Why is Reducing Salt in Our Food Important?


Last week, the Institute of Medicine (IOM) called on the US Food and Drug Administration (FDA) to mandate a maximum level of sodium in food (IOM report). They did this because high sodium intake contributes to high blood pressure, which is a contributor to heart disease and stroke.

The average person in the US takes in more than double the recommended amount of sodium. And for most people, the salt shaker on the dinner table isn’t the main culprit. It’s processed foods, which are often very high in sodium, even for foods one wouldn’t expect to be “salty.” A graphic in last Sunday’s New York Times shows this nicely (Graphic: Funny, they don’t taste salty). Two Eggo brand waffles have over a quarter of the daily recommended sodium intake, as does a half cup of some brands of cottage cheese.

If sodium is such a problem and such a contributor to high blood pressure, shouldn’t we just identify the folks with high blood pressure and have them lower their sodium intake? This is in fact, the approach our health system has used for the past decade or so, and without much success. Rates of high blood pressure in the US have remained largely steady since the late 1990s (Ostchega, et al. 2008). Taking a broader approach to the issue, by lowering sodium intake across the population can have a larger and more sustained impact.

Why? The answer can be a bit detailed and has to do with the science of prevention. But it’s well-established that making small, healthy changes across an entire population can have a much bigger impact on health than trying to greatly lower the risk in a small percentage of “high-risk” people who already have a condition. This “population-approach” runs counter to the way much of the US health care system works, which focuses so much on one-on-one care for people who already have a disease or a condition, like high blood pressure. Yet, while it’s important to continue to treat people who get sick, establishing small population-wide changes can greatly reduce or delay the number of people who actually do go on to get sick.

The biggest obstacle with the population approach, though, is figuring out how to affect such small changes across an entire population. Though people often know a lot of the steps they should take to improve their health – say, be more active, eat more fruits and vegetables, or lower their salt intake – enticing most people into doing these things can be difficult.

The sodium recommendation from the IOM is one effective way. Processed foods make up about 70 percent of the American diet, and so changing their composition would impact the health of most Americans, and in such a way that they don’t even have to think about it.

In an analysis by colleagues (Cook, Cohan et al. 1995) at Harvard Medical School, researchers compared whether they could more effectively lower rates of heart disease and stroke by taking a healthy lifestyle population approach or by offering medical treatment to all individuals whose diastolic blood pressure exceeded 95 mm Hg. What they found was that the population-based approach resulted in fewer cases of heart disease and stroke than the high-risk treatment approach.

The Harvard study found that even better than either approach alone was the combination of the two approaches, where the entire population was ‘treated’ through the food supply, and high-risk individuals received medical attention. This is what would happen if the FDA took up the IOM recommendation. The government would be facilitating a population shift in sodium intake and physicians would continue treating those with high blood pressure. Similar results have been reviewed by UK based researchers (Frost, Law et al. 1991).

Australian researchers have applied a similar model to shifting BMI and such an approach could be applied to numerous other risk factors for cancer and other chronic diseases. In the Australian study, Wendy Brown and colleagues reported that a middle of the road approach may be best. If a high-risk approach is taken where individuals in the top 20 percent are targeted for a large intervention to reduce their BMI by three units (about a 20 pound loss for someone 5’10”), diabetes is reduced by 17 percent and high blood pressure by seven percent. By shifting the whole population’s BMI by one unit (a typical prevention approach and the equivalent of altering the population’s sodium intake without also treating those with high blood pressure), they estimated diabetes would be reduced by 13 percent and high blood pressure by 10 percent. But, if a middle of the road approach is used, where those in the top 50 percent of BMI are shifted two units, diabetes decreases by 23 percent and hypertension by 12 percent -- the best scenario for both outcomes (Brown, et al. 2007).

What becomes clear from all these studies and all these data is that a population-based approach when used alongside the usual high-risk approach can have a huge affect on the health of a nation. When it comes to high blood pressure, and the burden of diseases it's associated with, it’s time to look beyond the usual and try something new. Reducing sodium in processed foods may just be the missing ingredient we need.

Related web resources:
Strategies to Reduce Sodium Intake in the United States - APHA webinar, May 4, 2010

Childhood and Adolescent Exposures Set Cancer Risk

At the annual meeting of the American Association for Cancer Research (AACR), I presented a review of evidence relating childhood and adolescent exposures to lifetime cancer risk (see slides from presentation here http://bit.ly/d2SY2s). One of many “meet the expert” sessions, this offered an opportunity for those in the audience to hear a synthesis of evidence on the importance of this time period and the value of considering where in the life course exposures may be most important for determining cancer risk.

The most compelling evidence that early exposure drives risk of cancer throughout life comes from the follow-up of the atomic bomb survivors in Japan (Land et al., 2003). For some 70,000 survivors, researchers calculated their exposure to radiation based on where they were located at the time of bomb explosion. During 40 years of follow-up cases of breast cancer were identified. Women exposed before age 20 had substantially higher risk for breast cancer through their adult life than those who were older when exposed. Another established example is the development of moles in response to sun exposure, as well as sun burns during adolescence, driving lifetime risk of melanoma. I next turned to smoking and lung cancer as another common piece of evidence in the puzzle of cancer risk accumulation. Importantly, with Stacey Kenfield and colleagues we had assessed age at starting to smoke and  the risk of lung cancer (Kenfield et al., Tobacco Control 2008). We showed that for each year earlier that an adolescent starts to smoke the risk of lung cancer increases by 5 percent. Given that the majority of smokers have become regular smokers by age 18 this shows the importance of late childhood and adolescence for susceptibility to the effects of carcinogens in tobacco smoke.

The strong and consistent relation between adult height and cancer risk points directly to the exposures during growth and development that account for increasing height in populations as children grow up in industrialized settings. A study of over 400,000 men and 300,000 women in Korea who were measured for height and weight in the mid 1990s and followed for 10 years showed that total cancer incidence rose steadily with height (Sung et al., Am J Epidemiol 2009). For each 5 cm (approximately 2 inches) increase in height, the risk of cancer rose by 5 percent in men and women. Over 300 studies have assessed this general relation and consistently show that height is related to cancers of the breast, prostate, colon, and endometrium, as well as to hematologic malignancies.

Height reflects the end result of growth through childhood. Increasing height over decades or generations reflects improved diet and access to abundant sources of energy intake, reduction in childhood infections and changes in the environment that impact physical activity and energy expenditure. The growth spurt of early adolescence also has an impact on risk. The more a young adolescent woman grows in a year the higher her lifetime risk of breast cancer (Berkey et al, Cancer 1999). No doubt, as the speed of growth increases the stress on cell mechanisms to repair errors in cell division is increased. 

I next reviewed other factors that may influence height including diet. Drawing on the data from the Growing Up Today Study, which I initiated back in 1996, I showed data relating milk intake to height in girls (Berkey et al., Cancer Epidemiology Biomarkers and Prevention 2009). Those who consumed more than 3 glasses of milk per day grew taller in the next year than those consuming less than a glass per day. One likely explanation for this added growth is hormonal exposures. A feeding trial shows that after consuming milk regularly for a month, insulin-like growth hormone levels are higher (Rich Edwards et al., 2007).

Drawing on data for breast cancer, I showed that age at menarche, the onset of menstrual periods in a young woman, has been younger since the industrial revolution. In the 1850 and 60s the average age for menarche was about 17. In Korea at the time of the second war this was still the average age at menarche. In Europe over 100 years the average age for menarche has dropped to about 13, but in Korea this drop happened in just 20 years after World War II (see figures in slides). For generations of women born after WWII in Korea the incidence of breast cancer breast cancer at age 45 to 49 has doubled in just 10 years and is expected to continue increasing. A drop in the number of children each women is having from an average of 6 to only about 1 child per women has added to this increase in risk within the population.

Adolescent diet and risk.
Given the importance of growth on age at menarche and height, we have explored the possibility that diet during adolescence may modify the subsequent risk for beast cancer. We had participants in the Nurses Health Study II recall their diet in high school. We then followed them over time and identified women who went on to develop benign breast disease and those who remained free from disease. Benign breast disease is a well established marker of subsequent risk of breast cancer. Changes in benign lesions follow a pattern of increasing lack of order until the lesions progress to invasive breast cancer over many decades. We showed that higher intake of fiber in adolescence significantly reduced the risk of benign breast disease (see related post http://bit.ly/9LR5ph). In another study we showed that alcohol intake during late teen years and the early 20s more than doubled a young women’s risk of benign breast disease (http://bit.ly/aXrwI3). In a study of women in Hawaii, Anna Wu and colleagues showed that intake of soy during childhood was most protective against breast cancer risk.

Turning to exercise, several studies now show that sustained activity from menarche through adult years brings the greatest reduction in breast cancer risk (see Maruti et al JNCI 2008). Higher activity can cut breast cancer risk by anywhere from a quarter to a half. Thus growing evidence points to childhood and adolescence as a key period in life when the trajectory for cancer risk is determined in part by diet and exercise patterns.

Related web resources: 

A Quick Guide to Soybeans (Edamame)

It seems like everywhere you turn these days products are touting how much soy protein they have. In some ways this is understandable as more and more evidence shows that soy can have important health benefits, like lowering the risk of breast cancer, prostate cancer, and heart disease as well alleviating symptoms of menopause.

Unfortunately, such labeling can also be misleading because the soy sources linked to these benefits are not those in highly processed food products, rather they are in less processed sources like tofu, tempeh (a sort of soy bean patty) and plain soybeans themselves.

On their own, soybeans make a great snack and are easy to prepare and mix in other dishes (like salads and pasta).

Never had them? Don’t know where to find them? Here’s a quick guide.

Cooking up soybeans is one of the easiest snacks or side dishes around. In most grocery stores you find them in the freezer section, where they are labeled as “edamame” – the Japanese word for baby soybeans. I found this bag at my big box shopping store in their small grocery section freezer.


They are soybeans still in the pod.


You can also find them frozen and shelled, which may be easier if you intend to just toss them into a salad or pasta dish. The process of cooking them is really simple (think boiled peanuts if you’re in the south!)

Get a pot and boil some water. You don’t need as much as if you are making pasta. When the water is boiling, add a bit of salt (this part is optional, I omitted it when my kiddo was small).


Now toss in your edamame/soybeans.


When the water returns to a boil, let those cook for about 5 more minutes and then drain.


They are HOT. Be careful. At this point, if you want them to taste like they do at a Japanese or sushi restaurant, toss with more salt. I’ve never found this necessary and would rather not have such a high salt intake, so I skip it.

Pour into a bowl, and when they are cool enough to touch, just pop the pod open and eat the beans inside.



*note for parents – my toddler loved these – pureed when she was very little, and then as an early finger food. Now she shells them herself.