Tag Archives: high-protein

January 14, 2013 · 5:48 AM

Is Low-Carb Killing Swedish Women?

MPj04384870000[1]A recent Swedish study suggests that low-carbohydrate/high protein diets increase the risk of cardiovascular disease in women.  I’m not convinced, but will keep an eye on future developments.  This is a critical issue since many women eat low-carb/high protein for weight loss and management.

Researchers followed 43,000 women, 30-49 years of age at enrollment, over the course of 16 years.  In that span, they had 1270 cardiovascular events: ischemic heart disease (heart attacks and blocked heart arteries), strokes, subarachnoid hemorrhages,  and peripheral arterial disease.  Food consumption was estimated from a questionnaire filled out by study participants at the time of enrollment (and never repeated).

In practical terms, … a 20 gram decrease in daily carbohydrate intake and a 5 gram increase in daily protein intake would correspond to a 5% increase in the overall risk of cardiovascular disease.

So What?

To their credit, the researchers note that a similar analysis of the Women’s Health Study in the U.S. found no such linkage between cardiovascular disease and low-carb/high protein eating.

The results are questionably reliable since diet was only assessed once during the entire 16-year span.

I’m certain the investigators had access to overall death rates.  Why didn’t they bother to report those?  Your guess is as good as mine.  Even if low-carb/high protein eating increases the rate of cardiovascular events, it’s entirely possible that overall deaths could be lower, the same, or higher than average.  That’s important information.

I don’t want to get too far into the weeds here, but must point out that the type of carbohydrate consumed is probably important.  For instance, easily digested carbs that raise blood sugar higher than other carbs are associated with increased heart disease in women.  “Bad carbs” in this respect would be simple sugars and refined grains.

In a 2004 study, higher carbohydrate consumption was linked to progression of blocked heart arteries in postmenopausal women.

It’s complicated.

Steve Parker, M.D.

PS: I figure Swedish diet doctor Andreas Eenfeldt would have some great comments on this study, but can’t find them at his blog.

Reference: Lagiou, Pagona, et al.  Low carbohydrate-high protein diet and incidence of cardiovascular diseases in Swedish women: prospective cohort study.  British Medical Journal, June 26, 2012.  doi: 10.1136/bmj.e4026

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August 28, 2010 · 7:09 AM

High-Protein Diets Harmful to Bones? Nah!

Contrary to accepted wisdom, high  protein intake does not seem to be harmful to mineralization of bone, according to Seattle-based researchers reporting in the American Journal of Clinical Nutriton.  Mineralization of bone is important because higher bone mineral content generally translates to lower risk of fractures.

A consistent criticism of low-carbohydrate diets in the past is that they are detrimental to bone health.  How so?  If you reduce carb consumption, you have to replace at least some of the calories with either fat or protein.  Some low-carb diets lean towards higher protein content, others towards higher fat, still others increase both fat and protein.  The building blocks of proteins are amino acids, and some amino acids are acidic.  Acid-rich biochemical states may promote removal of calcium from bone and, ultimately, loss of that calcium in urine.  The calcium-poor bones are more prone to fracture.

If that theory is correct, women eating greater amounts of protein should demonstrate lower bone mineralization.  [The primary bone minerals are calcium and phosphorus.] 

ResearchBlogging.orgInvestigators tested the theory in 560 women aged 14 to 40 by measuring bone mineral density (via DEXA scans) over two or three years and monitoring food consumption via yearly questionnaires.  This was an observational study, not interventional.

They found that bone mineral density had nothing to do with protein consumption.  Higher protein intake was not associated with lower bone density.

Women in the low-protein group ate 52 g of protein daily, compared to 63 g in the medium group and 77 g in the high-protein tertile.  As best I can tell, the low-protein third of participants ate 12% of total calories as protein, compared to 20% in the high-protein third.  [Study authors could have put this in the appropriate table, but, mysteriously, opted against that.]

Caveats

We can’t tell from this study whether these findings apply to protein intakes outside this range, to men, or to women older than 40.  To their credit, the study authors review much of the pertinent literature and note that research in this area produces results all over the map.  To me, this suggests that the association between dietary protein and bone mineralization in the general population is weak, if not nonexistent.

Bottom Line

Looks like you can stop worrying so much about hurting your bones if you’re on a low-carb, high-protein diet.

Steve Parker, M.D.

Reference: Beasley, J., Ichikawa, L., Ange, B., Spangler, L., LaCroix, A., Ott, S., & Scholes, D. (2010). Is protein intake associated with bone mineral density in young women? American Journal of Clinical Nutrition, 91 (5), 1311-1316 DOI: 10.3945/ajcn.2009.28728

 

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June 30, 2009 · 2:00 AM

Are High-Protein Weight-Loss Diets Safe and Effective?

Animal protein

Animal protein

According to researchers at Tufts University, high-protein weight-loss diets may be effective and safe except for people prone to kidney stones, chronic kidney disease, and people with diabetes.  Long-term effects on bone health – osteoporosis, specifically – might be a problem.

High-protein weight-loss diets have been popular for a while.  “Protein Power” by Drs. Michael and Mary Eades is an example.  The Atkins diet may be, too.  If you increase the protein in your diet, you generally are decreasing carbohydrates or fat, or both, at the same time.   

I found a scientific review article from way back in 2002 and thought I’d share some of the highlights.  The authors seem very thorough; the article has 150 citations of other research articles. 

Note that the RDA – recommended dietary allowance – for protein is 0.8 gm/kg.  The typical U.S. resident eats about 1.2 gm/kg of protein daily, which is about 15% of total energy (calorie) intake.   Public health agencies recommend that we get 15% of our energy from protein, 30% from fat, and 55% from carbohydrate.  The authors of the study at hand propose that a high-protein diet be defined as:

  • protein intake of at least 25% of energy in weight-stable individuals, or
  • at least 1.6 gm/kg (of ideal body weight)  in people actively losing weight

Here are some of the authors’ points I found interesting:

  1. Higher-protein meals do seem to suppress hunger and enhance satiety, so high-protein dieters probably eat less (average 9% less calories).  It’s unknown if the effect lasts longer than six months.  Most of the evidences is much shorter-term.
  2. High-protein intake increases the thermic effect of feeding, meaning energy expenditure increases simply as a result of eating protein.  In other words, it takes energy to process the food we eat.  Compared with fats and carbohydrates, protein contributes twice as much to the thermic effect of feeding.  Most of the thermic effect of protein results from protein synthesis, i.e., the production of new proteins, which requires energy.  This has a minimal influence on body weight. 
  3. The authors write that “these studies do not support a role for high dietary protein in preventing loss of lean tissue during negative energy balance [actively cutting calories to lose weight], provided that dietary protein intake at least meets the RDA.”   
  4. They found only one study comparing a high-protein diet (25% of calories) with a low-fat, high-carbohydrate diet (12% protein).  Both diets were 30% fat.  Both groups could eat all they wanted.  Weight and fat loss were greater in the high-protein group, about twice as much. 
  5. High-protein diets over the long run may cause low-grade metabolic acidosis, leading to net loss of body calcium through the urine, with associated weak bones and kidney stones.   Animal proteins in particular do this.  Bone loss may be alleviated by calcium supplementation.  Fruits and vegetables may counteract the acidosis effect.  Nearly all of these statements are based on short-term studies.
  6. People with chronic kidney disease (ask your doctor) have slower disease progression and live longer if they limit protein to the RDA level. 
  7. Animal protein intake is directly related to risk of symptomatic kidney stones.
  8. Protein produces a blood glucose response, although not as much as with carbohydrate.  Insulin response is also seen.  In type 2 diabetics, the insulin response to 50 grams of animal protein was the same as to 50 grams of glucose.  A few studies suggest that in type 2 diabetics a high-protein diet may be detrimental to glucose control and/or insulin sensitivity.  Also note that people with diabetes are prone to chronic kidney disease, which could be worsened with a high-protein diet.  

Take-Home Points

See first paragraph.  The article authors may have different opinions now, based research published over the last seven years. 

Steve Parker, M.D.

Reference:  Eisenstein, Julie, et al.  High-protein weight-loss diets:  Are they safe and do they work?  A revew of the experimental and epidemiologic data.  Nutrition Reviews, 60 (2002): 189-200.

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May 11, 2009 · 12:00 AM

High- vs Low-Protein Weight-Loss Diet in Type 2 Diabetes

 

Mucho protein, amigo

Mucho protein, amigo

A high-protein weight-loss diet yielded greater reduction in LDL cholesterol in both sexes, and greater loss of abdominal fat in overweight type 2 diabetics, compared to a lower-protein diet.  Lower LDL cholesterol levels are associated with lower risk of heart attack.

This scientific study caught my eye because it utilized a high-monounsaturated fat diet for weight loss.  The Mediterranean diet is rich in monounsaturated fats, mostly from olive oil.

Researchers in Australia ran a study to determine the effect of high- versus lower-protein wieght loss diets on fat and lean tissue, glucose levels, and blood lipids.  For perspective, remember that a typical American diet has about 15% of calories from protein, 30% from fat, and 55% from carbohydrates.

Methodology

This was their high-protein diet:  28% protein, 42% CHO, 28% fat (8% saturated fatty acids, 12% monounsaturated fatty acids, 5% polyunsaturated fatty acids).

The low-protein diet:  16% protein, 55% CHO, 26% fat (8% saturated fatty acids, 11% monounsaturated fatty acids, 5% polyunsaturated fatty acids).

They studied 54 obese men (19) and women (35) with type 2 diabetes during 8 weeks of energy restriction (1,600 kcal) and 4 weeks of energy balance.  Body composition was determined by dual-energy X-ray absorptiometry at weeks 0 and 12.

Results

Average weight loss for both groups was 5 kg.  However, women on the HP diet lost significantly more total (5.3 vs 2.8 kg) and abdominal (1.3 vs 0.7 kg) fat compared with the women on the LP diet, whereas, in men, there was no difference in fat loss between diets (3.9 vs 5.1 kg).  Total lean mass decreased in all subjects independently of diet composition.  LDL cholesterol reduction was significantly greater on the HP diet (5.7%) than on the LP diet (2.7%).  Blood glucose levels were reduced 5 or 10% by both diet interventions.  Trigylcerides dropped 20% in both groups.  Insulin concentrations were reduced in both groups.  Subjects lose 2.1% lean mass overall, with no difference between the groups.

Conclusions of the Study Authors

Both dietary patterns resulted in improvements in the cardiovascular disease (CVD) risk profile as a consequence of weight loss. However, the greater reductions in total and abdominal fat mass in women and greater LDL cholesterol reduction observed in both sexes on the HP diet suggest that it is a valid diet choice for reducing CVD risk in type 2 diabetes.

Take-Home Points

This was a relatively small study, so results may not be widely applicable.

Substituting proteins for carbs doesn’t seem to be detrimental to people with type 2 diabetes needing to lose weight, and may be advantageous:  greater total and abdominal fat loss in women, greater reductions in LDL cholesterol for both sexes.   At least in the short run.

Nephrologists will be concerned that the higher-protein diet, if sustained long-term, could lead to kidney damage.

Current dogma is that the lower-carb (high-protein) dieters should have had lower blood glucose, triglycerides, and HgbA1c levels:  not seen here.

Calorie-restricted diets tend to lower glucose levels and improve lipids, despite diet composition.

Reference:  Parker, Barbara et al.  Effect of a High-Protein, High–Monounsaturated Fat Weight Loss Diet on Glycemic Control and Lipid Levels in Type 2 Diabetes.  Diabetes Care,  25 (2002): 425-430.    From CSIRO Health Sciences and Nutrition, Adelaide, Australia.

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