Soduim Content in Foods is Almost Constant!

No doubt that sodium is an important risk factor for hypertension. The American Heart Association estimates that there are 78 million adults in the US (1 in 3) have high blood pressure. In a workshop organized by the National Heart, Lung, and Blood Institute (NHLBI) on sodium and blood pressure, the report stated

“There is an abundance of scientific evidence demonstrating a direct relationship with sodium intake and blood pressure”.

I came across an interesting article published in JAMA Internal Medicine this week titled “Changes in Sodium Levels in Processed and Restaurant Foods, 2005 to 2011”. Dr. Stephen Havas from Northwestern University Feinberg School of Medicine, and his colleagues collected the sodium content data in processed food from the nutrition facts label in 2005, and recollected the same data for the same food products in 2011.

The main finding with their analysis is that the sodium content in the 402 processed food products declined by only 3.5% over 6 years. On the other hand, the sodium content in 78 fast-food restaurants’ products increased by 2.6%. Table 1 in their paper shows that Caesar salad dressing and Turkey breasts are the top 2 food categories, with highest sodium content in 2005 to 2011. Canned tuna fish, canned tomato, sliced turkey breast, and vegetable soup had the highest decline of the sodium content by about 22%, from 2005 to 2011. For the rest of the processed foods, the sodium content either remained constant or changed by ±2%.

Among the restaurant foods, the sodium content in the French fries increased by 27% from 2005 to 2011. Cheese pizza’s sodium content increased by about 12% in the same period.

The authors outlined in Table 3 the names of some companies that committed to reduce sodium levels in their products. For example, the Domino’s Pizza committed to decrease the sodium content in the smart pizza slice for schools by a third. Wal-Mart committed to reduce sodium by 70% in fresh steaks and roasts.

The authors concluded that 

“It is clear from this analysis that reductions in sodium content in both processed and restaurant foods are both inconsistent and slow”

I think it is a time for the local, state and federal government to look into new ways to enforce sodium content reduction in processed and restaurant foods to alleviate the burden of preventable diseases (like hypertension). This could be similar to what Mayor Michael Bloomberg did by prohibiting the sale of soda cans more than 16 ounces. Although there has been a resistance against the implementation of this bill, public health advocates has long way to go. 

Eating Fish is Associated with Decreased All-Cause Mortality in Older Adults

Mozaffarian and his colleagues published a paper recently in the Annals of Internal Medicine analyzed data from 2692 U.S. adults aged 74 years (±5 years) without prevalent cardiovascular diseases at baseline, who participated in the National Heart, Lung, and Blood Institute (NHLBI)-funded cohort, The Cardiovascular Health Study (CHS). The investigators measured the blood circulating levels of 3 types of long-chain omega-3 polyunsaturated fatty acids (omega-3 PUFAs); eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). These were measured from the blood that was collected from the participants in 1992. They then followed them longitudinally for 16 years (1992 through 2008) to evaluate the relationship with total and cause-specific mortality and incident fatal or nonfatal CHD and stroke.

The authors found that the individual levels of EPA, DPA, and DHA, and their total levels (omega-3 PUFA) were associated with lower total mortality across three robust models of adjusted Cox proportional hazards models (age, gender, various demographic and co-morbid conditions, and dietary factors):

       The participants in the higher quintile of the total omega-3 PUFAs had 27% lower risk 

       The participants in the higher quintile of EPA had 17% lower risk 

       The participants in the higher quintile of DPA had 23% lower risk

       The participants in the higher quintile of DHA had 20% lower risk

All results were statistically significant with narrow 95% confidence internals.

For cause-specific mortality, and using the same adjustment models of the total mortality risk data, total omega-3 PUFAs, and most of the individual levels of the three subtypes, were associated with cause-specific mortality. Total omega-3 PUFAs was associated with: 

       35% lower risk from cardiovascular mortality

       40% lower risk from coronary heart disease mortality

       45% lower risk from arrhythmic coronary heart disease (CHD) mortality

       28% lower risk from non-arrhythmic CHD mortality

       40% lower risk from stroke mortality

       28% lower risk from total fatal and nonfatal CHD mortality

       17% lower risk from nonfatal myocardial infarction mortality

       25% lower risk from total fatal and nonfatal stroke mortality

       37% lower risk from Ischemic stroke mortality

This data strongly suggests that fish consumption or fish oil supplementation would reduce both total mortality and cause-specific mortality in older adults. The steepest dose-response relationship between the circulating blood levels of omega-3 PUFAs and the decreased risk came from as low as 400 mg per day dietary intake, or two servings of fatty fish per week. This will lead to an average increase of about 2 more years of life in those with higher levels compared to those with lower levels.

My opinion:

This conclusion is supported by the robust statistical analyses with adjustment to many confounders, as well as a quantification of the omega-3 PUFAs rather than the amount of fish intake from Food Frequency Questionnaires (FFQ) or similar tool. Despite some limitations in this paper, it is a landmark paper in supporting increased fish intake to decrease the risk of mortality in older adults.