD, RD

You may be aware that Vitamin D is important for helping make strong bones. But vitamin D often appears in the media because of its potential role in a host of other health effects, from preventing cancer, diabetes, and heart disease to simply living longer.  However, most of these "non-skeletal" (not having to do with your bones) roles of vitamin D are not clearly established and remain a topic of active investigation and debate. To add to the confusion, several recent scientific reviews of the vast data on vitamin D arrived at different conclusions about whether it helps prevent disease or not.

In this blog, I am going to focus on the evidence on vitamin D and cancer prevention, highlight some key unresolved questions, and give some advice to consider while we await more solid answers (which may take a while).

Where does vitamin D come from?


People can get vitamin D from exposure to sunlight, from certain foods, and from supplements.

Current vitamin D recommendations from the Institute of Medicine (IOM), the organization tasked with developing the Recommended Dietary Allowances (RDAs), are 600 International Units (IU) per day for most adults, and 800 IU of vitamin D per day for those over age 70. Very high doses of vitamin D over a long period of time can be toxic, so the IOM recommends that no one should exceed 4,000 IU/day. 

Vitamin D is found naturally in very few foods, including cod liver oil, fatty fish like sardines or salmon, and in smaller amounts in eggs and leafy greens. In the U.S., vitamin D is added to milk, some yogurts, orange juices, and cereals. One cup of milk or yogurt contains about 100 IU, whereas fatty fish contains about 500 IU per serving. Read about other sources of vitamin D. Vitamin D supplements are available in a range of doses. 

Sun exposure can provide a wallop of vitamin D, depending on amount of skin exposed, skin tone, time of day, time of year, location, and a variety of other factors. For example, a Caucasian adult wearing a bathing suit exposed to enough sun to have a light pink sunburn has received roughly 10,000-20,000 IU of vitamin D. It takes dark-skinned individuals 5-10 times longer to form the vitamin because of higher concentrations of melanin in the skin, and dark-skinned individuals often have lower vitamin D levels. Other factors that can influence vitamin D formation in the skin include use of sunscreens and sun-protective clothing (because they block UV rays). 

But don't look to the sun as a source of vitamin D because the same UV radiation that forms vitamin D in the skin also burns the skin and can lead to skin cancer. Studies have not identified a level of sun exposure that is safe for avoiding skin cancer. The American Cancer Society recommends limiting sun exposure to prevent skin cancer, including melanoma (the most serious type of skin cancer). 

What the studies say

It has been suggested that vitamin D itself may prevent, or even increase the risk for, some forms of cancer. Different types of studies are used to understand if this is true. All have their strengths and weaknesses and add a piece to the puzzle.

Laboratory studies provide some strong biological evidence to support a role for vitamin D in cancer prevention. Vitamin D can "turn on" or "turn off" a host of genes, including some that regulate cell growth, limit inflammation, and reduce levels of a signaling protein that can allow cancer cells to spread. The exact role of vitamin D in these processes is a very active area of research.

Observational Studies


In humans, the idea that vitamin D might help protect against cancer first came from studies that mapped cancer death rates in the US by region. These studies showed that Northern states, where sun exposure was lowest, had higher death rates from several different cancers compared to the Southern, sunnier states. Because the sun is a source of vitamin D, scientists thought that vitamin D might protect against cancer. However, different cancer rates by region also may be due to other factors that vary among people living in different parts of the country.

So far, the most support for a role of vitamin D comes from prospective studies of colorectal cancer (includes both colon and rectal cancer). In several studies, compared to people with low blood vitamin D levels, people with higher blood levels have a significantly lower risk of colorectal cancer. However, there are inconsistencies in results across studies, potentially due to different methods used, such as how vitamin D was measured.  An ongoing study, called the "Vitamin D Pooling Project of Breast and Colorectal Cancer" is carefully measuring blood levels of vitamin D and examining their association with colorectal and breast cancer in 21 prospective studies, using the same methods. These findings should be published in the next year. 

Observational studies of vitamin D and risk of other cancers do not provide clear evidence of benefit. In a combined analysis from 10 prospective cohort studies, the amount of vitamin D in the blood before diagnosis was not associated (no link was found) with the risk of kidney, lymphoid, ovarian, endometrial, or upper gastrointestinal cancers like stomach or esophagus. For other cancers, including prostate and pancreas, studies have had inconsistent results, some even suggesting increased risk of cancer in those with the highest levels.

A strength of observational prospective cohort studies is that they can typically examine wide ranges of vitamin D in the blood that occur naturally in a population. Their main limitation is that they cannot prove that it's the vitamin D in the blood that really prevents cancer. For example, people with low vitamin D levels may also tend to be less physically active and more overweight or obese, both of which are risk factors for certain cancers. For this reason, researchers conducting observational studies collect detailed information on other risk factors and account for them when they're examining the results.  

Randomized Controlled Trials (RCTs)


When conducted well, RCTs can prove if something prevents disease because people are randomly assigned to get vitamin D or a placebo (sugar pill). The randomization helps to ensure that on average people are more alike in other ways (e.g. body weight, physical activity, and other known or unknown risk factors), so researchers can isolate the effect of the vitamin D supplement. But these studies are very expensive and logistically difficult, and may not study the right dose, for the right amount of time, in the right (susceptible) population.   

So far, a large RCT did not find that 400 IU vitamin D combined with calcium lowered colorectal or breast cancer risk. In this study, women were allowed to take their own supplements, and by the end of the trial, most were. In other words, the placebo group as well as the intervention group were exposed to vitamin D, increasing the risk of results that aren't significant (null results). 

Other RCTs of vitamin D that reported on development of cancer or death from cancer had very small sample sizes and did not provide conclusive results. For some of these trials, the initial goal was to study bone health, not cancer, increasing the likelihood of "chance" findings. There are currently a handful of larger trials underway, including the large U.S. VITAL trial, which will examine vitamin D and fish oil supplements in relation to cancer outcomes and heart disease. Study results are not expected for several years.

What to do in the meantime?


The key for research will be to identify the amount of vitamin D that may lower the risk of certain diseases, but not increase the risk of others. Until we know more, make sure you meet the IOM recommendations for bone health of 600 IU for most adults or 800 IU of vitamin D/day for those over age 70. Even for people who are not exposed to the sun, the recommended doses are thought to be enough for 97.5% of people in the US. Depending on your health status, your doctor may choose to measure how much vitamin D you have in your blood, but routine vitamin D measurements are currently not recommended by any agency for cancer prevention or to avoid other serious illnesses.

Bottom line: we don't know yet if vitamin D can help prevent cancer or other diseases, but we're working on finding out. In the meantime, make sure to meet the IOM recommendations for bone health through food choices as much as you can, and discuss with your health care provider whether you need a supplement to help.

 

McCullough is strategic director of nutritional epidemiology for the American Cancer Society.

What keeps people from lifesaving colon cancer testing?

March 12, 2015

By Richard Wender, MD


We have made amazing progress in reducing colon cancer death rates. This progress is a direct result of increasing screening for colon cancer and pre-cancerous polyps. We are actually preventing thousands of cancers by finding and removing pre-cancerous polyps. The nation has embraced the goal of increasing national screening rates to 80% by the end of 2018 - an achievement that will substantially reduce the terrible toll that colon cancer exacts every year.  Everyone is at risk for colon cancer, whether or not someone in your family has ever had a colon polyp or colon cancer. For that reason, everyone has to start being screened for colon cancer at age 50, and people with inflammatory bowel disease or a family history of colon cancer or polyps have to start before they reach age 50. Colon cancer screening is one of the best opportunities to prevent cancer that we've ever discovered.

Despite this compelling reason to be screened, many people either have never had a colon cancer screening test or are not up-to-date with screening. Interestingly, nearly all of these unscreened people know that they should be screened, In fact, awareness about colon cancer screening recommendations approaches 100%. The American Cancer Society asked more than 2,000 unscreened adults a series of questions about screening, and we now have a pretty clear idea about what's stopping people from taking that lifesaving step:

  • Some people are concerned about the cost of the test
  • Others have heard that the test is difficult or painful, and they may be embarrassed to discuss colon cancer screening
  • Some people think screening is only for those who have symptoms
  • Others think that having no family history of colon cancer means that they are not at risk and don't have to be screened

Finally, and perhaps most importantly, many people are concerned about the complexity and cost of having a colonoscopy, like the need to take time off from work, the need to have a ride home, and the potential for high out-of-pocket expenses, which all combine to discourage them from having a colonoscopy. More...

Celebrating 25 Years of Smoke-Free Airplanes

February 25, 2015

By John R. Seffrin, PhD

Twenty-five years after a federal law passed banning smoking on all domestic flights, many of us don't even notice the lit "No Smoking" sign above our airplane seats. Until that landmark public health legislation took effect on February 25, 1990, flight attendants were subjected to deadly secondhand smoke during every flight and travelers who sat in "non-smoking" sections couldn't escape the fumes.

As a member of the American Cancer Society National Board of Directors 25 years ago, I agreed it was imperative for the Society to utilize its scientific expertise and passionate volunteer base to counteract the tobacco industry and protect non-smokers and flight attendants from the hazardous effects of secondhand smoke on every flight. We had the evidence to prove that smoke-free laws saved lives, so we decided to take the issue to Capitol Hill. The Society and its public health partners had champions in Senators Dick Durbin (D-IL) and Frank Lautenberg (D-NJ), whose unwavering support was instrumental in passing the legislation. (You can hear more about Senator Durbin's involvement in this video.)

The smoke-free airplanes legislation sparked a nationwide movement in support of smoke-free workplaces. In 2002, Delaware became the first state to enact a comprehensive smoke-free law covering all workplaces, including bars and restaurants. Since then, 23 other states and the District of Columbia have followed suit, and today nearly half of the U.S. population is protected by a comprehensive smoke-free law. 

The Society's advocacy affiliate, the American Cancer Society Cancer Action Network (ACS CAN), believes that the momentum that began 25 years ago cannot stall, especially with a tobacco industry that continues to use egregious tactics to addict kids to its deadly products. There are still 26 states lacking comprehensive smoke-free laws, 58 million Americans exposed to secondhand smoke and minority and low-income populations disproportionately subjected to the deadly impact of tobacco. It's hard to imagine that cigarettes were ever allowed on flights, and smoking in other workplaces, including restaurants and bars should become relegated to history books as well.

Tobacco will claim the lives of nearly half a million Americans this year. Evidence shows that enacting strong smoke-free laws that cover all workplaces, increasing tobacco excise taxes on a regular basis and fully funding tobacco prevention and cessation programs help people quit using tobacco and keep kids from ever starting. ACS CAN is working to make strong tobacco control laws a priority with elected officials at every level. From passing local smoke-free ordinances, to increasing the meager $1.01 federal cigarette tax, to funding tobacco education and cessation programs, to supporting strong federal regulation over the tobacco industry, ACS CAN is strengthening public policies in ways that help to change cultural views of tobacco use and will lead to a smoke-free, tobacco-free generation. 

 

Dr. Seffrin is the chief executive officer f the American Cancer Society and its advocacy affiliate the American Cancer Society Cancer Action Network.

Less Food Marketing, Healthier Children

January 20, 2015

By Colleen Doyle, MS, RD


Have you seen all those fun and flashy commercials encouraging your kids to eat more fruits and vegetables? No? Neither have I. And there's a reason for that. 

Out of the $1.79 billion that the Federal Trade Commission says major food and beverage companies spent marketing foods and beverages to kids and teens (in 2009 - the most recent data available), less than .05% was spent marketing fruits and vegetables. Unfortunately for those of us who care about children's health - which I hope is all of us - the majority of those dollars was spent on marketing unhealthy foods and beverages. Forty percent was spent to market fast food and other restaurant foods, and another 22% was spent promoting high-sugar sodas and other carbonated beverages.

And consider these additional statistics:

  • Two BILLION advertisements for foods and drinks appeared on websites directed at kids in 2009, mostly for sugary cereals and fast food.
  • Dollars spent to market foods and drinks to kids via online games, mobile apps, social network ads, and other digital media increased by 51% from 2006 to 2009.
  • Companies spent $149 MILLION in 2009 to market sugary drinks and food in schools.
  • Companies spent $113 MILLION in 2009 on packaging with marketing aimed at kids (think SpongeBob, Hello Kitty, and other characters).
  • Fast-food restaurants spent over $700 MILLION in 2009 on marketing to kids, nearly half of which was spent on kids' meal toys and giveaways.
  • Kids saw 12 to 16 TV advertisements per day for unhealthy foods or drinks in 2011.
  • Eighty-four percent of foods and drinks advertised to kids on Spanish-language television are unhealthy. More...

Indoors or outdoors, there's no such thing as a safe tan

May 22, 2014

By Gery P. Guy Jr., PhD, MPH


If you read no further, know this: there is no such thing as a safe tan. Indoor tanning is just as dangerous, if not more, than tanning outside in the sun. In fact, indoor tanning injures thousands of people each year badly enough to go to the emergency department. Indoor tanning can cause sunburn and damage to your eyes that could lead to vision loss. Indoor tanning can also cause premature skin aging, including loss of elasticity, wrinkling, age spots, and changes in skin texture.

Most dangerous of all, indoor tanning is a recognized cause of skin cancer, including deadly melanoma. Skin cancer is the most common form of cancer in the United States. Approximately 3.5 million cases of non-melanoma skin cancers are treated each year, and more than 70,000 melanomas are diagnosed yearly. While many cancers have been on the decline in recent years, rates of melanoma, which causes the most skin cancer-related deaths, have been on the rise. Increased exposure to ultraviolet radiation (UV) through indoor tanning may be partially responsible for the continued increase in melanoma, especially among young women. Indoor tanning is particularly dangerous for younger and more frequent users.

Tanning myths


There are a lot of misconceptions about indoor tanning, so it's important to know the following:

  • Tanned skin is not healthy skin. That "healthy glow" from the tanning bed indicates damage to your skin. Whether tanning or burning, you are exposing yourself to harmful UV rays. In fact, every time you engage in indoor tanning, you increase your risk of melanoma. The truly healthy glow is your natural skin color. More...

A national effort to help end colon cancer

March 12, 2014

By Richard C. Wender, MD

About a year ago, U.S. Assistant Secretary for Health Howard Koh, MD, invited a small group of people to his office to discuss the opportunity for the nation to start a full court press to end colorectal (colon) cancer as a major public health problem in the United States. The meeting idea came from a conversation on his back porch with his college friend Ron Vender, MD, who had just been elected President of the American College of Gastroenterology (ACG). Howard asked Ron how he could most effectively work with the ACG and, together, they decided that it was the right time to tackle colon cancer in a big way.

Dr. Koh invited leaders of the organizations that were at the center of public health efforts to increase colon cancer screening rates to attend the meeting. Screening is looking for cancer in people who have no symptoms of the disease. In the case of colon cancer, screening can find the disease at an early, more treatable stage, and it can also prevent it altogether. This is because colon cancer screening tests often find polyps, which can then be removed before they have a chance to become cancerous.

Leaders from the American Cancer Society and Centers for Disease Control and Prevention (CDC) were joined by leaders of several other vital governmental agencies, gastroenterologist organizations, and the National Colorectal Cancer Roundtable (NCCRT). The NCCRT is an organization co-founded 17 years ago by the American Cancer Society and CDC. Today, the NCCRT brings together close to 80 organizations with a single common goal: to increase colon cancer screening rates, our most effective way to fight the disease. The key to the NCCRT's success has been its commitment to joining diverse organizations as equal stakeholders, to do the kind of work that no one organization can accomplish alone. It's a great example of public health in action. More...

The HPV vaccine could do even more

January 23, 2014

EDITOR'S NOTE: The President's Cancer Panel has released a report that says increasing HPV vaccination is one of the most important opportunities in cancer prevention. The report calls for re-energized efforts to promote vaccination and reach the HPV vaccines' potential to save lives by preventing avoidable cancers in men and women. It explores underuse of HPV vaccines, identifies key barriers to increasing vaccine uptake, and provides actionable recommendations for overcoming these obstacles. To coincide with the release, here is our recent blog on the subject.

 

By Debbie Saslow, PhD

The HPV vaccines (Gardasil and Cervarix) have been recommended for girls in the US for nearly 10 years. They protect against human papillomavirus (HPV), the virus that causes most cases of cervical cancer, and Gardasil also protects against nearly all cases of genital warts. Uptake of HPV vaccination has been slow in this country, though; less than 35% of girls have gotten all 3 recommended doses.

Despite low vaccination rates, we have already seen HPV infections (related to the types of HPV targeted by the vaccines) drop by 56% in the United States. In countries that have higher vaccine rates, there are even larger drops. Indeed, data published last year suggest that higher vaccination rates could reap great benefits.

The potential to eliminate genital warts

 

A study from Australia, where more than 70% of adolescent girls are vaccinated, suggests that in countries where vaccine coverage is high, genital warts may be eliminated in the coming decades.

The government-funded Australian HPV vaccine program has provided free vaccine in schools to 12- and 13-year-old girls since 2007. From 2007-2010, free vaccine was also offered to girls and women ages 14-26.

The number of cases of genital warts among young people has dropped dramatically since the program began. More...

Should women at high risk for breast cancer take drugs to prevent it?

October 14, 2013

By James C. Salwitz, MD


Breast cancer will kill more than 450,000 women worldwide this year, and in the United States alone, 232,000 will be newly diagnosed. Two important recent events shift the conversation from disease treatment to prevention. The most public was the stunning statement of actress Angelina Jolie that she had both her breasts removed because she carried a breast cancer gene (BRCA1). This announcement served to greatly increase awareness and discussion of choice in preventing the disease. 

Second, was the decision by the U.S. Preventative Services Task Force (USPSTF) to recommend the use of medications for prevention of breast cancer in women who are at increased risk.

Many factors influence breast cancer risk


In order to prevent breast cancer, we must first understand its causes. While we do not know all, we do understand that certain factors increase the chance of getting breast cancer. Some of these risk factors can be reduced through improved lifestyle, but not all.

Most breast cancer occurs not because of known genetic mutations, but because of a combination of risk factors. One important risk factor is increasing age, with most breast cancers occurring in women 55 years of age and older.

Some risk factors include an early age for a first period (start of menses), a late first pregnancy, and no pregnancy at all. Breast-feeding decreases cancer rates. Prescription estrogen replacement, especially after menopause, increases breast cancer risk. The more alcohol a woman drinks, starting even with small amounts, the higher her chance of getting the disease. Obesity and low amounts of exercise increase the chance of developing breast cancer, too.

If a woman has increased breast density on mammogram, this increases the chance of being diagnosed with breast cancer. If a woman has any breast biopsies, particularly if the biopsies showed benign growth of the lining of milk ducts ("proliferation"), this increases risk. Certain benign duct changes, such as hyperplasia or atypia, greatly increase risk. Also, ductal or lobular carcinoma-in-situ (DCIS and LCIS) greatly increase the chance of developing invasive breast cancer.

Finally, family history, even without a defined cancer gene like BRCA1 or BRCA2, increases the likelihood a woman will get breast cancer. Each first-degree relative (mother, sister, daughter) who has breast cancer increases further the chance of breast cancer. The younger the breast cancer occurred, the greater the risk to the patient. More...

New cancer genes: should I run to be tested?

August 07, 2013

By Mia M. Gaudet, PhD


Scientists have long cautioned that a family history of cancer increases your personal risk of cancer. Some genetic changes (mutations) that are found in only a few families but tremendously increase risk of cancer (e.g., BRCA1/2) have been known since the 1990s.  These mutations are already used by doctors to identify high risk men and women. However, there is still much of the genetic component of cancer that is unknown. Advances in genetics and technology now allow scientists to look at common changes in the genetic code to see if these changes are related to risk of cancer. 

Researchers are trying to answer these questions. Recently, an international group of cancer investigators linked 74 genetic regions to cancer. These newly identified genetic regions contain common changes in their code (called polymorphisms) that have only small effects on the risk of cancer. But when you combine many polymorphisms, that risk increases.

These new polymorphisms were found by studying the genetic make-up of more than 200,000 people. Women with and without breast cancer, women who had mutations in BRCA1 or BRCA2, women with and without ovarian cancer, and men with and without prostate cancer participated in the studies. More...

The obesity-cancer connection, and what we can do about it

February 28, 2013

By Lewis E. Foxhall, MD

It's almost impossible to get through the holiday season without gaining a few pounds, and for many of us that means we are even more likely to be over our ideal body weight.  Sure, we all want to look good in our clothes, but being obese is not just a condition that affects our appearance.  And in March, during National Nutrition Month, it's a good chance to talk about it.

Weight gain happens when we take in more calories from food (energy) than we use up through our basic biological requirements and exercise. After a while, enough fat stores up and makes us obese. Our bodies are very efficient at taking in energy and storing it for times when it is hard to find, but in our modern environment this is working against us and our health.  For most of us it is easy to get as much food as we want, and most of us do not need to exert ourselves much for work or daily living activities.


Link between obesity and cancer


The problem with being overweight or obese, as measured by weight and height, is that it raises our risk of chronic diseases like diabetes and heart disease.  But did you know that being obese can actually increase our risk of getting cancer and may even worsen our chances of surviving after a cancer diagnosis?  In fact, the American Cancer Society Cancer Prevention Study II showed significant increases in cancer occurrence in people who are the most overweight.  This link is stronger in some cancer types --including breast cancer after menopause, and cancers of the colon and rectum, pancreas, kidney, esophagus, and endometrium -- and can be associated with a major increase in risk. More...

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