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Is a Low-Carb, High-Fat Diet a Heart-Healthy One?

8/7/2011

10 Comments

 
One of the questions that comes up repeatedly for me -- from  colleagues as well as friends -- is whether following a low-carbohydrate, high-fat diet could be detrimental to heart health.   A chief concern is  that eating foods high in fat, particularly saturated fat, will raise cholesterol levels, thereby increasing the risk of atherosclerotic heart disease.  It doesn't really surprise me; after all, for more than 30 year  fats  have been considered  the primary food we should all be cutting back on if we want to avoid coronary artery disease.  The USDA's  Dietary Guidelines for Americans and  My Plate promote whole grains, nonfat milk, fruits, and other foods that are high in carbohydrates and low in fat as a way of decreasing cardiac risk.   On the other hand, there is a large body of research showing that lowering carb intake and  increasing consumption of fat (both saturated and unsaturated) can result in favorable changes in serum lipids.  

Below are a some of the cardioprotective benefits of low-carbohydrate, moderate-protein, high-fat diets:

1. Significant decrease in serum triglycerides.  Carbohydrates are a potent stimulator of  hepatic triglyceride synthesis and  plasma concentration, particularly in the presence of insulin resistance.  Lowering carbohydrate intake can reduce triglyceride levels, resulting in lower cardiac risk.
2. Increase in HDL cholesterol.  Higher fat intake is positively correlated with improvements in HDL levels, and  high HDL cholesterol is considered cardioprotective.
3. Improvement in LDL particle size, glycation, and oxidation.  While triglycerides levels almost invariably decline with carbohydrate restriction,  LDL cholesterol response appears to be more individualized.  LDL has been classified as the "bad"  cholesterol for years, and elevated levels are often  seen as  increasing one's  risk of arterial plaque formation and heart disease. However, simply looking at the amount of serum LDL itself gives us very little information about cardiac risk.  It is primarily when LDL is oxidized and its particle size  small that this lipoprotein becomes most problematic.  Restricting carbohydrate intake has been shown to reduce glycation and  subsequent oxidation of LDL.  A lower-carb, higher-fat diet tends to produce an increase in LDL particle size (known as Pattern A), whereas an abundance of  dietary carbohydrate typically results in smaller, denser particles (Pattern B) that increase the likelihood of atherosclerosis. 

I also often hear, "If  people don't eat whole grains and legumes, how can they consume adequate fiber?"  Fiber, particularly the soluble type, has many health benefits.  A  low-carb diet can easily supply sufficient fiber if it contains plenty of nonstarchy  vegetables, nuts and nut butters, seeds, berries, and avocados.  Technically a fruit, an average avocado contains about 12 grams of fiber, as well as 16 grams of monounsaturated fat. 

As a registered dietitian, I can't endorse a low-carbohydrate diet consisting of 6 eggs fried in butter with 4 slices of bacon for breakfast, 3 hamburger patties for lunch, and a 20-oz steak with a tiny green salad for dinner.  While certainly nearly carb-free, it's missing a lot of beneficial phytochemicals found only in plant foods and contains only a couple of grams of fiber.  But I firmly believe that a carbohydrate-restricted plan that includes the high-fiber plant foods listed above can be a very heart-healthy way to go.  

Resources
1.   Tay, J., et al.  Metabolic effects of weight loss on a very-low-carbohydrate diet compared with an isocaloric high-carbohydrate diet in abdominally obese subjects.  J Am Coll Cardiol,  2008. 51:59-6
2. Volek, J.S., et al. Dietary carbohydrate restriction induces a unique metabolic state positively affecting atherogenic dyslipidemia, fatty acid partitioning, and metabolic syndrome. Prog Lipid Res, 2008, doi: 10.1016/j.plipres.2008.02.0033. 
3.  Hayek, T, et al.
 Dietary fat increases high density lipoprotein (HDL) levels both by increasing the transport rates and decreasing the fractional catabolic rates of HDL cholesterol ester and apolipoprotein (Apo) A-I. J Clin Invest, 1993; 91(4);1665-16714. 
4.  Siri-Tarino, P.W., et al. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr doi: 10.3945/ajcn.2009.27725
10 Comments
Peetie link
8/8/2011 06:31:32 am

This is great! Please keep it going!
Thanks,
Joanne

Reply
Todd
8/11/2011 08:57:35 am

I discovered a low-carb diet last year, five years after my type 2 dx. I modified Dr. Bernstein's methods by adding fruits and vegetables, eating the ones with higher fiber. I easily lost 25 lbs and became more active. I am encouraged from your validation and will continue my diet. I will also monitor your blog. Thanks.

Reply
Franziska
8/11/2011 10:59:31 am

Thanks, Todd. Congratulations on the 25-lb loss!

Reply
Natalie
8/15/2011 03:04:22 pm

I'm not doing strict Bernsteinian low-carb -- as a picky eater, I only like a few vegetables, so I will eat any vegetable I like, regardless of carb content. I'm also drinking some milk (in half-and-half) every day for the calcium, and because milk has good nutrients in it, too. What I'm NOT doing is eating grains, whole or not, and starches, because they invariably spike my BG, and also avoiding fruits, on the theory that anything you can find in fruits, you can also find in vegetables. (right?)
So far, it's working for me -- 30 lb. weight loss (gained back 5 lb. but I think I can get them off again), best lipid panel ever, and reduced insulin dosage. And I think I'm getting my nutritional needs met. Picky eating plus diabetes is a tough one!

Reply
Franziska link
8/16/2011 12:39:33 am

Thanks for sharing your experiences, Natalie! Congratulations on the weight loss, improvements in your lipid profile, and decreased insulin requirement. Yes, the micronutrients and phytochemicals found in fruits are also found in vegetables. Glad there are a few you like :)

Reply
BadMoonT2
8/22/2011 09:37:18 am

Thanks for the list of studies that support the idea that a low carb high fat is actually a healthy one. This is something that needs more publicity.

As a T2 diabetic adopting a carb restricted diet had an immediate positive effect on my blood glucose.

Reply
Franziska
8/22/2011 10:31:27 am

Thanks so much, BadMoonT2. I'm hopeful that in the near future most health professionals will regard the phrase "high-fat, low-carb" in a positive rather than negative light.

Reply
Paul
9/18/2011 07:59:09 am

I'm coming a little late to the party here, but I just discovered your site. Great job!

I am a T2 diabetic and followed my nutritionists's advice to to try to consume ~225 gm of carbs a day. I failed to make any improvements for years.

I finally made the change to a low carb diet after reading Dr. Bernstein's Diabetes Solution & Caubes Good Calories Bad Calories. Since making this change in June, my A1C dropped from 7.4 to 6.5 and my weight is down from 265 to 234.

I am glad to see dietitians starting to accept that T2 diabetes is a disease of carbohydrate intolerance and it can't be treated properly by lowering fat and pushing carbo.

Reply
Franziska
9/18/2011 10:28:36 am

Thanks so much for your comments, Paul. Yes, standard recommendations are 200+ grams of carbs per day -- far too much for anyone with endocrine dysfunction. So glad you found Dr. B and had such great improvement in glycemic control and weight. There are other dietitians out there who are like-minded, but unfortunately not too many yet. Hopefully that will change soon.

Reply
Weight loss tea link
5/5/2013 10:37:48 pm

Thank you for all your efforts that you have put in this. Very interesting information I like this site very much so much superb information.

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