On Nutrition

This week, I’m answering some reader questions. Enjoy!

Can you explain why exercise helps keep blood sugar levels lower? I never could get the connection.

Exercise lowers blood sugar (glucose) for a few different reasons. One is that it increases insulin sensitivity — during and after physical activity, your muscle cells are better able to use insulin to pull glucose out of your bloodstream and use it for energy. The second is that muscle contractions during activity allow your cells to take up glucose whether insulin is available or not.

The exact effect physical activity has on blood sugar depends on a number of factors, including how long you exercised. Physical activity can potentially lower your blood sugar up to 24 hours or more after your workout. Even better, when you are active on a regular basis, you might see a drop in your hemoglobin A1c, which reflects your average blood sugar levels over the past three months.

If you are at high risk of developing Type 2 diabetes, or already have prediabetes, the recommendations are that you get at least 150 minutes of physical activity per week, and don’t go more than two days in a row without exercising. Here are some more details of note:

  • Both aerobic and resistance exercise appear to be equally good at lowering A1c values in people with diabetes. Research on yoga and tai chi suggests that they might also have some benefits for blood sugar.
  • Research has found that interrupting periods of prolonged sitting with three to five minutes of standing, light walking or simple body weight resistance activities — such as squats or lunges — every 20 to 30 minutes improves blood sugar control.
  • In adults with Type 2 diabetes, going for a 15-minute walk after a meal helps improve blood sugar control.

Do I need supplements over age 50?

Probably. About one-third of adults age 50 and older no longer produce enough stomach acid to extract vitamin B12 from food, so the synthetic form found in supplements or fortified foods (many grain-based foods are fortified with B vitamins) offers insurance.

Because our skin’s ability to synthesize vitamin D declines with age, taking a vitamin D supplement is also good insurance, especially if you already spend a lot of time indoors, protect yourself from the sun or have dark skin. Vitamin D is important for many reasons, including bone health, which brings calcium to mind. Getting calcium from food is best, but if you know you don’t eat enough calcium-rich foods, bridging the gap with a calcium supplement may be a good idea.


If you have a longtime habit of taking a multivitamin/mineral, make sure it doesn’t contain iron (or doesn’t contain much), unless your doctor has indicated you specifically need iron. Males only need 8 milligrams per day through their entire adulthood — and generally meet this easily through diet alone — while female adults need 18 milligrams a day until age 50, when their needs also drop to 8 milligrams. This is why “senior” formulas generally contain less iron than “adult” or “adult women” formulas.

Do you have techniques for responding to family or friends who make comments about your body (e.g. weight changes) when you are trying to disengage from diet culture?

Once you see diet culture for what it is, you also see more clearly how harmful those body comments can be — even “positive” comments like, “You look great … have you lost weight?” How you respond largely depends on who’s making the comment (Parent? Close friend? Casual acquaintance?) and what the scenario is (one-on-one versus in a group setting).

One tactic is to simply fail to engage. If someone makes a comment that you appear to have lost (or gained) weight, you can simply shrug and say vaguely, “I honestly have no idea,” then change the subject. If the person presses the point, you could turn the questioning around on them, and ask, “Why are you so interested in my body?” Body comments are very personal and intrusive, so be as gentle or as forceful as you need to be.

When someone tries to engage in talk about their latest diet, or how “bad” they are because of something they ate, you could say, “Yeah, I’m not the right person for this conversation.” If you’re at lunch with friends, and the conversation turns to dieting, you could ignore it (at least you’re not “feeding” it), or say something like, “We’re all so amazing … why do we spend so much time talking about diets? Aren’t we more interesting than that?”

If someone in your life repeatedly comments on your body or weight, you may need to have a lengthier conversation with them in which you ask them to refrain from future comments. Once you’ve set that boundary, enforce it, and be clear about consequences. (“If you comment on my body again, I will leave, and if this pattern continues, I won’t be able to spend time with you … and I think that would be sad for us both.”)


Are there foods or ways to eat that can help lower blood pressure?

Absolutely! The best studied dietary pattern for helping to lower blood pressure is the Dietary Approaches to Stop Hypertension eating plan (nhlbi.nih.gov/education/dash-eating-plan). The DASH eating plan:

  • Emphasizes vegetables, fruits, and grains, especially whole grains.
  • Includes a few servings each of dairy products; fish, lean meat and poultry; beans, nuts and seeds; and vegetable oils.
  • Limits added sugar.
  • Limits sodium to 2,300 milligrams per day, or 1,500 milligrams per day for more significant blood pressure reduction.

The DASH eating plan is rich in potassium, calcium, magnesium and fiber, each of which is associated with lower blood pressure. Research has found that Mediterranean and vegetarian diets, which are similarly high in fruits, vegetables and whole grains, can also help lower blood pressure.