Hi Pro Pam,
I’m a middle-aged guy who needs to start eating a heart healthier diet to lower my cholesterol and reduce my salt intake to combat prehypertension. However, I’m also a cyclist who races and trains 10–12 hours a week. So how do I replenish the salt I’m losing through perspiration safely so as not to worsen my hypertension? And how do I make sure I’m ingesting enough fat in my diet that I won’t bonk, without worsening my cholesterol? Thank you!
Elevated blood pressure (BP) and cholesterol are very common in the U.S. adult population. Both high blood pressure and elevated cholesterol are important risk factors for cardiovascular diseases, including stroke, coronary heart disease, and heart failure. Nearly one-third of adult Americans have hypertension (systolic BP ≥140 mm Hg, diastolic BP ≥90 mm Hg), and another 31% have prehypertension (systolic BP of 120 to 139 mm Hg or diastolic BP of 80 to 89 mm Hg). Likewise, elevated LDL (“bad”) cholesterol is also prevalent among Americans, affecting 35% of U.S. adults.
Athletes and physically active individuals, especially those who regularly participate in endurance exercise, have significantly lower risk of cardiovascular disease. Although the prevalence of cardiovascular disease and high blood pressure are about 50% lower in athletes compared with sedentary individuals, these conditions affect fit, apparently healthy people. So, while cycling is beneficial, it cannot overcome a genetic predisposition to elevated risk factors for cardiovascular disease.
Both high blood pressure and elevated cholesterol result from genetics and environmental factors. Environmental factors that increase blood pressure include psychosocial stress, caffeine, alcohol, tobacco, non-steroidal anti-inflammatory drugs (NSAIDs), and decongestants. In addition, “energy” drinks and other dietary supplements that claim to increase energy levels often contain stimulants (e.g., guanara, ma huang, ephedra) that increase blood pressure. Cholesterol is increased by some medications (e.g., steroid hormones). Of course, diet is another factor that can affect both blood pressure and cholesterol, which brings us to your questions.
Let’s look at the effects of diet on blood pressure first. On average, as dietary salt (sodium chloride) intake rises, so does blood pressure. Therefore, a logical strategy to lower blood pressure is to reduce sodium intake. The recommended upper intake is 2.3 grams of sodium per day. However, not everyone has the same reduction in blood pressure with lowered sodium intake. Some individuals who limit their sodium intake exhibit significant reductions in blood pressure; these people are termed “salt sensitive.” However, other people exhibit smaller or even negligible decreases in blood pressure. To reduce sodium intake, people should limit added salt and avoid processed foods (e.g., lunch meat, fast food), which are the source of greater than 75% of dietary sodium.
As you note, however, reducing sodium intake for an endurance athlete who regularly loses significant amounts of sodium in sweat is somewhat tricky. I suggest you follow the above recommendations to avoid processed and fast food, along with added salt, except while riding. To help replenish the sodium lost in sweat, consume 0.5–0.7 g sodium per liter (32 ounces) of fluid per hour.
Another effective dietary strategy to lower blood pressure is to increase potassium intake. More than 90% of Americans do not consume the recommended intake of 4.7 g of potassium per day, which is not surprising when you consider potassium is found in fresh fruits and vegetables and in unprocessed meat and dairy products. Because a high potassium intake can be achieved through diet rather than pills and because potassium derived from foods is also accompanied by a variety of other nutrients, the preferred strategy to increase potassium intake is to consume foods such as fruits and vegetables that are rich in potassium, rather than supplements. The blood-pressure-lowering effects of potassium are greater in individuals with higher sodium intakes, which makes this strategy especially appealing to endurance athletes whose sodium needs exceed the recommended intake (2.3 grams).
In addition to reducing sodium and increasing potassium, alcohol intake should be limited to no more than two drinks per day for men and one drink per day for women. These dietary modifications can be as effective as treatment with medication without the negative side effects. Adopting a low-sodium, high-potassium diet may reduce systolic blood pressure by more than 10 mm Hg.
Dietary changes can also lower total and LDL cholesterol levels. The National Cholesterol Education Program recommends limiting total fat intake to 25–35% of total energy (e.g., at 9 calories per gram of fat, this would be 83–116 grams for a 3,000 calorie diet), saturated fat to less than 7% of total energy, and cholesterol to less than 200 mg per day. This restriction on fat intake will not increase your likelihood of bonking, which is dependent exclusively on carbohydrate intake. Bonking occurs when you run out of glucose (i.e., glycogen stored in skeletal muscle and liver). Because fat cannot be converted to carbohydrate, fat intake has no impact on glycogen stores and your chances of bonking.
While limiting your intake of fat, saturated fat, and cholesterol is beneficial, increasing consumption of other dietary components may also lower cholesterol and/or reduce risk of cardiovascular disease. Omega-3 fatty acids (especially those in fish oil), soluble fiber (e.g., oat bran), and soy protein all favorably affect blood lipids.
In addition, the combination of exercise and these dietary modifications is especially effective at reducing risk of cardiovascular disease because dietary strategies tend to lower “bad” cholesterol while exercise raises “good” (HDL) cholesterol. The combination treatment has been shown to reduce LDL up to 40% and increase HDL by nearly 10%.
In summary, exercise is medicine—cycling is one of the best things you can do for your health. And, with a few dietary changes, you should be able to continue your current training program while lowering your blood pressure and cholesterol.
Dr. Pam Hinton is an associate professor of Nutrition and Exercise Physiology at the University of Missouri–Columbia where she teaches Sports Nutrition and studies the effects of energy balance on bone health. Check out her full bio for more information. If you have a nutrition-related question, send it to Pro Pam.