Why a high fiber diet is key to heart health

Fiber seriously feels like it has become the new buzzword. From the F factor diet to the microbiome to IBS, everyone seems to be talking about a high fiber diet (good or bad!). But what is fiber anyway? Did you know there are two different types? Read on for everything you ever wanted to know about fiber, including how much you should be getting and my favorite tips and tricks for making it happen.

What is fiber?

Fiber is a type of carbohydrate that our bodies cannot digest or break down. And guess what? It’s only found in plant foods such as fruits, veggies, and grains! Importantly, there are two kinds of fiber - soluble and insoluble. Most plant foods have a combination of both soluble and insoluble fiber, although with varying proportions. They’re both good for us, but in somewhat different ways

• Soluble fiber - think of this as the heart healthy kind. It dissolves in water to form a gel. It slows down food transit time from the stomach to the intestine. Foods particularly high in soluble fiber include oranges, pears, beans, barley, and eggplant.

• Insoluble fiber - think of this as the kind that helps you poop. It’s often referred to as "roughage" because it does not dissolve in water. It does however, attract water to the gut, which helps prevent constipation. Foods particularly high in insoluble fiber include whole grains, nuts, root veggies like carrots, and cauliflower.

Why is fiber good for my heart and overall health?

Fiber has been shown repeatedly in several studies to be super important for heart health as well as overall health.

With regard to risk factor reduction, it

• Lowers cholesterol - Soluble fiber has been shown to lower cholesterol powerfully. It increases bile acid excretion by binding to them - since bile acids are composed of cholesterol that our body tries to recycle, this forces your body to use more cholesterol to make up for the lost bile acids, thus removing it from your bloodstream. Pretty cool huh? Studies have shown that an increased intake of soluble fiber (20 grams a day) can lower LDL-c by 5-10%, and together with other cholesterol lowering foods - known as the Portfolio diet - can lower LDL-c by as much as 29% (equivalent to a low dose statin and low saturated fat diet). Read more about the Portfolio diet here.

• Regulates blood sugar levels - Diets high in fiber are associated with a decreased risk of diabetes and reduce post-prandial blood sugar spikes. One large meta-analysis found that for every additional 10 g of fiber eaten per day, the risk of diabetes was reduced by 25%. This is likely due to several mechanisms, but it is thought that because a high fiber meal slows down the digestion of food in the intestines, this helps prevent a rapid rise in blood sugar levels. Fiber (aka prebiotics) also contributes significantly to the composition of our gut microbiome, favoring organisms associated with improved cardiometabolic health. Gut organisms may also break down soluble fiber into a metabolite called short chain fatty acids, which are also associated with improved insulin sensitivity and less weight gain.

• Helps with weight control - A diet high in fiber has also been linked to lower risk of weight gain and abdominal fat. Several studies have shown that those who eat more soluble fiber have less abdominal fat and improved weight loss. Several reasons are likely at play, but one is that fiber can help keep you fuller longer, which prevents overeating and hunger between meals. As mentioned above, fiber is also associated with a metabolically healthy gut microbiome. Soluble fiber also appears to help regulate the hunger hormones like gherlin.

In addition to controlling risk factors, increased fiber intake is associated with a decreased risk of hard endpoints like

• heart disease

• death due to heart disease

• stroke

• colorectal cancer

• death from any cause

In one meta-analysis of 7 prospective cohort studies, those with the highest dietary fiber intake (~ 27 g/day) versus the lowest (~ 15.0 g/day), had a 23% lower risk of total mortality. They also found a dose-response relationship, such each additional 10 g of fiber intake daily was associated with 11% lower total mortality risk.

How much fiber should I eat?

Current guidance from The Academy of Nutrition and Dietetics recommend consuming about 25-35 grams of total fiber per day (minimum of 14 g of fiber per 1000 calories).

However several studies demonstrate that closer to 40-50 grams per day might be optimal. In the above mentioned Portfolio diet, the target was about 20 grams of soluble fiber (which is about 40 g total fiber). A  few studies have shown modest HgbA1c improvement with dietary fiber intake over 50 grams daily. The American Diabetes Association recommends that people with prediabetes or diabetes eat at least the amount of dietary fiber recommended for the general population, noting that increasing fiber intake beyond that may help in modestly lowering HgbA1c.

With the average American consuming around 14 grams of fiber, the vast majority of us have significant room for improvement in order to achieve the bare minimum.

Tips to increase fiber in your diet

First and foremost, start low and go slow. Going too fast can cause GI discomfort. If you aren’t eating much fiber at the moment, slowly start to introduce these tips and aim to get to your target fiber amount over the course of several weeks. It’s also important to increase hydration as you do so. Be sure to drink at least 7-8 cups a day of water to prevent constipation. Beyond this, try to:

• Include at least one veggie per meal. Even breakfast!

• Switch to whole grain pasta or bean pasta instead of white pasta. Start at first with a 50/50 ratio if you aren’t a fan right away

• Add beans or lentils to your salads, soups, and pastas

• Amp up your fiber intake with seeds! Chia and ground flax seeds are great fiber boosters. Add them to smoothies, oatmeal, salad dressings and more

• Don’t peel your fruits and veggies. Just scrub them with a veggie brush!

• Even snack time is a great place to introduce fiber! Reach for nuts, an apple with nut butter, chia seed pudding, or veggies dipped in hummus

• If you buy packaged food, look for a “high fiber” label, which means it must contain 5 grams or more of dietary fiber per serving. Note, the first ingredient listed should be a whole grain, not enriched flour. For example, “whole wheat flour” is a whole grain, but “wheat flour” is not

Interested in working with Dr Harkin to improve your heart health?